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Structural Engineering Documents

This Structural Engineering Document addresses safety and regulations, integration concepts, and a sustainable approach to structural design. Life-cycle assessment is presented as a critical tool to quantify design options, and the importance of existing structures–in particular cultural heritage structures–is critically reviewed. Consideration is also given to bridge design and maintenance, structural reassessment, and disaster risk reduction. Finally, the importance of environmentally friendly concrete is examined. Consequently, structural engineers are shown to have the technical proficiency, as well as ethical imperative, to lead in designing a sustainable future.

Sustainable Structural Engineering

Sustainability is the defining challenge for engineers in the twenty-first century. In addition to safe, economic, and efficient structures, a new criterion, sustainable, must be met. Furthermore, this new design paradigm–addressing social, economic, and environmental aspects–requires prompt action. In particular, mitigation of climate change requires sustainable solutions for new as well as existing structures. Taking from both practice and research, this book provides engineers with applicable, timely, and innovative information on the state-ofthe-art in sustainable structural design.

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Structural Engineering Documents

14 Sustainable Structural Engineering

14

Sustainable Structural Engineering

John E. Anderson Christian Bucher Bruno Briseghella Xin Ruan Tobia Zordan

International Association for Bridge and Structural Engineering (IABSE)

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Copyright © 2015 by International Association for Bridge and Structural Engineering All rights reserved. No part of this book may be reproduced in any form or by any means, electronic or mechanical, including photocopying, recording, or by any information storage and retrieval system, without permission in writing from the publisher. ISBN 978-3-85748-141-3 Publisher: IABSE c/o ETH Zürich CH-8093 Zürich, Switzerland Phone: Fax: E-mail: Web:

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Int. + 41-44-633 2647 Int. + 41-44-633 1241 [email protected] www.iabse.org

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Preface

From resource consumption and water use to waste generation and greenhouse gas emissions, the built environment is critical for a sustainable future. While the challenges of sustainability have been known for decades, urgency of action is driven by the findings of the United Nations Intergovernmental Panel on Climate Change. Consequently, structural engineers face a new design paradigm: safe, economic, reliable, and sustainable. Sustainable development is defined by the Brundtland Report as “development that meets the needs of the present without compromising the ability of future generations to meet their own needs.” The three pillars of sustainability—environment, social, and economic—must be taken into account for engineering projects to achieve sustainability. This Structural Engineering Document presents the latest research and practical applications of sustainable structural engineering from around the world. In the opening chapter, Kanda details the role of the structural engineer in sustainable design with a focus on safety. This is followed by Limsuwan’s chapter on an integration concept of sustainability engineering. Zordan then outlines a sustainable approach to structural design. Lourenço, Branco, and Coelho illustrate the importance of existing structures in their chapter on cultural heritage and structural systems. Anderson and Yang discuss life-cycle assessment as a crucial analysis tool to evaluate environmental sustainability criteria. Matos, Neves, and Gonçalves subsequently present the importance of asset management for aging infrastructure. Martin and Kirk provide a crucial review of sustainability in bridge design and maintenance. Bucher and Brehm then present structural reassessment for the lifetime extension of structures. The importance of disaster risk reduction as a sustainability strategy is presented by Grundy. Finally, de Brito and Silva review green materials for concrete production. Sustainability is a broad and complex topic. Through this Structural Engineering Document we aim to provide practicing engineers and researchers with insights, tools, and recommendations to advance sustainable structural design. John E. Anderson, Christian Bucher, Bruno Briseghella, Xin Ruan, and Tobia Zordan August, 2015

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Table of Contents

1

Safety and Sustainability—the Structural Engineer’s Role (Jun Kanda) 1.1 1.2 1.3 1.4 1.5 1.6

2

Integration Concept of Sustainable Engineering (Ekasit Limsuwan) 2.1

2.2

2.3

2.4

2.5

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Introduction Major elements for architecture Environmental impacts Role of regulations Transparency and accountability Further considerations References

Introduction 2.1.1 Sustainable development 2.1.2 Sustainable engineering 2.1.3 Integration concept on sustainability engineering Integration concept in the building process 2.2.1 Emerging strategy 2.2.2 Planning and development 2.2.3 Design 2.2.4 Construction 2.2.5 Operation and maintenance Implementation solution 2.3.1 Public consciousness 2.3.2 Laws and regulations 2.3.3 Professional practices Examples of implementation solution 2.4.1 Thailand sufficiency economy 2.4.2 PTT sustainable development 2.4.3 SCG sustainable development Conclusion and recommendation References

1 1 2 3 4 5 7 7

9 9 9 10 10 11 11 12 13 13 14 14 14 15 16 17 17 18 20 21 22

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3

A Sustainable Approach to Structural Design (Tobia Zordan) 3.1 3.2 3.3 3.4 3.5 3.6

3.7

4

Sustainability and Cultural Heritage Buildings (Paulo B. Lourenço, Jorge M. Branco and Ana Coelho) 4.1 4.2

4.3

4.4

4.5 4.6

4.7

5

Introduction Definitions 4.2.1 Cultural heritage conservation specificities 4.2.2 Rehabilitation and sustainability Traditional materials and sustainability 4.3.1 Masonry 4.3.2 Wood Methodology for intervention in heritage structures 4.4.1 Principles 4.4.2 Guidelines Application of life-cycle assessment tools to existing buildings Cultural heritage buildings and sustainability 4.6.1 Environmental impacts 4.6.2 Economic impacts 4.6.3 Social impacts Conclusion References

Measuring Sustainability and Life-Cycle Assessment (John E. Anderson and Frances Yang) 5.1 5.2

5.3

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Introduction Ecological footprint and appropriate carrying capacity Some considerations on sustainability in integrated life-cycle structural engineering: conception and uncertainties in design approach Complexity versus complicacy within a sustainable conceptual design Structural art: a ruled freedom Sustainable conceptual design of structures 3.6.1 Design for structural efficiency 3.6.2 Choice of a suitable static scheme 3.6.3 Structural optimization 3.6.4 Design for durability, minimal maintenance, and life-cycle costs 3.6.4.1 Integral abutment concept 3.6.5 Design for value protection 3.6.5.1 Seismic isolation of existing buildings Conclusion References

Introduction 5.1.1 Sustainability goals Life-cycle assessment 5.2.1 Metrics 5.2.2 Methodology 5.2.3 Life-cycle inventory databases 5.2.4 Software tools Life-cycle assessment case studies of structures 5.3.1 Comparing case studies 5.3.2 Limitations of life-cycle assessment

25 25 26 29 32 35 39 39 39 41 42 43 46 48 49 50

53 53 55 55 57 58 59 60 61 61 62 63 64 64 65 65 66 66

69 69 70 71 75 75 76 77 77 83 84

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5.4

5.5 5.6

6

Asset Management (José C. Matos, Luís Neves, and Bruno Gonçalves) 6.1 6.2 6.3 6.4 6.5 6.6 6.7 6.8

7

7.4

7.5

7.6 7.7

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Introduction WLC: a tool for asset management Whole-life costing: a review Costs and condition Models and scenarios Data acquisition systems and model updating Optimization techniques and decision Conclusion References

Sustainability and Bridges (Andrew J. Martin and Martin J.D. Kirk) 7.1 7.2 7.3

8

Green design rating systems 5.4.1 Buildings 5.4.2 Infrastructure and bridges 5.4.3 Cities and the urban scale Emerging trends Conclusion References

Introduction Bridges and sustainability Aspects of sustainability related to bridges 7.3.1 Environment 7.3.2 Society 7.3.3 Economics The life-cylce of a bridge 7.4.1 Inception, feasibility, and option selection 7.4.2 Design and specification 7.4.3 Construction 7.4.4 Operation and maintenance 7.4.5 Assessment and strengthening 7.4.6 Demolition Case studies 7.5.1 Case study 1—Capilano River bridge replacement (Canada) 7.5.2 Case study 2—Queensferry Crossing (Scotland, UK) 7.5.3 Case study 3—Bridges for the Queen Elizabeth Olympic Park, London (UK) A sustainability checklist for bridges Conclusion Acknowledgements References Further reading

84 84 86 87 87 88 88

93 93 94 95 96 100 102 105 107 107

111 111 112 112 113 116 117 119 119 120 121 121 122 122 122 123 126 128 132 132 135 135 137

Structural Reassessment for Lifetime Extension (Christian Bucher and Maik Brehm)

141

8.1 8.2 8.3

141 142 143

Introduction General philosophy Best practice

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8.4

8.5

9

Review of methodologies useful for structural reassessment 8.4.1 Model calibration 8.4.2 Optimal sensor placement 8.4.3 Uncertainty quantification and propagation methods 8.4.4 System reliability analysis 8.4.5 Cost-benefit analysis 8.4.6 Structural health monitoring Conclusion References

Sustainability through Disaster Risk Reduction (Paul Grundy) 9.1 9.2 9.3 9.4

9.5

9.6

9.7

Introduction The triple bottom line Acceptable risk Basic features of natural hazards leading to disaster 9.4.1 Excessive hazard intensity 9.4.2 Synchronous failure Design for disaster risk reduction 9.5.1 Disaster limit state 9.5.2 Reconstruction 9.5.3 Retrofitting Obstacles to sustainability in disaster risk 9.6.1 Awareness of risk 9.6.2 Cost of disaster prevention measures Conclusion References

10 Green Materials for Concrete Production (Jorge de Brito and Rui V. Silva) 10.1 10.2 10.3 10.4

10.5 10.6 10.7 10.8 10.9

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Introduction Background How to make concrete more sustainable Recycled materials for concrete 10.4.1 Industrial wastes 10.4.2 Construction and demolition wastes 10.4.3 Converting CDW into usable aggregates Early age behaviour of structural RAC Mechanical behaviour of structural RAC Durability behaviour of structural RAC Successful case studies using structural RAC Concluding remarks References Introduction Industrial wastes Construction and demolition wastes Fresh behaviour of RAC Mechanical behaviour of RAC Durability behaviour of RAC

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153 153 153 154 155 155 156 157 157 160 160 161 161 162 162 163

165 165 166 168 169 169 170 172 174 177 180 183 183 186 186 187 190 191 193 194

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1 Chapter

1 Safety and Sustainability— the Structural Engineer’s Role

Jun Kanda, Prof.; College of Science and Technology, Nihon University, Tokyo, Japan. Contact: [email protected]

1.1

Introduction

The mission of structural engineering is to design and construct safe structures by making appropriate decisions. At the same time, society also has a strong demand for sustainability, to which structural engineers can contribute through their decisions. Such decisions are necessary at every step of the design, construction, maintenance, and demolition process. The appropriateness depends on people’s expectancy for a structure, which varies according to their cultural background and economic well-being, as well as technological development. Historically, when quantitative information of a design variable was not available, the structural safety was determined by engineers, based mainly on their own experiences. Materials and construction systems simply followed what had been successful in the past. Due to the scientific developments, structural analysis is now available to examine if structural materials are strong enough to withstand the likely forces on a structure, and these forces can be calculated for postulated unfavourable situations. Safety is one of the essential requirements for a structure, but the purpose of construction is to create comfortable spaces for human activities, with serviceability requirements being equally important. Economic efficiencies are also important in addition to safety and serviceability. Sustainability is now another important aspect for buildings and structures. Quantitative discussions on the balance between safety and sustainability has thus become possible. The availability of quantitative information to assess structural safety (e.g., probabilistic models for the physical characteristics of structural materials, environmental actions, and the physical dimensions of structural members) has enabled the reliability of a structure to be evaluated for required safety and serviceability limits. The reliability concept for structures is now commonly; the standard ISO 2394 becoming first available in 1986 [1]. Safety and structural requirements can be discussed at the design stage for new construction or at the maintenance stage for existing structures. Back to table of contents

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2

CHAPTER 1. INTRODUCTION

The introduction of the concept of sustainability has brought an additional dimension to the engineering decision process. In this chapter, the role of engineers is discussed in achieving an appropriate level of safety for structures in a society that expects sustainability of structures for the future. A greater demand for structural safety can result in overdesign with excess use of materials. However, a more durable structure has a longer life, which saves resource consumption. With diverse information available from different sources, an engineer is expected to be professional not only in engineering aspects but also in addressing the much wider topic of sustainability. At some stages of economic development, the focus tends to be on the efficiency over a rather short period of time. This can lead to the selection of a lower level of safety, particularly for natural hazards such as earthquakes and hurricanes. Sustainability considerations require life-cycle assessment of structural engineering aspects. Based on such considerations, engineers are expected to provide sufficient explanations to society as well as to their clients for the appropriateness of the structural safety. At the same time, engineers should make efforts to create sustainable structures.

1.2

Major elements for architecture

Marcus Vitruvius (80/70–15 BC) in the Roman period discussed the essence of architecture as a combination of firmness, functionality, and aesthetics. These three elements are still the principal elements for any architecture. Firmness refers not only to structural safety, but also to durability and stability. Functionality, refers largely to the mechanical, electrical, and environmental aspects, but the volume or height is also a part of the functionality of a structure. Aesthetics, which is not only the artistic impression but also encompasses the street view or impact on the landscape, is a common concern for architecture. Economy can be added as the fourth element to be considered by society. The balance between these four elements is an essential condition for the design of a high quality building as shown in Fig. 1.1. The degree of safety or durability tends to be treated as a given as these are often clearly specified in the regulations. However, Functionality when the budget for the construction is limited, how much is spent on the safety and functionality must be carefully examined beforehand. Sometimes the aesthetic requirements may be Safety Aesthetics sacrificed for the safety, and occasionally the opposite will occur. Economy is an important element of architecture, but it is different from the other three elements. Economy provides a common value but does not encompass the purpose of architecFig. 1.1: Balance between the four elements ture in a way that the other three elements do. of architecture When the balance between safety and economy is considered, the minimum total expected cost concept is applied to find an optimal solution as discussed later. It does not consider the balance between the degree of safety and degree of economy, but the whole economic efficiency Economy

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1.3 ENVIRONMENTAL IMPACTS

3

is introduced. Therefore, the economy element may be regarded as an evaluation system rather than an element of architecture. The monetary value is often used, but this could be substituted with environmental impacts or some other new measurement tool. The quality of aesthetics can be immediately judged by people when the architecture is visible, although the results can be very diverse. Functionality can be examined after one year by users or occupants. Safety is the most difficult quality to perceive as this metric can be observed only in the future. The expected failure cost or the risk potential is a measure for the safety. Science and engineering also play important roles. An important role of the structural engineer is justifying the appropriate safety of a structure, and taking the required functionality and aesthetics into account. Such overall consideration is always necessary, particularly in a society concerned with sustainability. The long-term consideration of economic parameters is also a basic aspect of sustainability. The concept of balancing between the four elements of architecture discussed above can be applied to any civil engineering construction such as bridges and tunnels or even to any manufactured product. The safety is not determined in isolation, but is rather determined as the balance with other elements, which are influenced by social as well as cultural environments.

1.3

Environmental impacts

When a structure is constructed, it influences the environment in many ways. It occupies a certain volume on a site and this itself produces an environmental impact. The use of the structure consumes energy. In addition, the structure contains embodied greenhouse gas emissions (i.e., CO2), which is a metric for environmental impacts and is a political issue as well. The materials that comprise the structure are products whose manufacture result in CO2 emissions. In particular, concrete have greater embodied CO2 emissions than natural materials such as wood or stone. Long-distance transportation also emits significant CO2. Consequently, the selection of materials can significantly affect the impact of a structure on the environment. Failures of structures can cause many undesirable consequences. If such failures occur in large numbers in a single event, they can cause major disasters. Disaster mitigation is a basic policy for the sustainability of structure. Disasters can be mitigated by increasing the safety of structures. If a higher reliability and importance for safety is given at the design stage or the rehabilitation stage, the probability of the occurrence of a failure will be reduced. A higher level of safety may, however, cause overuse of resources and energy. On the other hand, a level of safety lower than the appropriate level may cause frequent failures in the structure followed by extreme consequences, which will cost more than the mitigation measures. It becomes the role of the structural engineer to find the appropriate level for the safety of the building. Efforts to minimize total estimated costs can help in developing a solution based on probabilistic models [1–3]. A similar approach is required in the case of rehabilitation of structures [4]. The longer the service life of a structure, the lower the embodied CO2 emission per year of service life. A procedure for optimizing reliability while minimizing CO2 emissions is available from existing case studies [5]. The ratio of structural cost to the whole building cost is less than the

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4

CHAPTER 1. INTRODUCTION

ratio of structural CO2 emissions to the whole building CO2 emissions. A typical value for the former is 0.25, while that for the latter is 0.4. Then the minimization of total expected CO2 emissions leads to a significantly lower optimal safety than that based on the minimization of total expected costs. A further consideration is needed to make a decision based on these different measures. In general, safer and more durable buildings are essentially more environmentally friendly. How to determine the service life and the safety target are both essential questions for structural engineers.

1.4

Role of regulations

If engineers could confidently provide suitable decisions on structural safety, regulations would likely not be necessary. However, in order to avoid the construction of unsafe buildings, specification of minimum requirements for structures is a convenient tool and usually the subject of regulations. Although requirements are stated as the minimum, in most situations, such minimum requirements are regarded as standard criteria for society. This seems to be the result of an appreciation of economic efficiency at the construction stage and the negligence of the benefits resulting from the lower probability of failure in the future. Consequently, when some natural disasters, such as earthquakes and hurricanes cause significant damage, to structures in reality, some improvements for a safer society are proposed and discussed to reduce those damages. When the Hyogoken-Nambu earthquake shook Kobe city in Japan in 1995, serious structural damages occurred in a wide area. However, the statistical survey of the damage suggested that the current level of safety requirements in the regulations were sufficient [6]. Although some new buildings were destroyed, the ratio was very small. The return period of the maximum ground motion in Kobe city was assumed to be around 1000 years or more, while 500 years was considered for the safety level for design in the regulatory requirements of the Japanese law. For new construction, the 1995 experience effectively confirmed that the safety levels stipulated by the regulations were appropriate. Most of the damaged buildings were those constructed before 1981, when significant changes were made to the regulations with capacity design being specified. Nevertheless, the appropriateness of the safety level for buildings or civil structures needs to be examined, paying more attention to their long-term use or sustainability. Since the market mechanism often controls the quality of structures, the degree of safety may not be optimal. Structural safety needs careful attention as safety is not as visible as functionality or aesthetics are. Once the requirements according to the regulations are satisfied, people tend to think that the structure is safe without further considerations, but this is not entirely reliable. Regulations should be relatively simple but society should not forget that only the minimum requirements are regulated. Soil characteristics and seismic hazard are both site-dependent and regulations usually cannot provide sufficient requirements for these factors. In such cases, engineers should make complete use of the available technical information for the determination of design loads and explain and persuade the client to increase the level for safety when it is appropriate for long-term consideration. The Tsunami disaster of the East Japan earthquake on 11 March 2011 has shown that the certified regulations supported by experts and scientists can be wrong or at least greatly underestimated.

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1.5 TRANSPARENCY AND ACCOUNTABILITY

5

Those who are affected by the consequences of structural failure should have more commitment towards the safety decision. Regulations alone cannot provide optimal safety for individual structures, and engineers have to play an important role particularly in a sustainable society. Sustainability aspects will be included in future regulations; however, engineers have to provide sufficient information to the client and society regarding their decisions on safety after considering sustainability requirements rather than only regulatory rules. Similar effects of regulations as minimum requirements for the sustainability and safety of structures have to be considered. How to achieve an appropriate level of sustainability for society is dependent on individual elements, such as materials, construction, and transportation. Therefore, engineers have to provide sufficient information regarding the sustainability and safety beyond regulations.

1.5

Transparency and accountability

Only engineers can evaluate the safety of a structure. Of course, there are alternative safety measures, and assumptions and conditions for the evaluation can significantly affect the result. In other words, even professionals cannot collect ideal information, and so scientific evaluations are always insufficient. Nevertheless, the engineer should provide sufficient information to the client in order to make the best decision possible. Failures of a structure influence the surrounding environment, and thus people in the neighbourhood of the structure have a right to contribute to the decision-making on the safety of the building. Resource consumption and CO2 emissions also are a matter of concern for the overall society. Information regarding these is readily available. The minimum requirements according to the regulations may not be appropriate for the longterm interest of society. When strong demands arise for development of housings and buildings, minimization of construction cost tends to be the concern of society. The minimum requirements are then regarded as the target for safety. However, considering the future generation and the long-term economy, individuals have the responsibility for a sustainable society. The minimum safety requirements in the 1950s in Japan are not regarded as appropriate in the present society of Japan. The appropriateness depends on more specific conditions and cultural situations. Such specificities and diversities cannot be implemented as national regulations. The same applies to sustainability. Therefore, an engineer has a large responsibility for ensuring structural safety for the client as well as for the society. Communication between the professional engineer and the public is therefore extremely important. In order to have meaningful discussions for decision making, information transfer alone is not sufficient; knowledge also has to be shared [7]. There is an interesting comparison regarding the safety attitude of house owners and that of a structural engineer [8]. Figures 1.2 and 1.3 are answers of house owners to the question: “Are you provided explanations on the safety from experts?” and “Do you want to receive explanations on safety?”, respectively. People are concerned about the safety of a building and want to have more information on the safety as indicated in Fig. 1.3. Nevertheless, in most cases, there are no explanations provided by a structural engineer, as shown in Fig. 1.2.

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CHAPTER 1. INTRODUCTION

Houses and buildings have to satisfy regulatory requirements before construction. This means that all houses and buildings can be regarded as being safe. However, people tend to pay less attention to the structural safety. When they were questioned if they want explanations on the safety, however, 80% of people answered “yes” [8]. Engineers should find more opportunities to explain structural safety and sustainability to the general public. Explanations should not just be the compatibility of the regulatory requirements, but should justify rational safety measures based on scientific evidences. Regulations deal with the safety of buildings at the national level and tend to be focused on human safety. The safety of individual buildings also depends on the decision of clients based on the engineers’ explanation. When a community level is considered, the role of the engineer is more important because the cost of managing disasters increases exponentially with the size of the disaster as discussed in Ref. [9]. There are benefits from mitigation at the community level, which are not reflected in the benefits for individual buildings. Engineers are expected to play a leading role in ensuring safety of the community as well as that of the structures from the sustainability aspect [7]. Mutual agreement on the safety of a structure among the community supported by professional engineers is a key for sustainability. The safety decision as well as sustainability decision have to be made in a transparent manner.

Yes

No

Not sure

Non-Expert

Expert

Whole 0%

20%

40%

60%

80%

100%

Fig. 1.2: Answers to question, “Are you provided explanations on safety from experts?”

Yes

No

Either is good

Non-Expert

Expert

Whole 0%

20%

40%

60%

80%

100%

Fig. 1.3:Answers to question, “Do you want to receive explanations on safety?”

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1.6 FURTHER CONSIDERATIONS

1.6

7

Further considerations

The appropriateness of safety has to be determined from a sustainability point of view. For this, safety and sustainability have to be carefully defined. The local conditions of a site influence the safety as well as the sustainability. From the vast amount of information available, engineers have to choose rational and unbiased information and provide explanations that enable the client to make appropriate decisions on building safety. Clients or building owners usually do not have sufficient knowledge to make decisions on safety; therefore, information provided by engineers is essential for making decisions. In order to make situations simple, a few alternatives for the structural design with different degrees of safety or different levels of environmental impacts with possible consequences may be proposed to a client as options. The situation is similar to the case between a patient and a medical doctor when making a decision on medical treatment alternatives. Professionals have to provide unbiased information for a client to make a decision. The difference between the medical case and structural case is the social aspect. The medical case is rather private, but the structural case is concerned with the social consequences from both safety and environmental aspects. Minimum requirement regulations are convenient from an economic perspective, but a more conscientious outlook for sustainability is required. Finally, societal consensus on structural safety and durability have to be considered and discussed in a transparent manner.

References [1] ISO 2394. 1998. General principles on reliability for structures, ISO. [2] Kanda, J., Ellingwood, B. 1991. Formulation of load factors based on optimum reliability. Struct. Saf., 9: 197–210. [3] Walker, G.R., Musulin, R. 2012. Utilising catastrophe risk modelling for cost benefit analysis of structural engineering code changes, Proceedings of the Australasian Structural Engineering Conference 2012, Institution of Engineers Australia, Perth, Australia. www. engineersaustralia.org.au. [4] Walker, G.R., Musulin, R. 2011. Economic analysis of structures deficient in earthquake resilience, Proceedings of the 9th Pacific Conference on Earthquake Engineering, Auckland (CD-Rom). [5] Kanda, J., Kanda, S. 2002. Comparison of minimization of L.C.C. and L.C.CO2 emission for structures, Proceedings of IABSE Symposium, Melbourne, Australia. [6] Kanda, J., Takada, T., Choi, H. 2007. Target structural reliability in life cycle consideration. Int. J. Risk Assess. Manag., 7(6/7): 846–861. [7] Kanda, J., Elms, G.D. 2010. Communications in structural engineering from ethical aspects, Proceedings of IABSE Symposium, Venice. [8] Kanda, J., Takada, T., Choi, H. 2004. Internet-based system for structural safety evaluation in Japan, Proceedings of Third Asian-Pacific Symposium Structural Reliability and its Applications, Seoul, South Korea, 95–103. [9] Walker, G.R., Grundy, P., Musulin, R. 2011. Disaster risk reduction and wind engineering, Proceedings of 13th International Conference on Wind Engineering, Amsterdam (CD-Rom).

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9 Chapter

2 Integration Concept of Sustainable Engineering

Ekasit Limsuwan, Prof., Dr.; Department of Civil Engineering, Chulalongkorn University, Thailand. Contact: [email protected]

2.1

Introduction

Modern civil engineering mega-projects dealing with buildings, bridges, and infrastructures take sustainable engineering into consideration for the development and execution of their projects. Since sustainable development and sustainable engineering are rather broadly covered as global issues, each individual needs to take personal responsibility for environmental, social, and economic questions whose performance outcomes may impact the life cycle of the structure. An integration concept on sustainable engineering will deal with emerging criteria and concept for a strategic approach to the planning, execution, operation, and maintenance phase of the building process. It can be shown that approaches to and strategies for these issues result from individual consciousness, national policies, and global actions. Current research has been conducted on the sustainability perspective of areas such as global climate changes, CO2 levels, life-cycle assessment (LCA), green design rating, emerging trends in sustainable engineering, and sustainability monitoring and evaluation criteria. However, there may still be more areas requiring further research to apply an integrated concept to emerging strategies for building a process to achieve the goals. Then the methods and procedures appropriate for each community or society can be explored. However, a quantifying performance method also needs to be used as a measure to guarantee satisfactory findings.

2.1.1

Sustainable development

Sustainable development has played an important role in the environmental, social, and economic quotients of human beings and their individual contribution, perception, and response. Analysis of such behaviour is significant in order to reach a public consensus of a sociocultural perception, and to understand the environmental impacts on the macro-diversity of the ecology system. The responsibility of the public or community with regard to environmental problems should emphasize the ecosystem, health, well-being, and natural resources. It is also well

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CHAPTER 2. INTEGRATION CONCEPT OF SUSTAINABLE ENGINEERING

accepted that social aspirations should be addressed to bring satisfaction to society, in terms of not only human security but also public safety and sociocultural satisfaction. In the arena of economics, the principle of sufficiency economy has played an important role in developing countries, such as Thailand, where concepts of appropriate conduct and ways of living in balance with a development strategy to reduce wasteful consumption, minimize waste, increase the life cycle, and bring a sense of satisfaction of well-being have been introduced. The sustainable development coverage by such objectives is rather broad but their execution can be achieved when each individual makes a global commitment to every sector. However, assessment of the performance outcome will be a long-term project with respect to its monitoring system and the corresponding LCA. It should be noted that the outcome assessment addresses multiple indicators on an integration basis.

2.1.2

Sustainable engineering

Sustainable engineering has confined itself to the issues and solutions of a systematic approach to CO2 emissions, LCA, natural resources, energy consumption, and environmental impact. Sustainability goals have been set up as a long-term perspective of CO2 levels by the Intergovernmental Panel on Climate Change (IPCC) [1]. The LCA has been outlined by the International Organization Standardization (ISO), for environmental management [2,3] as a methodology and framework to determine environmental aspects and potential impacts. These frameworks have received reasonable attention from individual scientists, technologists, and engineers as well as the private and public sectors of design services and manufacturing. The International Association for Bridges and Structural Engineers (IABSE), through the Working Commission 7, has explored the role of structural engineering on sustainable engineering to lead in planning, designing, and building sustainable civil infrastructure systems. In addition, there has been a fundamental shift towards integrating sustainability into all aspects of the university curricula in order to achieve a global optimization regarding safety, durability, economy, and a minimum environmental impact, and to consider the ecological, economic, and sociocultural effects in every phase of the life cycle of a building[4]. Structural engineers have the responsibility for the sustainability of buildings and constructed assets as in traditional requirements, including structural safety and reliability, architectural design, site requirements, functionality, and construction costs. Furthermore, they have new additional requirements such as energy performance, environmental performance, life-cycle costs, functionality and serviceability, risk assessment, dismantling, and closed-loop-management. However, it will still be essential to merge concepts and criteria for a strategic approach towards the building process.

2.1.3

Integration concept on sustainability engineering

An integration concept of sustainability engineering introduced in this chapter will deal with emerging criteria and concepts for a strategic approach to the planning and development phase, the design and construction phase, and the operation and maintenance phase. Although sustainable issues focus on engineering approaches, criticism of the concepts will be accepted only when they are realistic and practically implemented. The most effective performance will be achieved when the strategic plan has been executed on a voluntary basis with the favourable interests of a green rating for buildings, bridges, and infrastructure systems. Some immediate

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2.2 INTEGRATION CONCEPT IN THE BUILDING PROCESS

11

outcome indicators may be publicly criticized and can be used to make suitable and appropriate adjustment to the local ecosystem, the sociocultural background, and the economic common interest of each community. This chapter will also introduce relevant laws or regulations that may be needed for each individual jurisdiction of national measures, codes of professional conduct, and the practice for engineering services to improve professional competency, as well as international standards, guidelines, and a framework within which to proceed with such important tasks of sustainability.

2.2

Integration concept in the building process

For civil engineering mega-projects such as buildings, bridges, and infrastructure systems, the important role of sustainability needs to be taken into account throughout the project from the planning and development phase through the life span to the end of the service life. Integration concepts in the building process should be introduced soon after emerging trends of technologies have come up with the most effective strategies. Then, the methodology’s rules and procedures can be exercised during the building process with monitoring measures and outcome performance indicators for further adjustment to improve the system as an integration concept.

2.2.1

Emerging strategy

Current research work on sustainability may be categorized under such areas as sustainability goals, LCA, and green design rating. Strategic approaches emphasize the three major areas of technology, outcome performance of research work, and the social perception of economic feasibility. The emerging technology for sustainability also depends on the trends of environment and social impacts balanced by economic status. Principal indicators of energy consumption to stabilize environmental improvement should be taken into consideration by using a green rating system as the benchmark for adjustment. International consensus has been achieved on the goal of sustainable development according to which global climate change is considered to be the most important environmental issue. The long-term perspective for CO2 stabilization levels as recommended by the IPCC can be a guideline for government, non-government, and private sectors to set their goals. For example, the European Union (EU) is aiming to reduce the 1990 CO2 emissions by 80–95% by 2050[5]. Similarly, in the construction industry, “The 2030 Challenge” has set the goal of reducing energy use by 60% for all new buildings and aims for carbon neutral buildings by 2030[6]. The LCA is most widely used as the methodology and framework for environmental assessment. The international standard for LCA has been outlined by the ISO in the ISO-14000 series for environmental management. However, there are three approaches of the LCA presented on the basis of process, economic input-output, and hybrid. For civil engineering, the processbased LCA would be a relevant utilization of the concept of material and energy balances for a specific process. The four steps of assessment are to define the goal and the scope of study, to perform a life-cycle inventory, to conduct a life-cycle impact assessment, and to interpret the results [2,3]. The state of research on LCA for structural engineers has found that reducing cementitious material in the concrete mix would lead to a reduction of gas emissions [7]. The

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life-cycle impact of steel structures in comparison to that of concrete structures has shown similar energy use and gas emission [8]. And lastly, the structures that use concrete and steel consume the most energy at 52 and 38%, respectively [9]. A green rating system has been developed for buildings, bridges, and infrastructural systems. For buildings, the green building rating system encourages sustainable building practices through the use of market forces on a voluntary basis with realism and economic feasibility. It should be noted that continuous requirements will lead to some improvement of design practices and display of sustainability consciousness by structural engineers. The construction of bridges and infrastructure is also placing increasing attention on the design of a green rating system such as Greenroads [10] for bridges and highways and Envision [12] for infrastructure systems. Sustainable design parameters for bridges and infrastructure will also be required to illustrate an effective green rating system.

2.2.2

Planning and development

The planning and development phase is considered to be the most important process for sustainability engineering. There are numerous ways to integrate sustainability into the process of a project’s execution. For example, an environmental impact assessment (EIA) could be conducted for environmental issues, a feasibility study (FS) for economic and technical issues, and an LCA for sustainability. A variety of ideas begin to emerge from technology for ways to set up the objective, the procedure, and the outcome by means of the terms of reference (TOR) for such processes. In particular, an EIA should include biotic factors and resources, human use value, quality of life value, and the direct or indirect environmental impact. The short-term and long-term conditions should be assessed as well as the severity of its service life on human beings. The measures to prevent and correct impacts to the environment and to compensate for the damage incurred should be provided in the review process reports and the decision making. The FS for traditional projects is concerned with the technical and financial feasibility with respect to expenditures, revenues, rates of return, and a project’s life cycle. However, current research related to technologies can emerge from these technical, financial, and sustainable elements of project development. For example, a sustainable engineering project may require use of advanced technologies that may reflect a negative signal for financial feasibility in the short term, but a positive signal in the long term. A strategic plan for this issue should be included in the overall study with the objectives, proposals, and reports that address various scenarios or alternatives of green design rating. The outlines of ISO-14040, principles and framework, and ISO-14044, requirement and guidelines, cover all aspects of LCA, that is, definition of goal and scope, life-cycle impact assessment, life-cycle interpretation, as well as reporting and a review of the LCA. From a general point of view, the LCA may be used for environmental management especially through the concept of material and energy balances for a specific process [11]. It may then be considered as one of the most appropriate approaches in the planning phase of the project. Furthermore, the life-cycle interpretation and a review of the procedure bring forth the outcome of decision making regarding the project execution.

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2.2.3

13

Design

Sustainability development is made with the consideration of global warming or gas emission. Five design strategies have been accepted among structural engineers [7] on materials, recycling, efficiency, energy, and adaptability. Then the design phase can play an important role within the scope of the work and professional conduct and practices. For traditional practices, the structural engineers may take responsibility for the materials, structural system, construction techniques, operation, and maintenance. In addition, the responsibility during its service life may be extended to rehabilitation, remedial work, strengthening, and demolition. To elaborate the design strategies to reflect real professional practices, numerous approaches are put into action, such as the LCA and green design rating. The research work concerning these five strategies may be used for bench marking as a guideline for professional practice. The framework for sustainable design has already been established as a green rating system for buildings, bridges, and infrastructure, but system analyses will be still required to compare the effectiveness among the design values, and monitor the results and the performance indicator at the end of the service life. Continuing on with the practical design can lead towards excellence in design proficiency for sustainability. The design process, in conjunction with the construction phase, should be based on the design documents of construction drawings, general conditions, and specifications. The integration concept on sustainability engineering should emphasize the construction materials, prefabrication and erection, and construction techniques of the methods, equipment, and sequences. The method statement should cover the construction simulation to show the effectiveness of the green rating in the construction phase.

2.2.4

Construction

The construction phase should cover the construction materials, techniques, management, and the quality assurance. The sustainability concept is integrated by means of key parameters through the construction sequences. Materials The green rating and the LCA have been evaluated in the design process for production or manufacturing. They are still present in some activities of the construction process, such as prefabrication and erection. Both specific and general conditions must cover some key indicators of the procedure. One of the most outstanding indexes would concern energy conservation and gas emission. Techniques This involves construction methods, equipment, and the sequences. The methods, as indicated in the method statement, are verified by construction simulation as well as the monitoring system by means of energy consumption and the outcome performance of the green rating and the LCA. The equipment associated with the construction sequence would have indicated some key performance during the operation.

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Management This concerns the construction sequence, the duration of each activity, the operating cost, and the resource allocation. Management can be carried out through the critical path method (CPM) to obtain a critical and sub-critical path whereby the resources of manpower or equipment, or other resources, can be managed to optimize the cost, the equipment, and the effective work done. Quality assurance can be done by means of setting up quality policies, followed by the drafting of the quality manual; followed by the activities with their internal auditing; finally, by the evaluation of the product. Here, the quality can be approved and certified by external auditing to ensure success through performance.

2.2.5

Operation and maintenance

The operation and maintenance phase should require a management system to monitor and adapt for effective outcome performance during the process. Thus the procedure should start with an established operation manual to provide measures for improvement or upgrading of the operation. The manual should set up inspection systems that can be categorized into periodic inspections, routine inspections, or special inspections. It would also require reports or records that may be used for some analysis and evaluation. For periodic or routine inspections, follow-up measures can be made automatically as per the manual, but special inspections may require some expert attention at each stage of the process for decision making regarding rehabilitation, repairs, or even for demolition or replacement. The sustainability strategies in these phases should concentrate only on how to extend the service life during which the green rating is to be improved. Maintenance work during its operation would also require some management for decision making regarding the extension of service life to ensure the most effective process of execution. However, there would still need to be a review procedure to guarantee the most satisfactory conditions for the best outcome performance.

2.3

Implementation solution

The Implementation phase should be considered as the most complicated solution of sustainability development since its criteria involve global problems that cover the whole diversity of the global biodiversity and human beings. The solution as shown in Table 2.1 would also include positive voluntary approaches, but it would require substantial cooperation for the green concept of restoration and improvement of global warming. The implementation measures are classified into three categories: the public consciousness of each individual, the cooperation of private or social enterprises, as well as local community, city, or nation; laws or regulations covering the jurisdiction of the community, economy, city, or nation; and codes of practice such as the professional tools or conducts associated with professional ethics and professional practices.

2.3.1

Public consciousness

The Integration concept of sustainability is derived by each individual consciousness. It is acceptable that education background and social communication form the public consciousness

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15

to reflect the social perception. The perception of sustainability engineering should be expressed in terms of responsibility and capacity building as the individual engineer, or in terms of accountability as cooperative social responsibility. Educational measures The sustainability concepts should be integrated in the university curriculums of each discipline. Some related technologies will then emerge and be adopted to serve each level of education. The phenomena of global warming or temperature rises should be interpreted in the most comprehensive ways that each graduate can form his/her own perception in similar patterns. This means that, some consciousness will be a cognitive response to the most appropriate functions. Some natural disaster events may be associated with the environmental impacts of global warming, which can induce formidable knowledge through the lifelong learning of natural phenomena. Public mass media can then be one of the most effective education tools for each individual’s perception of and corresponding reaction to the problems. Communication measures These shall be done through the mass communication media of the society or community and through an organization’s public relations activities. It is quite agreeable that the social or press media should be aware of the lessons of global warming and sustainable development and have the capacity to facilitate educational forums in the community or society. Social or public concerns may be driven by some proactive measures of campaigning on the national policies, sociocultural events of the community commitment, and the corporate social responsibility of the private sector or NGOs. Corporate social responsibility (CSR) CSR can be another tool for the private sector to communicate with the public, firstly to provide information, secondly to educate through learning lessons, and thirdly to perceive the reaction of the public. The corporate accountability of the CSR is quite essential for the private sector to establish key performance indicators (KPI). The CSR promotion of integrated approaches to multiple activities will ensure a process that gives optimal performance outcome. Social enterprise This would also be a way of creating public consciousness and social responsibility with economic indicators. It may not be as direct as an economic scale of benefit but it would bring about social benefit in terms of participation, the sharing of responsibility, and claiming back the gain of those impacts.

2.3.2

Laws and regulations

Even though the integration concept of sustainability can be successfully implemented by positive voluntary action, certain laws or regulations may be needed as tools to govern particular fundamental problems of global warming. The laws and regulations are categorized at national levels such as

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the jurisdiction, federation, and nation, and at local levels such as province, city, municipality and district. The laws and regulations may also be classified as control acts and promotion acts. Civil engineering mega-projects are concerned only with the environmental, city planning, and building control acts. They may also be differentiated by legal acts, ministerial regulations, local regulations, and rules and procedures. The most important laws and regulations shall refer to the following. The environmental impact assessment (EIA) The EIA is a part of the Environmental Act depending upon each jurisdiction, but the study must cover the impacts on the environment from activities in the project and the surrounding areas, affecting the living and/or non-living organisms and the environment on a short- and long-term basis. Information about plants, animals, soil, water, air, human health, and employment will be considered. The EIA report must also point out the impacts of the project on the environment and the natural resources. It should recommend suitable measures to prevent or correct the project impacts, as well as suitable methods to monitor environmental conditions. The report must also offer alternatives for consideration of site selection and project implementation. The city planning act City planning should cover environmental conditions, land use, and zoning. In addition, consideration of urban facilities that are of primary concern to the city planning act should concentrate on the geographic condition, sociocultural heritage, public functions, infrastructure systems, natural resources, environmental movements, historic or natural preservation, and human wellbeing. The objectives centre on the belief that man and nature can coexist in productive harmony and fulfill the social, economic, and other requirements of sustainability. The building control act Traditional concerns are usually about structural strength, public safety, fire protection, health and sanitation, environmental impacts, city planning, architectural functioning, and traffic convenience. Public safety such as risk of health shall be one of the most important concerns. From a modern view of globalization, sustainability development should be extended to broader scopes of life span of services, material production, energy consumption, and environmental friendliness. The building control acts also should be harmonized with current regulations by emerging technologies on sustainable engineering such as LCA and green rating, which represent the inclination of the owners, and the private or public sectors, who must take responsibility for sustainable engineering.

2.3.3

Professional practices

One of the most effective means to upgrade professional competencies would be to integrate the sustainability concept in academic or educational curricula and to continue the professional development (CPD) of professional practices. In professional practices, a code of ethics, a code of conduct, and a code of practices are considered as a part of the concepts in the process.

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2.4 EXAMPLES OF IMPLEMENTATION SOLUTION

Implement solution Public consciousness: • Corporate accountability • Proactive measures

Emerging technology

Planning and development

– Goal/ objective – LCA – Green rating

Policy Making Material Life cycle

Laws/ regulations

–

– EIA – Integrated engineering

Method/ – Recycle procedure – Efficiency – Energy – Adaptability

–

–

Code of practice –

Design

Construction Operation and maintenance –Materials –Method

– Inspection – Routine/ periodic – Maintenance – Special – Inspection – Evaluation

Management – Remedy/ monitoring repair – Rehabilitation – Strengthening

Table 2.1: Implementation solution The professional society should take responsibility to establish a competency standard to cover sustainability. The International Engineering Agreements (IEA) has committed engineering competencies to the following areas: to contribute to the development of engineering practice, to lead and manage significant projects, to demonstrate engineering leadership, to manage engineering business outcomes, and to identify opportunities for research and development.

2.4

Examples of implementation solution

Three sustainable development projects in Thailand can be used as examples of an implementation solution. The first project has been an outgrowth of the King’s projects[12] since 1997, and the other two projects were implemented at a later date and are associated with the proactive measures of the private sector to address the moral responsibility of the current generation as trustees of the environment for future generations. The projects have tried to achieve a balance between population and resource uses with better living standards, and to enhance the quality of renewable resources. The approaches are to assure the maximum attainable recycling of nonrenewable resources. The case study presents a philosophy on sustainable development through the implementation of corporate governance to achieve outcome performance that guarantees satisfaction for the public and the environment.

2.4.1

Thailand sufficiency economy

Sufficiency Economy is a philosophy of the middle path, underlining the principle for appropriate conduct and way of life at the level of individual, family, and community (Fig. 2.1). It provides a choice of balanced development strategy for the nation to harmonize with globalization. To achieve the goal, great care is needed in the application of theories, technical know-how, and

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CHAPTER 2. INTEGRATION CONCEPT OF SUSTAINABLE ENGINEERING

Middle path Sufficient Reasonable

Knowledge

Security

Ethic/moral

Resource/environment/socio-culture

methodologies for planning and implementation. It is also essential to strengthen the moral fibre of each individual, family, community, private and public sectors, as well as the nation. The balanced approach combining patience, perseverance, diligence, wisdom, and prudence is indispensable to cope appropriately with critical challenges and socio-economic, environmental, and cultural changes.

Balanced strategy to challenge the changes

The government sectors have to take immediate action on policy making, facilitate the productivity of the private sector, and integrate its public service aiming for equitable deals. The government must provide good governance through public policies, transparency, and accountability. It is recommended that power be decentralized to the local government of a city or township and the community. The government sector is also to take responsibility for education, economic opportunities, as well as social and public welfare. They are supposed to provide rules and regulations, security, national security, and services.

Fig. 2.1: Philosophy of sufficiency economy [13]

The private sector is categorized into the three levels of individual, community, and the nation. For sustainability, each individual must receive sufficient living space, health-promoting sanitation, sufficient food, and income to support a sufficiency economy. To implement this project, the philosophy must be integrated at all levels of the education curriculum. Individual character building will then be gradually developed for a sufficiency economy of a middle path approach to lifestyles to fulfill psychological satisfaction. The outcome From the time the project was introduced in 1998, up to now, 10 000 education institutions, 1261 communities, and 24 business organizations have committed to implement and operate the “sufficiency economy” approach. It should be noted that sufficiency economy should be harmonized as the initial stage of sustainability development, and the outcome must be in alignment with the green rating on the basis of limited resources, energy consumption, environmental impacts, and socio-economic issues. However, the psychological fulfillment has proved to be a satisfactory guarantee of success as surplus outcome in terms of happiness index calculated prior to and after the execution of the project.

2.4.2

PTT sustainable development

PTT, a Thai premier multinational energy company, is committed to a mission that stresses responsibility to all stakeholders: the nation, society, communities, shareholders, business

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2.4 EXAMPLES OF IMPLEMENTATION SOLUTION

(b) HPO

l governance and ona lea i t de iza rs n a Human Labour rights

High Performance Organization

rights

CSR reporting

Environmental management

Stakeholder engagement

Sustainable growth strategy

Product stewardship

CSR

CG

Corporate social responsibility

Corpotare governance

p hi

Or g

(a)

Supply chain management

Fair operating practices

Social investment and community development

Fig. 2.2: PTT sustainable development [14]: (a) sustainable growth strategy and (b) PTT CSR framework partners, customers, and employees. PTT has valued the fostering of national energy stability in parallel with taking responsibility for society, the community, and the environment through its operations. The company has in place a clear guideline for sustainable development by keeping a good balance among corporate social responsibility (CSR), corporate governance (CG), and high performance organization (HPO) in order to lay a strong foundation for the long-term development of the organization (Fig. 2.2). Corporate social responsibility (CSR) PTT is determined to conduct its business with concrete responsibility for society. This has been clearly stated in the company’s vision and mission throughout its three decades of operation to ensure that all business units translate the mission into practice, starting from the responsibility for each individual work process, strict compliance with laws and regulations, to constant development to meet international standards, to control, prevent, and minimize potential impacts on the company’s process to deliver products and services. Parallel with this, PTT has the responsibility for society, the community, and the environment to ensure that all sectors can coexist with sustainability. The practice of the CSR policy and guidelines is the responsibility of all, management and employees, and is embedded throughout the management hierarchy of each business. All business units and affiliates are allowed to draw up their own implementation plans considered suitable for their respective businesses. To encourage further development, best practices are shared through the CSR policy committee among PTT and PTT Group levels.

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Corporate governance (CG) PTT is committed to strict adherence to doing business under good corporate governance and applying the principles of good corporate governance along with the practical guidelines of the Securities and Exchange Commission (SEC) as its prime consideration enhancing its management efficiency and serving as a foundation of sustainable growth. To conform to the management approach of the PTT Group, PTT has taken group governance seriously through the projected upgrading of the group’s practices to make them comparable. Specifically, a suitable international set of approaches was investigated as a role model; all companies prepared themselves for good corporate governance ranking, and policies and rules were written for integrity and ethics for all personnel to comply with, including regulations on finance, hiring and procurement, and water-tight management practices to prevent fraud. In 2008, PTT pushed for and supervised risk management against the corporate risk profile for efficiency and alignment with the framework, and for managing and controlling risk satisfactorily. The performance outcome, as related to PTT’s CSR, consists of project execution risks, risks associated with operations, and operation risks from compliance with environmental and safety regulations. High performance organizations (HPO) PTT has synergy resulting from modelling the strong points of each PTT Group company by sharing and learning, for the benefit of business excellence and efficiency improvement in the world stage. This approach has led to what is known as the HPO model, with its six pillars: leadership, innovation, knowledge, management, information technology, and operational excellence. In addition, the PTT Group has successfully applied an international approach and the management tools in propelling the organization towards sustainable excellence. Corporate outcome PTT recognizes the criticality of fostering the company’s potential, which can be achieved by networking with other organizations having similar goals. It promotes cooperation and exchange of knowledge and practices, a mechanism to drive the organization to become a power to reckon with for a sustainable future. PTT, therefore, joined various externally developed initiatives both at the national and the international levels.

2.4.3

SCG sustainable development

The Siam Cement Group, SCG, a major construction material manufacturer in Thailand, has committed itself to corporate governance, which takes into account the economy, society, and the environment. It launched the SCG-Sustainable Development Guidelines in 2006 and has pushed forward to an action plan that is ready for implementation. For good governance, the SCG has emphasized corporate governance, integrated risk management, and disclosure and reporting. From an economic perspective, direct economic value generation and economic value distribution are taken into consideration. From a social perspective, the management is concerned with community investment, labour standards and practices, human

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2.5 CONCLUSION AND RECOMMENDATION

SCG SD roadmap

Governance Gap analysis/ benchmarking

Economy

Environment

Identify key issues for SCG

Society

Global concerns World class company practices

Global SD issues Source* ; Global institute/ organisation

*Source:

Global compact / UNFCCC / WBCSD / WRI / GRI / ISO 26000 / IEA / ILO - Labor standards / DJSI / FTSE

Fig. 2.3: SCG sustainable development process [15] rights, human resources and human capital development, occupational health and safety, and stakeholder engagement. Finally, environmental involvement includes five projects that have been executed, such as climate change, water management, waste management, ecosystem and biodiversity, and eco-products (Fig. 2.3). The outcome performance of water management through water retention with small coffer dams, Fig. 2.4: Outcome performance of water management as shown in Fig. 2.4, can be [15] well exemplified. The SCG ecoproducts of environment-friendly materials, following an integration criterion, have been initiated through a focus on research and development, eco-design and a technology roadmap, in addition to LCA, adaptive performance, and the achievement of a green rating. SCG issues a green label for the products and furthers their promotion in the building processes of erection or fabrication as well as operation and maintenance.

2.5

Conclusion and recommendation

The integration concept to implement sustainable engineering in the building process has been exercised in some enterprises at the community and society levels. However, global warming and climate change issues are extremely complex problems, and responsibility should be shared among individuals, communities, and nations of the entire world. This is true even if the initiative for commitment at each level of responsibility may take quite some time to be achieved. Up to now, research by the scientific, technological, and engineering sectors has revealed the facts and understanding behind climate change, CO2 emissions, LCA, and green rating systems. Further areas for consideration should be the objective or goal that may lead to policy making and strategic plans to be executed.

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In conclusion, in order to introduce an integration concept of sustainable engineering in the building process, first of all, a policy and a strategic plan would have to be developed through public awareness. The next step in the planning and development phase of the project would be to involve an action plan for project execution. Strategies, for example, such as the LCA and the green rating, should be taken into consideration. Relevant laws and regulations, the EIA, the FS, and integrated engineering, must be conducted for review, monitoring, and management. The execution phase, following a sustainable design should be integrated by service life, materials, recycling, efficiency, energy, and adaptability. The construction for sustainability would involve methods and procedures in the use of materials, techniques, management, and quality assurance. The operation and maintenance of the project, including its inspection and evaluation for remedy or repair, rehabilitation, or strengthening should be carried out. The project outcomes should be evaluated by an available and relevant review process according to the green rating system. Adjustable and/or adaptable measures shall be applied in order to obtain the most effective performance. For sustainable development, the following recommendations are offered: •

•

•

Principal concerns of reducing consumption of material energy and waste should be proportional to population growth. Social perception of reducing growth can be one of the objectives or goals of sustainable development. Potential reduction of gas emissions can also be done by changing the mode of living or the well-being standard to that which is environmentally friendly and harmonized well with nature. To minimize the requirement, the achievement will meet the needs and satisfaction of each individual. Critical issues for sustainable engineering can be addressed through immediate action by reducing growth in certain critical sectors.

References [1]

[2] [3] [4] [5]

[6] [7]

Working Group III Fourth Assessment Report of the Intergovernmental Panel on Climate Change (IPCC). http://www.ipcc.ch/publications_and_data/publications_ipcc_fourth_ assessment_report_wg3_report_mitigation_of_climate_change.htm International Organization for Standardization. 2006. ISO 14040 – Environmental management, Life Cycle Assessment, Principles and Framework, ISO. International Organization for Standardization. 2006. ISO 14044 – Environmental Management, Life Cycle Assessment, Requirements and Guidelines, ISO. Dirk M. Kestner, Jennifer Goupil & Emily Lorenz. (Eds.) (2010) “Sustainability Guidelines for the Structural Engineer” Structural Engineering Institute, ASCE. Commission to the European Parliament, the Council, the European Economic and Social Committee and the Committee of the Regions. 2011. A Roadmap for Moving to a Competitive Low Carbon Economy in 2050, European Commission, Brussels. Architecture 2030. 2012. The 2030 Challenge [Online]. http://architecture2030.org/2030_ challenges/the_2030_challenge/ Anderson, J.E., Silman, R. 2009. A life cycle inventory of structural engineering design strategies for greenhouse gas reduction. Struct. Eng. Int., 19(3): 283–288. http://www.scg. co.th/en/05sustainability_development/INDEX-1.html

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REFERENCES

[8] [9] [10] [11]

[12] [13]

[14]

[15]

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Guggemos, A.A., Horvath, A. 2005. Comparison of environmental effects of steel- and concrete-framed buildings. J. Infrastruct. Syst., 11(2): 93–101. Wu, H.J., Yuan, Z.W., Zhang, L., Bi, J. 2012. Life cycle energy consumption and CO2 emission of an office building in China. Int. J. Life Cycle Assess., 17(2): 105–118. Greenroads. Green Roads [Online]. (accessed March 1 2012). http://www.greenroads.org Hendrickson, C.T., Lave, L.B., Matthews, H.S. 2006. Environmental Life Cycle Assessment of Goods and Services: An Input-Output Approach. Resources for the Future Press, Washington, DC. Institute for Sustainable Infrastructure, 2015. “EnvisionTM Sustainable Infrastructure Rating System”, http://www.sustainableinfrastructure.org/rating/ National Economic and Social Development Board. 1997. H.M. the King’s Sufficiency Economy, “Sufficiency Economy: Basis to the Sustainable Development”, King’s Projects, NESDB. Petroleum Authority of Thailand (PTT). 2008. Guideline for Sustainable Development. Petroleum Authority of Thailand. http://www.pttplc.com/en/Sustainability/PTTSustainability/Governance/Pages/Sustainability-Governance-and-Framework.aspx Siam Cement Group (SCG). 2008. SCG-Sustainable Development Guidelines, Siam Cement Group. http://www.scg.co.th/en/05sustainability_development/INDEX-1.html

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25 Chapter

3 A Sustainable Approach to Structural Design

Tobia Zordan, Bolina Engineering Ltd., Venice, Italy. Contact: [email protected]

3.1

Introduction

A contemporary definition of civil engineering given by the American Society of Civil Engineers (ASCE) in 1961 [1] states that “Civil Engineering is the profession in which a knowledge of the mathematical and physical sciences gained by study, experience, and practice is applied with judgment to develop ways to utilize, economically, the materials and forces of nature for the progressive well-being of humanity in creating, improving, and protecting the environment, in providing facilities for community living, industry and transportation, and in providing structures for the use of humanity”. This definition implicitly embodies in the concept of civil engineering the concept of sustainability. Unlike other branches of civil engineering, however, where the concept of “sustainability” can boast a rather standardized and globally accepted meaning, for structural engineers, this concept can still lead to a certain degree of misunderstanding and interpretation. The concept of sustainable structural design can embody the canonical idea of “meeting present needs without compromising the ability of future generations to meet their needs” [2], but for this category it still represents a fancy idea rather than an operational and encoded approach to design. Nonetheless, from the statement above [2], two meaningful concepts can be retrieved: (a) the concept of need, fundamental for the developing countries and for the poorer areas of the planet, where the care of the wealthier population should be addressed and (b) the idea of limit, associated to the available and finite resources, unable to meet the aspirations of the global population. How can therefore structural engineers contribute to a sustainable and controlled decrease of the most developed areas of the world based on the idea that available resources have to be shared with the greater majority of the world’s population that rightfully claims for improved life conditions? How can this goal be reached in the era of digital tools, where the claim is that every shape that can possibly be “implemented” and “solved” by a software, even if fantastically conceived and aesthetically stunning, is sustainably buildable in a continuous search for amazement (Fig. 3.1),

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CHAPTER 3. A SUSTAINABLE APPROACH TO STRUCTURAL DESIGN

despite the associated uncertainties in terms of costs and life-cycle demands and disregarding the scale problem associated with mechanical properties of available building materials? If the process of “form finding” is defined as the search for the most suitable structural shape able to optimally fit a set of applied loads under given boundary conditions, the example of Robert Le Ricolais and his motto: “the art of structure is where to put the holes” (Fig. 3.2) [3] sounds particularly up-to-date when confronting two of the most important schools in contemporary building trends such as those of Form Finding and Free Form Design, the first based on a strict control of the consequences of any formal choice on the structural response, with the search for the minimum material consumption, and the second based on the mere expressive freedom disregarding any other issue and thus involving ethical issues about the sustainability of this approach to design because of related uncertainties about life-cycle costs, durability, and reliability in general.

3.2

Ecological footprint and appropriate carrying capacity

In relatively recent times, the idea that the development ratio and wealth demand of the increasing world population would be not compatible with the available Earth’s resources has become

Fig. 3.1: Zaha Adid, project for the Nuragic and Contemporary Art Museum Cagliari, Italy (a)

(b)

(c)

Fig. 3.2: The lesson of Robert Le Ricolais and his motto “Structural Engineering is the Art of where to put the holes” (a), seem to be perfectly applied by Pier Luigi Nervi—exhibition hall in Turin, Italy (b), but less present in some recent examples of free form design (FFD) applied to free form building (FFB) (c)

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3.2 ECOLOGICAL FOOTPRINT AND APPROPRIATE CARRYING CAPACITY

a reality. A possible and effective way to measure this statement is represented by the so-called ecological footprint (EF) [4], or appropriate carrying capacity, defined as the comparison between the demands for natural resources that can be balanced by the planet’s ecological ability to regenerate [5]. Ecological footprint analysis compares human demand on nature with the biosphere’s ability to regenerate resources and provide services. The EF represents the extension of biologically productive land and sea area necessary to balance the consumption of the Earth population granting, at the same time, the disposal of waste. In 2006, the average biologically productive area per person worldwide was approximately 1.8 global hectares (gha) per capita. The U.S. EF per capita was 9.0 gha, and that of Switzerland was 5.6 gha per person, while China’s EF was estimated to be 1.8 gha per person [5] (Fig. 3.3). It is somehow worrisome that these figures, in their totality, are just by a mere 33% composed by primal necessities such as food and water (Fig. 3.3). It originally estimated that the available biological capacity for the 6 billion people on Earth at that time was about 1.3 hectares per person, which is smaller than the 1.8 gha published for 2006, because the initial studies neither used global hectares nor included bio-productive marine areas [4]. A number of non-governmental organization (NGO) websites allow estimation of the ecological footprint. According to 2007 data, the EF was estimated as 1.5 planet Earth, meaning that, according to the average level of lifestyle of the time, the world’s population should use 50% more than the surface of land and sea available in order to allow for the natural renewal of available natural resources [6] (Fig. 3.4). From the data presented above, it clearly appears that: DE > AE = 1

(3.1)

Human welfare and ecological footprints compared 1.000

Norway Canada

Australia

USA

0.900 2%

0.700 0.600 0.500 0.400 Sierra Leone

0.300

Earth’s biocapacity = 2.1 hectares per person

Human development index

Cuba

0.800 Africa Asia-Pacific Europe (EU) Europe (Non-EU) Latin America and Caribbean Middle East and Central Asia North America Data sourced from: Global Footprint Network 2008 report (2005 data) UN Human Development Index 2007/08

0% 6%

0% 16%

17% 50% 9% Food Transportation Electricity Water

Housing Goods and services Natural gas Waste

0.200 0.0

1.0

2.0

3.0

4.0

5.0

6.0

7.0

8.0

9.0

10.0

Ecological footprint (global hectares per capita)

Fig. 3.3: Human welfare and ecological footprint comparison (2007/2008)

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28 (a)

CHAPTER 3. A SUSTAINABLE APPROACH TO STRUCTURAL DESIGN 1.4

1961 to 2005

Number of Planets Earth

UK France Mexico Germany Brazil Japan Russia India China USA

Total

1.2 World Biocapacity 1.0 0.8 0.6 0.4 0.2 0

(b)

1.4

1960

1970

1980

1990

2000

05

1961 to 2005

Number of Planets Earth

1.2 World Biocapacity

Built areas Fishing areas Forests Pastures Cultivated areas Carbon

1.0 0.8 0.6 0.4 0.2 0

1960

1970

1980

1990

2000

05

Fig. 3.4: EF estimated in planet Earth for single states(s) (a) and by components (b)

Ecological footprint (in number of Earths)

Projecting ecological debt to 2050 with IPCC scenarios 2.5 2.0 1.5

Biocapacity Footprint A2 Footprint B2 Footprint A1 Footprint B1 Footprint A1B

1.0 0.5 0.0 1960

1970

1980

1990

2000

2010

2020

2030

2040

2050

Fig. 3.5: Projection of the EF in terms of number of Earths to 2050 according to different possible scenarios [7]

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29

3.3 CONCEPTION AND UNCERTAINTIES IN DESIGN APPROACH

where DE is the demand of Earth needed to sustain the world’s population, while AE is the available number of Earths at present average level of resource consumption. The statement supported by Eq. (1), projected to the year 2050 through the application of different scenarios according to different possible strategies adopted by different countries, appears to be expected to worsen [7] (Fig. 3.5). The same approach, applied on the total amount of available resources, can also be applied to single activities, such as manufacturing and building industry.

3.3

Some considerations on sustainability in integrated life-cycle structural engineering: conception and uncertainties in design approach

Talking about sustainability in structural engineering, among all possible topics within the general framework supplied by the ISO 14000 standards, with specific reference to ISO 14001 [8], some considerations on the issues of conceptual design and uncertainties evaluation seem to be appropriate in order to focus on some important aspects related to structural design, considered as one of the main disciplines, which are part of the concept of sustainability applied to constructions [9] (Fig. 3.6), where the optimization of different aspects of the service life of structures through an optimum integrated life-cycle design process must be performed [10].

Sustainable construction Dimensions of sustainability

Ecological sustainability

Economic sustainability

Objectives of protection

Ecosystem – Waste avoidance – Emissions – Pollutants – Land use

Human health – Human toxicity of building materials – Pollutants – Sick building syndrome

Natural resources

– Regional spin-offs – Maintenance – Mobility costs – Risk management – Life cycle costs – Flexible use – Reliability

Social sustainability – Satisfaction – Employment – Regional spin-offs – Sick building syndrome

– Resource efficiency: materials (biotic, abiotic, energy, soil) – Recycling economy

Fig. 3.6: Dimensions of sustainability and objectives of protection [9]

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30 Design phase Investment planning

CHAPTER 3. A SUSTAINABLE APPROACH TO STRUCTURAL DESIGN

Tasks – Define objectives and schedule of the project – Create alternative investment plans – Calculate life-cycle costs (LCCs) – Calculate cash flows of alternative plans – Evaluate benefits of alternative plans – Compare LCCs and take final decision Analysis of – Identify customers’ requirements clients’ and – Estimate the rate of importance of users’ needs each attribute as weight Functional – Translate the results of needs specifications of analysis to demands project – Identify relevant functional properties – Define weight of each property Technical – Translate functional properties performance and related weights from previous specifications task to demands – Identify technical performance properties – Identify weight of each property Creation and – Create and outline alternative outlining of altersolutions for the object of design, native structural its static schemes, and structural solutions systems, in cooperation with other designers – Define the number of modules Modular lifeand requirements for the design cycle planning service life of each component of and service life the project optimization of – Identify the design life costs of each alternative different modules on the basis of a minimum total cost criterion Multiple – Evaluate the performance propercriteria ranking ties of each alternative and selection between alternative solutions and products

Life cycle design methods – Multiple criteria analysis, optimization and decision making – LCCs (financial and environmental)

– Modular design methodology – Quality function deployment method QFDa – Modular design methodology – QFD method

– Modular design methodology – QFD method

– Modular design methodology

– Modular design methodology – Modular service life planning – Life-cycle (financial and environmental) costs calculation

– Modular design methodology – QFD method – Multiple criteria analysis, optimization, and decision making

Table 3.1: Continued

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3.3 CONCEPTION AND UNCERTAINTIES IN DESIGN APPROACH

Detailed design of the selected solution

– Perform conceptual and final design of each identified modulus

– – – – – –

Design for safety Design for serviceability Design for aesthetics Design for structural efficiency Design for adaptability Design for durability, minimal maintenance, and life-cycle costs – Design for risk reduction and value protection – Design for minimal ecological footprint (embodied energy, minimal material use, emissions, reuse, recycling, disposal)

a

QFD method transforms user demands into engineering characteristics combining quality assurance and quality control issues; its first formulation is adapted from Ref. [11] and it is embodied in the ISO 9001 standard for quality assurance. ISO 9001, 2008. Quality management. International Organization for Standardization, Geneva, Switzerland. Terms in Bold refer to those that include structural engineers also. Table 3.1: Example of possible integrated life-cycle design process and sustainable approach to design (adapted from Ref. [10])

Structural design is certainly a multiple objective activity, based on the application of a number of different requirements concerning: • • • • • • •

material technology, manufacturing, assembly and erection, life-cycle response, adaptability, demounting and reuse, disposal.

Optimization processes have to be applied to the single aspects mentioned above or to the overall process in evaluating all aspects related to the above points within an integrated structural design, capable of meeting the requirements of sustainable development. Conceptual design, understood not only in its limited meaning as the first design ideas but also as the ability of identifying and optimizing all the aspects related to an integrated approach to design capable of optimizing the multi-objective function describing the overall performance of a structure during all the service-life, plays a fundamental role in ensuring the achievement of the goals mentioned above together with the identification and evaluation of the associated uncertainties. Table 3.1, adapted from the original proposal in Ref. [10], can serve as a base of discussion and as an operational model.

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32 (a)

CHAPTER 3. A SUSTAINABLE APPROACH TO STRUCTURAL DESIGN

(b)

Services 24%

6% 7%

Construction

13%

Demolition 48%

Finishes Renovation 44%

26% Envelope

New construction 8%

Site work

24% Structure

Fig. 3.7: Initial embodied energy for an office building (a) and waste production during life cycle (b)

Uncertainties related to the life-cycle response structures have led the research activity of structural engineers of the past centuries mainly searching for: • efficient use of new construction materials within different static schemes and structural shapes during the 19th and first half of 20th centuries, • maintenance of existing structures during the second half of 20th century, • life-cycle analysis and use of “green materials” (Fig. 3.7) (embodied energy (Fig 3.7a), reusable, recyclable, biodegradable) and waste reduction at the beginning of 21st century.

3.4

Complexity versus complicacy within a sustainable conceptual design

The lesson learnt from the masters of structural engineering of the last century, with their utmost attention in the definition of the most suitable shape able to fit the structural requirements under given boundary conditions in a real “form finding” process, seems to acquire the greatest importance within a sustainable approach to design, where the limitation of “uncertainties” (unpredictable long-term consequences) appears to meaningfully contribute to the reliable quantification of the life-cycle costs and resource consumption through a predictable structural response. The intensive use of digital tools (for three-dimensional architectural and structural modelling) not just as suitable “means” for a more appropriate and sustainable design in the contemporary meaning defined above but as the real “goal” of the design itself, in the continuous and exasperated search for a spectacular Free Form Architecture, with the creation of sculpted shapes inspired by art (Janet Elchman—Fig. 3.8b) deriving from the realm of industrial design (Fig. 3.9a, b), despite huge “scale” problems (Figs. 3.8 and 3.9) related to the mechanical properties of available construction materials, the appropriate choice of static schemes, the ease of erection, and maintenance, has triggered a process where, according to Ref. [12], the “know how” has widely exceeded the “know why” (Fig. 3.10). This has, as a clear consequence, led to the introduction of an increasing ratio of uncertainty, which is at the basis of larger future possibilities of “failure”, suitably defined as “performance not consistent to expectation” [13].

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3.4 COMPLEXITY VERSUS COMPLICACY WITHIN A SUSTAINABLE CONCEPTUAL DESIGN

(a)

A cloud

(b)

A cloud sculpture

(c)

33

A cloud building

Fig. 3.8: Free form shapes inspired by natural forms (a) can originate evocative light structured sculptures—Janet Elchman (b), but when translated into architecture without the application of a structural conceptual design from the early stages of the creative process (c) can lead to the creation of massive supporting structures, requiring a remarkable use of structural material per unit volume, with the potential introduction of uncertainties related to construction costs, long-term behaviour and life-cycle performance A table

A show room

A theatre hall

Fig. 3.9: Free form shapes inspired by the realm of industrial design often originate scale problems related to the mechanical properties of available structural materials and the choice of suitable static schemes Contrarily to the philosophy characterizing the Italian Renaissance, where the activity of Leonardo Da Vinci in the field of construction, able to influence future generations of architects and engineers till present times, was a science assisted by a creative act in an attempt to have total control on the resulting object, and the logical sequence of each step of the design and construction process was scheduled by a kind of self-evident necessity ruled by a mathematical order; in present times, any logical sequence seems to be forgotten and architecture is somehow, and within a certain thread, more related to advertisement, fashion, visual art. If Leonardo Da Vinci and the Classical Architects are defined as the ancestors of what is presently defined as “form finding”, related to the search for predictable consequences (engineering is a

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CHAPTER 3. A SUSTAINABLE APPROACH TO STRUCTURAL DESIGN

KNOW “HOW” AND KNOW “WHY” Understanding

Predictable consequences Ethics of CONTEMPORANEITY

Not completely predictable consequences Ethics of RESPONSIBILITY

c “WHY” “HOW”

BACON

Δt(c;p)

Uncertainty b

(~1600) f “WHY”

Δt(p;c)

ac = full understanding ab = contribution of science bc = contribution of art

e

“HOW” “HOW” “WHY” Engineering is ART + Science

Engineering is science assisted by art df = full understanding = contribution of science

d

Engineering is art assisted by science

a

Time

Fig. 3.10: Free form design, denying the centrality of structural engineering, increases the level of uncertainty related to design lowering and at the same time the possibility of fully understanding the consequences (adapted from Ref. [12]) (a)

(b)

Fig. 3.11: Complexity and complicacy as characteristics of form finding (a) and free form design (b) processes applied to two of the most representative buildings recently realized in China, such as the main corridor of the 2010 Shanghai Expo and the Bird’s Nest Arena for the 2008 Beijing Olympic Games science assisted by art with the “know why” exceeding the “know how”), with the beginning of the age of integrated digital tools, the practice of “free form design” and the introduction of a consequent increased level of uncertainties, engineering is finally a practice assisted by science and the level of understanding of the process can be seen as lower than the possibility of accomplishing it (Fig. 3.10): the “know how” exceeds the “know why”, supported by the revolutionary opportunities given by the use of geometrical algorithms implemented for families of software originally coming from the field of industrial design and applied in the field of engineering and architecture, raising issues pertaining to the fields of ethics and sustainability.

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3.5 STRUCTURAL ART: A RULED FREEDOM

35

Usual uncertainties due to random variability or lack of data, use of non-representative simplified models, or due to human factors such as ignorance and carelessness are consequently increased. The concepts of complexity and complicacy can therefore be evaluated and briefly compared. Complex is different from complicated. Complexity in design has historically led to advancement in knowledge with the creation of new theories and new achievements in structural engineering: Complexity is challenging in relation to the concept of necessity. On the contrary, complicacy does not account for any process related to necessity and it is somehow detached from any self-evidence or search for objective rules. The history of structural engineering is studded by milestone “complex structures”, while it is way more difficult to have the chance to count within the same category any “complicated” structures (Fig. 3.11).

3.5

Structural art: a ruled freedom

In an era of global access to information, responsibilities are also global. The role and diffusion of knowledge is therefore a key issue and the history of structural engineering has to be transferred to younger generations of structural engineers as the origin and cause of present knowledge. The choice of suitable and countless examples, within the schools of civil engineering, is therefore fundamental in order to make structural designers aware of the chances they are given, and capable in potential to judge and choose, instead of limiting their profile to that of mere “calculating men”, even if greatly qualified and skilled. According to Ref. [14], “Engineering works can boast the title of art when responding most gracefully to the structural requirements that they must meet”. This definition, far from any kind of simplification in the practice of structural engineering and not worried by possible associated complexities, is pervaded by that concept of “necessity” presented above, and struggles for codified rules, without seeking for any kind of free complicacy and embodying the concept of sustainability in that, “most gracefully”. Furthermore, a suitable definition for a correct approach to structural design can be derived from the world of architecture, quoting the motto of one of the Masters of Modern Architecture between the 19th and 20th centuries, such as Louis Sullivan: “Form follows Function”. This sounds particularly interesting in remembering the common origin of the two complementary disciplines of architecture and structural engineering, united, until the beginning of the 19th century, in the single knowledge related to construction. The search for the optimal and minimal use of available construction materials (Fig. 3.12), and a clear and suitable use of static schemes (Fig. 3.13) identified on the basis of the available structural components, has characterized the history of structural engineering and the landmark achievements in this field. The feasibility and suitability of the work of the masters in structural

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CHAPTER 3. A SUSTAINABLE APPROACH TO STRUCTURAL DESIGN

Fig. 3.12: The minimal use of construction materials: Vladimir G. Shukov; Piezometric tower, Niznij Novgorod, Russia, 1853

Fig. 3.13: The clearness of the static scheme: James Fowler, Benjamin Baker; Forth bridge on Firth of Forth, Scotland (L = 570 m), 1890

engineering have always been a clear goal, even if not explicitly categorized under the recent definition of “sustainable”. These concepts are almost self-evident peering at the work of some of the most renowned structural engineers of earlier centuries, whose activity can truly boast the title of “art”, not because they are characterized by freedom and absence of rules in the way their works are shaped, but thanks to the search for strict rules, and often “new” rules, able to give each single structural component within that shape, a true character of “necessity” despite the overall complexity of the final geometry and questionable aesthetical issues. Conceptual design is therefore related to “intuition” and “control” (Fig. 3.14). Creativity must be firmly linked to the possibility of foreseeing and evaluate the outcomes of the design process, minimizing the uncertainties related to the mentioned process with a suitable combination of structural schemes and use of materials and structural components (Fig. 3.15). Structural art can be then suitably associated to the oxymoron: “ruled freedom” (Fig. 3.16). In this context, architects are privileged partners, with architecture and structural engineering today being complementary aspects of the same knowledge [15]. The spoken language must be the same in the common pursuit of global quality. The history of architecture and the history of

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3.5 STRUCTURAL ART: A RULED FREEDOM

(a)

(b)

Fig. 3.14: Intuition and control: (a) Eduardo Torroja, Secundino Zuazo: Fronton Recoletos, Madrid, Spain, 1936; (b) Frei Otto, Leonhardt und Ändra: German Pavillion, Montreal, Canada, 1967 (a)

(b)

Fig. 3.15: Wise use of construction materials and structural components: (a) Li Chun, Zhaozhou stone bridge, in Zhaoxian, Ebei Province, China (L = 35 m), Seventh Century; (b) Carlo Cestelli Guidi, Bruno Zevi, Garibaldi bridge over the River Tiber in Rome, Italy (L = 50 + 50 m), 1955

Fig. 3.16: The Ruled Freedom: Sergio Musmeci, bridge over Basento river in Potenza, Italy, 1976 structural engineering are the bases for a common action and the study and knowledge of the past are fundamental for a conscious design (Fig. 3.17). Structural engineers are called to an effort to regain that role of “structural designers” that pertained to their category and that today seems to be fading in favour of that of “structural verifiers”.

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38 (a)

CHAPTER 3. A SUSTAINABLE APPROACH TO STRUCTURAL DESIGN

(b)

Fig. 3.17: Contemporary Structural Art inspired by past examples: (a) Albert Fink, five span Green River railway bridge in Munfordville, KY, USA, 1859; (b) Lifschutz Davidson Sandilands and Techniker, Royal Victoria Dock footbridge in London, UK, 1996 (a)

(b)

Fig. 3.18: Outstanding realizations where structural design plays different roles: (a) Frank Gehry: BP bridge at Millennium Park, Chicago, USA, 2004; (b) Rosales & Partners in collaboration with Schlaich Bergermann & Partner: Liberty Bridge at Falls Park on the Reedy, Greenville, SC, USA, 2004 The concept of “necessity” expressed before, together with the idea of “ruled freedom”, as the possibility to innovate within a fixed set of rules and with the awareness of the consequences deriving from each single line traced on paper by the designer, can lead to a more conscious and sustainable result, even when the structural engineer has the challenge to deal with extremely complex structures. “Complex” and outstanding structures are rarely “complicated”, because the “rule” is the leading element of the design and there is usually no space for anything lacking that character of “necessity” that can be expressed as the logical sequence of actions linking the final goal to the starting point of the process under given boundary conditions and requirements. If the concept of “necessity” is accepted as a reference feature in structural design, truly outstanding structures can be evaluated in a different way. As an example, two magnificent and well-known curved footbridges whose design was inspired, respectively, by the leading architect Frank Gehry and the leading structural engineer Jörg Schlaich deeply involved in outstanding architectural works [16] can be compared with the purpose mentioned above (Fig. 3.18).

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3.6 SUSTAINABLE CONCEPTUAL DESIGN OF STRUCTURES

39

In the first case, the footbridge is a landmark sculpture, a purely stunning shape, and the final result could be reached, from a structural point of view, in many different ways. Structural members are disguised and the overall layout does not possess any character of necessity from a structural point of view. In the second case, the layout possesses a true character of necessity: structural members efficiently shape the structure and constitute its main aesthetical features. There is no space for change: there is nothing more and nothing less than what is necessary to achieve the stated goal. The structural solution is intimately and efficiently related to the final shape and purposely conceived: structure and architecture coincides. The freedom of the designer in creating an outstanding shape is strictly ruled and the “know how” and the “know why” are perfectly blended within the concept of structural efficiency.

3.6

Sustainable conceptual design of structures

Structural designers have the chance to apply the principles of sustainability, taking into consideration some of the principles listed in Table 3.1: • • • • • • • •

design for safety, design for serviceability, design for structural efficiency, design for adaptability, design for durability and minimal maintenance and life-cycle costs, design for risk reduction and value protection, design for aesthetics, design for minimal ecological footprint (embodied energy, minimal material use, emissions, reuse, recycling, disposal).

In the following, some of the above-mentioned points will be briefly examined through a number of case studies.

3.6.1

Design for structural efficiency

Structural efficiency constitutes a key feature within a sustainable design process. Structural efficiency embodies the ideas of a correct choice of static scheme, appropriate use of construction materials and structural solutions and, last but not least, the concept of structural optimization.

3.6.2

Choice of a suitable static scheme

The choice of the correct static scheme will influence the life-cycle behaviour of the structure with remarkable consequence in terms of maintenance costs. The choice of the static scheme is fully part of the conceptual design of a structure and must be clarified from the very beginning of the design process and be very much related to the boundary conditions and available resources.

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CHAPTER 3. A SUSTAINABLE APPROACH TO STRUCTURAL DESIGN

For some special cases, and especially for moveable structures, a single structure can have more than one static scheme and the structural design, in order to be led by the concept of efficiency, must take this aspect into consideration. This is the case of the design for a swinging footbridge characterized by a varying stiffness according to the different static schemes [17]. The change from the condition of simply supported to the condition of cantilevering girder is accompanied by a change in stiffness of the cross section that varies its shape from “flat” to “U-shaped” (Fig. 3.19). The recent and well-known construction of the fourth bridge over the Grand Canal in Venice, Italy, designed by the Spanish Architect Santiago Calatrava (Fig. 3.20), greatly emphasized the consequences of the choice of a certain static scheme under special boundary conditions [18].

Fig. 3.19: Swing bridge with variable stiffness according to the different static schemes: Bruno Briseghella and Tobia Zordan [17]; 2002 IABSE Award for outstanding paper from young authors (a)

(c)

H Fourth bridge 1) Cross section with poor bending stiffness 2) Cross section with high bending stiffness

(b)

2

1

SCALZI

0 h 0.5 l

0.4

0.3 Arches

0.2

0.1

0.05 0.02 Girders

Fig. 3.20: 300 m and 74 years away: comparison of the horizontal thrust H at the abutments of outstanding bridges in Venice, Italy. The fourth bridge from Santiago Calatrava (2008) and the Scalzi bridge from Eugenio Miozzi (1934), respectively, (a) and (b). (c) The Venetian tradition in bridge design and construction before the fourth bridge, because of the poor mechanical properties of local soil, displayed the utmost attention in limiting the horizontal forces transmitted by the superstructure to the foundations and in controlling the raise/span ratio of the arched structures

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3.6 SUSTAINABLE CONCEPTUAL DESIGN OF STRUCTURES

41

This stunning landmark bridge is built on a soil with poor mechanical properties. The bridge has a total span of 80.8 m and a raise/span ratio of approximately 1/16. This figure implies a great horizontal thrust that necessitates massive diaphragm foundations reaching a depth of 22.5 m. The response of the steel superstructure, weighing approximately 6.5 kN/m2, is highly sensitive to settlements. The final unit cost of the bridge is approximately of 6000 €/m2. The Venetian tradition shows a different approach to bridge design, characterized by much more favourable raise/span ratios and, contrarily to the fourth bridge, characterized by stocky abutments and slender keys, in order to provide a quasi-vertical force applied to the foundation by dead-loads. This is the case of the Scalzi bridge, just 300 m away from the new fourth bridge, designed in 1934 by Eugenio Miozzi with a raise/span ratio of 1/4 (Fig. 3.20). The fourth bridge is characterized by the presence of a system of jacks. It is based on finite element (FE) modelling, carried out with the purpose of optimizing the erection phases; the parts were pre-assembled prior to final on-site welding, and located at the abutments. The FE model displayed the high sensitivity of the structure to foundation settlements because of the unfavourable raise/span ratio. Jacks are used to reset the bridge in its original geometrical configuration in case of unexpected foundation settlements.

3.6.3

Structural optimization

Structural optimization, which is a commonly used tool in mechanical and aeronautical engineering, is also becoming a common and useful tool in structural engineering to help the designer to find the most suitable shape of a structure allowing for a better exploitation of construction materials with a consequent reduction in structural weight and decreased lifecycle costs. Structural optimization, if guided step by step by the ability and intuition of the designer, can represent an effective tool in reaching the condition of “necessity” that can lead to the creation of a piece of structural art within the context of “ruled freedom”, as expressed in Section 3.5. In recent years, intuitive approaches to topology optimization based on the concept of removing inefficient material have been introduced. The two most popular ones are the solid isotropic material with penalization (SIMP) method [19] and the evolutionary structural optimization (ESO) method [20]. In general, performing an optimization process, of every kind, means taking into account the following problem [21]:

(3.2)

where x=[x1,x2,…,xn] is the vector of the n design variables, continuous or discrete, f ( x ) is the vector of the i = 1,2…,Q object criteria function f i ( x ) that are each to be minimized for the design, and g j ( x ) defines the sets of equality or inequality constraint governing the design.

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CHAPTER 3. A SUSTAINABLE APPROACH TO STRUCTURAL DESIGN

A structural optimization procedure, with the purpose to minimize the overall weight of the bridge and therefore allow for the minimum use of construction material, was carried out through the SIMP method in the Granatieri di Sardegna bridge over the River Piave in the Province of Venice, Italy (Fig. 3.21) [22], as designed by Enzo Siviero. The bridge has a total length of 500 m arranged on five arched bays of 100 m each. The cross section has a width of almost 18 m. Structural optimization was performed in two stages. Firstly, a structural optimization was performed to measure the thicknesses of the webs and flanges, assumed as discrete variables, to minimize the self-weight of the deck. Plate thicknesses were assumed as discrete design variables whose optimum arrangement was found by minimizing the plate’s total weight with the conditions that the stress level was lower than an allowable value and the plate thickness higher than a minimum value (to avoid local stability problems). Furthermore, unnecessary material was removed from the bottom flange through topology optimization in the second stage. A design solution with holes was thus obtained. Different configurations of holes were obtained, varying based on the percentage of volume reduction assigned by the designer. Topology optimization [23] through the SIMP method was performed using Ansys, in which the design variables are internal pseudo-densities that are assigned to each i-th FE in the topological problem. Based on the hypothesis about the relationship between the variation of material properties and density, the stiffness matrix of each element is assumed as proportional to ηE, where E is the actual elastic modulus; η = r q is the internal pseudo-density of the element; r is the relative density compared with the actual density of the material and continuously varying between 0 and 1; Eef = ηE is the “effective” elastic modulus, lower than E in regions with relative density r lower than 1. From a structural point of view, all of the previous assumptions mean that the elements with a nearly 0 value give very little contribution to the global stiffness matrix (and therefore to the model compliance), so that the effect of their removal is negligible. Constraints were given from the designers in order to obtain elliptical holes, once the structural material was removed. This choice was derived from a formerly step-by-step manually controlled optimization based on engineering judgement and past experience (Fig. 3.21). Among the design solutions obtained from the increasing ratios of removed material, a good compromise between the competing requirements of volume reduction and structural performance was identified by defining an appropriate Optimization Index that assigned a suitable score to each design solution. The optimization process led to the best score being assigned to a design solution with two elliptical holes such as the one named D3a in Fig. 3.21 and corresponding to the minimal weight.

3.6.4

Design for durability, minimal maintenance, and life-cycle costs

Life-cycle maintenance costs of ageing structures and infrastructures have proved to be much higher than construction costs. For more developed countries, the building investment ratio for new structures and infrastructures is rapidly decreasing while the amount of money invested for the maintenance of existing stocks is dramatically increasing. Developing countries are probably going to face the same situation within a few years.

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3.6 SUSTAINABLE CONCEPTUAL DESIGN OF STRUCTURES

T1

D1

T2

D2

T3a

D3a

T4a

D4a

T3b

D3b

T4b

D4b

T5

D5

T6

D6

TOP

DOP

Fig. 3.21: Design for minimal use of construction materials and weight reduction. An example of structural optimization applied to the design of the Granatieri di Sardegna bridge over the Piave river in Venice, Italy. The final solution is the result of the comparison between an iterative topology optimization procedure (TOP) based on pseudo-density of elements and a stepby-step manually controlled design optimization procedure (DOP) based on Von Mises stress. Final optimal design with reference to the minimization of structural weight, according to the Optimization Index set at the beginning of the design process, has been D3a [22] This represents a non-sustainable trend that can be faced due to a sudden change of direction towards a more sustainable design approach that can be supported by life-cycle assessment [24] and minimization of life-cycle–associated costs for construction, inspection, maintenance, repair, upgrade, demolition, disposal, reuse, recycle, together with environmental and social impacts [25]. In this view, evaluation and prediction of future performance plays a fundamental role in defining long-term strategies, even if the uncertainties and the risks associated with this process make the definition of evaluation models capable of reliably assessing the life cycle of a structure (or of a stock of structures) and the related cradle-to-grave costs, at the moment, still rather uncertain. 3.6.4.1 Integral abutment concept Together with global strategies, single tools able to mitigate the usual vulnerabilities limiting the lifespan of structures can be introduced both in the design of new structures and in the upgrading of existing structures.

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CHAPTER 3. A SUSTAINABLE APPROACH TO STRUCTURAL DESIGN

For instance, talking about bridges, the great majority of the overall value of the existing stock is represented by small- or medium-span, simply supported inexpensive bridges, whose initial quality is sometime questionable and whose long-term behaviour displays non-sustainable maintenance costs, which creates an overall deterioration of the stock. Bearings and expansion joints are known as vulnerable elements, whose maintenance usually has a strong impact on the social environment, because of the associated indirect costs due to the limitation or the interruption of the traffic flow. The integral abutment bridge concept, based on the elimination of bearings and expansion joints, has recently become a topic of remarkable interest among structural engineers, not only for newly built bridges but also for refurbishment or upgrading of existing bridges [26]. The superstructure of integral abutment bridges can be fully or partially restrained to the abutments and the foundations. The system constituted by the substructure and the superstructure can achieve a composite action responding as a single structural unit; this principle is clearly applicable in converting existing simply supported bridges into integral abutment bridges (IABs). Several guidelines for the design of IABs have been published in the last few years. The main idea is to lead the designers towards this type of structures, limiting their total length, the skewness, and the inclination of the deck. No. Name

State/Country

Length

Remarks

1

Isola della Scala, Verona

Veneto, Italy

400.8 m

Prefabricated pre-stressed V-shaped concrete girders

2

SR 50 (over Happy Hollow Creek)

Tennessee, USA

358.4 m

Precast, prestressed concrete bulb-T girders, curved, nine-span (Fig. 3.8)

3

Unknown

Colorado, USA

339.2 m

Precast girder

4

Unknown

Oregon, USA

335.5 m

Precast girder

5

Unknown

Colorado, USA

318.4 m

Steel girder

6

SR 249 (over US 12)

Indiana, USA

302.0 m

Composite pre-stressed bulb-T girder, ten-span (26.4–35.0 m)

7

Unknown

Colorado, USA

290.4 m

Cast-in-place

8

SR 34 (over Southern Railway & Whitehorn Creek)

Tennessee, USA

250.0 m

Pile-supported stub-type abutment; 12-span precast/ pre-stressed box beams with composite concrete deck

9

Unknown

Virginia, USA

235.5 m

Precast girder

10

Bushley Bayou (LA 124)

Louisiana, USA

221.0 m

Nine-span, semi-integral abutment

11

Unknown

South Dakota, USA

209.2 m

Precast girder

Table 3.2. Super long integral abutment bridges [27]

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3.6 SUSTAINABLE CONCEPTUAL DESIGN OF STRUCTURES

The maximum lengths usually recommended for this type of structures are around 100 m or even less. This limitation derives from the uncertainties related to the prediction of the soil– structure interaction associated with main factors such as temperature variations affecting the response of this kind of structures. The longest IAB ever built [27] (Table 3.2), the “Isola della Scala Bridge” in Verona, Italy, was completed in 2007 as the result of an upgrading of a partially existing, simply supported, pre-stressed concrete bridge (Fig. 3.22). The total length of the structure, arranged on 13 spans, is approximately 400 m. The construction of the bridge, which began in 2001 on a simply supported static scheme, was halted after 2 years because of financial problems faced by the contractor. At that time, all pre-stressed concrete girders and the main prefabricated elements had already been purchased. In early 2006, works resumed with a new proposal that aimed to improve the quality of the structure and change the static scheme from “simply supported” to “fully integral”. The main bridge data are listed in Fig. 3.22. During this kind of “refurbishment” process, in order to achieve an IAB, by eliminating all bearings and expansion joints, resistance to bending moment was attained at the pier caps with the casting of concrete diaphragms between the beams of adjacent spans at the pier tops. Hogging and sagging moment resistance was also determined using a similar technique at the abutments for the end bays: The connections between the beams of adjacent spans were built by casting the concrete of the diaphragms also inside the V-shaped girders for a length of 2 m. The connections between the pier caps and the transverse diaphragm were achieved with a segment of steel for every beam. During construction, the average air temperature remained approximately 10 to 15°C. The construction sequence of the transverse diaphragms started from the central part of the bridge and proceeded symmetrically towards the abutments.

SP1

P1

P2

P3

P4

P5

P6

P7

P8

P9

P10

P11

P12

SP2

400.8 29.9

31.0

31.0

31.0

31.0

31.0

31.0

31.0

31.0

31.0

31.0

31.0

29.9

Spans length

29.9 m + 11 × 31.0 m + 29.9 m = 400.8 m

Static scheme: (pre-to postrefurbish.)

Simply supported to continuous

Deck width/height

13.5 m/(1.5 m + 0.3 m)

Piers column diameter

3.0 m

Piers height (cap + column + footing):

1.8 m + (3.775–5.385) m + 2.5 m

Piles type

RC/friction

Piles section

Circular D = 1.2 m

Piles length

15–20 m

Piles number

Six for each pier and abutment

Fig. 3.22: Design for minimal maintenance and life-cycle cost reduction: an example of upgrading of an existing simply supported bridge into an integral abutment bridge. The Isola della Scala bridge in Verona, Italy [26]

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CHAPTER 3. A SUSTAINABLE APPROACH TO STRUCTURAL DESIGN

Temperature pushover parametric analyses were performed in order to assess the failure pattern of the structure and attaining the rotation limit of internal joints within the range of ±40°C [28]. The bridge was opened to traffic in 2007; no mentionable damages have been noticed until now, except for some uniformly distributed cracks of limited width in the approach slabs. The greatly extended life-cycle span of the IAB, compared with the one expected for the initial simply supported solution, mainly depends on the durability of the construction materials.

3.6.5

Design for value protection

The concept of value protection deals with uncertainties related to life-cycle and risk assessment and represents an interesting subject both for new buildings and infrastructures and for existing ones. This topic represents a real key feature for a sustainable development, especially for seismic areas and, in general, for areas prone to extreme events. While the need to protect buildings and infrastructures from structural damages caused by seismic events is well known and considered [29], in relatively recent times, the need to preserve non-structural components and contents has also become evident within the sustainable approach to long-term management strategies of existing stock of buildings. The damage to non-structural elements and components occurs even for levels of ground acceleration much smaller than those creating an appreciable structural damage. At the same time, the value of a building is mainly attributed to its components and non-structural elements (Fig. 3.23) together with the possibility of keeping its functioning uninterrupted [30]. In case of an earthquake, the non-structural elements such as partitions, claddings, floors, furniture, and plants, can be easily damaged and lose their value. Furthermore, in case of damaged partitions, the intervention of the civil protection or equivalent national authorities implies building evacuation with a temporary loss of function and consequent relevant economic losses for the community. In 2009, the case of the L’Aquila earthquake, in Italy, with the debate that follows about the opportunity of performing different retrofitting techniques [31], confirmed the necessity of protecting a large stock of buildings from damages involving

100% 20%

17%

80%

44%

60%

Structural 62%

Non-structural

70%

Contents

40% 48% 20% 18%

13%

8%

Offices

Hotels

Hospitals

0%

Fig. 3.23: Total value distribution according to different type of buildings

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3.6 SUSTAINABLE CONCEPTUAL DESIGN OF STRUCTURES

non-structural components and contents as well, because of the evacuation of a large part of the local population and the related costs.

(a)

1.2

1.0 LS of NC LS of SD

0.8

Sa/g

LS of DL 0.6

0.4

0.2

0.0 0.0

(b)

0.5

1.0

1.5

2.0 T (s)

2.5

3.0

3.5

4.0

Base shear demand

Very rare events Tr = 2475 (2%/50 years) Rare events (10%/50 years)

(SLU) SLDS

Tr = 475 Occasional events (20%/50 years) Frequent events (50%/50 years)

SLCO

Operational

(SLD) SLDL 10%/10 years Tr = 95 years

Life safe

Structurally stable

Fig. 3.24: The effect of base isolation with the increment of the fundamental vibration period of the structure allows for a reduced level of acceleration so that the elastic state is not exceeded for seismic events characterized by higher return periods (from: Pacific Earthquake Engineering Research Center) (LS - Limit State, NC - Near Collapse, SD - Significant Damage, DL - Damage Limitation)

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CHAPTER 3. A SUSTAINABLE APPROACH TO STRUCTURAL DESIGN

3.6.5.1 Seismic isolation of existing buildings Among the possible strategies that can be applied in the ambit of a value protection strategy within a sustainable approach to risk assessment, seismic isolation (SI) has proved to be a sustainable technique to preserve the value of a building. SI, which is becoming a “standard” for new buildings, can also be conveniently applied to existing buildings. As it is known, the idea

Fig. 3.25: Scheme of the “lift-up” system achieving base isolation on existing buildings. Construction phases are as follows: a concrete slab is built underneath the existing foundations (the use of piles can be an option for special cases); a second slab is realized incorporating lifting devices and tightly connected to the existing foundations; a system of jacks is connected to the second slab; building is raised by the jacks, thanks to the contrast applied to the lower slab; seismic bearings are positioned and the building is lowered to its final position; jacks are removed. Several buildings have been upgraded using internationally patented Italian technology. [32] Type of intervention

Average unit cost in L’Aquila (€/m2)

Fig. 3.26: The building (formerly damaged during the 2009 L’Aquila earthquake in Italy) at the end of “lift-up” and detail of the isolation system. The system proposed appears to be cheaper than traditional strengthening methods and other isolation techniques such as cutting at the base or at the top of columns

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3.7 CONCLUSION

49

behind SI is to disconnect the superstructure from the foundation system at the base of the building by the insertion of suitable devices characterized by high vertical stiffness associated with a low horizontal stiffness and suitable damping ratio. In this way, the fundamental vibration period of the structure in the response spectrum is shifted towards higher values associated with lower levels of acceleration. As a consequence, just a limited part of the ground acceleration is transferred to the building, which is meant to remain within the elastic limit state also for seismic events characterized by the highest return periods, allowing for a immediate use of the building after the earthquake under fully operational conditions (Fig. 3.24). After the earthquake of L’Aquila, base isolation has been introduced to a rather consistent number of damaged buildings in the city downtown and surroundings. Works have been completed by using internationally patented Italian technology. This technology is based on the possibility of raising the building, disconnecting the superstructure from the foundation system after realizing a concrete slab immediately below the level of the existing foundations, as a contrast to the hydraulic jacks responsible for the “lift-up” [30]. The system can be used for both masonry buildings (Fig. 3.25) and frame structures (Fig. 3.26) and it is suitable to protect the value of the building for its future lifespan. Realization costs are comparable to the ones necessary to strengthen same kind of buildings with conventional techniques.

3.7

Conclusion

In the era of real-time communication and information, the claim for better life conditions is global and involves the amount of available resources in all aspects of real life. The increasing world population will not be compatible with the available Earth’s resources unless the ecological footprint or carrying capacity, defined as the comparison between the demands for natural resources that can be balanced by the planet’s ecological ability to regenerate, would be decreased rapidly in the coming years. Conceptual design of structures, understood not only in its limited meaning as the initial design ideas but also as the ability of identifying and optimizing all the aspects related to an integrated approach to optimize the multi-objective functions describing the overall performance of a structure during its entire service life, plays a fundamental role in ensuring the achievement of goals pertaining to the ambit of sustainability in this specific field. Sustainable structural design, even if not influenced by codified measuring indexes, should relate to issues such as safety, serviceability, structural efficiency, adaptability, durability, minimal maintenance, life-cycle costs, risk reduction, value protection, and minimal ecological footprint. The history of structural engineering with its great past achievements demonstrates that its masters and pioneers have always struggled to reduce uncertainties and to operate within a “ruled freedom”, in order to realize structures of structural art generated from “necessity” and internal coherence, even when characterized by the highest level of complexity, in an iterative process characterized by “intuition” and “control”. Today, the latest architectural trends based on the opportunities rendered by digital tools and information technology are generating worldwide examples that are in contrast to the aforementioned character, introducing an increasing level of uncertainty with reference to the long-term behaviour and life-cycle costs of structures. Structural engineers are called upon to regain the leading role of “designers” that appears to be fading in favour of that of “verifiers” and give their highest contribution towards a more sustainable built environment.

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CHAPTER 3. A SUSTAINABLE APPROACH TO STRUCTURAL DESIGN

References [1] [2]

[3] [4] [5] [6] [7]

[8] [9] [10] [11] [12] [13]

[14] [15] [16] [17]

[18] [19] [20]

American Society of Civil Engineers (ASCE). 2008. Civil Engineering Body of Knowledge for the 21st Century, ASCE. World Commission on Environmental and Development Report, 1987. From one Earth to one World – World Commission on Environment and Development (WCED). Oxford University Press. Le Ricolais, R. 1960. Grids and Space Frames – An Investigation on Structures. College of Architecture and Design, University of Michigan. Rees, E.W. 1992. Ecological footprints and appropriated carrying capacity: what urban economics leaves out. Environ. Urban., 4(2): 121–130. World Wildlife Found (WWF). 2006. Living Planet 2006, WWF, Gland, Switzerland. Ewing, B., Goldfinger, S., Wackernagel, M., Stechbart, M., Rizk, S.M., Reed, A., Kitzes, J. 2008. The Ecological Footprint Atlas 2008. Global Footprint Network, Oakland, CA. Nakicenovich, E., et al. 2008. Report on Emissions Scenarios: A Special Report of Working Group III of the Intergovernmental Panel on Climate Change, Cambridge University Press, Cambridge, UK. ISO 14001. 2004. Environmental management systems – Requirements with guidance for use, International Organization for Standardization, Geneva, Switzerland. Maydl, P. 2004. Sustainable engineering: state-of-the-art and prospects. Struct. Eng. Int., 14(3): 176–180. Sarja, A. 2004. Integrated Life Cycle Design of Structures. Taylor & Francis, New York, NY, USA. Akao, Y. 1994. Development History of Quality Function Deployment. Asian Productivity Organization, Tokyo, Japan. Majowiecki, M. 2007. Ethics and structural reliability in free-form-design. J. Int. Assoc. Shell Spatial Struct., 48(4): 29–50. Carper, K. 2001. Lessons architects can learn from failures, Proceedings of International Conference on Structural Failures and Reliability of Civil Structures, Venice, Italy, 6–7 December 2001. Billington, D. 1983. The Tower and the Bridge: The New Art of Structural Engineering. Princeton University Press, Princeton, NJ, USA. Siviero, E. 2011. Bridgescape. La Scuola di Pitagora Editrice, Napoli, Italy. Schlaich, J., Bergermann, R. 2003. Light Structures. Prestel Publishing, New York, NY, USA. Briseghella, B., Zordan, T. 2002. Design and analysis of a variable stiffness moveable footbridge, Proceedings of the 2002 IABSE Symposium “Towards a Better Built Environment – Innovation, Sustainability, Information Technology, Melbourne, Australia, (IABSE Award for Outstanding Paper by Young Authors). Zordan, T., Briseghella, B., Siviero, E. 2010. The IVth bridge over the Grand Canal in Venice: from the idea to analysis and construction. Struct. Eng. Int., 20(1). Bendsoe, M.P., Kikuchi, N. 1988. Generating optimal topologies in structural design using a homogenization method. Comp. Meth. Appl. Mech. Eng., 71(2): 197–224. Xie, Y., Steven, G.P. 1992. Shape and layout optimization via an evolutionary procedure, Proceedings of the International Conference on Computational Engineering Science, University of Science and Technology, Hong Kong, PRC.

BackBack to table ofofcontents to table contents

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REFERENCES

51

[21] Scott, A.B. 2002. Recent Advantage in Optimal Structural Design. Structural Engineering Institute of the American Society of Civil Engineers, Reston, VA, USA. [22] Briseghella, B., Fenu, L., Lan, C., Mazzarolo, E., Zordan, T. 2012. An application of topology optimization to bridge design. ASCE J. Brid. Eng. [23] Bendsoe, M.P., Sigmund, O. 2003. Topology Optimization: Theory, Methods, and Applications. Springer-Verlag London Ltd., London, UK. [24] ISO 14044. 2006. Life cycle assessment – Requirements with guidance for use. International Organization for Standardization, Geneva, Switzerland. [25] Chen A. 2008. Bridge Design Processes based on given Structural Life. China Communications Press, Bejing, PRC. [26] Zordan, T., Briseghella, B. 2007. Attainment of an integral abutment bridge through the refurbishment of a simply supported structure. Struct. Eng. Int., 17(3): 228–234. [27] Lan, C. 2012. On the Performance of Super Long Integral Abutment Bridges, PhD thesis, Joint Doctoral School in Civil and Mechanical Structural Systems Engineering, University of Trento, Trento, Italy. [28] Zordan, T., Briseghella, B., Lan, C. 2010. Pushover analysis on integral abutment bridge superstructure. Eng. Struct., 33(2). [29] Manfredi, G. 2001. Evaluation of seismic energy demand. Earthquake Eng. Struct. Dyn., 30(4): 485–499. [30] Briseghella, B., Zordan, T. 2007. On the Evaluation of the Seismic Risk for the Hospital Buildings. Ingegneria Sismica, Patron Ed., Quarto Inferiore BO, Italy. [31] Nuti, C., Vanzi, I. 2003. To retofit or not to retrofit? Eng. Struct., 25(6): 701–711. [32] Briseghella, B., Zordan, T., Romano, A., Zambianchi, L., Simone, G., Liu, T. 2012. Liftup and base isolation as an upgrading technique for R.C. existing buildings, Proceedings of the 15th World Conference on Earthquake Engineering, Lisbon, Portugal, September 24–28, 2012.

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53 Chapter

4 Sustainability and Cultural Heritage Buildings

Paulo B. Lourenço, Prof.; Jorge M. Branco, Dr.; Ana Coelho, Researcher; ISISE, Department of Civil Engineering, University of Minho, Guimarães, Portugal. Contact: [email protected]; [email protected]; [email protected]

4.1

Introduction

Conservation of cultural heritage buildings is a demand from society, which recognizes this heritage as a part of their identity, but it is also an economic issue. In Europe, tourism accounts for 10% of the gross domestic product (GDP) and 12% of the employment, if linked sectors are considered [1]. The European Union (EU) is the world’s number one tourist destination, with 40% of arrivals in the world and with seven European countries among the top ten [2]. According to the World Trade Organization (WTO) estimates, international tourist arrivals in Europe will increase significantly. The built European heritage, namely monuments or historical centres, is a main attractor for tourism, with 45% of the United Nations Educational, Scientific and Cultural Organization (UNESCO) World Heritage sites situated within the EU. Therefore, the need for their conservation is unquestionable. Cultural heritage buildings are particularly vulnerable to disasters because they may be deteriorated and damaged, they were built with low-resistance materials, they are heavy, and the connections between the various structural components are often insufficient. The main causes for damage are the lack of maintenance, water-induced deterioration (from rain or rising damp), soil settlements, and extreme events such as earthquakes, but there are many other causes of damage, namely: high stresses due to gravity loading, alterations in layout or construction, cyclic environmental actions, climate change, physical attack from wind and water, chemical and biological attack, vegetation growth, fire, floods, vibration and micro-tremors, and anthropogenic actions. Nevertheless, extreme events often lead to disasters, in light of the high vulnerability. A disaster is an event caused by nature or man, which causes great physical damage, destruction or loss of life, or a drastic change in the natural environment. Danger is the level of threat to life, property, or environment, but it is important to understand that danger is not correlated to damage, and that disasters are the result of poor risk management. Risk management involves,

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CHAPTER 4. SUSTAINABILITY AND CULTURAL HERITAGE BUILDINGS

first, the perception and communication of risk to society. It is then essential not only to have proper tools for assessment and diagnosis but also to define a set of possible solutions, and their costs, to implement a risk mitigation strategy. Over the past 30 years, economic losses due to disasters have increased tenfold, while earthquakes caused 80 000 deaths per year in the last decade (Figs. 4.1 and 4.2). Studies indicate that investment in mitigation provides society an average of four times the amount invested [3]. In addition to savings to society, the US Federal Treasury can redirect an average of 3.65 times the money spent on mitigation resulting from disaster relief costs and tax losses avoided. This result was published in December 2005 in a report prepared by the Multi-hazard Mitigation Council of the National Institute of Building Sciences, called “Natural Hazard Mitigation Saves” [4]. The report was the culmination of a 250 000

Million current US$

200 000

150 000

100 000

50 000

1975

1980

1985

1990 Year

1995

2000

2005

Fig. 4.1: Effects of disasters. Economic losses associated with natural disasters, see Ref. [7] 350 000

320.120

300 000 228.802

250 000 200 000 150 000

88.003

100 000 33.819

50 000

21.953 15.848

1.685 0

88.011

2002

2003

2004

2005

6.605

712

2006

2007

1.790 2008

2009

2010

2011

2011

Haiti earthquake East Japan earthquake Kashmir earthquake

Sichuan earthquake

Indian Ocean earthquake and tsunami

Fig. 4.2: Effects of disasters. Number of deaths in the last 10 years, see Ref. [27]

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4.2 DEFINITIONS

55

3-year, Congressional mandated independent study. Another interesting example is given by the World Bank [5] and the United Nations where a study about retrofitting of buildings to increase earthquake resiliency provides a cost-benefit ratio of up to 8, for a discount rate of 5%. [6] The same study provides a cost-benefit ratio of 4.6 for earthquakes, based in Istanbul, and stressed the obvious fact that the world population exposed to earthquakes will rise dramatically in 2050 from that in 2000. As risk mitigation of the existing built heritage implies a large investment, it is necessary to set priorities and consider an extended period of time to get communities physically, socially, and economically resilient. The approach for risk reduction is known as being necessary to (a) characterize the existing built heritage; (b) perform simplified analysis at the territorial level to estimate the vulnerability and risk of this heritage; (c) perform detailed analyses to confirm the vulnerability and risk, in cases identified with higher risk in the previous step; (d) define a plan with long-term intervention measures and their costs, taking into account the observed risk; and (e) implement the plan, with periodic reviews of time and costs, considering the economic constraints and the costs incurred in actual interventions. It is also true that a strategy like this requires political and societal commitment to become a reality. Another important question is if heritage buildings can be somehow related to the sustainability agenda. It is currently accepted that the improvement of the energy performance of existing building plays an important role in the decrease of the overall energy consumption, which is a key feature of the sustainability profile of buildings. Nevertheless, heritage buildings have a cultural and symbolic function that might limit the need for comfort, with energy performance often being a minor concern in the conservation and rehabilitation of monuments and other protected buildings. On the contrary, the safety of cultural heritage assets cannot be negotiated and several interventions are made for this purpose. The same does not hold for minor assets and historic city centres, where comfort, reuse, and rehabilitation should address energy performance. Despite the minor importance for energy issues in monuments and major cultural heritage assets, intervention to heritage buildings may be an important part of sustainability policies, as far as it produces impacts on the different sustainability dimensions: economy, environment, and society. This chapter presents an overview of the role of cultural heritage buildings in the sustainability goals, focusing on the construction materials, the methodology of interventions, the application of life-cycle assessment tools to existing buildings, and, finally, a summary of the impacts produced on the sustainability dimensions. Because it can be an unusual topic for some engineers, it also intends to provide a background on cultural heritage and historic preservation engineering. Only with a correct understanding of the global methodology for the preservation of cultural heritage buildings, one can seek sustainability in this specific area of engineering.

4.2

Definitions

4.2.1

Cultural heritage conservation specificities

A first relevant question is what is “cultural heritage”? The concept is reviewed in Ref. [8], and refers to a cultural resource involving technical, artistic, and spiritual merits and a landmark providing identity to cultures, world regions, and towns. Cultural heritage also provides a

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document on ancient knowledge, practices, culture, technology, and history and a live document of outstanding cultural and technical achievements, from which one can still learn and improve. Finally, cultural heritage is an economic resource with extremely large capacity to generate secondary economy, while contributing to cultural diversity, global cultural wealth, and human development. Cultural heritage can be distinguished as the Built Environment (such as buildings, townscapes, and archaeological remains), the Natural Environment (such as rural landscapes, coasts and shorelines, and agricultural heritage), and Artefacts (such as books and documents, objects, and pictures). The first type is referred to as the built cultural heritage and in order for people to understand, value, want to care for, and enjoy, the idea of authenticity, i.e. truth free of deviation, as well as novelty and creativity, arises. Depending on the nature of the cultural heritage, its cultural context, and its evolution through time, authenticity judgements may be linked to the values of a great variety of sources of information, such as form and design, materials and substance, use and function, traditions and techniques, location and setting, spirit and feeling, and other internal and external factors. The built cultural heritage thus includes not only archaeological remains, monuments, dwellings and vernacular buildings, groups of buildings, ancient city centres, and historical urban texture but also outstanding engineering works from antiquity to present, industrial heritage from 19th and 20th centuries, 20th century heritage in steel or reinforced concrete, and even modern heritage. Value is not related to age or to the fact whether an asset is being listed or not. Still, it is obvious that most of the existing built heritage structures are constructed with the so-called traditional materials (masonry and timber) and special attention is devoted here to these materials. The concept of a “historic monument” embraces not only the single asset but also the urban or rural setting in which is found the evidence of a particular civilization, a significant development, or a historic event. The criterion of “historic significance” is often used to justify the need to protect individual objects or groups of buildings. Despite the extension of cultural heritage legislation and protection to groups of buildings and urban spaces, irrespective of the listing (inventory) of complete town centres, the instruments and the application of monument protection are still fundamentally “object” centred. A significant risk and threat to groups of buildings, urban spaces, and isolated buildings tends to affect the prominent objects less and the loss of density, historic nature, complexity, and quality of urban fragments more [9]. The importance of the building stock as cultural heritage and the consideration of the building stock as “resource” are discussed in detail elsewhere [10]. Conservation is defined in the Nara Charter [11] as “all efforts designed to understand cultural heritage, know its history and meaning, ensure its material safeguard and, as required, its presentation, restoration, and enhancement”. A more technical oriented definition can be: all actions or processes that are aimed at safeguarding the character-defining elements of a cultural resource so as to retain its heritage value and extend its physical life. A different concept is restoration, an action or process of accurately revealing, recovering, or representing the state of a cultural resource or of an individual component, as it appeared at a particular period in its history, while protecting its heritage value. Restoration is a complex concept for the built heritage as this heritage was hardly produced in any given period of time. On the contrary, the built heritage evolved together with the society, the needs, and the building styles and techniques. The concept of restoration is in fact very controversial and encompasses many different interpretations,

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ranging between reconstruction/full “repristination”, even involving the reconstruction of parts historically collapsed or which may have never been actually built, to that of minimal intervention oriented to strict preservation/conservation. The understanding of restoration connected to reconstruction/repristination is clearly out of fashion and in contradiction with modern conservation principles. Other technical concepts are stabilization, an action aimed at stopping a deteriorating process involving structural damage or material decay (also applied to actions meant to prevent the partial or total collapse of a deteriorated structure); repair, an action to recover the initial mechanical or strength properties of a material, structural component, or structural system (also applied to cases where a structure has experienced a deterioration process that produced a partial loss of its initial performance level); and strengthening, an action providing additional strength to the structure (needed to resist new loading conditions and uses, to comply with a more demanding level of structural safety, or to respond to increasing damage associated with continuous or long-term processes). In the context of conservation of historical structures, repair is not meant to correct any historical deterioration or transformation (including those man-made), which only affects the appearance or formal integrity of the building and does not compromise its stability. Repair should be only used to improve structures that have experienced severe damage conveying a loss of structural performance and thus causing a structural insufficiency with respect to either frequent or exceptional actions. Strict conservation will normally require stabilization or repair operations. Conversely, rehabilitation will frequently lead to strengthening operations. Rehabilitation is defined as the upgrading of a building to comply with modern uses and standards. Rehabilitation constitutes an activity substantially different to conservation and frequently leads to alteration of the structure to an extent incompatible with the strict conservation principles. Rehabilitation is also often defined as an action or a process of making possible a continuing or compatible contemporary use of a cultural resource or an individual component, through repair, alterations, and/or additions, while protecting its heritage value. The problem with this definition is that making possible a modern use according to modern standards and codes may be incompatible with sound protection of heritage value. Rehabilitation will often require significant transformation with loss of authenticity and cultural value. Still, a cost-benefit analysis must be made in all cases, as the modern requirement of a living cultural heritage allows for a change of use and it is economically impossible to maintain the built heritage only for touristic and “monumental” use. The built cultural heritage includes residential and commercial buildings, meaning that, even if the regulations for new buildings cannot be blindly adopted, adequate performance is required in terms of comfort, accessibility, and thermal efficiency, among others, and adequate performance must be demonstrated in terms of structural safety, fire protection, and other non-negotiable requirements. Nevertheless, the intervention in cultural heritage buildings may be regulated by specific policies and rules, which tend to vary according to the classification and the location of the building.

4.2.2

Rehabilitation and sustainability

Sustainability may be assessed through three different perspectives: economic, environmental, and social impacts, which should work in harmony. Rehabilitation of cultural heritage buildings produces impacts in the three categories, some of them being more remarkable than the others.

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From the economics point of view, rehabilitation represents a significant initial investment, due to the specifics imposed by heritage buildings, including keeping their original features, using traditional techniques and materials, difficult accessibilities, and unexpected findings during the works, among others. Rehabilitation is often more expensive than new construction, partly because many interventions are too extensive and fail to reuse the original fabric. The investment in the rehabilitation of ancient buildings has important economic outcomes, such as the creation of jobs (considering that the use of traditional techniques demands more manpower than modern techniques), local employment (small and medium enterprises are mode competitive to do these works than major contractors), and the value added to a certain region (due to the increase of its touristic potential and/or the improvement of the region’s self-esteem) (see also Ref. [12]). According to the Whitestone’s Facility Cost Forecast System originally developed for the US Army, the cost of a building per year is 6% of the initial cost, including 35% for operation; 46% for preventive maintenance, repair, and part replacement; and 19% for recapitalization. Even if the cost of maintenance is lowered from about 3% per year to a value of only 1 to 2% per year, the building heritage by itself (which has no operation costs) implies significant costs. Therefore, the sensible option is to rehabilitate and reuse, with a positive economic impact. Considering the environmental issues, the rehabilitation of ancient buildings usually produces lower impact than making a new building. In fact, rehabilitation is a form of reuse of an existing fabric, thus extending its life span. Conservation works are frequently limited to surgical interventions, demanding few material quantities and low amounts of energy, which cause very low environmental impacts. Also, efficient rehabilitation can provide a similar result. It should be noted that the use of traditional materials and techniques, when applicable, is characterized by a very low environmental impact, due to the low amounts of energy required for its manufacture and processing. From the social perspective, rehabilitation of cultural heritage buildings may be analysed under two major aspects: the valorization of a region and the creation of jobs. On the local valorization issue, it is supported by the fact that people are likely to feel a higher connection to a place and its history, through the rehabilitation of historical buildings or urban texture. The increase in awareness for history and traditions may have remarkable positive impacts on the society as well. The creation of jobs, in addition to the economic benefits, also helps in retaining people in a certain region, which may help to boost the region’s social performance. Thus, it is possible to provide better quality of life to the users of a building or at an urban scale, by revitalization of economic activities, by attracting new users, or by providing new urban equipment.

4.3

Traditional materials and sustainability

Masonry and timber are the oldest building materials that still find wide use in today’s building industries. Important new developments in materials and applications occurred in the last decades but the techniques are essentially the same as the ones developed some thousand years ago. Ancient buildings are often characterized by a remarkable durability, which has enabled them to remain in good condition over the long time periods. The role of masonry and wood in sustainability issues is described in this section.

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4.3.1

59

Masonry

Innumerable variations have occurred in masonry materials, techniques, and applications during the course of time. The influential factors were mainly the local culture and wealth, the knowledge of materials and tools, the availability of material, and aesthetic reasons. The most important characteristic of masonry construction is its simplicity. Laying pieces of stone or bricks on top of each other, either with or without cohesion via mortar, is a simple, although adequate, technique that has been successful ever since ancient times. Other important characteristics are the aesthetics, solidity, durability and low maintenance, versatility, sound absorption, and fire protection. The first masonry material to be used was probably stone. Evolution of housing was from huts, to apsidal houses, and, finally, to rectangular. Several legacies of stone masonry have survived until now as testimonies of ancient and medieval cultures. In addition to the use of stone, mud brick was also started to be used as a masonry material. It was a product that could be easily produced. It was lighter than stone, easy to mould, and formed a wall that was fire resistant and durable. The practice of burning brick probably started with the observation that the brick was stronger and more durable. With the Industrial Revolution, traditional handwork procedures were replaced by machinery. Since then, further research and developments led to the creation of efficient brick-making industries. Another component of masonry is the mortar, which, traditionally, was mostly clay or lime mixed with sand and silty soil. The first aspect related to masonry sustainability is its longevity and durability [13]. Structures that last the longest, require less maintenance, and can be adapted for reuse cast a smaller shadow on the environment. Moreover, masonry recyclability is very high, helping in saving virgin materials and reducing construction waste. A second sustainability aspect in masonry is resource efficiency, as stone, earth, and mortar (in its forms of lime or mud) are some of the most abundant materials found on earth. The manner in which materials are collected, transported short distances, and incorporated into manufactured products with relatively little energy provides minimal negative impact on the environment. Modern masonry manufacturers use more than 95% of extracted material in their production, and the modular design of the manufactured block helps to reduce construction waste. A third sustainability aspect in masonry is energy efficiency [14]. Masonry has high thermal mass, meaning that they provide very effective thermal storage. Masonry walls remain warm or cool long after the heat or air conditioning has been shut off. This benefit results in lower energy consumption in buildings. With proper design, either new or rehabilitated masonry walls, especially cavity walls, can reduce peak heating and cooling loads; shift peak loads; moderate indoor temperature swings; and reduce the size of heating, ventilation, and air conditioning (HVAC) systems. Also, passive design strategies can be successfully implemented by utilizing masonry materials. Other sustainability aspects in masonry are safety and protection, aesthetics, enclosure and finish, and natural fit. Masonry provides excellent fire safety and shelter from hurricanes, tornadoes, blasts, bullets, and others. The variety of sizes, shapes, colours, textures, and patterns available means that people will hold on to their attractive, inviting buildings longer and use them adaptively. Masonry walls can provide both structural support and exterior/interior finish. This simplified wall system can eliminate the need for additional materials that require manufacture, installation, maintenance, and repair. This reduces cost and conserves building

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materials. Masonry is using natural materials, instead of oil-based chemical products. An overview of masonry and sustainability is given elsewhere [15].

4.3.2

Wood

Wood is a largely available material in most regions of the world. Since ancient times, it has been used by humans to build shelter, to light fires, and to produce artefacts. It is not as durable as the stone; nevertheless, one can find several ancient buildings that have used wood in their structures. Several centuries of building construction with wood across the world have created a significant heritage of wood-building know-how. Wooden construction is empirically known for its sustainability. When performing a life-cycle assessment (LCA) of wooden buildings, it is usually considered that trees store carbon dioxide in their tissues, which will only be released by decay or combustion of wood. This feature is highlighted in long lifespan wood-based products, which are able to store carbon for a significant period of time, among which are the main construction materials Ref. [16]. In this discussion, [17] points out that the ability of wood to store carbon is not significant when compared with the total carbon emissions of building products manufacturing, as all wood products have a finite life, being the CO2 released to the atmosphere by wood decay, the carbon storage balance will remain constant over time, considering that the overall use of wood worldwide will eventually reach a steady state. Due to this fact, the carbon storage of wood products cannot offset the manufacturing emissions in the long term. Reference [17] concludes that wood products require small amounts of energy in their manufacture, compared with bricks, aluminium, steel, and concrete. In summary, the low energy requirements of wood products manufacturing are more significant towards the aim of carbon emission reduction in the long term, in comparison with the ability of wood to store carbon. Forestry industry has social and economic importance in many regions of the world. Besides that, it also contributes to control soil erosion, helps to regulate the climate, and has a decisive role in the efficiency of water cycle and on the biodiversity of wildlife and flora. Besides low energy requirements of wood products manufacture, it can be assumed that the transformation process of wood produces virtually no waste, since all the “waste” can be used for the production of wood-based products or fuel, decreasing the demand for fossil fuels [18,19]. Although wooden constructions need maintenance throughout their lifetime, common wooden building systems allow partial replacement of modules or damaged elements, without compromising the entire structure. The use of wood also contributes to the energy efficiency of buildings, since it is a material with low thermal conductivity. When dismantling a wooden building, the recovered wood can be directly reused in another building or used as raw material for wood-based products, either by extending its useful life or simply using as biofuel, avoiding the need for fossil fuels. On landfill, wood decomposes slowly, further extending the carbon storage period. This is particularly efficient in modern landfills, equipped to capture methane emissions. Otherwise, the methane emissions partially offset the benefit from the carbon storage in the landfill [19]. Nevertheless, both combustion and decomposition of wood result in the release of stored CO2 back to the atmosphere [17]. Some European countries do not allow wood deposition in landfill, because it is a combustible material. In these cases, wood residues have necessarily to be burned as biofuel or reprocessed into new products [20].

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4.4 METHODOLOGY FOR INTERVENTION IN HERITAGE STRUCTURES

4.4

Methodology for intervention in heritage structures

Europe is the world leader in the field of conservation of cultural heritage buildings, from the very first approaches, through the Renaissance and the Industrial Revolution, to the first restoration theories and the Milan School. Until the end of the 19th century, the value of cultural heritage buildings was mostly associated with their use. With the end of the First World War, internationalization of culture received a boost and the famous early Charters for Conservation appeared, such as the Athens Charter for the Restoration of Historic Monuments [21], the International Charter for the Conservation and Restoration of Monuments and Sites [22], and the European Charter of the Architectural Heritage [23]. The first conservation approaches are nowadays considered outdated. They resulted in accumulation of significant negative experience, such as blind confidence in modern materials and technologies, mistrust towards traditional materials and original structural resources, devaluation of ancient structural features, and insufficient importance attributed to diagnostic studies before an intervention. On the contrary, modern conservation respects the authenticity of ancient materials and building structure, meaning that interventions must be based on understanding the nature of the structure and the real causes of damage or alterations. Interventions are kept minimal, using an incremental approach, and much importance is attributed to diagnosis studies comprising historical, material, and structural aspects. Only recently, in 2001, these aspects were condensed in a document issued by the International Council of Monuments and Sites [24], recognizing that conventional techniques and legal codes or standards oriented towards the design of new buildings may be difficult to apply, or even inapplicable, to heritage buildings, and stating the importance of a scientific and multidisciplinary approach involving historical investigation, inspection, monitoring, and structural analysis. Many developments have been made recently, namely on investigation procedures for the diagnosis of historic fabric, e.g. Ref. [25] and structural analysis techniques, e.g. Ref. [26].

4.4.1

Principles

A multidisciplinary approach is obviously required in any conservation or rehabilitation project, and the peculiarity of cultural heritage buildings, with their complex history, requires the organization of studies and analysis in steps that are similar to those used in medicine, such as anamnesis, diagnosis, therapy, and controls, corresponding, respectively, to the condition survey, identification of the causes of damage and decay, choice of the remedial measures, and control of the efficiency of the interventions. Thus, no action should be undertaken without ascertaining the likely benefit and harm to the building. A full understanding of the structural behaviour and material characteristics is essential for any project. Diagnosis is based on historical information and qualitative and quantitative approaches. The qualitative approach is based on direct observation of the damage and material decay as well as historical and archaeological research, while the quantitative approach requires material and structural tests, monitoring, and analysis. Often, the application of the same safety levels used in the design of new buildings requires excessive, if not impossible, measures. In these cases, other methods, appropriately justified, may allow different approaches to safety.

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Therapy should address root causes rather than symptoms. Each intervention should be in proportion to the safety objectives, keeping intervention to the minimum necessary to guarantee safety and durability and with the least damage to heritage values. The choice between “traditional” and “innovative” techniques should be determined on a case-by-case basis with preference given to those that are least invasive and most compatible with heritage values, consistent with the need for safety and durability. At times, the difficulty of evaluating both the safety levels and the possible benefits of interventions may suggest “an observational method”, i.e. an incremental approach, beginning with a minimum level of intervention, with the possible adoption of subsequent supplementary or corrective measures. The characteristics of materials used in restoration work (in particular new materials) and their compatibility with existing materials should be fully established. This must include long-term effects, so that undesirable side effects are avoided. Finally, a most relevant aspect is that the value and authenticity of cultural heritage buildings cannot be assessed by fixed criteria because of the diversity of cultural backgrounds and acceptable practices.

4.4.2

Guidelines

A combination of both scientific and cultural knowledge and experience is indispensable for the study of cultural heritage buildings. The purpose of studies, research, and interventions is to safeguard the cultural and historical value of the building. The evaluation of a building frequently requires a holistic approach considering the building as a whole, rather than just the assessment of individual elements. The investigation of the structure requires an interdisciplinary approach that goes beyond simple technical considerations because historical research can discover phenomena involving structural issues while historical questions may be answered from the process of understanding the structural behaviour. Knowledge of the structure requires information on its conception, its constructional techniques, the processes of decay and damage, changes that have been made, and finally, on its present state. The recommended methodology for completing a project is shown in Fig. 4.3, where an iterative process is clearly required, between the tasks of data acquisition, structural behaviour, and diagnosis and safety. In particular, diagnosis and safety evaluation of the structure are two consecutive and related stages on the basis of which the effective need for and extent of treatment measures are determined. If these stages are performed incorrectly, the resulting decisions will be arbitrary: poor judgement may result in either conservative and therefore heavy-handed conservation measures or inadequate safety levels. Evaluation of the safety of the building should be based on both qualitative (documentation, observation, etc.) and quantitative (experimental, mathematical, etc.) methods that take into account the effect of the phenomena on structural behaviour. Any assessment of safety is seriously affected by the uncertainty attached to data (actions, resistance, deformations, etc.), laws, models, assumptions, and so on used in the research, and by the difficulty of representing real phenomena in a precise way. The methodology stresses the importance of an “Explanatory Report”, where all the acquired information, the diagnosis, including the safety evaluation, and any decision to intervene should be fully detailed. This is essential for future analysis of continuous processes (such as decay

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4.5 APPLICATION OF LIFE-CYCLE ASSESSMENT TOOLS TO EXISTING BUILDINGS

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Historical investigation (documents) Data acquisition

Survey of the structure = document Field research and laboratory testing Monitoring Structural scheme: model

Structural behaviour

Material characteristics Actions Historical analysis

Diagnosis and safety

Qualitative analysis Quantitative analysis

Explanatory report

Experimental analysis Masonry Remedial measures

Timber Iron and steel

Execution documents

Concrete

Fig. 4.3: International Council on Monuments and Sites (ICOMOS) methodology processes or slow soil settlements), phenomena of cyclical nature (such as variation in temperature or moisture content), phenomena that can suddenly occur (such as earthquakes or hurricanes), and for future evaluation and understanding of the remedial measures adopted in the present.

4.5

Application of life-cycle assessment tools to existing buildings

The LCA methodology is not designed to a specific kind of product, but can be applied to buildings, after the definition of a functional unit, for instance: “provide shelter to four people during a 50-year period, in predetermined comfort conditions”. ISO 14040:2006 [28] states “The essential property of a product system is characterized by its function and cannot be defined solely in terms of the final products”. The boundary of a unit process is determined by the level of modelling detail that is required to satisfy the goal of the study. Nevertheless, it is important to fix a reference flow in each product system, expressed in the amount of products needed to fulfil the predefined function. An LCA study comprises four phases, namely: (a) the goal and scope definition phase; (b) the inventory analysis phase; (c) the impact assessment phase; and (d) the interpretation phase. It is clearly stated in this standard that the reduction of LCA results to a single overall score or a number is made by means of weighting, which requires value choices, and therefore is not possible to be performed under a scientific basis. LCA of buildings, according to ISO 14040:2006 [28], adaptable to new and existing buildings, is a methodology used to assess the actual and potential impacts of the life cycle of a product, from raw material acquisition through production, use, end-of-life treatment, recycling, and final

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disposal. One of the core issues in LCA is the consideration of time. The time scale adopted in the analysis strongly influences the results of the assessment, as the impacts are distributed over a certain period of time, which influences its importance. In the specific case of heritage buildings, this feature may be highlighted. In fact, all data concerning building stock are time sensitive, presenting historical, present, and future time scales and very different time constants [10]. Through simulation, different periods can be linked, whereby the consequences of decisions can be appreciated. In practice, with respect to time issues, the period of the analysis should be determined according to the goals of the assessment. There are several options, including or excluding the existing structure: the analysis may start before the construction of the building, decades or centuries ago, with the calculation of all the present materials and the embodied energy related to their manufacturing and to the on-site construction, as well as all the conservation and maintenance operations performed over time. Alternatively, if the focus of the analysis is on the intervention and further utilization of the ancient structure, the defined timeline may start at present, avoiding the quantification of the existing materials, as well as the energy embodied in the building. This second option is suitable, for instance, for the comparative analysis of several different rehabilitation strategies, in order to assess their impacts, dismissing the consideration of the existing fabric, because of the fact that it is common to all the options, and therefore not producing any impact in the comparative results. Nevertheless, when the aim of the analysis is to assess the percentage of impacts related to the rehabilitation of the asset in its overall life cycle, the consideration of the existing structure may be important. The assessment of an ancient structure calls for an in-depth analysis of its features and materials, allowing an accurate quantification of the involved processes since the time of its original construction, which may be a time-consuming task. In many cases, rehabilitation has been shown to be a sustainable process, due to the remarkable increase of the use phase. According to Ref. [10], from the resource conservation perspective, preliminary calculations show that conservation and transformation strategies induce significantly smaller mass-flows than new constructions over the average life time. Nevertheless, the difficulties presented by the assessment of the existing building stock demands the development of specific methodologies, in order to make its inclusion in LCA simpler and more feasible. There is a need for rapid and comprehensive evaluation methods to measure the resource value of buildings. Some aspects that should be included in the assessment of ancient buildings are the resource value, the protection of cultural diversity, as well as the preservation of historical or technical information that may be encapsulated in the building [10].

4.6

Cultural heritage buildings and sustainability

The reuse of existing buildings to suit the needs of the present and future generations, while avoiding demolition and reconstruction, is one of the most sustainable forms of urban development [29].

4.6.1

Environmental impacts

The reuse of existing structures and materials is itself a sustainable option under an environmental perspective, owing to the avoidance of new products manufacturing, as well as the prevention of demolition operations and consequent residue production, with subsequent waste rubble and landfill.

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The increase of existing structures’ service life means that a past investment in energy and capital will be further amortized, avoiding new construction. Avoiding new construction, besides avoiding new material production, further transport, and energy consumption necessary up to the construction phase will also be saved, along with the reduction of associated pollution ([29]; [30]). Moreover, the conservation of significant heritage values, by means of a “green” adaptive reuse, provides economic, environmental, and social benefits, which are the core of sustainable development [29].

4.6.2

Economic impacts

Environmental and economic impacts are usually related. Avoiding new construction needs, while preventing materials and energy consumption related to a new construction, provides cost savings. Although there was a general line of thought that considered the conservation of historical centres and development of cultural heritage as restrictions to economic development, present analyses show a complementarity between both [31]. Practice has shown that a wellpreserved heritage provides visibility and recognition to a region’s value and potential, creates feelings of belonging and pride to the inhabitants, as well as valorization by foreigners. Regarding labour and employment issues, rehabilitation may play an important role, because of the intensive labour that it requires, compared with modern construction practice. To support this statement, Ref. [30] shows that rehabilitation of historic buildings in Norway allowed the creation of 16.5% more direct jobs, not to mention the 26.7% indirect jobs, in comparison with the new construction industry. Besides the direct effects of construction, the investment in cultural heritage produces effects in tourism and on intangible values, like the public popularity of history. Therefore, its secondary effects may be linked to the generation of economic value [32], although it may be hard to quantify it precisely, due to the multiplicity of influences and effects related to the phenomenon. The consideration of secondary effects should also be addressed by the specific assessment methodologies currently under development.

4.6.3

Social impacts

Social impacts, in the overall sustainability assessment, are a more recent concern, compared with economy and environmental issues. For this reason, and because impacts in society are frequently the result of multiple influences that are difficult to measure, this sustainability dimension is the least developed so far, remaining rather subjective. Nevertheless, some aspects of rehabilitation of cultural heritage buildings should be assessed and must be considered in the social analysis, namely: the promotion of collective memory, improving people’s relationship with history; the effects of job creation on local communities, especially the ones that need investment in economic activities that enable population retention in the region, avoiding emigration; and the importance of reviving ancient techniques as intangible heritage, namely through the preservation of traditional building know-how, that would otherwise be lost. Through rehabilitation process, local craftsmen are trained and have gained experience in traditional building techniques, and today some of these specialists are being “exported” to other sites or regions to assist in rehabilitation projects or educate other craftsmen. This is a secondary effect linked to the heritage strategy [12].

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Conclusion

Rehabilitation of cultural heritage buildings plays an important role in sustainability policies, mainly due to its role in: (a) the documentation of ancient knowledge, practice, and culture, among others, which should be used on actual source of improvement; (b) the reuse of existing structures, frequently made of sustainable building materials such as masonry and wood; (c) the promotion of historic values and local valorization, which produce positive impacts both in the economy and the society; and (d) the promotion of job creation, because of the labour-intensive techniques used.

References [1]

[2] [3] [4]

[5]

[6] [7]

[8]

[9] [10] [11]

[12] [13]

European Commission. 2010. Europe, the world’s No 1 tourist destination – a new political framework for tourism in Europe, European Commission, Brussels, COM, 352, http:// eur-lex.europa.eu/ ECORSYS SCS Group. 2009. Study on the Competitiveness of the EU tourism industry, ECORYS Macro & Sector Policies, Rotterdam, http://ec.europa.eu/ FEMA. 2011. Fact sheet – Mitigation’s value to society, Federal Emergency Management Agency Washington, D.C., USA. MMC. 2005. Natural Hazard Mitigation Saves: An Independent Study to Assess the Future Savings from Mitigation Activities. Volume 1 – Findings, Conclusions and Recommendations. Volume 2 − Study Documentation, Multihazard Mitigation Council of the National Institute of Building Sciences Washington, D.C., USA. The World Bank and United Nations. 2010. Natural Hazards, Unnatural Disasters: The Economics Of Effective Prevention. The World Bank and The United Nations, Washington, DC, USA. Sanghi, A. 2010. Presentation on “Natural hazards, unnatural disasters: The economics of effective prevention”, The World Bank, Bangkok, Thailand. UNISDR. 2009. Global Assessment Report on Disaster Risk Reduction. United Nations International Strategy for Disaster Reduction Secretariat, United Nations, Geneva, Switzerland, ISBN 9789211320282, 207 pp. ICCROM. 2005. Definition of Cultural Heritage. Revised by Jokilehto, J., Definition of Cultural Heritage: References to documents in history, ICCROM Working Group “Heritage and Society” http://cif.icomos.org/pdf_docs/Documents%20on%20line/ Heritage%20definitions.pdf. Dupagne, A., Mathus, P., Servotte, C. 2001. Les espaces urbains – Extrait du rapport final du thème 1.3 – les espaces, LEPUR-ULg, Liège, Septembre 2001. Kohler, N., Hassler, U. 2002. The building stock as a research object. Build. Res. Inf., 30(4): 226–236. UNESCO: World Heritage Committee. 1994. The Nara Document on Authenticity, International Council on Monuments and Sites, 12–17 December 1994, Phuket, Thailand, http://www.international.icomos.org/charters/nara-e.pdf Bowitz, E., Ibenholt, K. 2009. Economic impacts of cultural heritage – research perspectives. J. Cult. Herit., 10: 1–8. Grimm, C.T. 1985. Durability of brick masonry: a review of literature. In: Masonry: Research, Application, and Problems. Grogan, J.C., Conway, J.T. (eds.), ASTM STP 871, American Society for Testing and Materials, Philadelphia, PA, USA, 202–234.

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[14] Reddy, B.V.V., Jagadish, K.S. 2003. Embodied energy of common and alternative building materials and technologies. Energ Buildings, 35(2): 129–137. [15] Verhelst, F., Kjaer, E., Jäger, W., Middendorf, B., Van Balen, K., Walker, P. 2011. Masonry – sustainable, contemporary and durable: anachronism, bold statement or visionary outlook? Mauerwerk, 15(2): 118–122. [16] Börjesson, P., Gustavsson, L. 2000. Greenhouse gas balances in building construction: wood versus concrete from life-cycle and forest land-use perspectives. Energ Policy, 28(9): 575–588. [17] Buchanan, A., Levine, S. 1999. Wood based building materials and atmospheric carbon emissions. Environ. Sci. Policy, 2(6): 427–437. [18] Sathre, R., Gustavsson, L. 2009. Using wood products to mitigate climate changes: external costs and structural change. Appl. Energ., 89: 251–257. [19] Lippke, B., Wilson, J., Meil, J., Taylor, A. 2010. Characterizing the importance of carbon stored in wood products. Wood Fiber Sci., 42 (Corrim Special Issue): 5–14. [20] Dodoo, A., Gustavsson, L., Sathre, R. 2009. Carbon implications of end-of-life management of building materials. Resour. Conserv. Recy., 53: 276–286. [21] International Council on Monuments and Sites. 1931. Athens Charter for the Restoration of Historic Monuments – 1931. http://www.icomos.org/en/charters-and-texts/179-articles-en-francais/ressources/charters-and-standards/167-the-athens-charter-for-the-restoration-of-historic-monuments [22] International Council on Monuments and Sites. 1964. International Charter for the Conservation and Restoration of Monuments and Sites (1964). http://www.icomos.org/ char-ters/venice_e.pdf [23] International Council on Monuments and Sites. 1975. European Charter of the Architectural Heritage, 1975. http://www.unescobkk.org/fileadmin/user_upload/culture/cultureMain/Instru-ments/European_Charter.pdf [24] ICOMOS. 2003. Recommendations for the Analysis and Restoration of Historical Structures, ISCARSAH. [25] Binda, L., Saisi, A., Tiraboschi, C. 2000. Investigation procedures for the diagnosis of historic masonries. Constr. Build. Mater., 14(4): 199–233. [26] Lourenço, P.B., Mendes, N., Ramos, L.F., Oliveira, D.V. 2011. Analysis of masonry structures without box behavior. Int. J. Archit. Herit., 5: 369–382. [27] U.S.G.S. 2012. U.S. Geological Survey. http://www.usgs.gov/ (accessed 27/01/2012). [28] ISO 14040. 2006. Environmental Management – Life Cycle Assessment – Principles and Framework. International Organization for Standardization, Geneva, Switzerland. [29] Yung E.H.K., Chan, E.H.W. 2012. Implementation challenges to the adaptive reuse of heritage buildings: towards the goals of sustainable, low carbon cities. Habitat Int., 36(3): 352–361. [30] Gražulevicˇiu-te, I. 2006. Cultural heritage in the context of sustainable development. Environ. Res. Eng. Manage., 37: 74–79. [31] Fusco Girard, L., Nijkamp, P. 1997. Le valuazioni per lo sviluppo sostenibile della cittá e del territorio. FrancoAngeli, Milano. [32] Stubbs, M. 2004. Heritage-sustainability: developing a methodology for the sustainable appraisal of the historic environment. Plan. Prac. Res., 19(3): 285–305.

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69 Chapter

5 Measuring Sustainability and Life-Cycle Assessment

John E. Anderson, Dr., PE; Technische Universität München, Munich, Germany. Frances Yang, SE, LEED AP, Structures and Sustainability Specialist, Arup, San Francisco, CA, USA. Contact: [email protected]; [email protected]

5.1

Introduction

Structural engineers make design decisions based on objective criteria. From the strength of materials to finite element analysis, engineers rely on quantifiable metrics to design structural systems. With the emergence of sustainability objectives within the design profession, engineers have a unique opportunity to utilize their analytical expertise to produce structural systems with a positive impact on the natural environment. This chapter presents sustainability goals, an overview of lifecycle assessment (LCA), life-cycle assessment case studies answering common engineering questions, green design rating systems, and emerging trends in measuring environmental performance. The concept of sustainability has achieved widespread acceptance and support from design professionals and in particular from the international structural engineering community (e.g., American Society of Civil Engineers (ASCE) Structural Engineering Institute, Sustainability Committee; IABSE Working Commission 7: Sustainable Engineering). Although sustainability has become a central pillar of contemporary design, there remain significant challenges in achieving sustainability objectives due to the opaqueness and qualitative nature of terminology used and its numerous interpretations. The U.N. Report of the World Commission on Environment and Development defines sustainable development as “development that meets the needs of the present without compromising the ability of future generations to meet their own needs” [1]. The ASCE defines sustainable development as “the process of applying natural, human, and economic resources to enhance the safety, welfare, and quality of life for all of society while maintaining the availability of the remaining natural resources” [2]. An overarching challenge for sustainable design is in verification: defining and quantifying metrics in order to achieve sustainability objectives. In addition to defining and quantifying sustainability metrics, it is necessary to ensure that all impacts and a systems-based approach are considered. For example, reducing the operational energy use of a building alone omits the trend of increasing building size [3], increasing use

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of electricity [4], and increasing material quantities required for additional structural materials and insulation [5]. Thus, focusing solely on operational energy use may be an insufficient metric for reducing net energy consumption. Further, systems-based analysis is required to ensure that sustainability goals do not lead to unsustainable results. To illustrate, “green roads” (i.e., roadways designed using sustainable guidelines [6]) focus attention on infrastructure for one transportation system (i.e., personal automobiles) rather than considering more environmentally preferred modes (e.g., mass transit, walking, biking). A system-wide analysis as a prerequisite can offer better overall solutions to meet sustainability objectives. Consequently, complex and integrated methods and tools are required to understand interrelated impacts and ensure that actual environmental improvements are achieved. This chapter presents the state-of-the-art methods for measuring sustainability of structures. Contemporary sustainability goals are reviewed, followed by a detailed presentation of “LCAthe most” common and comprehensive methodology for quantifying environmental performance of a product or process. The chapter then presents the latest research from LCA for structures—enabling structural engineers to quickly identify areas for environmental improvement during the design process. Common questions for practicing structural engineers are then answered. Finally, green rating systems for buildings and infrastructure are discussed along with emerging global trends in the construction industry. The chapter aims to provide the reader with practical knowledge on how structures relate to overall sustainability objectives and how tools such as LCA can be utilized to improve the environmental performance of structural design.

5.1.1

Sustainability goals

There are numerous metrics to quantify the three aspects of sustainability—social, economic, and environment. The European Union uses ten sustainable development indicators (SDIs) and associated indicators to track progress of sustainable development. Their themes and associated indicators (in parentheses) are socioeconomic development (real gross domestic product [GDP] per capita), sustainable consumption and production (resource productivity), social inclusion (risk of poverty or social exclusion), demographic changes (employment rate of older workers), public health (life expectancy and healthy life years), climate change and energy (greenhouse gas emissions, consumption of renewables), sustainable transportation (energy consumption of transport relative to GDP), natural resources (abundance of common birds, conservation of fish stocks), global partnership (official development assistance), and good governance (no indicator) [7]. Common metrics for LCA tend to concentrate on environmental impacts. They include global warming, stratospheric ozone depletion, acidification, eutrophication, photochemical smog, terrestrial toxicity, aquatic toxicity, human health, resource depletion, land use, and water use [8]. Sustainability consequently comprises numerous metrics, which can have interrelated and inverse relationships. To illustrate the process of defining sustainability goals, one metric is examined in detail: greenhouse gas emissions. Contemporary environmental targets predominately focus on global climate change metrics because climate change is currently considered to be the most important environmental issue with severe implications and time-sensitive mitigation and adaptation strategies. Scientific research substantiating global climate change and recommendations for mitigation and adaptation have been put forth by the Intergovernmental Panel on Climate Change (IPCC). Based on their research, the IPCC outlines six ranges of global changes based on when CO2 and CO2-

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equivalent concentration levels are stabilized. For each range of stabilization, the change in global CO2 emission in 2050 (as a percent of 2000 emissions), global average sea level rise, and global average temperature increase are presented (see Table 5.1) [9]. According to the IPCC, the lowest feasible CO2 concentration level at stabilization (Category I) represents a CO2 equivalent level of 445 to 490 ppm with CO2 emissions peaking between 2000 and 2015. This corresponds to global CO2 emissions in 2050, which are −50 to −85% of 2000 emissions, an average temperature change of 2.0 to 2.4°C, and an average sea rise of 0.4 to 1.4 m [9]. These findings gave way to the Kyoto Protocol [10], an international treaty by numerous governments to mitigate climate change as a part of sustainable development. Consequently, the scientific results and recommendations of the IPCC form the basis for a majority of environmental goals set by governmental, non-governmental, and private organizations. For example, in keeping with the recommendations of the IPCC, the European Union is aiming to reduce CO2 emissions by 80 to 95% (based on 1990 emissions) by 2050 [11]. These goals also help organizations specifically concerned with the construction industry (e.g., Architecture 2030 [12]) to define environmental objectives by concentrating on climate change indicators. The 2030 Challenge sets forth the goal of reducing energy use by 60% for all new buildings and aims for carbon neutral buildings by 2030 [12]. The above is an example of the motivation for one environmental goal: climate change mitigation. After defining environmental objectives, it is then crucial to determine whether these objectives are being met based on the chosen metrics and measurement tools. Choosing proper metrics and tools is greatly aided by LCA—the most widely used methodology and framework for environmental assessment. The following section examines LCA in detail.

5.2

Life-cycle assessment

Which structural material, concrete or steel, is better for the environment? Producing concrete requires extensive energy to convert limestone to clinker. Steel structures, on the other hand, often lack thermal mass, thereby possibly losing an opportunity to reduce the operational energy requirements of the building. The materials also differ in their end-of-life phase. Steel can be recycled to create a similar quality material, whereas concrete can only be down-cycled (a process whereby after recycling the final material is of lower quality or value than the initial input) to a material commonly used as sub-base aggregate. What might first appear to be a simple question is in fact extremely complex and requires advanced analysis tools to determine a quantitative and conclusive answer. To help with this challenge, many in the design industry have turned to LCA Life-cycle assessment is a methodology and framework to determine “the environmental aspects and potential impacts throughout a product’s life (i.e., cradle-to-grave) from raw material acquisition through production, use, and disposal” (see Fig. 5.1) [13]. International standards for LCAs are outlined by the International Organization for Standardization in ISO 14040, principles and framework, and ISO 14044, requirements and guidelines [13,14]. These standards cover the four phases of an LCA: goal and scope definition, inventory analysis, impact assessment, and interpretation [13,14] (see Fig. 5.2).

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400–440

440–485

485–570

570–660

660–790

II

III

IV

V

VI

2060–2090

2050–2080

2020–2060

2010–2030

Table 5.1. Long-term perspective for CO2 stabilization levels [9]

855–1130

710–855

590–710

535–590

490–535

2000–2020

2000–2015

350–400

I

445–490

Peaking year for CO2 emission (year)

Category CO2 concen- CO2-equivalent tration at concentration stabilization at stabilization (2005 = 379 including GHGs ppm) and aerosols (2005 (ppm) = 375 ppm) (ppm)

+90 to +140

+25 to +85

+10 to +60

–30 to +5

–60 to –30

–85 to –50

Change in global CO2 emissions in 2050 (percent of 2000 emissions) (%)

4.9–6.1

4.0–4.9

3.2–4.0

2.8–3.2

2.4–2.8

2.0–2.4

Global average temperature increase above pre-industrial at equilibrium, using “best estimate” climate sensitivity (°C)

1.0–3.7

0.8–2.9

0.6–2.4

0.6–1.9

0.5–1.7

0.4–1.4

Global average sea level rise above preindustrial at equilibrium from thermal expansion only (m)

5

9

118

21

18

6

Number of assessed scenarios

72 CHAPTER 5. MEASURING SUSTAINABILITY AND LIFE-CYCLE ASSESSMENT

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5.2 LIFE-CYCLE ASSESSMENT Recycling/ Reuse/ Disposal Resource extraction

Demolition

Life cycle of building products

Manufacturing

Occupancy/ Maintenance On-site construction

Fig. 5.1: Diagram of the life-cycle assessment process for building products. Graphic courtesy of Athena Sustainable Materials Institute The objective of the ISO 14040 is to ensure consistency, transparency, and robustness in the implementation of an LCA. As per the ISO, there are four main phases of an LCA. The first phase, defining the goal and scope, is foundational for carrying out the next three phases. In the second phase, the inventory analysis defines the process flows within the system and compiles the inputs (resources) and outputs (emissions) to and from the environment over its life-cycle into an inventory. In the impact assessment, one relates the inventory items to environmental impact categories, called “classification,” and applies a set of equivalency factors to arrive at the metrics of the chosen set of impact categories, called “characterization.” The general equation for characterization is: Impact = Σ (characterization factor × inventory item)

Life cycle assessment framework

Goal and scope definition

Inventory analysis

Interpretation

Impact assessment

Fig. 5.2: Four main phases of a lifecycle assessment [13]

Figure 5.3 illustrates this relationship between inventory data and impact categories.

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Process

Resource use and emissions

Environmental impacts

Coal use

Abiotic depletion (fossil fuels)

Carbon dioxide

Global warming potential

1 25

Methane

Summer smog

Coal fired electricity Sulfur dioxide

1.2

Acidification

0.5 Nitrogen dioxide

Eutrophication

Other emissions...

Other impacts...

Fig. 5.3: Illustration of the relationship between inventory data and impact categories for coal fired electricity. The numbers represent the different weights of the emission on the impact category [15] Looking specifically at global warming potential (GWP), the equation that relates GWP to the inventory items of carbon dioxide (CO2) and methane (CH4) is: GWP = 1 × CO2 + 25 × CH4 + … where CO2 and CH4 are in kg and GWP is in units of kg CO2 equivalent. Similarly, for acidification potential (AP), the equation is: AP = 1.2 × SO2 + 0.5 × NO2 + … where SO2 and NO2 are in kg and AP is in units of moles of H+ equivalents. The figure also demonstrates how one inventory item can contribute to more than one impact factor. For instance, while methane relates to GWP, it is also the base unit for smog potential. It should also be noted that carbon dioxide and methane, and sulphur dioxide and nitrogen dioxide, are not the only emissions that contribute to GWP and AP, respectively. There are numerous others that are accounted for in the impact characterization equations. The factors for GWP are typically based on the International Panel for Climate Change recommendations. Many other

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inventory items under “other emissions” relate to the impact categories shown, while the inventory items shown also relate to “other impacts.” If performing a comparison between options, one could stop at the impact categories and move to interpretation, where data quality and sensitivity of results to the various assumptions and uncertainty are explored. Alternately, additional steps of normalization and weighting could be applied to further the impact assessment and refine the final comparison. With normalization and weighting, however, certain points of view are introduced that are not always appropriate for the decision at hand. Thus, many LCA practitioners encourage presenting results according to the raw impact category metrics.

5.2.1

Metrics

The metrics of an LCA depend on the impact categories one chooses for reporting LCA results. The most common impact categories, relevant metrics (in parenthesis), and what they mean are provided below [15]: • Global warming potential (kg CO2 equivalent)—increase in the temperature of the Earth’s atmosphere and oceans [8] • Acidification (moles of H+ equivalent)—increase in acidity of oceans, freshwater, and soil, thus affecting aquatic life [8] • Eutrophication (kg N or PO4 equivalent)—excess nutrients in water bodies leading to oxygen depletion and algae growth, which adversely affect aquatic life [8] • Stratospheric ozone depletion (kg CFC-11 equivalent)—reduction of the ozone layer that protects against UV rays [8] • Photochemical ozone creation (kg NOx or C2H6 equivalent)—air pollution affecting human health [8] Other indicators commonly provided in an LCA include: renewable and non-renewable primary energy, water consumption, waste disposal, toxicity to ecosystems and humans, resource depletion (covering various minerals, scarce chemical elements), and radioactivity [15]. The set of categories most used in the USA is defined by EPA (US Environmental Protection Agency); TRACI (Tool for the Reduction and Assessment of Chemical and Other Environmental Impacts) EPA’s TRACI methodology and include: the five listed above, plus three human health indicators: air pollutants (i.e., particulate matter), cancer and non-cancer, and eco-toxicity [16]. Designers should be aware that other impact categories and classification systems are more popular in other countries.

5.2.2

Methodology

There are three approaches to LCAs (i.e., process-based, economic input–output-based, and hybrid-based [17]) that can be selected to fit the goals and resources of the LCA. Each approach has advantages and disadvantages and can yield very different results. Process-based The process-based LCA was developed by the Society of Environmental Toxicology and Chemistry and the U.S. Environmental Protection Agency using the concept of material and energy

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balances for specific processes [17]. While process-based LCAs are extremely useful in determining the environmental performance of a product or process, there are also several challenges to this methodology. The first step in the process requires that the scope, or boundary, of the LCA be defined. This implicitly creates an omission error (i.e., truncation error) in the analysis as specific processes are not included in the final study. At the same time, the larger criticism of process-based LCA is that it is extremely time-consuming and financially expensive [17]. The most popular set of tools that uses process-based LCA for North America comes from the Athena Sustainable Materials Institute. Economic input–output In order to address the challenges of process-based LCA, an alternative method, economic input–output LCA, was developed [17]. Economic input–output (EIO) LCA provides a more general analysis and is based upon the sectors of the economy as defined by economic input– output tables [17]. Thus, this methodology allows for a relatively quick and inexpensive analysis of basic LCA questions and eliminates the truncation error. A challenge for the EIO LCAs is the requirement for accurate and up-to-date economic input–output tables. Moreover, as the methodology is based on sectors of the economy, comparisons within sector groups (e.g., two steel plants, or differentiating between gypsum and cement) are likely unfeasible. A free and publicly available tool is the EIO–LCA developed by the Green Design Institute of Carnegie Mellon University [18]. Hybrid The third methodology, a hybrid LCA, melds process-based and EIO LCAs together to provide process-specific results (e.g., the two steel plants or difference between cement and gypsum) in a timely and inexpensive manner, while minimizing the truncation error. The specific use of one methodology over the other depends on the resources (i.e., finance, time, in addition to the quality and quantity of the process and economic data) on hand and the specific question to be answered. In the end, the multiple methods offer a wide range of techniques to arrive at quantitative and comparable environment performance results. In the USA, the only published data set produced by the hybrid method is CEDA® Comprehensive Environmental Data Archive.

5.2.3

Life-cycle inventory databases

Analyzing structural design choices based on environmental criteria is facilitated through LCA, which in turn necessitates access to high-quality and verifiable data sources. In lieu of performing a full LCA (i.e., defining the goal and scope, performing a life-cycle inventory (LCI), assessing the impacts (LCIA), and interpreting the results), conducting an LCI and determining the inherent margins of error alone is often sufficient in making design decisions. Regardless of whether a full LCA or only an LCI analysis is completed, LCI data for materials and processes are required. The numerous public and private LCI databases are summarized below to aid the readers in conducting their own review of different structural choices based on environmental performance. One of the most popular inventories for construction materials utilized by designers worldwide is the Inventory of Carbon and Energy (ICE) created by the University of Bath and made

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available through BSRIA [19]. The ICE summarizes survey findings of embodied energy and carbon emission factors across industry and academic literature for more than 200 construction materials. In general, embodied energy factors are similar across countries, but emission factors can vary if the fuel profile of a given region is different from that in the UK. In the USA, the federal government has created a publicly available LCI database to assist LCA practitioners [20]. The U.S. Life Cycle Inventory Database focuses on providing transparent and consistent LCI data. Support for the database is provided by the federal government, private companies, and professional organizations [20]. In Europe, the European Commission Joint Research Centre offers the ELCD core database, another LCI database [21]. In addition, the Federal Republic of Germany has created a database of 650 different building materials and construction and transportation processes [22]. The United Nations Environment Programme has also created a useful summary of global LCI data resources [23].

5.2.4

Software tools

LCA software tools allow users to utilize a variety of databases to perform complex environmental analysis of products, systems, or processes. The array of tools in existence falls on a spectrum of intended use, ease of use, allowance for customization, and cost among many other characteristics. On the one hand, there are tools that aim to reduce the computation and research efforts required in performing an LCA. They essentially perform mini-LCAs for common materials, assemblies, or products used in buildings and have made numerous assumptions to simplify the LCA process for non-LCA professionals. These include Building for Environmental and Economic Sustainability (BEES) [24] and Athena Sustainable Materials Institute’s Impact Estimator—a simplified spreadsheet version of EcoCalculator [25]. These are free and publicly available LCA tools created especially for design practitioners. Both tools also currently use process-based LCA (although BEES is shifting to a hybrid LCA model) and focus heavily on structural materials. Another free resource is the economic input–output tool by the Green Design Institute at Carnegie Mellon University [18]. In contrast, privately developed LCA software packages are numerous and include GaBi [26], LEGEP [27], SimaPro [28], and Umberto [29]. These allow for more customization, as they are meant for use by LCA practitioners working with intimate knowledge of a product supply chain and manufacturing process. If the tools specific for buildings lack particular materials or products, a custom material or product would have to be modelled to obtain usable LCA data. These software packages can also be costly. Further developments in LCA software are heavily focused on embedding LCA information directly into building information modelling (BIM), thereby integrating LCA information more intimately into the building design process. In addition, openLCA is a freely available LCA software, which allows users to conduct an LCA using either private or public LCI databases [30].

5.3

Life-cycle assessment case studies of structures

Substantial research has been published based on LCAs, which can provide interesting insights into the design of environmentally optimized structural systems. This section outlines

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research, case studies, and findings of interest to structural engineers. As stated earlier, LCA is a measurement tool and, as such, case studies using LCA offer quantified answers to questions commonly asked by structural engineers. The information presented acts as a guide for preliminary decisions based on LCA and can be used as a first reference by practicing engineers (see Table 5.2). What is the relative effectiveness of different structural design strategies? An LCA was performed to determine the potential of structural design strategies to minimize greenhouse gas emissions [31]. The five design strategies examined were design for materials (i.e., using environmentally preferred materials), design for recycling (i.e., end-of-life recycling for the materials), design for efficiency (i.e., maximizing the efficiency of the structural system to the highest degree possible), design for energy (i.e., minimizing operational energy use), and design for adaptability (i.e., providing a structural system with redundancy to accommodate future uses). The LCA results showed that maximizing the thermal mass of the structural system (i.e., design for energy) offered the largest possible greenhouse gas reductions: 8% savings including both operational and embodied emissions. Focusing solely on embodied emission, design for materials showed the most dramatic emission reductions of 44% for concrete and 41% for steel. However, for steel, this optimal value relies on reuse and not traditional recycling, which is not a readily available practice. Thus, designing for materials using high percentages of complementary cementitious materials (CCM) in the concrete mix was found to be the best structural strategy for reducing greenhouse gas emissions [31]. Reinforcing the importance of high CCM (i.e., low cement) concrete mixes, Ref. [32] reports on a study conducted on behalf of the Concrete Centre in the UK. The study compared the embodied carbon of eight different steel and concrete structural systems for three different building types: office, hospital, and school. The analysis found that there was a greater difference between embodied carbon of building results between using high cement and low cement concretes than between whether the structural system was of concrete or steel. The cradle-togate embodied carbon of any system could be made lower or higher than another simply by specifying higher or lower cement in the concrete. Furthermore, on average 50% of the embodied carbon came from the structural elements, and the margin of difference that is within the control of the structural engineer was found to be as great as the margin due to different carbon calculation methodologies. These last two results convey the importance of the decisions made by the structural engineer in influencing the cradle-to-gate carbon emissions of the most common commercial building types [32]. Which is better: steel- or concrete-framed structure? The life-cycle impacts of steel- and concrete-framed structures were compared in Ref. [33]. The authors found that during the construction phase, the concrete-framed structure had higher energy use, CO2, CO, NO2, particulate matter, SO2, and hydrocarbon emissions; whereas the steel-framed structure had higher emissions of heavy metals (Cr, Ni, Mn) and volatile organic compounds [33]. The research found that accounting for the entire life cycle of the two buildings (i.e., production, construction, operation, and end-of-life) had similar energy use and emissions [33].

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Source

Finding 1

Finding 2

Finding 3

Anderson and Silman, 2009 [31]

Design for energy offers the largest GHG (greenhouse gas) savings when including operational and embodied energy

Using CCMs (complementary cementitious materials) offers the largest GHG savings when considering embodied energy only

There are numerous different design strategies for the structural engineer to reduce GHG emissions

Kaethner There is a greater difand Buckley, ference between the 2010 [32] embodied carbon in using high cement and low cement concretes than between whether the structural system was concrete or steel

The margin of difference that is within the control of the structural engineer is as great as the margin due to different carbon calculation methodologies

Approximately 50% of the embodied carbon came from the structural elements

Guggemos During construction, and Horvath, concrete-framed struc2005 [33] tures have higher energy use, CO2, CO, NO2, particulate matter, SO2, and hydrocarbon emissions

During construction, steel-framed structures have higher emissions of heavy metals (Cr, Ni, Mn) and volatile organic compounds

Accounting for all phases of a building from manufacturing to end-of-life, concreteand steel-framed buildings had similar energy use and emissions

Masanet et al., 2012 [34]

Reinforced concrete and structural steel buildings require similar amounts of energy and result in similar levels of CO2 emissions when assessed over the full building life-cycle

Changes in climate zones and technological options in material pathways could switch the superior option

–

Fernandez, 2008 [35]

Using the Alcorn coefficients, the steel building embodies the equivalent of 27 years of operating energy consumption and 12 years of operating CO2 emissions The timber building embodies the equivalent of 11 years of operating energy consumption and stores the equivalent of 3.6 years of operating CO2 emissions

Using the GaBi coefficients, the steel building embodies the equivalent of 19 years of operating energy consumption and 14 years of operating CO2 emissions, while the timber building embodies the equivalent of 8 years of operating energy consumption and 8 years of operating CO2 emissions

For embodied energy, the Alcorn results average 32% higher than the GaBi results, for the embodied CO2, the Alcorn results average 62% lower than the GaBi results, major differences in the results are due to different approaches to CO2 sequestration in timber materials

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CHAPTER 5. MEASURING SUSTAINABILITY AND LIFE-CYCLE ASSESSMENT

Finding 1

Finding 2

Finding 3

Marceau and The ICF house outperVanGeem, formed the wood-framed 2008 [36] house due to a higher R-value of the insulation and thermal mass of the concrete

Most of the environmental load is from the household use of natural gas and electricity during the lifetime of the houses, which are primarily a function of climate and occupant behavior

Most of the environmental impacts from construction materials are due to aluminum siding, ceramic tiles, paint, roof shingles, polystyrene insulation, cement-based materials, steel, and cast iron

Kofoworola and Gheewala, 2009 [37]

The operational phase accounts for 52% of global warming potential, 71% of photo-oxidant potential, and 66% of total acidification potential

For the embodied impacts, concrete and steel were responsible for 74 and 24% of global warming potential, 30 and 41% of photo-oxidant formation potential, and 42 and 37% of acidification potential, respectively

–

Wu et al., 2012 [38]

The use-phase of the building accounted for 86% of energy consumption and 81% of CO2 emissions

For embodied impacts, concrete and steel consume the most energy at 52% and 38%, respectively

–

Stephan et al., 2012 [39]

Embodied energy can be up to 59% of total energy; compared to operational energy at only 41%

Low (operational) energy homes (e.g., passive homes) shift energy use from the operational phase to the embodied phase

It is important to include the recurrent embodied energy for maintenance and use a comprehensive LCA tool

Junnila et al., 2006 [40]

The proportion of energy used and emissions for each phase of the building is comparable between the USA and Europe

For office buildings in the USA and Europe, the use-phase dominates energy demand (70%) and emissions

The European building has lower energy demands (a third), CO2 emissions (a half), and NOx emissions (a third)

Siantonas and Fieldson, 2008 [41]

Differences in the assumptions, scope, and boundaries of two case studies are highlighted to demonstrate sensitivity in results and that, if taken out of context, comparisons between studies can be unfair

Both case studies demonstrate that as GHG emissions are reduced by progression towards zero carbon operation, emissions embodied in the materials and processes of the construction supply chain become increasingly important

–

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Source

Finding 1

Finding 2

Finding 3

Comber et al., 2010 [42]

Includes the effect of seismic systems within active earthquake locations in order to achieve a more accurate sense of a building’s full lifecycle impacts

Pairs cost of structural and non-structural elements with environmental impacts using EIO–LCA

A more robust structural system that limits damage in non-structural elements can save approximately 18%–25% over a 50year lifespan

Yang, 2011 [43]

Describes three case studies using LCA to evaluate structural systems for different purposes: (1) avoided impacts, (2) comparing conventional structural systems, and (3) design for deconstruction

Third case study showed that based on a discounting methodology, the greater amount of material needed for a deconstructable floor system counteracted all reuse benefits

Second case study demonstrated a greater significance in reducing cement within the concrete mix than in choosing any particular steel/concrete system—same study as [32].

Table 5.2. Significant LCA results for structural engineers A more recent study commissioned by the Portland Cement Association, confirms this finding [34]. The difference between steel and concrete options for the same building was not statistically significant. Meanwhile, the study found that changes in climate zones and technological options in material pathways could switch the superior option, meaning that the material supply chain and climate-appropriateness of the design matter most. For structural engineers, this means that specifying more environmentally friendly options for how a material is manufactured and delivered, and designing a more climate-responsive system, is more influential than choosing between steel and concrete [34]. Is wood always better than steel or concrete? A study in New Zealand compared four different types of construction for the same six-storey office building [35]. The first two types of construction were typical timber and a more intensive use of timber, while the third and fourth were steel and concrete construction, respectively. Initially, this investigation found that the building with greatest use of timber had a net negative GWP and was far less than the steel and concrete options, and even the traditional timber option. Taking the analysis a step further, the study used a different set of GWP factors that did not include the carbon sequestration that occurs during tree growth, since this accounting method is controversial. The result was that the timber options were still less than concrete and steel, but were not nearly so different, and the intensive use of timber option was no longer net negative for GWP [35]. At the other extreme, a more recent study compared a two-story, wood-framed, single-family home to one built using insulated concrete forms (ICF) [36]. It found that over the total life cycle, the ICF home used less energy. Most of the environmental load was from the household use of natural gas and electricity during the lifespan of the homes, primarily a function of climate and occupant behavior. Secondary to the operational energy, the environmental impacts

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from construction materials were mostly due to aluminum siding, ceramic tiles, paint, roof shingles, polystyrene insulation, cement-based materials, steel, and cast iron [36]. Although the two different studies give mixed results, together they show how drawing different boundaries in the LCA study leads to different results. The first investigation utilized LCIs that used different boundaries on the life-cycle of the wood products. And while the first only considered cradle-to-gate, the second analysis extended the life-cycle study of the building to include the operational phase. Together, the studies also offer an overarching message that materials affect the total life-cycle impacts on two counts: (a) their embodied impacts and (b) their participation in the energy performance of the building. It should be noted that, as with evaluating any research results, the stated conclusions should take into account any bias that might come from the researchers or the project sponsors. Which life cycle has the greatest environmental impacts? Researchers conducted an LCA of an office building in Thailand and found that the operational phase of the building accounted for 52% of global warming potential, 71% of photo-oxidant potential, and 66% of total acidification potential [37]. The report also showed that for the embodied impacts, concrete and steel were responsible for 74 and 24% of global warming potential, 30 and 41% of photo-oxidant formation potential, and 42 and 37% of acidification potential, respectively [37]. Another study of an office building, this time in China, illustrated that the usephase of the building accounted for 86% of energy consumption and 81% of CO2 emissions; the building material production was the second largest source of energy consumption at 12% [38]. However, the latest research revises these earlier results and shows that embodied energy can dominate operational energy (59% compared to 41%) [39]. Furthermore, the tendency to focus on low operational energy buildings was shown to shift energy from the operational phase to the embodied phase owing to increase in materials needed in the construction of low operational energy buildings [39]. These findings show the importance of accounting recurrent embodied materials (i.e., maintenance and replacement) and using a comprehensive LCA to remove truncation errors [39]. While studies traditionally found the operational phase to dominate environmental impacts, recent studies utilizing comprehensive input–output-based LCA and accounting for replacement of materials and components show the increasing importance of embodied impacts. Taking the life-cycle view a step further, a tool called EnVISA estimates the anticipated embodied carbon (and cost) from probable seismic losses. The conclusions show that a more robust structural system can provide approximately 18 to 25% savings in embodied carbon incurred from repairs and replacements due to seismic damage when using a traditional system designed to minimum code requirements. The results show how much additional embodied carbon the probable damage of natural hazards such as earthquakes can incur, when it is specifically accounted for, and offers a methodology for the accounting. It also showed how protective systems designed to performance levels higher than code requirements can significantly limit damage to the non-structural building elements over a 50-year lifespan [42]. What factors affect environmental impacts the most? As highlighted above, climate and occupant behavior play the leading role in total environmental impacts. On top of this, some other studies have found that location, use type, and how the LCA is conducted are major factors of influence.

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An LCA was conducted for office buildings in the USA and Europe [40]. The research found that for each location, the proportion of emissions for each building phase was similar. The usephase of the building resulted in 70% of the energy consumption (based on a 50-year lifespan) and dominated all emissions aside from PM10 emissions [40]. The European building was found to use a third of the energy, emit half the CO2, and one-third of the NOx of the US building, illustrating the overall differences among the office buildings [40]. The authors found that the differences result in part from the varying energy mixes used for electricity production and the use of combined heat and power production in the European building [40]. A study of two different warehouse buildings showed that differences in the assumptions, scope, and boundaries can lead to drastically different results. The two case studies demonstrate sensitivity in results to these parameters and how comparisons between studies can be unfair, if taken out of context. Both case studies demonstrate emissions embodied in the materials, and processes of the construction supply chain are especially significant for buildings with low operational demands [41]. How much of total embodied comes from structure? In the aforementioned study of an office building in China, of the materials used, concrete and steel consume the most energy at 52 and 38%, respectively [38]. The previously mentioned investigation arrived at a similar range of 45 to 60% for the three buildings studied, as an average of the different structural systems studied [32]. Together, these studies illustrate the importance of the structural materials within the embodied impacts of a building. Is there a benefit in considering design for deconstruction as part of structural design strategy? A methodology to account for design for deconstruction within embodied carbon calculations is proposed in Ref. [43]. The study employed a discounting methodology used by World Steel that assumes a rate of recovery and recyclability of the materials through future life-cycles. In this case, reuse factors were substituted for recycling, wherever applicable. The analysis results showed that the greater amount of material needed for a deconstructable precast concrete slab over a steel beam system did not generate significant embodied carbon savings over conventional composite systems. The lesson learned was that any sacrifices in material efficiency from composite systems should be evaluated carefully when aiming to design for deconstruction, so as not to sacrifice one benefit for another.

5.3.1

Comparing case studies

In attempting to compare results across LCA studies, encountering conflicting conclusions can be common. This is because the ISO 14040/14044 standards allow a great amount of flexibility in the choices one can make in conducting an LCA, as long as they are appropriate to the goal and scope initially set out as required. Therefore, when comparing LCA case studies, it helps to gauge the parameters involved in the LCA. Within the scope, one must define the type, extent, impact categories, and indicators. Type refers to whether it is a comparative study or absolute. Extent refers to which of the life-cycle phases will be included (e.g., cradle-to-gate, or to site, or to grave). Impact categories refer to the metrics discussed above, and indicators mean, which unit of measurement will be used for those impacts, as different classification systems may have

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different characterization methods and equivalent units. Additionally, as the functional unit, data sources, methodology, and system boundaries for the inventory flow analysis must all be decided within the process of performing an LCA, one can use these to differentiate between case studies. This is particularly helpful for figuring out if a difference in results between seemingly comparable case studies is due to variations in methodology or due to real differences in the environmental burden incurred by the supply chain processes themselves.

5.3.2

Limitations of life-cycle assessment

Despite the many insights offered by LCA-based evaluations, the methodology has limitations. Whether process-based, input-output-based, or hybrid-based, the data collected come from reporting by industrial processes, and the environmental impacts are based on scientific models. Thus, the results tend to be limited to aggregations of what is reported by representative industry practices, and what is well understood by the scientific community. This means that environmental effects that do not have robust models, such as biodiversity, land use, scarcity of resources, and toxicity, are consequentially less robust. Although there has been some attempt at models for these metrics, they are not well agreed upon within the LCA and environmental science community, and thus left out of most categorization systems. As an example, currently accepted LCA metrics do not differentiate well between forest management practices because the models and metrics of greatest concern are not widely accepted, and the data are collected across such a large region—forests with differing types of management practices are all aggregated. Similarly, human health effects of products in use are not covered by the LCA methodology because the variety of exposure conditions are too numerous: one cannot possibly model a representative scenario for the different ways a building product could be installed and an occupant could interact with that product. Thus, it is necessary to supplement LCA with other evaluation methods and tools, as is often found in green design rating systems.

5.4

Green design rating systems

In contrast to LCA, there are a variety of more qualitative forms of assessment that benchmark projects against best practice. These types of sustainability evaluations within the construction industry are increasingly found in green design rating systems. These systems offer a framework to evaluate built structures based on numerous environmental, social, and economic criteria, not all of which are quantitative. Balancing the variety of metrics and goals across the three spectra requires a departure from metrics solely used in LCAs. Incorporating issues such as quality of life presents particular measurement challenges. In spite of the quantification challenges of rating systems, it is crucial for structural engineers to understand the overarching objectives, possible conflicts, and their own role in such systems.

5.4.1

Buildings

Green building rating systems have proliferated globally since the formation of the World Green Building Council in 1999 [44]. In general, green building rating systems encourage

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sustainable building practices through the use of market forces. The typical voluntary nature of these systems ensures that requirements are realistically and economically feasible, while also continually requiring improvements to help advance sustainable practices and objectives. There are numerous green building rating systems that tend to be country specific (e.g., CASBEE, Japan; BREEAM, U.K.; GreenStar, Australia/New Zealand; LEED, North America; DGNB, Germany). This section will focus on LEED (Leadership in Energy and Environmental Design) and DGBN (German Sustainable Building Council) as they represent the spectrum of LCA integration within rating systems. LEED does not currently require LCA and is focusing on requirements that will transition the construction industry to LCA in the long-term. On the other hand, DGNB has already incorporated LCA into their system. This section illustrates common sustainability themes and issues associated with rating systems and buildings and how they affect structural engineers. The predominant rating system used globally is the LEED system, and thus worth some examination in how it measures sustainability of structures. Created by the United States Green Building Council, LEED (LEED for New Construction, Version 3, 2009) is currently (LEED NC 2009/v3) adopted in many countries outside the USA and has versions for different building types. The points-based system is built upon five performance areas: sustainable sites, water efficiency, energy and atmosphere, materials and resources, and environmental quality [45]. The categories are then subdivided further into credits with each category that have different total weighting and potential scores. The weight of the categories and the credits are based on an important weighting scheme. The credits of main concern for structural engineers are found in the materials and resources (MR) category, which deal with building reuse (MR Credit 1), construction waste management (MR Credit 2), material reuse (MR Credit 3), recycled content (MR Credit 4), regional materials (MR Credit 5), rapidly renewable materials (MR Credit 6), and certified wood (MR Credit 7). The structural engineer’s specification of supplementary cementitious materials (e.g., fly ash, ground granulated blast furnace slag) is directly captured in MR Credit 4 – recycled content [45]. Other structural issues affecting the overall sustainability are indirectly captured in the rating system (e.g., MR Credit 1, building reuse). A significant change from current and past versions of LEED to LEEDv4 is the move towards LCA in the Materials and Resources credits. LCA underpins two new proposed credits: “Building Life-Cycle Impact Reduction, Option 4: Whole Building Life Cycle Assessment” (MRc1) and “Building Product Disclosure and Optimization – Environmental Product Declarations” (MRc2). The first confers improvement of the proposed design compared to a reference design, when measured on particular LCA metrics, and only requires embodied impacts (operational is covered by the energy performance credits). The second confers the production of Environmental Product Declarations (EPDs) for a given number of building products, including recognition of EPDs for structural products. Together, these account for up to five points in the LEED scoring system, compared to the one point attainable from recycled content and regional materials—the attributes in the current system that LCA essentially supplants. These attributes now appear in the proposed “Building and Product Disclosure and Optimization – Sourcing of Raw Materials” (MRc3) and the points available have been reduced significantly from four points in current system [46]. Moreover, these credits have moved from construction-phase credits, under the responsibility of the general contractor, to design-phase credits, under the responsibility of

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the design team. Numerous LCA case studies have shown that structure accounts for a significant portion of the embodied environmental impacts; the structural engineer may now have a much greater role to play in the design team for projects pursuing LEED certification. However, most of the proposed LEEDv4 limits structural materials in credit calculations to 30%, thereby directly impacting the role of the structural engineer in influencing the final score of the rating system. In contrast to LEED, the German Sustainable Building Council (DGNB) employs LCA at its core. Similar to LEED, the DGNB system has six criteria areas as follows: ecological quality, economical quality, social and cultural quality, technical quality, process quality, and location quality [47]. The criteria groups are awarded a weighting of 22.5, 22.5, 22.5, 22.5 and 10.0% respectively, with location quality residing outside the final evaluation. A unique aspect of the DGNB system is that it requires LCA in accordance with ISO 14040 and 14044 utilizing the German Ökobau.dat LCI database. Life-cycle aspects of the structure are captured through the evaluation criteria of greenhouse gas potential, ozone depletion potential, ozone formation potential, acidification potential, and fertilization potential during the production, maintenance, deconstruction, and disposal of building. As found in a study by the Institute of Structural Engineers on the relevance of structural engineering in rating systems, a survey respondent attested that “the structure does contribute largely to the LCA, because it is mostly the largest building element by volume” and “alternatives can be assessed using the LCA method” [15]. However, unlike LEED, the DGNB system is used almost exclusively in Germany. The LEED and DGNB systems show the evolution of LCA as a more integrated methodology within green building practice.

5.4.2

Infrastructure and bridges

Bridges and infrastructure are also increasingly designed based on green rating systems. These rating systems aim to meet sustainability objectives similar to green building rating systems (i.e., the triple bottom line, which accounts for social, economic, and environmental objectives), and should be understood by structural engineers working in these fields. A few of the currently available bridge and infrastructure rating systems include the Institute for Sustainable Infrastructure Sustainable Infrastructure Rating System (Envision) [48], Greenroads [6], CEEQUAL [49], and the IS Rating Tool from the Infrastructure Sustainability Council of Australia [50]. The Institute for Sustainable Infrastructure’s Envision system is a performance-based, scalable tool composed of five criteria groups including quality of life, leadership, resource allocation, natural world and climate, and risk [48]. Greenroads, developed by the University of Washington and CH2M Hill, is a rating system more specifically focused on roadways and bridges [6]. Athena Institute’s Impact Estimator for Highways is a LCA–based tool for the analysis of roadway material manufacturing, construction, and maintenance of roadways [51]. The Consortium on Green Design and Manufacturing at the University of California, Berkeley, developed an LCA-based tool for pavement: PaLATE (Pavement Life-cycle Assessment Tool for Environment and Economic Effects). For structural engineers in the field of infrastructure and bridge design, there is an increasing requirement for fluency in sustainable design parameters as illustrated through the numerous green rating systems.

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5.4.3

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Cities and the urban scale

While the expansion of building, bridge, and infrastructure green rating systems is laudable, it remains to be seen if object-specific (e.g., a single building) tools are capable of meeting global sustainability objectives [52]. The refinement of rating systems to include life-cycle analysis, as is the case with the DGNB, is a significant achievement in providing quantitative results for rating systems. However, the challenge of achieving sustainable goals requires system-wide analysis. The motivation for transition towards system-wide analysis can be illustrated through a simple example. A common criterion of green building rating systems is the reduction of operational energy use. Despite this improvement in the environmental performance of the single object (i.e., the building), it is possible that this reduction is not compatible with larger sustainability objectives (e.g., climate change stabilization [9]) if system-wide trends (e.g., increased housing size per person) and system-wide effects (e.g., suburbanization) are not quantified. For infrastructure, a similar case can be made for environmental improvements made to roads and bridges for automobile use, while ignoring the larger issue of transitioning towards more sustainable forms of transportation (e.g., walking, biking, mass transit). Consequently, systemwide analysis is emerging as the next frontier in the refinement of rating systems to achieve sustainability objectives. Numerous frameworks for systems-based sustainable design already exist and will be reviewed here to present a general overview. The Swiss Federal Institute of Technology in Zürich developed the 2000 Watt Society, which is a system-wide framework where all individuals in the developed world meet their needs using only 2000 watts without lowering their standard of living [53]. The 2000 watts are to cover all aspects of an individual’s life including living, working, transportation, infrastructure, and so on. Expanding upon single building rating systems, the United States Green Building Council has developed the LEED Neighborhood Development [54]. While this rating system expands upon LEED to include issues such as community connections and transportations, it does not provide a single quantitative result such as the 2000 Watt Society. A major challenge in system-wide analysis is that many issues such as transportation modes available are beyond the control of the design team for a stand-alone project such as a single new building. However, these issues must be addressed if sustainability, rather than merely improving the environmental performance of an item, is to be achieved.

5.5

Emerging trends

Systems-based thinking requires that environmental improvements are correlated to sustainability goals. As previously discussed, it is not sufficient to look at stand-alone items (i.e., one residential building) without understanding the larger impacts and emerging trends that will inevitably influence whether sustainability objectives can be met. In particular, trends in the built environment are important as such developments may remove any operational efficiency improvements being made. A fundamental trend directly affecting sustainable design is the increase in home size. In the USA, there was a 10.9 and 7.3% increase in square meters for average residential homes and apartments, respectively, between 1993 and 2001 [3]. The U.S. Energy Information Administration (EIA) also predicts an increase in electricity production of 84% between 2008 and 2020

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driven by increased energy demand in non-OECD countries [4]. Transportation is also expected to play a critical role over the coming decades, and the U.S. EIA states that this sector will increase demand for liquid fuel more than any other sector with an annual increase of 1.4% in global transportation energy from 2008 to 2035 [4]. These emerging trends, and many others, must be fully understood if environmental improvements to buildings and structures are to achieve overarching goals.

5.6

Conclusion

Sustainability is a new design criterion and simultaneously an area of opportunity for structural engineers. This chapter has outlined sustainability goals, LCA, case studies answering common structural engineering questions, green design rating systems, and emerging trends in assessing environmental performance of the built environment. To date, sustainability in the built environment focused predominately on operational energy use, and thus may appear to be of minor relevance to structural engineers. However, the trend to conduct full system LCA reveals the increasing importance of engineers. As the operational impacts decrease, the embodied impacts (e.g., from structural materials) increase as a percentage of total impacts. Thus, structural engineers are of increasing importance in achieving sustainability goals. This chapter illustrates that system-wide analysis throughout a product’s entire life-cycle is an essential requirement to meet environmental objectives. Achieving sustainability goals requires moving beyond simple assumptions and utilizing verified assessment methods. LCA has proven itself as a robust, extensive, and usable methodology for evaluating environmental performance across industries, and in particular, the construction sector. As LCA becomes an increasing part of the design process for sustainable projects, structural engineers can capitalize on their analytical knowledge to use LCA to provide structures with the best environmental performance. Sustainability offers structural engineers the unique opportunity to expand their influence, while structural engineers can offer their analytical skills to continue improving sustainable design.

References [1] United Nations. 1987. Our Common Future: The World Commission on Environment and Development. Oxford University Press, Oxford, 374. [2] American Society of Civil Engineers. 2006. Code of Ethics [Online]. Available at: http:// www.asce.org/code_of_ethics/ [accessed on March 31, 2015]. [3] U.S. Energy Informatin Agency. 2001 Residential Energy Consumption Survey: Square Foot Measurements and Comparison [Online]. Available at: http://www.eia.gov/emeu/ recs/sqft-measure.html. [accessed on March 31, 2015]. [4] IEA. 2011. World Energy Outlook. Organisation for Economic Co-operation and Development/International Energy Agency, Paris, France. [5] Sartori , I., Hestnes, A.G. 2007. Energy use in the life cycle of conventional and low-energy buildings: a review article. Energ. Build., 39(3): 249–257. [6] Greenroads. Greenroads Rating System [Online]. Available at: http://www.greenroads. org/ [accessed on March 31, 2015].

BackBack to table ofofcontents to table contents

sed_1405.indd 88

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REFERENCES

89

[7] Bolla, V., Capek, A., Jung, D., Lock, G., Popova, M., Savova, I., Tronet, V. (Eds.) 2011. Sustainable development in the European Union: 2011 monitoring report of the EU sustainable development strategy, Luxembourg. [8] Curran, M.A., 2006. Life Cycle Assessment: Principles and Practice. US Environmental Protection Agency, Cincinnati, OH. [9] Metz, B., Davidson, O.R., Bosch, P.R., Dave, R., Meyer, L.A. (eds.). 2007. Contribution of Working Group III to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change. Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA, 851. [10] United Nations. 1998. Kyoto Protocol to the United Nations Framework Convention on Climate Change. United Nations, New York, NY, USA. [11] European Commission. 2011. A Roadmap for moving to a competitive low carbon economy in 2050, Brussels. [12] Architecture 2030. 2010. The 2030 Challenge [Online]. Available at: http:// architecture2030.org/2030_challenge/the_2030_challenge [accessed on March 31, 2015]. [13] ISO. 2006. ISO 14040 – Environmental management – Life cycle assessment – Principles and framework. International Organization for Standardization, Geneva, Switzerland. [14] ISO. 2006. ISO 14044 - Environmental management – Life cycle assessment – Requirements and guidelines. International Organization for Standardization, Geneva, Switzerland. [15] Anderson, J., Thornback, J. 2012. A guide to understanding the embodied impacts of construction products. Construction Products Association, London. [16] Bare, J. Tool for the reduction and assessment of chemical and other environmental Impacts (TRACI). US Environmental Protection Agency, Cincinnati, OH, USA. [17] Hendrickson, C.T., Lave, L.B., Matthews, H.S. 2006. Environmental Life Cycle Assessment of goods and Services: An Input-Output Approach. Resources for the Future, Washington D.C., 262. [18] Carnegie Mellon University Green Design Institute. Economic Input-Output Life Cycle Assessment (EIO-LCA) [Online]. Available at: http://www.eiolca.net [accessed on March 31, 2015]. [19] BSRIA. Embodied Carbon: The Inventory of Carbon and Energy [Online]. Available at: https://www.bsria.co.uk/information-membership/bookshop/publication/embodied-carbon-the-inventory-of-carbon-and-energy-ice/ [accessed on March 31, 2015]. [20] United States Life Cycle Inventory Database. National Renewable Energy Laboratory [Online]. Available at: http://www.nrel.gov/lci/ [accessed on March 31, 2015]. [21] European Commission – Joint research Centre. 2010. European reference life cycle database – version II. European Commission, Directorate-General Joint Research Centre, Institute for Environment and Sustainability (JRC-IES), European Platform on Life Cycle Assessment (EPLCA), Brussels, Belgium. [22] “Ökobau.dat. Bundesministerium für Verkehr, Bau und Stadtentwicklung [Online]. Available at: http://www.nachhaltigesbauen.de/baustoff-und-gebae [accessed on March 31, 2015]. [23] Curran, M.A., Notten, P. 2006. Summary of Global Life Cycle Inventory Data Resources. [24] National Institute of Standards and Technology. BEES: Building for Environmental and Economic Sustainability [Online]. Available at: http://www.nist.gov/el/economics/ BEESSoftware.cfm [accessed on March 31, 2015]. [25] Athena Sustainable Materials Institute. EcoCalculator [Online]. Available at: http://www. athenasmi.org/about-asmi/overview/ [accessed on March 31, 2015].

BackBack to table ofofcontents to table contents

sed_1405.indd 89

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CHAPTER 5. MEASURING SUSTAINABILITY AND LIFE-CYCLE ASSESSMENT

[26] PE International. GaBi Life Cycle Assessment Software [Online]. Available at: http:// www.gabi-software.com/america/index/ [accessed on March 31 2015]. [27] LEGEP. LEGEP-Software: A tool for integrated life-cycle analysis [Online]. Available at: http://www.legep.de/?lang=en&page_id=2 [accessed on March 31, 2015]. [28] PRE Product Ecology Consultants. SimaPro LCA Software [Online]. Available at: http:// www.pre-sustainability.com/simapro-lca-software [accessed on March 31, 2015]. [29] ifu Hamburg. Umberto [Online]. Available at: http://www.umberto.de/en/ [accessed on March 31, 2015]. [30] GreenDelta. 2013. openLCA [Online]. Available at: http://www.openlca.org/ [accessed on March 31, 2015]. [31] Anderson, J.E., Silman, R. 2009. A life cycle inventory of structural engineering design strategies for greenhouse gas reduction. Struct. Eng. Int., 19(3): 283–288. [32] Kaethner, S. C., Burridge, J. A. 2012. Embodied CO2 of structural frames. Struct. Eng., 90(5): 33–40. [33] Guggemos, A.A., Horvath, A. 2005. Comparison of environmental effects of steel- and concrete-framed buildings. J. Infrastruct. Syst., 11(2): 93–101. [34] Masanet, E., Stadel, A., Gursel, P. 2012. Life-Cycle Evaluation of Concrete Building Construction as a Strategy for Sustainable Cities. Portland Cement Association, Skokie, IL, USA. [35] Fernandez, N.P. 2008. The Influence of Construction Materials on Life-Cycle Energy Use and Carbon Dioxide Emissions of Medium Size Commercial Buildings, Victoria University of Wellington. [36] Marceau, M.L., VanGeem, M. G. 2008. Life Cycle Assessment of an Insulating Concrete Form House Compared to a Wood Frame House. PCA R&D SN3041 Series, Portland Cement Association, Skokie, IL, USA. [37] Kofoworola, O.F., Gheewala, S.H. 2009. Life cycle energy assessment of a typical office building in Thailand. Energ. Build., 41(10): 1076–1083. [38] Wu, H.J., Yuan, Z.W., Zhang, L., Bi, J. 2012. Life cycle energy consumption and CO2 emission of an office building in China. Int. J. Life Cycle Assess., 17: 105–118. [39] Stephan, A., Crawford, R.H., de Myttenaere, K. 2012. Towards a comprehensive life cycle energy analysis framework for residential buildings. Energ. Build., 55: 592–600. [40] Junnila, S., Horvath, A., Guggemos, A.A. 2006. Life-cycle assessment of office buildings in Europe and the United States. J. Infrastruct. Syst., 12(1): 10–17. [41] Siantonas, T., Fieldson, R. 2008. Comparing methodologies for carbon footprinting distribution centres, The Construction and Building Research Conference of the Royal Institution of Chartered Surveyors, RICS, London, United Kingdom. [42] Comber, M., Poland, C., Sinclair, M. 2012. Environmental impact seismic assessment: application of performance-based earthquake engineering methodologies to optimize environmental performance. Struct. Cong., 2012: 910–921. [43] Yang, F. 2011. Integrating life cycle and carbon assessments: what life cycle assessment can teach structural engineers and design and specification. Struct. Cong., 2011: 495–506. [44] World Green Building Council. [Online]. Available at: http://www.worldgbc.org/ [accessed on March 31, 2015]. [45] United States Green Building Council. Leadership in Energy and Environmental Design: New Construction and Major Renovations [Online]. Available at: http://www.usgbc.org/ leed/rating-systems/new-construction [accessed on March 31, 2015].

BackBack to table ofofcontents to table contents

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[46] United States Green Building Council. LEEDv4 for Buidling Design and Construction: Ballot Version [Online]. Available at: http://www.usgbc.org/leed/v4 [accessed on March 31, 2015]. [47] German Sustainable Building Council. Neubau Büro- und Verwaltungsgebäude, Version 2012 [Online]. Available at: http://www.dgnb.de/de/ [accessed on March 31, 2015]. [48] Institute for Sustainable Infrastructure. Envision: Sustainable Infrastructure Rating System [Online]. Available at: http://www.sustainableinfrastructure.org/rating/index.cfm [accessed on March 31, 2015]. [49] CEEQUAL Ltd. CEEQUAL [Online]. Available at: http://www.ceequal.com/ [accessed on March 31, 2015]. [50] Infrastructure Sustainability Council of Australia. IS Rating Tool. [Online]. Available at: http://www.isca.org.au/is-rating-scheme/is-overview/is-rating-tool [accessed on March 31, 2015]. [51] Athena Sustainable Materials Institute. Athena Impact Estimator for Highways [Online]. Available at: http://www.athenasmi.org/our-software-data/impact-estimator-for-highways/ [accessed on March 31, 2015]. [52] Humbert, S., Abeck, H., Bali, N., Horvath, A. 2007. Leadership in energy and environmental design (LEED) – a critical evaluation by LCA and recommendations for improvement. Int. J. Life Cycle Assess., 12(1): 46–57. [53] 2000 Watt Society. [Online]. Available at: http://www.2000watt.ch/ [accessed on March 31, 2015]. [54] United States Green Building Council. LEED for Neighborhood Development [Online]. Available at: http://www.usgbc.org/DisplayPage.aspx?CMSPageID=148 [accessed on March 31, 2015].

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6 Asset Management

José C. Matos, Prof.; Dr.; Civil Engineering Department, Guimarães, Portugal. Luís Neves, Dr.; Nottingham Transportation Engineering, University of Nottingham, Nottingham, UK. Bruno Gonçalves, Dr.; Production and Systems Department, Guimarães, Portugal. Contact: [email protected]; [email protected]; [email protected]

6.1

Introduction

The increase in the number of ageing infrastructures in Europe, North America, and Japan over the last three decades, has led to the development of a set of tools that allow a more consistent and optimized management procedure. Asset management can be defined as the systematic activities and practices used by an organization to manage its infrastructures, by optimizing performance, risk, and expenditures over the structure’s entire life cycle. These tools and procedures are fundamental in reducing costs during the use of the structure, as well as in extending their service life, and minimizing decommissioning and replacement expenditures. Although the methods and principles described in this chapter can be applied to any infrastructure, their emphasis is placed on large stocks, owned or managed by a single entity, either public or private. In fact, in this case, the potential benefits are larger and clearly justify the required investment. In this context, the most advanced civil asset management systems can be found associated with transportation networks, in particular, for bridges and pavements. Nevertheless, significant developments can also be found in other areas, including water and oil transportation systems, airport pavements, ports, and buildings among others. The management of such stocks requires a clear definition of objectives, in terms of performance, risk, and costs, as well as a long-term strategy to achieve these objectives. An asset management system must be based on three fundamental modules: database, performance prediction models, and optimization. The first is an inventory of the infrastructure network and contains all relevant information regarding each infrastructure, including design information, past maintenance actions, and performance evaluations results. The second includes models for predicting future performance, considering the effects of deterioration, use, and maintenance actions.

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The third is an optimization tool that helps the decision maker in defining optimal policies and updating these policies as new information become available. Asset management involves a combination of methods and tools to effectively manage infrastructures. Asset management (and respective methods and tools) implies a standardization of inputs and outputs in the management system, concerning information (gathering and flow) and decision making. The awareness of these inputs and outputs and their parameterization and structuring is a key element in the design phase of any infrastructure. The structural engineer plays a predominant and active role in the design phase defining these inputs and outputs that will rule the management philosophy during the infrastructure lifetime. Since the design phase, the structural engineer should instill to the management team that the economics of an infrastructure are far beyond the initial investment. Mastering the methods and tools of asset management will allow the structural engineer to foresee the economics beyond the initial investment, that is, the economics of the infrastructure’s entire service life. This will provide the structural engineer with the vision that infrastructure management is the seeking of the best possible tradeoff between investment, maintenance, repair, upgrade, serviceability, and safety. The goal is to apply this vision in the design phase, and the structural engineer is the main player.

6.2

WLC: a tool for asset management

Asset management procedures are supported by whole-life costing (WLC) models, which consist in determining the total cost of any infrastructure from its initial conception to the end of its service life. In the past, construction designs aimed at minimizing the initial costs and the alternative of lowering initial cost alone was selected. Rapidly, operators discovered that running costs too impact the budget significantly. The WLC approach is more suitable for this problem because it encompasses the total cost over the infrastructure lifetime. This cost is distributed among the following components: economic, environmental, and societal. While the first indicates the spent money, the others are, respectively, characterized by the impact on the surrounding environment and society. These two latter costs are, consequently, more difficult to quantify. By definition, WLC is “a tool to assist in assessing the cost performance of construction work, aimed at facilitating choices where there are alternative means of achieving the client’s objectives and where those alternatives differ, not only in their initial costs but also in their subsequent operational costs” [1]. For operators, a WLC tool offers a first-level support in the decisionmaking process for effective choice between several competing alternatives and a second-level support for continuous management of infrastructures. Although it can be done in any stage of a project, the maximum benefit of applying WLC is achieved when applied in the early stages (e.g. 80–90% of the cost of running, maintaining, and repairing an infrastructure is determined in the design stage [2,3]). In the second level, WLC may be used as a management tool allowing the identification of the actual costs related to infrastructure operation. Compiling this information with data from operation and inspections, WLC models may be used to estimate future running costs, which is an important input for budgeting purposes. Invariably, there is always risk associated with new projects. Thus, risk assessment is incorporated into WLC models to strengthen them and to provide more reliable outputs and more confident decisions from the decision-maker. This implies the use of risk assessment tech-

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niques in WLC ranging from simple deterministic approach methods to uncertainty assessment (e.g. sensitivity and break-even analysis), to extremely sophisticated methods based on probabilities, artificial intelligence, and a hybrid of both.

6.3

Whole-life costing: a review

Nowadays, it is much more important to be aware of the total investment than only the initial investment needed for an infrastructure during its entire lifetime. This means that all type of costs along the structure’s lifetime must be considered since the early design stage, such as the ones related to design, construction, inspection, maintenance, repair, upgrade, environmental and social impacts, and demolition. As for costs, it is very important to assign to each element of a structure, a condition state. This is due to the need of ranking the infrastructure (and its components) according to pre-defined attributes (e.g. degradation condition, budget needed to repair/upgrade, level of urgency to repair/upgrade, remaining service lifetime). Obtaining such condition states may be easy for the technical part of an infrastructure (e.g. by inspection, non-destructive and destructive tests), but for certain others it is difficult (if not impossible) to implement precise metrics of obtaining condition states (e.g. effects of an infrastructure in the environment and society). In addition, there is a need to convert those condition states into normalized condition indexes, and furthermore it is necessary to translate those condition indexes to proper (or equivalent) monetary values. As an example, an index to support the decision-making at design phase for products and processes, based on weighed attributes such as environment, health and safety, cost, technical feasibility, and sociopolitical factors was developed in Ref. [4]. To predict costs and the time they will occur is a hard task, and the computed total cost will not have a high degree of accuracy. Nevertheless, it is important to know all the costs over an infrastructure’s lifetime, and there exist techniques that allow the comparison of several alternatives by being aware of those costs. For this intend, the time value of money must be considered. The principle is that an amount of money today represents an equivalent (but different) amount of money in the future (and vice versa) due to the existence of interest (or discount) rates. The present value analysis is widely used to convert all costs over the infrastructure’s lifetime into current money costs. This analysis takes into consideration the instant of time when cost occurs and the adopted interest rate (or discount rate). When comparing projects using this analysis, the one with lower total costs (lower NPV [net present value]) should be selected. There are more analyses taking into account the time value of money for comparison and evaluation of alternative projects, such as those described in Ref. [5]: 1. Equivalent annual cost (EAC) converts all the costs to a uniform EAC, rather than a singletime NPV. The alternative with minimum EAC should be selected. 2. Discounted payback period (DPP) is defined as the time needed for the annual savings to accumulate in order to pay back the invested amount. The alternative with lower DPP should be selected. 3. Internal rate of return (IRR) is defined as the percentage earned on the capital invested (in each year) after the repayment of the total capital invested. The alternative with maximum IRR should be selected.

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4. Net savings (NS) is defined as the difference between the present worth of the income generated by the investment and the invested amount. The alternative with maximum NS should be selected. 5. Savings to investment ratio (SIR) is defined as the ratio of the present worth of the income generated by an investment to the initial investment capital. The alternative with maximum SIR should be selected. In general, WLC models use the NPV approach for evaluation of alternatives (almost all WLC models adopt the NPV approach [5]). These models use a very simple equation to evaluate the alternatives, such as the model presented by the American Society for Testing and Materials [6]: NPV = C + R − S + A + M + E, where C = investment costs; R = replacement costs; S = resale value at the end of the studied period; A = annually recurring operating, maintenance, and repair costs (except energy costs); M = non-annually recurring operating, maintenance, and repair costs (except energy costs); E = energy costs. Several derivations of this model were carried out by researchers in order to adapt the model such that a best match to the real-world problem is achieved. Nowadays, WLC models also include in a much more explicit form, the costs related to environment and society. Environmental considerations too are taken into account in recent WLC models thanks to the awareness of the impact of an infrastructure on the surrounding environment among the scientific community. As a result, several standards and regulations have been established and are mandatory nowadays. On the other hand, society as a cost should also be considered in WLC models. There is no consensus among the scientific community regarding this problem. By far, this component is the least developed as of now. Uncertainty and risk are intrinsic to WLC. It deals with the future and the future is of course unknown. Several data may be forecast within known limits (associated to a treatable risk), but some of the data predicted, even by experts based on all information available, could simply result in a guess (it is not just a matter of risk but uncertainty instead—e.g. environmental behaviour such as seismic activity may occur unexpectedly). Thus, treatment of uncertainty and risk in information and data is vital for successful implementation of a WLC model. In this way, WLC models incorporate risk assessment techniques to deal with risk and uncertainty. Techniques such as sensitivity analysis are being used including probability-based techniques and simulation models. Recent WLC models apply the fuzzy set theory (FST) to deal with uncertainty. WLC software is available with different characteristics ranging from simple spreadsheet to sophisticated commercial software. Table 6.1 presents a comparison of some applications of WLC models in terms of availability, models, risk analysis, and scope of application [5].

6.4

Costs and condition

By definition, WLC deals with present and future costs spread across all phases of the infrastructure lifetime. These costs may be of several natures from economic to environmental and societal. Depending on the project, these types of cost will have different weights in the final WLC model. Economic costs are the most tangible and easy to understand, and there are several costs of this nature during an infrastructure’s lifetime, such as: 1. Initial costs: These costs embrace the project development costs including the design and other professional fees, and the construction costs.

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6.4 COSTS AND CONDITION

Software

Availability

ACEIT 5.x

Commercial; Windows

NPV

Yes

Integrated suite of analysis tools; WLC decision-making; generic CBS

Ampsol

Free; web-based

NPV

No

Basic WLC calculations only; generic CBS

AssetDesk 1.1

Commercial; Windows

None

No

WLC management; activity-based CBS

BLCC 5.1

Free; platformindependent

NPV NS SIR IRR DPP

Yes

WLC decision-making; generic CBS: single energy and water cost items and unlimited items for other categories

BridgeLCC Free; 2.0 Windows

NPV

Yes

WLC decision-making; specific CBS: suitable only to analyze bridges

CAMSLCC Free; 2.2 Spreadsheet

NPV

No

WLC decision-making; generic CBS: single cost item per cost category

CASA

NPV

Yes

WLC decision-making; generic CBS

EDCAS 3.1 Commercial; Windows

NPV

No

WLC decision-making; generic activity-based CBS

PipeCost

Free; Windows

NPV

Yes

WLC decision-making; generic CBS: single cost item per cost category

RelexLCC 7.3

Commercial; Windows

NPV

Yes

WLC decision-making; user-defined CBS: unlimited cost items per category

Free; Windows

Models Risk analysis Scope of application

CBS = cost breakdown structure.

Table 6.1:- Existing WLC software and its characteristics [5] 2. Maintenance and repair costs: Maintenance relates to the costs involving regular interventions to take care of the infrastructure, while repair relates to costs involving replacement of items of minor values (or having relatively short life) [7]. Maintenance is a special case because there are different sources of maintenance data that may lead to different costs in maintenance depending on the source used. 3. Replacement costs: This refers to costs of restoring the initial function of the infrastructure by replacing those infrastructure elements having a shorter life cycle than the one planned for the entire infrastructure and not being maintenance or repair costs [7]. 4. Refurbishment and alteration costs: These costs are usually related to changing the function of the infrastructure or modernization purposes [7]. Handling these costs may lead to lifecycle changes, which may be very difficult to evaluate.

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5. Operating costs: These costs relate to cleaning procedures, dispended energy, general rates, insurance, and other necessary costs for operating the infrastructure [7]. 6. Taxes: Taxes play a crucial role in WLC models owing to their direct influence on the time value of money. 7. Denial-to-use costs: Represent the extra costs during the construction or occupancy periods (or both). These costs may reflect an income delay being relatively easy to compute, or may reflect penalties due to negative effects in society and/or environment (these costs being harder to quantify). 8. Salvage value: This is the difference between the infrastructure value (at the end of its service life) and the disposal costs. The concept of cost breakdown structure (CBS) is widely used and its main objective is to define all costs at a satisfactory detailed level. The CBS includes all costs the project will incur at different phases. A common example of a CBS for a general construction project is presented in Table 6.2 [4]. This process requires a lot of analysis and efforts because of the need to identify as precisely as possible all costs the project is likely to incur during its lifetime. Taking into account the general three cost components of a WLC model (infrastructure, environmental and society), the infrastructure costs, although complex to compute, are straightforward to define, as they are direct costs directly imputed to the asset owner and explicitly included in the business model. Extra complexities arise when trying to assess and translate environmental and societal impacts into equivalent costs. The life-cycle environmental impact assessment aims to evaluate the significance of potential environmental impacts. It is divided into two different parts; the first (and mandatory) is the classification and characterization phase and the second (and optional) is the normalization, ranking, weighting, and grouping phase [8]. According to ISO 14044 [9], category indicators for environmental assessment may be chosen between the intervention and the endpoint. Thus, existing methods for life-cycle environmental assessment are grouped into two main types: (a) mid-point methods (also known as problemoriented methods) in which the objective is to determine the category indicator related to the environmental impact (e.g. global warming potential) and (b) endpoint methods (also known as damage-oriented methods) in which the objective is to determine environmental damage indicators at the level of the ultimate societal concern (e.g. damage to human health) [8]. Examples of impact categories for mid-point approaches may be depletion of abiotic resources, impacts of land use, climate change, stratospheric ozone depletion, human toxicity, eco-toxicity, photooxidant formation, acidification, and eutrophication [10]. Of course, other categories can be included depending on the type of project and infrastructure and on the scope of the life-cycle environmental assessment. For the endpoint approaches, the damage categories may be defined according to several grouping criteria: biotic (living organisms in nature), abiotic (non-living elements of nature), human population and also man-made environment [11]. There is also an impact pathway approach that links the environmental processes from the pollutant emission process through transport with the end of the chain, meaning the impact on various receptors (e.g. human beings or ecosystems) [12]. This approach also permits the translation of the environmental impacts into monetary values. A European project (ExternE) developed a tool to support the quantification and valuation of the environmental impacts of electricity generation technologies [12]. A detailed description

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Energy

Financing cost

Finance for land Cleaning purchase and construction

Loan charges

General

Land

Fees on acquisition

Manpower

Taxes

Plumbing and sanitary services

Finishes, fixtures and fittings

Internal decorations

External decorations

Main structure

Maintenance cost

Electrical installations

Equipment associated with occupier’s occupation

Table 6.2: General example of a cost breakdown structure (CBS) [4]

External works

Lift and conveyor system

Gas installations

Ventilation and air treatment system

Land charges (rates)

Staff Management and Heat source building administration

Security and health

Construction cost

Insurance

Operation cost

Capital/initial cost

Residual value

Renovation/refurbishment cost

Demolition and site clearance

Client occupancy Resale value cost

Occupancy cost

6.4 COSTS AND CONDITION

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of several mid-point and endpoint approaches and a comparison between them can be found elsewhere [8]. Examples of mid-point approaches are (a) EDIP97; (b) CML 2001—Dutch Handbook on LCA; and (c) TRACI (The Tool for the Reduction and Assessment of Chemical and other Environmental Impacts). Examples of endpoint approaches are: (a) EDIP2003, (b) Eco-Indicator 99, (c) Environmental Priority Strategies (EPS) 2000, (d) Swiss Eco-Scarcity Method (Eco-Points), and (e) LIME. In addition to life-cycle environmental assessment tools, other approaches try to consider environmental concerns and their translation of effective costs into life cycle analysis. The life-cycle costing (LCC) becomes useful in environmental decision-making (with its monetary unit and extended scope), but fails in its practical usefulness because of being constrained by the lack of reliable data, conceptual confusions, and limited ability to make rational decisions under uncertainty [13]. With respect to life-cycle social assessment, contrarily to life-cycle environmental and economic analysis, there is no framework to perform this task. In fact there is no framework, there is no standard and there is no consensus among the scientific community on how to do it. A general framework was proposed by UNEP-SETAC Life Cycle Initiative to integrate social aspects into life-cycle analysis [14] and a suite of standards is under development by the European Committee for Standardization (CEN) on Sustainability of Construction works [15]. There exist two trends about the integration of social costs in life-cycle assessment. Some authors affirm that is possible and feasible, and others do not [16]. According to Ref. [16], social impacts rely on relations and are very local dependent, which means there is a need for developing local (or regional), social indicators and not a global approach to the life-cycle social analysis. Nevertheless, some approaches to overcome this problem were developed [16–18]. The fact is that social impact is the less developed component of WLC models, and there are key issues to be solved such as the problem of relating societal impacts with the functional unit of the system, the problem of obtaining site-specific data, and the problem of the selection and proper quantification of social indicators [19].

6.5

Models and scenarios

Civil engineering infrastructures are assets related to large life cycles, in general, 50 years or more, with an enormous environmental and societal impact, and a key in the business model of most owners and managers. In this context, it is fundamental to define measures of performance that allow the continuous monitoring of the condition of the infrastructure, permitting the identification of deterioration mechanism long time before they can impair the use of the infrastructure itself. Although very difficult to quantify, these measures should also consider both environmental and societal performance of the evaluated infrastructure. Different infrastructures require different indicators, but significant aspects are common for a manifold of infrastructures. In fact, considering the extension and number of elements comprising one infrastructure network (e.g. number of bridges in a highway or kilometres of pavements in a transportation network), as well as, the limited available budget, the performance must be evaluated by considering inexpensive and expedite methods, frequently based on visual inspections and/or simple non-destructive tests. For pavements, the so-called pavement condition rating is generally adopted that quantifies the pavement’s overall performance based on measurements of roughness, surface distress, skid

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resistance, and deflection [20]. For bridges, usually a discrete condition index, related to visible defects detected in a visual inspection, is used. However, this index cannot be considered as an accurate measure of the remaining life of a bridge as it does not directly measure the deterioration or its effects on safety. Alternatively, indicators of performance, based on more consistent measures, including the safety index are presented [21]. Nevertheless the costs associated with the periodic evaluation of these indicators are too high for current infrastructures, and so a combination of both is recommended. Predicting future deterioration and performance is one of the major challenges in asset management. In fact, civil engineering infrastructures are unique, in the sense that no similar structures, under the same environmental stresses, same load and material properties, exist. Considering that deterioration depends on all these factors, it is clear that accurate predictions are impossible and that uncertainty in future performance must be explicitly taken under consideration. The prediction of future performance can be, in principle, evaluated considering either structural models or statistical models (Fig. 6.1). Structural models are similar to those used during design, but it must be considered that material properties and geometry will change over time due to deterioration processes (e.g. corrosion of reinforcement bars, ingression of chloride in concrete structures). These models, although familiar to engineers and consistent with design practices, have three major limitations. Firstly, the prediction of component deterioration is related to a large uncertainty that propagates to the performance prediction. Secondly, the use of these models involves the detailed information of each infrastructure, which is frequently unavailable. Thirdly, this analysis is complex and expensive, requiring a different model for each infrastructure, making it inapplicable to stocks containing large number of infrastructures. Statistical models are much less familiar to engineers. These models are based on the use of simple analytical and/or soft computing algorithms, adjusted to the observed performance deterioration in large stocks of similar infrastructures. The main advantages of these models are their simplicity, the direct use of inspection data, and the uniformity over the entire asset, as the same model, with different parameters, can be used for all infrastructures. Improvement Repair 2

New specifications

Repair 1 Initial condition Condition

Time

Expected performance

Unacceptable level T1 intervention

T2 intervention

TD

Deterioration

Fig. 6.1: Deterioration model (Units: –)

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Among the statistical models, Markov chain models have gained importance over the last decades [22]. These chains are of stochastic nature and represent transitory probability matrices. These probabilities express the possibility of a certain element to move from condition state i to condition state j during the time interval Δt. Markov chain models have been applied in different areas for predicting the evolution of systems between discrete states and have been included in WLC models [22]. The main limitations of these models are the associated “lack of memory” as future performance is predicted based only on the last inspection results and the homogeneity that defines the transition probability, as this value is based on results from the last inspection and for a fixed time interval, thus disregarding the infrastructure age and the time interval since the last transition. In the same line of thought (prediction and forecasting), new techniques are being implemented to deal with risk and uncertainty. The application of such sophisticated techniques to WLC models is recent. Examples of such techniques are the artificial neural networks (ANNs) and the FST. ANNs are a specific application of the artificial intelligence technology. The objective is to imitate the human brain processes: how it learns new information and how it organizes the information. ANNs may be trained to make decisions. They have advantages over traditional methods in cases where the degree of complexity is so high that the process cannot be explicitly expressed in mathematical terms due to oversimplification [23]. Suitable applications of ANNs in WLC models are: (a) ANNs can classify and rank risk factors at any stage of the infrastructure life cycle and (b) ANNs can be used as a risk-forecasting tool at the operation stage. The FST is suitable for situations where uncertainty is complex and there is a lack of information. Although dealing with imprecise information and complex uncertainty, fuzzy logic is based on sound quantitative mathematical theory [23]. Suitable applications of FST in WLC models are: (a) when probabilistic data for risk assessment are extremely rare and insufficient, the utilization of subjective judgement data based on expert’s experiences and fuzzy concepts; (b) use of fuzzy membership curves to model uncertainty ranges in risk factors and wholelife estimates; (c) use of FST in assessing construction and operational risks; (d) use of FST in assessing and estimating service life risks; (e) use of fuzzy linguistic variables to describe imprecise whole-life risk factors; (f) use of subjective fuzzy probability to represent risks and estimates; (g) use of fuzzy sets to represent whole-life costs when historical data are not available to define the underlying statistical distribution.

6.6

Data acquisition systems and model updating

The WLC model relies on the collection and treatment of infrastructure data by application of several methods, analyses, and tools. Accordingly, the quality of the outcome of a management system is strongly dependent on the quality of available data. These data usually contemplate information about structural performance but sometimes they may include information about environment (e.g. excess of rock salt on pavement) and society impacts (e.g. presence of traffic due to maintenance actions). There are several techniques for in-field data collection, commonly divided into four major groups: visual inspection techniques, photographic and optic methods, non-destructive (and destructive) evaluation methods, and smart sensors [24]: 1. Visual inspection: This technique is suitable for buildings, highways, bridges, and other infrastructures. It is fundamentally dependent on the observation of the structure by a trained

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inspector who, through comparison of the observed state of the infrastructure with descriptions or photographs of pre-defined deterioration states, evaluates the infrastructure performance. The inspection can be carried out using basic equipment as input manual (writing down notes on infrastructure element’s condition, afterwards entered into a computerized management system) and audio dictation (information recorded in audio format which is then transcribed). Recently, advances in portable computer technology has allowed the evolution to more advanced methodologies such as handheld computers (allows a one-step input method because data may be directly stored in the management system) and wearable computers (suitable when hands-free condition is needed by the inspector). The equipment necessary for performing a visual inspection is, in general, quite simple, such as measuring tapes, cameras, portable computers, and recorders. Performing measures may contemplate support movements, elevation changes, deflections, misalignments, cracks, dents, and corrosion. Visual inspection may be most useful in buildings and bridges. Although inexpensive, it is subjective and prone to errors. 2. Photographic and optic methods: Suitable for bridges, highways, and underground utilities. The condition is assessed by analysis of images. Examples of required equipment are video/digital/scan cameras, closed-circuit television, and mechanical gyroscope. It may measure roughness, cracks, and damaged areas. It is a fast and accurate method and safe for inspectors. 3. Non-destructive evaluation: This group of methods is suitable for any type of infrastructures, as it permits accurate evaluation of geometry, material properties and deterioration progression, among others. There are several commercially available, manifold of equipments for non-destructive testing of existing infrastructures, including infrared thermography, laser, ultrasonic sensors, or ground penetration radar. These are accurate methods for assessing particular aspects of the infrastructure performance and can be extremely useful as a complement to visual inspections. However, these techniques are costly when compared to others. 4. Smart sensors: These methods consist in applying small self-contained battery-powered transducers to continuously measure structural displacements, strains, rotations, and acceleration of key elements. They allow for real-time data collection and processing and are extremely efficient in monitoring bridges or buildings. They present a high cost and are usually considered in special infrastructures when significant damage is observed. Improving the quality of inspections is a fundamental task in asset management. In fact, inspections are often the single link between management system and infrastructures, and errors and inaccuracies in inspection can result in inadequate policies or, in some cases, exposure of users to inadmissible risks. In order to assure the quality of inspections, two major aspects must be guaranteed. Firstly, and probably most important, is the adequate training of inspectors. It is fundamental to guarantee that initial and continuous training is provided and that used procedures are frequently tested. Recent experience has shown that the implementation of a quality management system for inspections has significantly improved the results of inspections, reducing the scatter in obtained evaluations. The second aspect is the development of inspection procedure less prone to errors. In this respect, some tools have been developed, such as check and deficiency lists, in order to avoid errors from inspectors and to standardize the inspection process. Examples of such lists (Fig. 6.2) are the BUILDER [25] and the RECAPP [26].

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Fig. 6.2: Check list example

The evolution of the management and inspection systems aims to maximize the amount and quality of data gathered in the field and the ease to upload, retrieve, and analyse such data in real time and anywhere. Taking advantage of the growing capabilities of mobile devices and software evolution, the inspection process tends to be normalized, in order to avoid epistemic errors. The “Mobile Model-Based Bridge Lifecycle Management System” [27] presents a management system with four dimensional (4D) capabilities extended to mobile devices. The communication between inspector (mobile device) and database (management system) is, in part, automatic and correlated with the inspector’s position (due to Geoinformatics technologies available in the system, such as Geographic Information Systems [GISs], and tracking methods, such as the Global Positioning System [GPS]). After collecting data, it is important to update the WLC with the most recent data available. Logically, this updating process will occur over the infrastructure lifetime. This means that WLC models must be able to deal with dynamic series of data. A suitable method for updating dynamic series of data is the Bayesian inference. This technique updates the estimated probability of a hypothesis as new data are available. In this technique, as more data are collected, prior statistical distribution will be defined more precisely and more reliable will be the estimation of probability of future data points. This method is used for updating the transition probabilities usually associated with Markov chains [28].

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6.7

Optimization techniques and decision

After inspections, evaluations, and prediction of future performance, it is fundamental to define long-term strategies for keeping structures safe and serviceable, minimizing the associated costs. Decisions on asset management must be taken considering the overall network, acknowledging that choices must be made, and some infrastructures take priority over the others. In this respect, it must be clearly understood that WLC models do not take decisions, they only provide informed advice, and the final decision must always be made by the infrastructure manager. The minimization of maintenance and repair costs can be defined as an optimization procedure, considering performance constraints. For this, two aspects must be considered. Firstly, a robust optimization algorithm must be defined. It should be noted that the algorithm will be used by infrastructure managers or operators with little or no experience in optimization. Therefore, the capacity of the algorithm to always converge to a solution close to optimal is fundamental. On the other hand, the algorithm should find which maintenance actions to apply and when, but the precise timing is of little significance, as no scheduling can be defined for time intervals less than weeks or even months. The other challenge is the definition of the optimization problem, which must clearly define the objectives (e.g. minimizing cost and maximizing performance) and constrains (e.g. minimum acceptable performance). There are, fundamentally, two types of optimization algorithms: local and global (Fig. 6.3). Local algorithms start from an initial solution and iteratively generate new improved solutions until a local optimum is found. As advantages, these methods are faster in reaching a solution and precise, in the sense they find the exact optimal, rather than a point close to optimal. As disadvantages, although they are very effective in finding a local optimum, the use of these methods does not always lead to a global optimum, as they can easily be trapped into local minima. Thus, although suitable to find local optima, local search algorithms may be very unsatisfactory in dealing with scenarios with multiple local optima, especially when robustness is fundamental. Global methods are more robust because only information regarding the objective function is necessary, the initial starting point is not important and often generated randomly, and the global

f(x)

Local min.

Global min.

x

Fig. 6.3: Local versus global minima (Units: –)

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optimum is found with a higher probability. The main drawback of these methods is the computational cost, which grows significantly with the number of design variables. Traditional local optimization methods apply measurements for parameter estimation [29]. A common method for local search is the sequential quadratic programming (SQP) algorithm, generalized from the Newton method in which the current point is found by minimizing a quadratic model of the problem. Conjugated gradients have also been used in WLC models with success. Several global search algorithms were developed in the last decades. Examples of global search methods are: 1. Genetic algorithms (GA) is defined by an algorithm that acts in one population of search points and generates new populations using randomized operators that mimic those of natural evolution, such as the selection, crossover, and mutation [30]. 2. Simulated annealing (SA) is based on an analogy between the annealing of solids and the problem of solving optimization problems. This algorithm was applied by several authors for optimization of civil engineering structures [31]. 3. Evolutionary strategy (ES) is also a search procedure that mimics the natural evolution of species in natural systems [32]. This algorithm has two distinct types of selection procedures, respectively, the comma and the plus strategy. 4. The ant system (ASO) [33] and the particle swarm (PSO) [34], in which the algorithms mimic the social behaviour of animals in a flock. 5. The probabilistic global search Lausanne (PGSL) [35,36], in which it is assumed that better points are likely to be found in the neighbourhood of families of good points, being the search intensified in regions containing good solutions. Global search algorithms may find better global optima but may be ineffective with respect to time consumption. Thus, several authors developed combined methods to overcome this inefficiency. The coupled local minimizer (CLM) is a hybrid method [37] that combines the advantage of local algorithms (relative fast convergence) with global algorithms (parallel strategy and information exchange). In the same way, various hybrid EAs such as the GA-SQP and the ES-SQP applied to large-scale structural problems were developed [38]. The optimization definition problem poses more challenging difficulties. If future performance could be defined without uncertainty, the problem could be posed as either a single objective problem (e.g. minimize cost respecting a minimum performance threshold for all structures) or as a multi-objective problem (e.g. minimize cost and maximize performance). However, as described above, the future performance of existing infrastructures is associated with significant uncertainty. If uncertainty in future performance is considered, the problem becomes significantly more complex, as the objectives and thresholds must be defined probabilistically. In terms of cost, the objective is usually to minimize the life-cycle mean cost. However, the financial risk, related to unexpected costs in a short period of time, could also be considered in the analysis. In terms of performance, the objective is usually to reach the best mean performance, over the entire stock, guaranteeing that the probability of a structure reaching a low performance level is sufficiently small. Moreover, it must be considered that not all infrastructures in a network have similar

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importance. In fact, the redundancy of the network (e.g. alternative routes of similar length) can significantly reduce the impact of works in one infrastructure, while others are critical to the network.

6.8

Conclusion

Asset management procedures are on the increase in the last few years, especially in developed countries, due to the increase of old infrastructure stock and the existent budget limits for maintaining such stock. These procedures are supported in WLC models. The objective of such models is to obtain the maximum performance of the asset during a specific period of time and, at the same time, minimizing costs related to maintenance and repair. Several mathematical tools for generation of scenarios and for optimization are implemented. These tools are served by data obtained from the stock of infrastructures. Accordingly, they are tested and further implemented to help infrastructure managers in establishing the right decision at the right time. However, there still exist several obstacles that must be overtaken. One of these difficulties resides in the accuracy of collected data and the way these data are processed. Others are related to using algorithms for predicting scenarios and optimization and to the way uncertainties are considered in these models. Recently, some authors introduced both environment and societal costs in WLC models [39– 43]. In fact, these two components are increasing in importance when compared to traditional economic costs, especially in developed countries. Accordingly, these costs, although more difficult to be quantified, are tentatively introduced in such models. Within this chapter, a compendium of all algorithms is made, which are implemented in WLC models. A special focus is made on uncertainty and how this component is introduced in such algorithms. Additionally, a resume of costs is made from economic, societal, and environmental sources, which are integral to these models.

References [1] [2] [3] [4] [5] [6] [7]

BSI BS ISO 15686-1:2000. 2000. Buildings and Constructed Assets: Service Life Planning: General Principles. British Standard Institution. Kirk, S.J., Dell’Isola, A.J. 1995. Life Cycle Costing For Design Professionals. McGrawHill Book Company, New York. MacKay, S. 1999. Building for life. The Building Economist. pp. 4–9. Khan, F.I., Sadiq, R., Veitch, B. 2004. Life cycle iNdeX (LInX): a new indexing procedure for process and product design and decision-making. J. Clean. Prod. 12(1): 59–76. Kishk, M., Al-Hajj, A., Pollock, R., Aouad, G., Bakis, N., Sun, M. 2003. Whole life costing in construction – a state of the art review. RICS Foundation Res. Pap., 4(18): 1–39. ASTM E917-83. 1983. Standard practice for measuring life-cycle costs of buildings and building systems. Designation: E917-83, American Society for Testing and Materials. Kirk, S.J., Dell’Isola, A.J. 1995. Life Cycle Costing for Design Professionals. McGrawHill Book Company, New York.

BackBack to table ofofcontents to table contents

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108 [8]

[9] [10]

[11]

[12] [13]

[14]

[15] [16]

[17] [18] [19] [20] [21] [22]

[23] [24] [25]

CHAPTER 6. ASSET MANAGEMENT

Gervásio, H. 2010. Sustainable Design and Integral Life-Cycle Analysis of bridges. Doctoral of Philosophy Dissertation, University of Coimbra, Institute for Sustainability and Innovation in Structural Engineering, Portugal. ISO 14044. 2006. Environmental management – Life cycle assessment – Requirements and guidelines. International Organization for Standardization, Geneva, Switzerland. Guinée, J.B., Gorrée, M., Heijungs, R., Huppes, G., Kleijn, R., Koning, A. de, Oers, L. van, Wegener Sleeswijk, A., Suh, S., Udo de Haes, H.A., Bruijn, H. de, Duin, R. van, Huijbregts, M.A.J. 2002. Handbook on Life Cycle Assessment. Operational Guide to the ISO standards. I: LCA in Perspective. IIa: Guide. IIb: Operational Annex. III: Scientific Background. Kluwer Academic Publishers, Dordrecht, The Netherlands, ISBN 1-40200228-9, 692 pp. Jolliet, O., Brent, A., Goedkoop, M., Itsubo, N., Mueller-Wenk, R., Peña, C., Schenk, R., Stewart, M., Weidema, B. 2003. Final report of the LCIA Definition study. Life Cycle Impact Assessment Programme of the Life Cycle Initiative. European Commission (EC). 1995. DG XII, Science, Research and Development, JOULE. Externalities of Fuel Cycles “ExternE” Project. Report no. 2 – Methodology, EUR16521. Gluch, P., Baumann, H. 2004. The life cycle costing (LCC) approach: a conceptual discussion of its usefulness for environmental decision-making. Build. Environ., 39: 571–580. Griebßammer, R., Benoît, C., Dreyer, L., Flysjö, A., Manhart, A., Mazijn, B., Méthot, A., Weidema, B. 2006. Feasibility Study: Integration of Social Aspects into LCA. Freiburg, Germany. Global Reporting Initiative. Available from: www.grig3.org/guidelines.html/. prEN 15643-3. 2009. Sustainability of construction works—Sustainability assessment of buildings—Part 3: Framework for the assessment of social performance. CEN/TC 350. Spillemaeckers, S. 2007. The Belgian social label: A governmental application of Social LCA. Available from: web.fu-berlin.de/ffu/calcas/Spillemaeckers_Belgian.pdf (last accessed on 19 February 2009). Dreyer, L., Hauschild, M., Schierbeck, J. 2006. A framework for life cycle impact assessment. Int. J. LCA, 11(2): 88–97. Hunkeler, D. 2006. Societal LCA methodology and case study. Int. J. LCA, 11(6): 371–382. Kloepffer, W. 2008. Life cycle sustainability assessment of products (with comments by Helias A. Udo de Haes, p. 95). Int. J. LCA, 13(2): 89–95. Deighton, R., Sztraka, J. Pavement Condition dTV. Technical Guide, (Volume 3). Deighton and Associates Ltd., Bowmansville, Ontario, July 1995. Ryall, M.J. 2010. Bridge Management, 2nd edn. Harding, J.E., Gerard, P., Ryall, M. (eds.). Butterworth-Heinemann, Oxford. Ng, S.K., Moses, F. 1996. Prediction of bridge service life using time-dependent reliability analysis. Third International Conference on Bridge Management, University of Surrey, Guildford, UK, April 14–17, pp. 26–33. Boussabaine, A., Kirkham, R.J. 2004. Whole Life-Cycle Costing: Risk and Risk Responses. 1st edn, Blackwell Publishing Ltd., Oxford, UK, ISBN 1-4051-0786-3. Ahluwalia, S.S. 2008. A framework for efficient condition assessment of the building infrastructure, Doctoral of Philosophy Dissertation, University of Waterloo, Ontario, Canada. BUILDER. 2002. BUILDER User Guide, U.S. Army, Engineering Research and Development Centre – Construction Engineering Research Laboratory (ERDC-CERL), Champaign, IL, USA, May 2002.

BackBack to table ofofcontents to table contents

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[26] RECAPP. 2006. RECAPP® 1.0 Training Manual. Physical Planning Technologies Inc., Toronto, Canada. [27] Hammad, A., Zhang, C., Hu, Y., Mozaffari, E. 2006. Mobile model-based bridge lifecycle management systems. J. Comp. Aided Civil Infrastruct. Eng., 21: 530–547. [28] Hu, Y., Kiesel, R., Perraudin, W. 2002. The estimation of transition matrices for sovereign credit ratings. J. Banking Finan., 26(7): 1383–1406; [29] Sanayei, M., McClain, J.A.S., Wadia-Fascetti, S., Santini, E.M. 1999. Parameter estimation incorporating modal data and boundary conditions. J. Struct. Eng., 125(9): 1048–1055. [30] Holland, J. 1975. Adaptation in Natural and Artificial Systems. University of Michigan Press, Michigan. [31] Kirkpatrick, S., Gelatt, C.D., Vecchi, M.P. 1983. Optimization by simulated annealing. Science, 220: 671–679. [32] Rechenberg, I. 1994. Evolutionsstrategie. Frommann-Holzboog, Stuttgart. [33] Dorigo, M., Di Caro, G. 1999. The ant colony optimization meta-heuristic. In: New Methods in Optimization. Corne, D., Dorigo, M., Glover, F. (eds.), McGraw-Hill, Maidenhead, UK. [34] Eberhart, R.C., Kennedy, J. 1995. A new optimizer using particles swarm theory. Sixth International Symposium on Micro Machine and Human Science, Nagoya, Japan, 39–43. [35] Raphael, B., Smith, I.F.C. 2003. A direct stochastic algorithm for global search. J. Appl. Math. Comput., 146(2–3): 729–758. [36] Robert-Nicoud, Y., Raphael, B., Burdet, O., Smith, I.F.C. 2005. Model identification of bridges using measurement data. Comput. Aid. Civil Infrastruct. Eng., 20: 118–131. [37] Suykens, J.A.K., Vandewalle, J. 2002. Coupled local minimizers: alternative formulations and extensions. 2002 World Congress on Computational Intelligence – International Joint Conference on Neural Networks IJCNN, Honolulu, USA, 2039–2043. [38] Lagaros, N.D., Papadrakakis, M., Kokossalakis, G. 2002. Structural optimization using evolutionary algorithms. Comput. Struct., 80(7–8): 571–589. [39] Steen, B. 2005. Environmental costs and benefits in life cycle costing. Manag. Environ. Qual., 16(2): 107–118. [40] Sterner, E. 2002. Green procurement of buildings: estimation of life-cycle cost and environmental impact, Ph.D. dissertation thesis, Department of Mining Engineering, LuleXa University of Technology. [41] Bennett, M., James, P. 1997. Environment-related management accounting: current practice and future trends. Green. Manag. Int., 97(17): 32–52. [42] van der Veen, M. 2000. Environmental management accounting. In: Economics of Environmental Management. Kolk, A., (ed.), Pearson Education Ltd., Harlow, UK, 155–75. [43] Spitzer, M., Elwood, H. 1995. An introduction to environmental accounting as a business management tool: key concepts and terms. EPA, Washington, DC.

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111 Chapter

7 Sustainability and Bridges

Andrew J. Martin, Civil Eng.; COWI A/S, Kongens Lyngby, Denmark. Martin J.D. Kirk, Civil Eng.; Arup, London, UK. Contact: [email protected], [email protected]

7.1

Introduction

How should bridges be considered with regard to sustainability? Should it be by maximizing the use of recycled materials and minimizing CO2 emissions and the use of water? Alternatively, should it be by taking its impacts on local communities during their planning and execution into account? Or, might it be by designing bridges to minimize the need for maintenance and repair during their intended service lives? None of these approaches is necessarily right or wrong, but none on its own sufficiently addresses the breadth and complexity of the challenge posed by sustainability and sustainable thinking to all those involved with bridges—as owners, designers, constructors, maintainers, and users. This chapter seeks to identify the attributes of a sustainable approach to bridges and how such an approach could be achieved in practice. Firstly, a view of the relevance and importance of sustainability to bridges is presented. Then, the fundamental component aspects of sustainability that relate to bridges will be identified and discussed, under the headings of environment, society, and economics. The life cycle of a bridge is then examined, with the purpose of identifying how and when the competing priorities of these “aspects” can be brought together to give integrated and comprehensive solutions. Three case studies are then presented to illustrate practical examples of sustainability in action in real bridge projects. An annotated selected bibliography of relevant references is presented as Further Reading at the end of this chapter. The current work does not propose to offer a “one size fits all” template for a sustainability approach to bridges. All bridges are unique and as such—whether small or large—each deserves a proportionate level of individual consideration in terms of sustainability. Also, from a global perspective, it would be highly presumptive to suggest standard solutions to sustainability issues, regardless of location and irrespective of local concerns and priorities. Instead, it is hoped that a unifying theme will emerge, namely the importance of broad-based structured thinking and informed, responsible and accountable decision-making for delivering sustainable solutions to bridge projects. In this way, bridge engineers and others can make a meaningful, tangible, and accountable response to the challenge of sustainability made 25 years ago in the frequently cited “Brundtland

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Report” of “Meeting the needs of the present without compromising the ability of future generations to meet their own needs” [1].

7.2

Bridges and sustainability

Bridges of all types and sizes are key components of the physical infrastructure that connects and underpins society in all regions of the world. As such, bridges are also large investments by public and private organizations in society and are valuable assets for our collective future prosperity. Bridges consume large quantities of materials in their construction, which have a significant impact on the environment and on their location. Also, most are conceived for the long-term and so are typically designed and specified with the intention that they have service lives of 75–100 years or more. These considerations among many others illustrate the relevance and importance of sustainability in relation to bridges. A central theme to the sustainability of bridges is ensuring that a bridge performs as intended for its full anticipated service life, and perhaps longer. Most of the direct impacts of bridges on the environment (material use, energy, greenhouse gas emissions (GGEs)) take place during its construction, although maintenance and renewal of certain components will be required from time to time.1 It is therefore important that the design of a new bridge takes reasonable account of the functional demands of the future and also that the construction is carried out to the standard necessary to achieve the intended level of durability. Premature loss of durability performance or loss of operational functionality will require either significant remedial repair or strengthening work, or perhaps even complete replacement of the bridge. In a future world of scarcer resources and ever greater focus on the environmental consequences of human actions, it may not be as acceptable as it has been in the past to replace or make significant repairs to prematurely unserviceable bridges, although there will almost certainly be no other alternative. Bridges and infrastructure in general will become even more valuable assets and investments, in environmental as well as in economic terms, and with this, the engineering profession will become more accountable to society for its actions and decisions. To date, a significant amount of effort towards sustainable structures has been focussed on the environmental aspects of construction materials and how they are used. However, the areas of economics and society must not be ignored. Many of the issues in these fields are already familiar to bridge engineers. Sustainability asks that each is given proportionate and timely consideration, rather than the focus being placed on “first cost” alone. Engineers are used to dealing with multifaceted and multidisciplinary design problems and are therefore well positioned to take on the mind-set of balancing the numerous and varied demands of sustainability.

7.3

Aspects of sustainability related to bridges

The most common aspects of sustainability, which relate to bridges, are presented in Table 7.1 and are described in outline in this section under the broad headings of “Environment”, “Society” and “Economics”. 1

This is in contrast to a typical commercial building where, historically, up to 80% of these impacts occur during its 40- to 50-year service life. Improvements to building design in recent years have reduced this ratio but the overall burden from operational impacts remains.

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Environment • • • • • • • •

Materials Energy Emissions Transportation Waste Land use Biodiversity Water

Society • • • • • • •

Aesthetics Design Diversity Access Noise Health, safety, and welfare Community issues

Economics • • • •

Lifetime costs Local effects Employment Long-term value

Table 7.1: Aspects of sustainability related to bridges

Each of these aspects should be given due consideration when a new bridge is being planned or when an existing bridge is being appraised in terms of its future life. As will be described later, this should be done in a balanced way, looking at the aspects together and seeking to minimize negative impacts and maximize positive outcomes. An annotated selected bibliography of sources providing further information is presented in the Further Reading section.

7.3.1

Environment

Materials, energy, and emissions The materials from which a bridge is constructed are a major sustainability issue, which includes consideration of where the raw materials are sourced from, of embodied energy (EE) and of GGEs associated with their extraction, processing, manufacture, and fabrication. The most common materials used in the construction of modern bridges are concrete and steel, both of which place a significant burden on the environment. Other materials such as timber, aluminium, and composites can be used in appropriate situations, each material having its own tariff of associated environmental impacts. In concrete construction, the use of blended cements, in which waste materials are used as partreplacement for Portland cement, is well established. These offer the advantages of reduced demand for new-won raw materials and lower EE and GGE impacts per ton of finished product. The most commonly used cement replacement materials are fly ash and blast furnace slag, both waste products from other industries, and there is active research into other suitable materials. The demand for aggregates for use in construction creates a need for quarrying that has significant environmental impacts. Alternatives to new-won aggregates are therefore beneficial, including crushed recycled concrete and secondary materials arising from mineral extraction. In steel construction, the quantities of iron ore and scrap used in steelmaking vary between different products and different manufacturers. Steel is a readily recyclable material with a high recovery rate from demolition and waste. However, although the use of scrap gives a saving in raw materials, the EE and GGE impacts of steelmaking are repeated in the recycling process. The developments of carbon steels with higher yield strengths offer the possibility of savings in steel quantities, particularly for long-span and cable-supported bridges, but these steels frequently have associated cost implications. In suitable environments, weathering steel provides

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an option where painting is not required. Stainless steel has been used as the main structural material for a small number of bridges. More commonly, where steel is used as reinforcement in concrete structures, stainless steel can give improved long-term durability in areas subject to aggressive environments (e.g. road salt spray) or where access for inspection and maintenance is difficult, dangerous, or impossible. Timber was one of the first materials to be used to build bridges. It has a high strength to weight ratio and has the environmental advantage of being renewable. Timber construction is also well suited to prefabrication. The long-term durability of timber depends on how well it is protected from water in the environment. This can be achieved by structural detailing and by preservatives. Timber is well suited for smaller, more lightly trafficked bridges. However, examples exist of timber bridges with longer spans designed for modern traffic loads. Aluminium offers advantages to bridge designers where self-weight is at a premium, in particular in moving or moveable bridges, and where live loading is relatively low, such as footbridges and cycle bridges. For these reasons, aluminium is frequently used for mobile inspection and maintenance gantries installed on larger bridges. Aluminium is resistant to corrosion in normal environments, although care must be taken at junctions with other metals to prevent bi-metallic corrosion. The manufacture of aluminium uses large quantities of electrical energy and usually takes place in locations where cheap hydroelectric power is available. The place of composite materials in bridges has grown steadily over the past 30 years. Composites can be used as the main structural material, but they also have applications in lightweight enclosures to provide protection from the environment to steel or concrete structures beneath and to provide safe working platforms for inspection and maintenance. Composites have been used with success in the strengthening and repair of existing structures and as reinforcement and pre-stressing in new concrete structures. Transportation Transportation to the site of the components and materials used in bridge construction has impacts in terms of energy use and emissions. These can be reduced by sourcing construction materials locally where possible, especially bulk materials such as aggregates for concrete. The indirect transportation impacts of using alternative materials instead of newly won aggregates should be taken into account when considering their direct benefits. Economic globalization and technical advances in transportation imply that it is both physically possible and economically advantageous to prefabricate major structural components or even complete structures in one location and then to transport them great distances for assembly and erection. However, it is important that due account is taken of the environmental aspects of transportation when such arrangements are proposed. Waste Planning for the construction or rehabilitation of a bridge should include planned consideration of issues concerning waste. Minimization of construction waste gives direct cost savings and

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is a significant way by which the negative environmental impacts of construction materials can be reduced. The generation of hazardous waste should also be avoided. Where waste cannot be eliminated, plans should be made for its proper treatment and disposal. The potential for all construction waste to be reused or recycled should also be maximized. A major source of waste on construction sites arises from the use of bulk, loose, or unbound materials, for example aggregates, cement, and road surfacing. Although this cannot be entirely eliminated, reductions in waste can be achieved by prefabrication of components in conditions where material use can be better controlled. Land use In general, the area of land used by a new bridge should be minimized. New infrastructure wherever possible should be located to avoid using land of special value, such as previously undeveloped ‘green field’ sites, high quality agricultural land, land protected for environmental or historical reasons and land in areas of outstanding natural beauty. Wherever possible, the reuse of previously developed and derelict land should be maximized. The Medway Viaduct (UK) is an example of bridge constructed partly on contaminated land [2]. The alignment of the viaduct dictated that the approach spans on the south side should cross a disused tip containing asbestos waste. The tip was capped to contain the waste and an innovative piling technique was developed to allow construction of the bridge foundations without excavation and without the associated risk of releasing free asbestos dust into the atmosphere. Biodiversity All construction work should take due account of the surrounding flora and fauna, both on land and in watercourses, rivers, and the sea, and seek to minimize the impact of the works on the species affected and on their habitats. Although the construction of new infrastructure can frequently be seen as the enemy of the natural world, the application of one particular type of bridge can help minimize the negative impact of a new road or railway. “Land bridges” (also called “eco-ducts”) have wide decks that carry soil and vegetation, thus providing a green corridor, which maintains the connection between the natural habitats on either side that would have otherwise been lost. The movement of wild animals both large and small is thus allowed to continue.2 The proposed 42 km Qatar-Bahrain Causeway is an example of a major bridge project where biodiversity has been an important consideration [3]. Minimization of long-term changes to sea currents and salt transport were important considerations in setting the alignment of the fixed link. Mitigation methods were also developed for the protection of marine species (e.g. seagrass, coral, fish, turtles, dugongs, and dolphins) including use of the embankments and bridge piles as new habitats for marine life. The construction of Bingley South Bog Viaduct (UK) used an innovative approach to construct a 200 m long highway viaduct across an environmentally sensitive natural peat bog [4]. For this structure, a “jetty”-type incremental construction method was used to erect the precast concrete 2 Significant work has been carried out in the Netherlands on the interaction of nature and infrastructure, including the design of “land bridges” and other facilities for use by wildlife (see Further reading).

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deck, which minimized the footprint of construction activities in the bog. Precast concrete was chosen in preference to steel for the bridge deck, in part to reduce the risk of pollution to the bog arising from maintenance activities during the lifetime of the bridge. Water The construction of bridges that cross watercourses, rivers, estuaries, and sea straits presents a threat to the environment during construction. Bridges also provide an environmental threat in service when considering the potential for pollution from spillages on the carriageway and how they are managed. For long bridges, including multi-span viaducts and long-span cablesupported bridges, there are significant structural and practical consequences in providing continuous positive drainage from gullies in the carriageway back to land. In the past, it has been the practice to discharge carriageway run-off directly into the water below. However, the consequences of pollution following a significant carriageway spillage may make reconsideration of this practice desirable in the future. Depending on the use of road de-icing salts, or their equivalent, there is tremendous scope to use sustainable urban drainage systems (SUDS) such as by retaining rainfall in underground storage basins for later use.

7.3.2

Society

Aesthetics and design The design of a bridge should take into account the visual aspects of its appearance in its setting and surroundings, whether this is an urban, semi-urban, or rural location. Several issues are involved including form, scale, span arrangement, material finishes, and details. This is particularly important as, by their long design lives, bridges usually become semi-permanent features in the local landscape or townscape. Consideration of human scale and interaction is important for bridges intended for pedestrian use. The input of an architect to the design team may be beneficial in appropriate cases, in terms of both overall appearance and consideration of details. Diversity and access Bridge design should take the needs of all potential users into account. In particular, the design of footbridges and of footways for highway bridges should make adequate provision for the disabled and mobility impaired, most readily by avoiding steep gradients and steps. In many jurisdictions, such issues are the subject of statutory regulations or guidelines. The objective of infrastructure is to provide connections. However, it also has the power to divide by cutting across existing communities. Bridges are an important means by which the connections between those living on either side of a major road or railway can be maintained or, where they have been severed in the past, be reinstated. A successful example of this is the Hulme Arch Bridge (UK) [5] where an iconic bridge was used as part of an urban regeneration scheme to reconnect a local road, and thereby reconnect two halves of a community, which had been cut by the construction of a motorway link road 30 years before.

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Noise Noise and vibration from road and rail traffic can have a significant impact on the quality of life in the local community and these should be addressed in the bridge design. The provision of mitigating measures such as noise barriers may be appropriate in populated areas. Health, safety, and welfare The health, safety, and welfare of all those who use, construct, operate, or maintain bridges are important aspects of the contribution of bridge engineers to society and to sustainability. These issues are most commonly the subject of laws and regulations. It is good practice for the engineer to seek ways in which risks to the health and safety of workers can be avoided at source during design. In the UK, and elsewhere, this approach is a legal requirement [6]. Typical examples include maximizing prefabrication in order to minimize the number of man-hours spent working at heights on site, or the substitution of potentially harmful construction materials with more benign alternatives. Designing bridges with safe access for inspection and maintenance activities is also of high importance. By their nature, many bridge construction sites have difficult access and may also be in remote locations, so the provision of adequate welfare facilities for the workforce is particularly important. Community issues Responsibility for the design of bridges rightly belongs in the hands of qualified professional engineers. However, there is a place for the local community to have a voice in the design process, where this is appropriate, over issues such as aesthetics and the planning of critical construction activities. An example of this is provided by the replacement of Ballingdon Bridge in Sudbury (UK). Public involvement in the decision to replace a life-expired highway bridge allowed the client to find an acceptable solution to a politically, environmentally, and technically sensitive and complex problem, in a situation where there were significant concerns about environmental impact, aesthetics, and transport severance during the construction phase [7]. Maintenance of good community relationships with the local population is important throughout any construction project. In particular, the impact of construction on the daily lives of site neighbours should be given careful consideration.

7.3.3

Economics

Lifetime costs Cost is a major driving influence in the development of all new bridges. Indeed, it may be argued that cost is the primary influence as all such schemes must be affordable to their clients at the outset; otherwise, their construction cannot be justified. It is, however, important that costs are taken into account considering the whole life of the bridge and not just its initial construction cost. This is most readily done by considering the net present value (NPV) of each aspect of the

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bridge during its lifetime, including construction, routine operation and maintenance, planned major maintenance (painting, renewals of bearings and movement joints, etc.), and end-of-life demolition. Consideration of costs will affect decisions on other sustainability issues concerning a bridge. It is here that a balanced approach is necessary to understand what level of sustainable performance is desired and what can be achieved, taking into account the available financial resources. Local effects The construction of new infrastructure can have both temporary and permanent effects on the local economy and care should be taken to avoid the negative impacts that may arise. Roads and railways by their nature are linear and thereby have the power to block physical communication across their alignments. The effects on communities have already been mentioned but those on the local economy and businesses also need to be considered. Bridges in new infrastructure offer the opportunity to maintain existing linkages or create new ones for the benefit of the transportation of workers and of goods. The construction of civil engineering works has the potential to be disruptive. If not minimized or mitigated, such disruption could have a permanent detrimental effect on the viability of local businesses. Construction projects offer opportunities to local businesses and it is important to maximize these opportunities during design and procurement, in order to maximize local economic benefits. A striking example is the construction of the Second Hooghly Bridge (India) where, in response to a client requirement, the steelwork for a major cable-stayed highway bridge was designed to be executed using rivets rather than by bolting in order to maximize employment in the local workforce [8]. The construction of the bridge therefore had a direct positive effect on the local economy. Employment The construction of a new bridge creates the opportunity to generate employment and to increase the level of skill among the local workforce. Larger projects give greater opportunities for steps to be taken towards these ends through training schemes and partnerships with local government agencies. However, globalization in the construction industry means that construction activities may be spread around the world, with prefabricated parts being transported significant distances to site prior to final assembly and erection. This particularly applies to structural steelwork. Resisting the economic benefits offered by global procurement for the sake of local workers presents a significant challenge to all concerned. Long-term value As has previously been mentioned, bridges are significant investments by society, not least in financial terms. The need for premature or unplanned maintenance, repair, strengthening, or replacement of a bridge will mean that the necessary funding will need to be diverted from other purposes. As key links in infrastructure, the resilience of bridges to extreme events also needs to be given due consideration in design. The importance of ensuring that a new bridge gives the expected long-term value anticipated at its inception is a core aspect of sustainability.

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The life-cycle of a bridge

It is essential to see the various aspects of sustainability involved and to understand their interrelationships within the context of the whole life of a bridge, from initial inception to final decommissioning and disposal. In this section, possible approaches to the more important decisions with regard to sustainability are discussed within the framework of the bridge life cycle.

7.4.1

Inception, feasibility, and option selection

In the early stages of a bridge project, decisions are made that define the character of the project and the nature of the opportunities that lie ahead during its development. As has already been emphasized, a key aspect of the sustainability of a bridge is its ability to deliver the anticipated level of service for the defined service life. The degree to which this can be achieved will depend greatly on the decisions made at the beginning of the project and their future consequences. Bridge engineers, and others in related disciplines, have the technical knowledge with which to advise the planners of infrastructure projects on the feasibility of different alternatives during route selection. It is important that the right choice of crossing is made for particular obstacles (e.g. viaduct versus embankment, bridge versus tunnel). Although this has been a traditional role for bridge engineers, the input from specialists in other disciplines is needed in order that the “aspects” identified earlier in this chapter can be given due and proportionate consideration as alternative proposals are considered and developed. In particular, such active interdisciplinary collaboration increases the chance that otherwise unseen “win-win” solutions will be identified and developed. Proactive dialogue is also important in this respect. It surely makes sense that disciplines that have traditionally worked in an auditing role to assess the impacts of an already defined scheme (e.g. environmental impact) should be invited to participate “upfront” in the creation of the scheme and take a positive role in seeking innovative multidisciplinary solutions. Two fundamental sustainability aspects of option selection for a bridge are its environmental impact and its cost. Both should be considered on a full life-cycle basis and should be based on a set of defined assumptions about the construction and through-life interventions associated with the bridge. Environmental impact can be determined for the construction materials in terms of their resource depletion, EE, and GGEs using typical values of unit impacts taken from established and verified databases. Materials used for planned maintenance and renewals during the full lifetime of the bridge should also be taken into account (e.g. carriageway resurfacing, which may take place several times). The quantities of the various materials to be used are required for this analysis. This presents a difficulty, in that detailed quantities are not available until the detailed design has been completed. However, feasibility designs for alternative bridge schemes will generate approximate quantities, which should be sufficiently accurate to allow options to be compared on an equal basis. Data on quantities can then be updated and re-evaluated as more accurate information becomes available during design, giving better assurance to the choices and decisions previously made. The assessment of environmental impacts of construction materials must also include the impact of transportation from the “factory” to the site and the impact of the

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activities that take place on site before the materials reach their final location in the bridge (e.g. on-site handling and lifting). Economic impacts should be assessed on the same basis as environmental impact with respect to assumptions regarding initial construction and full life interventions for maintenance and renewals. As previously noted, this can readily be done by the calculation of NPV of each set of actions and comparison of the totals. However, NPV cost calculations can be misleading if a realistic discount rate is not used. In particular, an artificially high discount rate will give an unduly optimistic picture of future costs. An increasing number of tools and methodologies for quantifying sustainability are becoming available for use by bridge owners and designers. Among those developed specifically for bridges are an approach for quantifying sustainability principles in bridge projects [9] and tools for bridge life cycle optimization (life-cycle cost [LCC], life-cycle assessment [LCA], bridge aesthetics, and cultural values) [10].

7.4.2

Design and specification

Once a preferred option has been identified for a bridge and the sustainability objectives of the project agreed, then detailed design and specification of the bridge can commence. Design and specification are key factors in achieving resource-efficient and durable structures. Also, at this stage, there will be the opportunity to maximize the use of sustainable construction materials and to verify the life cycle impact of the preferred solution. Water, especially water containing dissolved carriageway de-icing salts, is the enemy of structural durability for both steel and concrete structures. Places where rainwater or carriageway run-off can collect become sites for corrosion in steel structures. Likewise, surfaces saturated with water promote the deterioration of concrete structures by both physical and chemical processes. In many cases, these problems can be avoided at the design stage by good detailing practice. For example, the incorporation of “drip” details on the bottom edges of cantilever slabs is effective in preventing water running back down and across the faces of adjacent structural elements and thereby their subsequent saturation. Specifications should be written to promote the use of sustainable construction materials and practices, although there is a point at which over prescription can become uneconomic. For example, the availability of recycled concrete for use as aggregate is highly geographically dependent so an absolute requirement for its use in locations of low availability will have unsustainable cost and environmental implications (e.g. transport). The following may seem self-evident, but it is included here as a reminder that the provision of safe structures is a cornerstone and prerequisite of sustainability. Responsibility for the structural safety of a bridge, in both its completed condition and during construction, should only be given to a suitably qualified and experienced engineer. It is common for a design statement or similar report to be prepared defining the requirements for the design of the bridge, which includes items such as purpose, loading, constructability, environmental considerations, and sustainability (e.g. how aspects such as those listed in Table 7.1 will be addressed). The best practice for an independent checking engineer is to verify that the design meets the require-

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ments of the design statement and confirms the adequacy of the drawings without reference to the designer’s own calculations. This is particularly important for large, complex, and unusual structures.

7.4.3

Construction

The intention of the design for a sustainable bridge will not be realized in practice unless the principles and solutions identified earlier in the project are achieved on site. This has two aspects—the construction work itself and the way in which the construction work is carried out. Adequacy of the construction work to produce a durable structure should normally be achieved through appropriate specification by the designer and by adequate supervision of execution by the constructor. The way in which the construction work is carried out has much broader implications with regard to sustainability, particularly with respect to environmental and social aspects. Many of these will frequently be covered by statutory requirements but the construction contract and procurement method also has an important role to play. Relationships with the local community are particularly important with respect to the impact that the construction work will have on people’s daily lives and long-term health, particularly in terms of noise, dust, transportation, and general disruption. When selecting a contractor for the construction of a bridge, there is the opportunity to gain commitment from the prospective contractors to adopt sustainable practices across the broad range of issues presented in this chapter (e.g. see Case Study 3 in Subsection 7.5.3). Selection of a contractor to build a bridge on the criterion of cost alone is unlikely to achieve sustainable outcomes in this regard. Whilst it may be hoped that sustainable practices will become the norm in the future, the wording of construction contracts will remain an important means by ensuring that they are delivered. It is essential that the client and contractor adopt a realistic programme. All too often, the contractor finds himself forced to provide multiple sets of formwork and falsework so that construction can be carried out on a number of different work-fronts simultaneously, in order to achieve a short construction programme. A more sustainable option would be to use less construction equipment, consequentially extending the programme. This is, however, very much dependent on the client being willing to agree to a later project completion date.

7.4.4

Operation and maintenance

Sustainability in the operation and maintenance of bridges depends on timely inspection and the implementation of suitable remedial measures. There is no such thing as a maintenance-free construction material and most modern bridge owners have inspection and maintenance regimes in place. However, although preventative maintenance can avoid more serious problems developing in the long term, it is frequently seen as an expense without a tangible return. This way of thinking goes against the principles of sustainability. Bridges generally do not have significant direct operational impacts (e.g. power usage), with the possible exception of moving bridges. Where operational impacts do exist, they should be minimized by design.

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7.4.5

Assessment and strengthening

Assessment and strengthening are well-developed fields of bridge engineering and are important in terms of sustainability. The increasing weight of goods vehicles on the roads during the last four decades has required the strength of many existing bridges to be assessed. Physical deterioration because of durability problems has also led to many structural assessments being carried out. The same has applied to many bridges supporting railways where increased loading and physical deterioration have also been significant. Structural standards and methodologies have been developed by many bridge owners to allow a realistic picture of the capacity of a bridge to be assessed and this is important in the sustainable direction of resources towards remedial work. Hand in hand with increased loading and physical deterioration has come the need for bridges to be strengthened and also, in some cases, widened. In cases where future increased requirements can be foreseen, new bridges can be constructed with them in mind. For example, if a new road is constructed with dual two-lane carriageways to meet current requirements, but where the best estimate of predicted traffic growth will require dual three-lane carriageways in 20 years’ time, it may be considered sustainable to build the overbridges to span three-lane carriageways in order to avoid the need for future demolition and reconstruction.3 It is a sustainable practice that, where possible, provision for known future modification should be taken account of in the design of a new bridge, even if this is only by means of passive measures or by not allowing arbitrary decisions in the present to prevent future change.

7.4.6

Demolition

As has already been stated, most modern bridges are designed to have a service life of 100 years or more. There are also many old bridges in service today that have been in use for at least a century and in many cases much longer. By virtue of their size and value, bridges are not frequently demolished. Rather, if over time they begin to fail to meet prevailing requirements, for reasons of cost, they are more usually repaired, strengthened, or widened. However, when bridge demolition is carried out, it is important that this is done safely. The design of new bridges should take into account their eventual demolition in terms of safety and also in terms of how readily their constituent materials can be separated and recycled for other uses.

7.5

Case studies

Three case studies are presented, taken from recent and ongoing projects, each of which gives a practical example of sustainable outcomes and of sustainable thinking in action. •

Capilano River Bridge replacement. How a bridge construction project can deliver a range of important sustainability outcomes.

3

The judgement of this issue is made more complex because the unchecked growth of road transport powered by the internal combustion engine is not in itself considered to be sustainable itself. In any case, prediction of long-term future traffic demand—and hence the need for this approach—is also difficult.

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Queensferry Crossing. How sustainability was integrated into the development of a major bridge and infrastructure project. Bridges for the Queen Elizabeth Olympic Park, London. How a major contribution to sustainability may be achieved by considering a project in its broadest context.

•

7.5.1

Case study 1—Capilano River bridge replacement (Canada)

The Capilano River Bridge carries a major highway link across the Capilano River between North and West Vancouver in British Columbia, Canada. The project to replace part of the existing crossing and upgrade the bridge presented significant technical, organizational, and constructional challenges to the owner, consulting engineer, and contractor [11]. The project also illustrates how a bridge construction project can deliver a range of important sustainability outcomes. The existing Capilano River Bridge comprised two separate structures. The original bridge, which carried the narrow westbound carriageway, was a steel through truss bridge with a 76 m span, constructed in 1930, which had been lengthened by the addition of a second 55 m span in 1949. Additional traffic capacity was provided in 1956 by the construction of a three-lane girder bridge immediately alongside the existing structure. By 2009, the physical condition of the steel truss bridge was assessed to be beyond economic repair. The bridge was also considered to be functionally obsolete as the two-lane westbound carriageway formed a bottle neck for traffic, which numbered over 25 000 vehicles a day. Provisions for pedestrians and cyclists were also poor. The steel truss bridge therefore needed to be replaced. Funding for the project became available at short notice in early 2009 with the condition that substantial completion was achieved by 31 March 2011, giving an exceptionally short 2-year period for all design and construction activities. Major challenges • • • • •

To replace the existing steel truss bridge, on the existing alignment, without interruption to traffic. To complete the project within a 2-year programme to meet project funding availability. To protect the natural environment in the Capilano River, including accommodating a restriction limiting construction work in the river to a 2-month “fish window” each summer. To carry out major construction work on a restricted site in the heart of a residential area and a commercial area. To accommodate further programme restraints arising from a moratorium on construction work during February and March 2010, during the period of the Olympic and Paralympic Games in Vancouver and neighbouring Whistler, between which the highway crossing the Capilano River Bridge formed a key link.

Solutions •

Sliding the existing 1300 ton steel truss bridge sideways onto temporary supports to make space for construction of the new bridge, whilst creating a temporary construction detour for westbound traffic (see Fig. 7.1). The bridge slide was completed during one overnight

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Fig. 7.1: Capilano River Bridge during bridge slide (Image Courtesy: British Columbia Ministry of Transportation and Infrastructure)

•

• • •

possession between 19 and 20 June 2010, with westbound traffic being temporarily diverted in contra-flow onto the eastbound carriageway. The truss bridge was reopened to traffic in its new location the next morning. Limiting construction work in the river for the detour structure to the one temporary pier required for the bridge slide solution, constructed during the summer 2009 “fish window”. Alternative solutions for the detour using proprietary panel bridge systems required more temporary piers in the river bed. Provision of a new bridge with three wider traffic lanes, a dedicated lane for public transport transit buses and a shared pedestrian footpath/cycleway. Designing the new bridge deck with steel plate girders, which could be launched into position, thus minimizing the construction work to be carried out in the river. Collaboration planning between owner, consultant, and contractors to meet tight programme deadlines, including streamlining technical and environmental approvals, advanced planning, and early construction works.

Sustainability outcomes Environment •

Reducing construction material usage, by reusing the existing truss bridge as the temporary construction detour.

•

Recycling of materials from the truss bridge and temporary detour route once the project was complete.

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Minimization of adverse ecological impacts on the Capilano River. Reduction in emissions and fuel consumption due to traffic, by reducing congestion through the provision of an additional traffic lane on the new westbound bridge.

Society •

Improved road safety by the provision of wider traffic lanes, a shared footpath/cycleway, better highway lighting and upgraded safety barriers. • Improved public transportation by the provision of a dedicated lane for transit buses. • Increased pedestrian and cycle traffic opportunities, encouraged by the provision of the footpath/cycleway. • Improved aesthetics created by the low profile of the new bridge. • Improved air quality for the local community because of decreased traffic congestion. • Minimization of construction impacts on local residents. Economics • • •

• •

Direct cost savings of approximately CAN$ 500,000 by sliding the existing truss bridge to become the temporary construction detour. Utilization of the available project funding within challenging time constraints. Minimization of whole-life costs of the new bridge by reducing maintenance requirements (weathering steel girders, integral abutments without bearings and movement joints). Reduced economic disruption due to traffic delays caused by congestion. Maximization of long-term value of the new bridge by including passive provision to allow widening when the existing eastbound bridge reaches the end of its useful life.

Commentary The replacement of the life-expired steel truss spans of the Capilano River Bridge serves as an example of a challenging bridge engineering project that delivered a solution that fulfilled a number of diverse but interdependent challenges. In terms of sustainability, the decision to slide the old bridge to form the construction detour added significant value to the project both economically and in terms of benefits to the environment and society. Without the bridge slide, the project would still have yielded benefits. However, the outcomes achieved were significantly greater because of the imagination and innovative approach of those involved with the project. Key project participants Bridge owner: British Columbia Ministry of Transportation and Infrastructure Structural engineer: Buckland & Taylor Ltd General contractor: Neelco Construction Inc.

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7.5.2

Case study 2—Queensferry Crossing (Scotland, UK)

On completion in 2016, the Queensferry Crossing (formerly called the Forth Replacement Crossing [FRC]) will be a critical link in the road infrastructure of Scotland by providing a replacement route for vehicles to the neighbouring Forth Road Bridge. The scheme includes a major cable-stayed bridge with three towers supporting two adjacent 650 m long navigation spans and an innovative arrangement of crossing stay cables (Fig. 7.2). There are also an approach viaduct, major link roads, and junction upgrades at connections to the road network [12–14]. The planning and design of the new crossing prior to its tender as “design and build” construction contract gave the owner, Transport Scotland, the opportunity to be proactive with regard to sustainability, in particular in response to the sustainable development policies and commitments of both the Scottish and UK governments. A key outcome of this was the publication by Transport Scotland of the “Forth Replacement Crossing Sustainable Development Policy”, which contained statements on its vision, policy, and objectives for sustainability [15]. The policy statement contained in the document was as follows: The Forth Replacement Crossing project will place Sustainable Development (SD) principles—that embrace sustainable economic growth, equality and social inclusion, environmental quality, climate change, and protection of the natural and cultural heritage—at the centre of its management, planning, and delivery. The project’s sustainability objectives will define our priorities for the use of resources, carbon management, sustainable communities, and environmental management and will focus on our efforts to embed sustainability in the key aspects of the project. This statement clearly reflected both the ambition and the determination of the bridge owner with regard to embedding sustainability and sustainable development in the project.

Fig. 7.2: Queensferry Crossing cable-stayed bridge (right) and the existing Forth Road Bridge (left) (artists impression) (Image courtesy: Transport Scotland ©)

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Sustainability appraisal The practical realization and integration of the sustainability policy into the project took place through a sustainability appraisal process undertaken by Transport Scotland and its consultants. This was a dynamic process that took place over 18 months during the development of the employer’s requirements for the “design and build” contract and the specimen design of the scheme. The sustainability appraisal was built around a framework of sustainability objectives, targets, and indicators developed during an initial high-level workshop. In addition to the client’s project team and consultants, the participants in the workshop included key stakeholders from elsewhere in the client organization. The sustainability objectives looked at the project from a life cycle perspective—considering design, contract preparation, tendering, construction, and operation—and were framed wherever possible in objective terms (i.e. SMART—Specific, Measurable, Achievable, Realistic, and Time-bound). In total, 17 sustainability objectives were defined, comprising between them 41 targets and 81 indicators. The sustainability objectives are summarized in Table 7.2. Each sustainability objective was assigned to a “sustainability champion” from within the project team, who was given responsibility for seeing that the objectives and targets were integrated into the approach and outputs of the many and various disciplines involved in defining the project and preparing the contract documentation. This process was supported by regular meetings of the sustainability champions to report on progress against the indicators and to share ideas.

• • • • • • • • • • • • • • • • •

To design, build and operate a reliable crossing To contribute to the improvement of cross-Forth access to economic opportunities To contribute towards the development of cross-Forth Public transport opportunities To minimize the scheme footprint and severance of land To adopt sustainable resource management in design and construction To ensure that community engagement takes place at all key stages in the project process To improve local accessibility and reduce community severance To provide a scheme that accommodates the needs of disabled people To contribute to the promotion of healthy lifestyle opportunities and social inclusion To provide a safe design for both vehicle travellers and non-motorized users To reduce, reuse and recycle materials and products where practicable Seek to minimize embodied energy and carbon associated with key materials and their transport to site To minimize carbon emissions once the scheme is open to traffic To protect and enhance the natural heritage including local biodiversity To protect the landscape, historic environment and natural heritage To reduce noise and air emissions To protect water quality, geomorphology and maximize the use of sustainable drainage systems for environmental and hydrological benefit

Note. For details of the targets and indicators relating to the sustainability objectives, see Appendix 2 of Ref. [16].

Table 7.2: Queensferry Crossing—sustainability objectives

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Design innovations that addressed sustainability issues were also sought out and reported. The outcome of the sustainability appraisal was reported in the “Forth Replacement Crossing Sustainability Appraisal and Carbon Management Report” [16]. Resources, energy, and carbon In parallel with the sustainability appraisal, two other significant sustainability initiatives were undertaken, both related to the project sustainability objectives and the details of which are reported in the appendices to Ref. [16]. A “sustainable resource management framework” was developed with the aim of establishing a coordinated approach to the supply, management, and use of materials and other resources on the project. Seven key stages of the project were identified in the framework (material specification, material and resource sourcing, transportation of materials, workforce travel, storage and handling of materials, use of resources and materials, and disposal of materials) and objectives and indicators were established for each. An “energy and carbon assessment” was also carried out, including an audit of the energy and carbon footprint of the specimen design. The assessment had the joint objectives of allowing comparison of the impacts of options during scheme development, the comparison of contractor designs presented at tender and ongoing monitoring and accounting. Commentary The Queensferry Crossing illustrates how a bridge owner with a commitment to sustainable development embedded the principles of sustainability within a major project to construct a world-class bridge and its associated works. The project offers considerable learning opportunities for all involved with bridge projects and has been comprehensively reported in the public domain [16]. Key project participants Bridge owner: Transport Scotland (an agency of the Scottish Government) Consultants: Jacobs Arup JV, Natural Capital

7.5.3

Case study 3—Bridges for the Queen Elizabeth Olympic Park, London (UK)

London hosted the Olympic and Paralympic Games in 2012 with the majority of the events being held in the new Queen Elizabeth Olympic Park (Fig. 7.3). In addition to providing major venues such as the Olympic Stadium, Basketball Arena, Velodrome, and Aquatics Centre, the park required extensive infrastructure including more than 30 bridges and underpasses, 20 km of highways and landscaping [17]. The London Games have been described as one of the most sustainable Games ever and has allowed a semi-derelict industrial area of London to be upgraded. A large number of temporary structures have been used, with designs catering for the clear and

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Fig. 7.3: Queen Elizabeth Olympic Park (Image courtesy: M. Kirk/Arup ©) differing objectives both during the Games and afterwards in “legacy”. After the Games, many of the structures and venues will be either removed or downsized. Major infrastructure redevelopment With 5 years until the opening of the park, the Olympic Delivery Authority (the body tasked with delivering the new park) had formed a positive sustainability plan developed during preparation of the overall scheme for planning approval in 2007 [18]. The mission was to “deliver venues, facilities and infrastructure and transport on time and in a way that maximises the delivery of a sustainable legacy within the available budget” [19]. With such a big infrastructure project involving redevelopment of the railways, new venues, new structures, bridges, highways, and housing, the sustainability aspirations were crystallized. Starting with five key themes of climate change, waste, biodiversity, inclusion, and healthy living, sustainability aspirations were extended to the widest possible view and considered the following topics [19]: • • • • • • • •

Carbon Water Waste Materials Biodiversity and ecology Land, water, noise, and air Supporting communities Transport and mobility

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Access Employment and business Health and well-being Inclusion (easy access for all)

Real and measurable targets Having set aspirations to deliver the ‘greenest’ Games ever, positive and measureable targets were set. These included Refs. [20,21]: •

• •

• • • •

The aspiration was to reduce carbon dioxide emissions in permanent buildings by 50%, and 58% reduction was achieved. This included providing a new combined cooling, heating, and power plant. The target was to reduce potable water use by 40%, and 60% reduction was achieved by recycling of rainwater and reuse of both grey and treated black water. The target was to achieve 90% in reuse, recycling, or recovery of demolition materials and 98% was achieved. Extensive soil cleaning and washing or bio-remediation was carried out for excavated material [22]. The target was to achieve 25% recycled aggregate and 42% was achieved. 45 ha of new bio-diverse habitats to be delivered and 25 were provided during the Games and 45 should be achieved in the long term (in legacy). All timber was to be obtained from legal and sustainable sources and was achieved. The target was to deliver 50% by train or waterways rather than by road, and 67% was achieved.

These targets were achieved through a positive attitude towards sustainability between all parties concerned with the design and construction. Indeed, sustainability clauses were included within the contracts [20]. Bridge specifics Consider now the bridges in further detail in relation to major gains in the sustainability topics [23]. Carbon—minimize embodied carbon emissions •

•

The carbon footprint of the bridges was estimated. The most effective way to reduce use of embodied carbons is to minimize the size and material quantities of the bridges. As a starter, reuse of and modification to existing bridges was considered. With the majority of the bridges being for pedestrian use, the bridge width requirements were studied carefully. Pedestrian flow studies were carried out, which predicted the density of the crowd flow during the Games in line with the Games event schedule. Some bridge widths needed to be considerably wider during the Games reaching up to 60 m width [23]. It was therefore realized that splitting the bridges into temporary and permanent com-

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ponents gave opportunities not only to recycle or reuse the temporary section, but it also afforded additional area for landscaping and planting. A few bridges did not require permanent portions and were purely provided for the Games. After the games, the temporary bridges will either be used elsewhere or recycled. One of these was created by reusing a modified version of a bridge provided for construction of the works. Plans are in hand to relocate the bridge to an alternative location within the Park [24].

Waste—reduce and recycle •

Approximately 2700 ton of crushed concrete was recycled from the site for use within the abutment and wing-wall facings and contributed to achieving the intended target.

Materials—use environmentally and socially responsible materials • •

The concrete mix was developed to include both secondary/recycled aggregate and either ground granulated blast furnace slag or pulverized fuel ash as a cement replacement. All timber used was from sustainable sources.

Biodiversity—provide habitats for birds, bats, and reptiles •

•

A high quality habitat has been achieved for flora and fauna with nesting places attached to bridges and within the embankments. This has included fitting more than 130 bird and bat boxes. The bird boxes were formed from waste pipe offcuts. The reduction in the width of bridges will have a positive impact on improvement and reestablishment of the park’s natural ecology. This has also been improved by detailing the bridges with cantilevers and inclined webs, and the careful design of lighting level under the bridges. Shade-tolerant plants have been selected for the river edges below bridge decks. Removal of temporary bridge components will reduce shading considerably in legacy.

Transport—sustainable transport via water or rail •

The site was adjacent to waterways linking the River Thames and to railways linking to Stratford and Liverpool Street stations in central London. This afforded the opportunity to limit the use of the road network and keep carbon use for material delivery to a minimum. Whilst the highways were used for many items, both the railways and waterways were used to enable the desired target to be achieved overall.

Inclusion—disabled and mobility impaired fully included within the design •

To deliver against the accessibility targets, the Olympic Park is designed generally to provide gradients of 1:60 but no more than 1:20 in publicly accessible areas [25]. This has a tremendous effect on the landscaping and ramp lengths.

Sustainability assessment Reviews were taken with a positive attitude to sustainability and records of the reviews were kept. This enabled an independent assessment to be carried out by CEEQUAL. This

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is an evidence-based Sustainability Assessment and Awards Scheme for civil engineering, infrastructure, landscaping and the public realm in the UK [26]. This scheme can be used worldwide but similar schemes should also exist. Separate submissions were made for the different contracts. For example, the bridge design and construction for the stadium bridges have achieved the highest possible “Excellent” award with a score of 95% [23]. Commentary A prime point of learning from this project was that although limited gains in sustainability may be achieved when considering building bridges alone, but when a full account is also taken of the approaches, embankments, and infrastructure, significant gains may be made. As the world populations increase, so the requirement for new infrastructure increases; it is for the engineer to promote more efficient use of our world’s resources. Further details of sustainability studies on the Queen Elizabeth Park are available at the websites listed as references [27]. Key project participants Client: Olympic Delivery Authority Delivery Partner: CLM (formed from CH2M Hill, Laing O’Rourke and MACE) Lead infrastructure/bridge consultants: Arup and Atkins

7.6

A sustainability checklist for bridges

A checklist to assist in the development and review of sustainability options for bridges is presented in Table 7.3. This is for guidance and is not intended to be exhaustive.

7.7

Conclusion

Sustainability is a broad subject with far-reaching consequences in day-to-day lives, and the global construction industry is not the least among the sectors of human activity, which is giving attention to sustainability issues. Bridges are one of many discrete but interrelated fields within that sector. It is hoped that this chapter has provided an overview of sustainability in relation to bridges. Our understanding of these issues is incomplete and the means by which we incorporate sustainability into bridge engineering are still being developed. However, a key to achieving sustainable bridges will be the willingness by all concerned—and perhaps by bridge engineers in particular—to look beyond the traditional boundaries of their own technical disciplines and to seek more integrated, better solutions that address the multiple challenges with which they are presented. Above all, bridge engineers will need to be able to communicate better regarding sustainability and their work for their clients, project collaborators, and to the public at large.

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7.6 A SUSTAINABILITY CHECKLIST FOR BRIDGES

Aspect

Prime party

Fundamental Owner, Designer

Action Carry out environmental impact assessment (EIA)

Remarks Consider independent certification through CEEQUAL or similar sustainability rating system. Carry out a sustainability assessment using proprietary tools or from first principles, including embodied carbon calculations

Fundamental Designer

Minimize structural sections and the use of materials. Design all sections to their limit

Use continuous rather than simply-supported spans. This will also limit use of expansion joints and water/de-icing salt ingress points. Minimize pier sizes to reduce likelihood of flooding on river banks if piers are in a river

Fundamental Owner

Accept that additional upfront costs may arise for being sustainable

The challenge: the owner may not necessarily gain direct benefits for being sustainable but society does

Fundamental Owner, Designer

Reuse and modify existing structures where realistically practicable

Save material

Transport

Owner, Designer

Bridges with provision Discourage individual diesel/petfor rail, bus, electric cars, rol car use cyclists and pedestrians (including mobility impaired/ disabled) to be encouraged

Transport

Owner, Designer

Bridges that will last for 120 years rather than 20 years

Encourage use of public transport, shared driving such as by using priority lanes

Transport

Designer, Contractor

Materials to be brought in by rail and water rather than road where possible

Limit use of direct supply by lorry

Materials

Designer, Contractor

Use recycled aggregate, pulverized fuel ash (PFA) or ground granulated blast furnace slag (GGBS)

Use waste by-products of manufacture and minimize use of cement

Materials

Designer, Contractor

Reuse existing steelwork sections

Primarily for standard section sizes and hence small spans

Materials

Contractor

Provide materials from local sources

Consider carefully if materials are to be sourced from the other side of the world

Table 7.3: A sustainability checklist for bridges (continued)

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Aspect

Prime party

Action

Remarks

Materials

Designer

Timber to be from sustainable sources

This generally precludes hardwoods

Materials

Designer

Use of weathering or stainless steel in place of painting

May be some benefit to remove requirements for painting and repainting

Materials

Designer

Use of stainless steel reinforcement

Extend durability life of reinforced concrete structure

Construction Owner, Designer

Compare short-and longterm needs

Provide a temporary reusable or recyclable structure if functionality is only required in the short term (e.g. wide deck width required for a major special event)

Construction Owner, Contractor

Avoid too tight a time table Greater reuse of formwork/falsefor construction work

Construction Contractor

Reduce quantities of exported and imported fill to a minimum

Avoid transportation impacts and landfill tax (if applicable)

Environment Designer, Contractor

Provide local flora

Translocate surface topsoil and plant to other location to compensate for areas of lost vegetation

Environment Contractor

Avoid works during breed- May extend construction proing season of local wildlife gramme

Environment Owner, Designer

Consider not providing Give scope for retrofit if safety deck lighting but make pas- requirement for lighting changes sive provision if installation becomes necessary later

Environment Designer

Limit width of bridges or use box structures with large cantilevers

Maximize light under bridge to promote plant growth and minimize requirement for artificial lighting

Environment Designer

Provide habitats for flora and fauna

Provide bird and bat boxes Provide badger tunnels if route displaced by bridge

Society

Owner, Designer

Choose site location to benefit the local area and society

Use of a brownfield site so that greenfield sites are available for other uses Maximize benefits to local people and trades

Society

Designer

Limit noise to local residents

Provide functional and aesthetic noise barrier (Continued)

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ACKNOWLEDGEMENTS

Aspect

Prime party

Action

Remarks

Society

Designer

Improve the landscaping and include planting

Provide aesthetic structure and earthworks layout

Society

Owner, Designer

Allow for access and stopping places for mobility impaired

Ensure walkway slopes limited

Water reduction

Designer

Use low water cement ratio Use high strength concrete and high strength concrete

Water reduction

Designer

Recycle rain water

Use SUDS and rainwater-harvesting systems

Maintenance Owner

Limit use of de-icing salts

Extend life of concrete

Maintenance Designer

Use of dehumidification for Carefully consider running costs steelwork boxes and cables

Table 7.3: A sustainability checklist for bridges

Acknowledgements The authors acknowledge the part played by colleagues, project co-collaborators, and friends in stimulating their thinking on sustainable development. In particular, the authors acknowledge the work and achievements of the owners, engineers, contractors, consultants, and all other parties involved in the projects used in the Case Studies. Permissions to use copyright images in the figures are gratefully acknowledged.

References [1]

World Commission on Environment and Development. 1987. Our Common Future. Oxford University Press, Oxford. [2] Martin, K., Bennett, S., Kirk, M. 2003. Channel tunnel rail link section 1: Medway viaduct. Proc. ICE Civil Eng., 156: 36–39. [3] Ostenfeld, K.H. 2009. An Integrated Multidisciplinary Approach to Design of Major Fixed Links, IABSE Venice Symposium Report, Volume 97. [4] Thomas, G. 2005. A650 Bingley Relief Road – South Bog Viaduct, Concrete, November/ December 2005, 65–67. [5] Hussain, N., Wilson, I. 1999. The Hulme Arch Bridge, Manchester. Proc. ICE Civil Eng., 132: 2–13. [6] United Kingdom. 2015. The Construction (Design and Management) Regulations. [7] Parker, D. The ballad of Ballingdon Bridge, New Civil Engineer, 10 August 2000. [8] Holgate, A. 1997. The Art of Structural Engineering: The Work of Jörg Schlaich and his Team, Edition Axel Menges, Stuttgart/London, 156–169. [9] Spencer, P.C., Hendy,C.R, Petty, R. 2012. Quantification of sustainability principles in bridge projects. Proc. ICE Brid. Eng., 165: 81–89. [10] Salokangas, L. (ed.). 2013. ETSI Bridge Life Cycle Optimisation Stage 3, Aalto University, Science + Technology 4/2013, Helsinki.

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[11] Johnson, M., Queen, D. 2011. Owner, consultant and contractor collaboration for rapid delivery of the marine drive transit priority project, Transportation Association of Canada Annual Conference, Edmonton, Alberta, 11–14 September 2011. http://www.tac-atc.ca/ english/annualconference/tac2011/docs/m2/johnson.pdf. [12] Carter, M., Kite, S., Hussain, N., Minto, B. 2010. Design of the Forth replacement crossing, Scotland. Proc. ICE Brid. Eng., 163(BE2): 91–99. [13] Curran, P., Elnegaard, J., Patsch, A., Bolton, I., Goldie, I. 2011. Forth replacement crossing – tender design, IABSE Symposium, London, September 2011. [14] Carney, C.T., Nowak, D. Forth Replacement Crossing – Construction Proposals, IABSE Symposium, London, September 2011. [15] Transport Scotland. Forth Replacement Crossing Sustainable Development Policy, January 2009, http://www.transportscotland.gov.uk/files/documents/projects/forth-replacement/ frc_-_sustainability_development_policy_-_January_2009.pdf. [16] Transport Scotland. Forth Replacement Crossing Sustainability Appraisal and Carbon Management Report, November 2009, http://www.transportscotland.gov.uk/strategyand-research/publications-and-consultations/j11364-00.htm. [17] Baird, D., Thurston, M., Triggs, C., Corrigan, H., Samaras, S. 2011. Delivering London 2012: Structures, bridges and highways. Proc. ICE, Civil Eng., 164: 23–29. [18] Nimmo, A., Frost, J., Shaw, S., McNevin, N. 2011. Delivering London 2012: master planning. Proc. ICE Civil Eng., 164: 13–19. [19] Olympic Delivery Authority. Sustainable Development Strategy (Publication code: LOSD/4/07), ODA, London, January 2007, http://learninglegacy.independent.gov.uk/ documents/pdfs/sustainability/22-sustainable-development-strategy-sust.pdf. [20] Epstein, D., Jackson, R., Braithwaite, P. 2011. Delivering London 2012: Sustainability strategy. Proc. ICE, 164: 27–33. [21] Olympic Delivery Authority. Delivering change (3-pre-games-sustainability-report_Neutral.pdf), ODA London 2012, website, April 2012. http://learninglegacy.independent.gov. uk/documents/pdfs/sustainability/5-london-2012-post-games-sustainability-report-interactive-12-12-12.pdf. [22] Hellings, J., Lass, M., Apted, J., Mead, I. 2011. Delivering London 2012: geotechnical enabling works. Proc. ICE, 164: 5–10. [23] Baird, D., Kirk, M., Dhanipersad, S., Cook, S. 2011. Bridges, short and long term solutions for the London 2012 Games, IABSE Symposium, London, September 2011. [24] Kvist, E. Bridge linking Greenway to Stratford to be relocated to Olympic Park. Newham Recorder, 16 November 2012. http://www.newhamrecorder.co.uk/news/bridge_ linking_greenway_in_stratford_to_be_relocated_to_olympic_park_1_1695380#. [25] Olympic Delivery Authority. 2012. Inclusive Design Standards, ODA, London, http:// learninglegacy.independent.gov.uk/documents/pdfs/equality-inclusion-employment-andskills/62-inclusive-design-standards-eies.pdf. [26] Burgess, C., Connolly, S., Jorgensen, R. 2012. Achieving CEEQUAL Excellent in the Olympic Park, ODA, London, June 2012, http://learninglegacy.independent.gov.uk/publications/achieving-ceequal-excellent-on-the-olympic-park.php. [27] The London Organizing Committee of the Olympic Games and Paralympic Games. Learning Legacy. http://learninglegacy.independent.gov.uk/themes/sustainability/index.php.

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FURTHER READING

137

Further reading In this section, a selection of published material relevant to sustainability and bridges is presented. This is not a comprehensive review of information contained in the literature, but it intends to provide a starting point for further reading and investigation. General The following provide an overview of sustainability in relation to civil engineering, infrastructure and bridges. • • •

• • • • • •

• • •

Head, P.R. 2009. Entering an ecological age: the engineer’s role. Proc. ICE Civil Eng., 162: 70–75. Willets, R., Burdon, J., Glass, J., Frost, M. 2010. Fostering sustainability in infrastructure development schemes. Proc. ICE Eng. Sustainability, 163(ES3): 159–166. Fenner, R.A., Ainger, C.M., Cruikshank, H.J., Guthrie, P.M. 2006. Widening engineering horizons: addressing the complexity of sustainable development. Proc. ICE Eng. Sustainability, 159(ES4): 145–154. Silman, R. 2007. Sustainable engineering – a philosophical perspective. Struct. Eng., 85(9): 38–42. Institution of Structural Engineers (UK). 2011. Sustainability for bridge engineers – part 1. Struct. Eng., 89(5): 12–13. Institution of Structural Engineers (UK). 2011. Sustainability for bridge engineers – part 2. Struct. Eng., 89(5) 14–15. Martin, A.J. 2004. Concrete bridges in sustainable development. Proc. ICE Eng. Sustainability, 157(ES4): 219–230. Steele, K., Cole, G., Parke, G., Clarke, B., Harding, J. 2003. Highway bridges and environment – sustainable perspectives. Proc. ICE Civil Eng., 156: 176–182. Daniel, R.A. Environmental considerations for structural material selection for bridges, European Bridge Engineering Conference – Lightweight Bridge Decks, Rotterdam, March 27–28, 2003. Collings, D. 2006. An environmental comparison of bridge forms. Proc. ICE Brid. Eng., 159(BE4): 163–168. Spencer, P.C., Hendy, C.R., Petty, R. 2012. Quantification of sustainability principles in bridge projects. Proc. ICE Brid. Eng., 165: 81–89. Salokangas, L. (ed). 2013. ETSI Bridge Life Cycle Optimisation Stage 3. Aalto University, Science + Technology 4/2013, Helsinki.

Sustainable concrete •

Swamy, R.N. 2001. Holistic design: key to sustainability in concrete construction. Proc. ICE Struct. Build., 146(4): 371–379.

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CHAPTER 7. SUSTAINABILITY AND BRIDGES

Desai, S. 2011. Sustainable concrete construction and engineering. Struct. Eng., 89(9): 30–33. Oyawa, W.O. 2004. Eco-materials for developing countries. Struct. Eng. Int., 14(3): 208– 212. Nielsen, H.O. 2002. Demo project green bridge, Proc. XVIII Nordic Concrete Research Meeting, Helsingør, Denmark, June 2002, 41–43. Mathiesen, D., Berrig, A. 2002. Centre for Grøn Beton – Demobro. Teknologisk Institut, Beton, Denmark, (In Danish).

Cements •

Price, W. 2009. Cementitious materials for the twenty-first century. Proc. ICE Civil Eng., 162: 64–69.

Concrete aggregates •

Marsh, B. 2006. One Coleman Street – A Case Study in the Use of Secondary Materials in Concrete. Institute of Concrete Technology Yearbook 2006–7, Institute of Concrete Technology, Camberley, UK, 45–55.

Steel • •

Dolling, C.N., Hudson, R.M.. 2003. Weathering steel bridges. Proc. Institut. Civil Eng. Brid. Eng., 156(BE1): 39–44. Sobrino, J.A. 2006. Stainless steel road bridge in Menorca, Spain. Struct. Eng. Int., 16(2): 96–100.

Timber • • •

Lawrence, A. 2008. Modern timber bridges – an international perspective. Struct. Eng., 86(18): 26–31. Ekeberg, P.K., Søyland, K. 2005. Filsa Bridge, Norway – a record-breaking timber bridge. Proc. Institut. Civil Eng. Brid. Eng., 158(BE1): 1–7. Gerold, M. 2006. Economy and efficiency of modern timber bridges – life expectancy and costs of maintenance. Struct. Eng. Int., 16(3): 261–267.

Aluminium • •

Siwowski, T. 2006. Aluminium bridges – past, present and future. Struct. Eng. Int., 16(4): 286–293. Radbeck, C., Dienes, E., Kosteas, D. 2006. Aluminium structures – a sustainable future? Struct. Eng. Int., 16(4): 339–344.

Composites •

Head, P. 2004. New bridge technology for sustainable development. Proc. ICE Brid. Eng., 157(BE4): 193–202.

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FURTHER READING

•

139

Firth, I., Cooper, D. 2002. New materials for new bridges – Halgavor Bridge, UK. Struct. Eng. Int., 12(2): 80–82.

Environment and biodiversity Assessment and mitigation of environmental issues for the major bridge forming the HongKong Shenzhen Western Corridor are described in: •

Lee, J.K.T., Yiu, S.F.L., Lau, J.Y.Y., Li, M.S.M., Chan, S.Y., Kwan, S.C.F., Wan, M.M.O., Wong, C.H.Y. Hong-Kong – Shenzhen Western Corridor: Environmental Challenges from EIA Study to Construction. http://ev.hkie.org.hk. Extensive work has been carried out in the Netherlands into land bridges and the optimal aspects of their design to promote their successful use by animals. Rijswaterstaat (the Netherlands): Nature Across Motorways, Rijswaterstaat, Delft, 1995.Where it is not possible to avoid particular areas of natural habitat, translocation may be a viable alternative to destruction. •

Box, J., Stanhope, K. 2010. Translocating wildlife habitats: a guide for civil engineers. Proc. ICE Civil Eng., 163: 123–130.

Aesthetics and design The following give practical advice on the aesthetics and appearance of bridges. • • •

Leonhardt, F. 1982. Brücken - Bridges. DVA, Stuttgart. Gottemoller, F. 1998. Bridgescape – The Art of Designing Bridges. John Wiley & Sons, New York. Highways Agency (UK). 1996. The Appearance of Bridges and Other Highway Structures. HMSO, London.

Further relevant discussion can be found in: • • •

Menn, C. 1996. The place of aesthetics in bridge design. Struct. Eng. Int., 6(2): 93–95. Walther, R. 1996. Engineers, architects and bridge design. Struct. Eng. Int., 6(2): 77–79. Gimsing, N.J. 1999. Bridge aesthetics and structural honesty, IABSE Symposium, Rio de Janeiro.

Issues relating to the landscape design of a major infrastructure project are discussed in: •

Armour, T. 2003. Channel tunnel rail link section 1: landscape design. Proc. ICE Civil Eng., 156: 54–59.

Health, safety, and welfare The following document describes how health and safety can be incorporated into construction through the design process. Although it is written in terms of legal requirements in the United Kingdom, the principles are worthy of more general consideration.

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CHAPTER 7. SUSTAINABILITY AND BRIDGES

United Kingdom. 2015. The Construction (Design and Management) Regulations 2015, TSO, London.

Community participation Experiences of community participation and of community relations during the construction of major infrastructure projects are given in: •

•

Bordoley, S., Gilham, A., Abbott, J. 2002. Adding a Social Dimension to Engineering to Aid the Sustainable Development Process, International Sustainable Development Research Conference, University of Manchester, UK. Gambrill, B. 2003. Channel tunnel rail link: community relations during implementation. Proc. ICE Civil Eng., 156: 24–27.

Employment •

Martins, L., Bowsher, K., Eley, S., Hazelhurst, G. 2011. Delivering London 2012: workforce diversity and skills. Proc. ICE Civil Eng., 164: 40–45.

Demolition •

Clarke, R. 2010. Role of the structural engineer in demolition. Struct. Eng., 88(11): 28–33.

Decision-making •

Faber, M.H., Rackwitz, R. 2004. Sustainable decision making in civil engineering. Struct. Eng. Int., 14(3): 237–242.

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8 Structural Reassessment for Lifetime Extension

Christian Bucher, Prof.; Center of Mechanics and Structural Dynamics, Vienna University of Technology, Wien, Austria, Maik Brehm, Dr. Ing.; Division Director Structural Mechanics, Merkle & Partner GbR, Heidenheim, Germany, Contact: [email protected]; [email protected]

8.1

Introduction

As existing structures are modified, as engineering knowledge advances, and as the requirements to extend life increase, it must be demonstrated that operations can continue safely and economically. There is a general recognition not only in structural engineering but actually also across all industrial sectors that this reassessment process is different from the design process. As a minimum, the known conditions and the specific functional requirements of existing structures need to be taken into account (with design uncertainty factors removed where site-specific parameters are available from as-built information and inspections). Nowadays, several highly specific rules and guidelines for certain problems are available. However, most of them are neither general enough to use in another context, nor do they reflect the complete state of the art. Due to an increasing number of ageing structures, there is a high potential to save a substantial amount of money with a more comprehensive approach. This section presents a framework for the cost optimal reassessment of existing structures consistent with the available information and such that any requirement for the safety of the structure is achieved. It is formulated as general as possible so as to be useful for each reassessment problem. The guideline presented here should help engineers, managers and owners to undertake their assessment of existing structures. Of course, the specific knowledge about the particular object being reassessed and the numerical and experimental assessment methods are indispensable. The following sections are based on a review paper [1], from which several passages are taken. In contrast to Chapter 6, where the cost optimal continuous assessment and maintenance of the structure during its normal lifetime is addressed, this section concentrates on the reassessment of existing structures in the case of serious doubts on its safety level. Therein, three main scenarios can be distinguished:

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1. Completing the design life of a structure or serious unexpected damage has been identified by maintenance actions 2. Significant decrease of the structure’s resistance (e.g. by extraordinary events, such as earthquakes, flooding, and accidents) and 3. Significant change of use (e.g. conversion of the building, for example a bridge designed for passenger trains needs to be used for heavy trains). Hence, the information provided in this section needs to be considered along with the recommendations given in Chapter 6, if an in-depth investigation of the structure may be justifiable. In particular, the current section provides the general philosophy and a summary of current best practice with respect to reassessment across various industrial sectors. In addition, advanced methods useful for the reassessment of structures are briefly discussed.

8.2

General philosophy

Independent of the kind of structure, every reassessment consists of three main steps: 1. Triggering and preliminary investigation: Includes the reason to initiate the reassessment process as discussed before. Furthermore, a collection and first review of data from available documents and monitoring is required. If necessary, simple measurements can be arranged. 2. In-depth investigation and reassessment: This is the main step of the reassessment process, which involves a combination of numerical assessment, experimental assessment, measurements, and inspections to increase the knowledge about the object. To balance cost and benefits, the process should be organized in steps from coarse assumptions to more exact assumptions, from little effort to significant effort, with the simpler approaches being exhausted before more complex and expensive steps are taken. 3. Conclusion and consequences: In this step, the best solution for the reassessed structure based on the results of the second step has to be identified considering all cost-benefit aspects (e.g. economic, ecological, social, and individual aspects). Within each step, various decisions are necessary, which can result in a fairly complex decisionmaking process. In order to avoid subjective decisions, a cost-benefit analysis or cost analysis is recommended, tagging each future event with all advantages and disadvantages in monetary units. These cost-benefit relations should be considered in each step, which can be reused and updated within the assessment process. The quality and success depend on the current state of the art (codes, standards, generally accepted technical guidelines, etc.), the individual expertise, and the experience of the assessor. Furthermore, some additional aspects should be considered: •

The process of collecting information, updating the understanding of the object’s performance through analysis, and devising repair and strengthening measures is a decision process that aims to identify the most effective investigations and modifications required to satisfy the new requirements for the use of the structure and to remove any doubts with regard to its condition and future performance. It is important that this process is optimized, considering the total service life costs by integrating the cost-benefit analysis.

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•

•

•

143

Responsibilities: The owner is responsible for the structure and has to initiate the reassessment. It is recommended that the expertise and experience of engineers be engaged for certain tasks. Hence, the responsibilities are distributed between the engineers and the client or owner. In general, the engineers have to advise and explain the preferred solutions, but the client makes the decision in collaboration with the relevant authority. Only if the decision is not in accord with common societal and safety rules, the engineer is allowed to assume higher authority. Rapid decisions by the engineer to ensure safety aspects are also justifiable. Reporting results: At each stage, when a decision has been made, the results have to be summarized in a report for the owner. In particular, the report must contain all the necessary information on the safety and conclusions with recommendations for the next decisionmaking step. Additionally, a final report must summarize the main results of the reassessment. The results should be stored in a database to simplify the exchange of information with other projects. Reuse of results: Since for many objects each design is redesign, the reuse of results can avoid double work and consequently save money. There is a considerable advantage if many similar kinds of objects having similar environmental conditions and exposure levels (e.g. offshore structures, standardized bridges, pipelines) are present. The benefits can almost be multiplied by the number of objects, while the costs for the reassessment are lower for additional objects. Worldwide, Europe-wide, or company-wide databases should be used to save and recall the data. Furthermore, the results of a reassessment should not be restricted to the reassessment itself. They are also useful in updating the asset management (see Chapter 6).

8.3

Best practice

Nowadays, many industrial sectors have established their own strategies for the reassessment and life extension of existing facilities and structures. A common approach is a step-by-step reassessment from basic visual inspection to a detailed numerical assessment (e.g. structural reliability analysis). The general aspects for the reassessment of existing structures can be found in the JCSS guideline [2]. However, each industrial sector has developed its own concept for reassessment. The most advanced and common codes are ISO 2394(1998) [3] and ISO 13822 (2010) [4]. The flow chart, shown in Fig. 8.1, summarizes the best practice of all industrial sectors to one framework for the reassessment of existing structures, applicable to all structures of all industrial sectors. Additionally, special standards and codes should be established to reflect the special requirements of each industrial sector at the specific reassessment stage. ISO 19902 (2007) [5] and underpinning American Petroleum Institute recommended practices providing such an example for offshore structures under extreme environmental loading. However, all the general principles given in Section 8.2 have to be taken into account. Section 8.4 is recommended for a more detailed explanation regarding specific advanced methods useful in the reassessment process. In the following, all specific reassessment steps depicted in Fig. 8.1 are explained: (a) Reassessment initiator: A reassessment initiator, also called a trigger, is the motivation to activate the reassessment procedure. Fundamentally, the need for a reassessment is based on a significant decrease of the structure’s resistance, a significant change of use, completing the design lifetime or the observation of severe damage.

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Assessment initiator is triggered History data and simple measurements (b)

(a)

Review system, actions and conditions of object (b) Trigger confirmed? (c)

i = 0 Yes Further experimental assessment

Refine system, actions and resistances

(g)

(d)

Refine uncertainties and/or target safety level (e) Numerical assessment at level Li

(f) Yes

All requirements met?

(f)

No i=i+1

Yes

L < Lmax?

(f)

No Object not fit-for-purpose

Reduction of exposure level (h) Demolish object Preservation of similar objects

(f)

Restoration

(i) Object fit-for-purpose

(j)

Preservation of this and similar objects (k)

(k)

Cost-benefit analysis

(l)

Fig. 8.1: Flow chart of an assessment for structures (adapted from Ref. [1]) (b) Review system, actions and condition: The current system, actions, and condition have to be compared with the original design performance (or previous assessment of this or other similar objects, wherever applicable). The information is available from original design

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8.3 BEST PRACTICE

(c)

(d)

(e)

(f)

(g)

145

data, construction data, history data (e.g. structural health or condition monitoring data, special events), analyses, and simple visual inspection and measurements (e.g. size of components). Code revisions since the design should be considered. Assessment records and a database of similar reassessments should also be examined, wherever relevant/ available. Trigger confirmed or assessment required? In the case where the preliminary investigations show that a full assessment is not necessary, the procedure can be stopped, for example, if doubts are not confirmed or the knowledge from a similar object can be used. Refine system, actions, and resistances: If new information from the first review (step b) is available, the assumptions of actions, resistances, model, and system have to be revised. In advanced levels of numerical assessment, it is possible to refine these assumptions by increased knowledge from experimental assessments (step g) (e.g. measured thicknesses or yield stress tests). Refine uncertainties or target safety levels: In the first level of calculation, L0, the latest common codes and standards shall be used to determine the uncertainties of exposure and resistance as well as the target safety level. Very often, these codes use a partial safety factor approach. Within more advanced experimental assessments, the uncertainties and safety levels can be revised based on increased knowledge or reduced uncertainty concerning the actual composition of an existing object when compared with assumptions necessary in design. The refinement of model and system assumptions has to be considered as well. Numerical assessment: Numerical assessments of the safety or reliability of the considered structure are performed using the refinements in steps (d) and (e). A general overview regarding probabilistic assessment can be found in Ref. [2]. There are several possible levels; the first (reference) analysis should always be using current recognized codes. Although, based on experience, the engineer may decide to jump from L0 to a significantly more sophisticated numerical assessment, there are advantages in improving the understanding of the performance of a structure in stages, working through the levels of assessment sequentially. If the object does not pass the code requirements, a more advanced numerical assessment can be applied taking account of real aspects of performance, often not included explicitly in codes. Some possibilities are: considering non-linear as opposed to linear approaches and investigating system performance of a whole structure and not just individual components. The most advanced method is the system reliability analysis based on a generic approach. Obviously, it is difficult to define a firm hierarchy of such methods. The range of more advanced levels depends on the object and differs from one industrial sector to another. Risk analysis and cost-benefit aspects shall be considered throughout. If a numerical assessment demonstrates that all requirements are met, the object may be deemed fit for purpose. Additional experimental assessments may be required (see step g) to increase the knowledge of the exposure level, resistance level, and model and system assumptions of the investigated object, which finally leads to a loop with different numerical assessment levels, Li, with increased accuracy. The highest level Lmax depends on the available numerical and experimental assessment methods and cost-benefit relations. Assuming that all tools are used and the object does not pass the numerical assessment, the loop ends and the object is declared as NOT fit-for-purpose. Experimental assessment: Experimental assessment includes decisions about what should be measured, which method has to be used and the subsequent interpretation of the results.

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(h)

(i)

(j)

(k)

(l)

CHAPTER 8. STRUCTURAL REASSESSMENT FOR LIFETIME EXTENSION

Obviously, it depends on the next numerical assessment step and the cost-benefit relation (or may be needed to overcome particular uncertainties about the construction or condition of the object). A pretest analysis might be useful to select measurement positions and sensor types to profit optimally from the experiments. An overview of several experimental assessment methods (e.g. visual inspection, non-destructive methods) can be found in Chapter 6 and in Ref. [1]. Reduction of exposure level: If the structure is not fit-for-purpose, an option to keep it operating in some form can be allowed by limiting the exposure level. To adopt this approach, it has to be guaranteed that no higher exposure level is possible. This assurance may be achieved operationally (e.g. by de-manning) or additional modification of the object may be necessary with restoration or mitigation measures (step i). A typical example is the introduction of a speed limit at road bridges to restrict vibrations. Condition monitoring or structural health monitoring systems can help to observe the compliance of such measures. Restoration: Restoration (sometimes known as mitigation) is defined as an essential or minimum set of retrofit steps that aid in extending the service or ultimate life for a specified time period. The main restoration methods are the increase of resistance and the reduction of the exposure level. After restoration or mitigation, an additional general assessment is necessary to verify the performance of the new object for the new conditions. This information is important to update the asset management (see Chapter 6). Demolition of object: The investigated object will be decommissioned and destroyed if it cannot be shown, or made to be, fit-for-purpose. Therefore, aspects of environment-friendly recycling or reuse of parts of the object have to be considered, and the health and safety issues in demolition process are of particular importance. Any reused part needs an additional intensive experimental assessment and an advanced maintenance programme. The reassessment data should be used to verify similar existing or further objects. Preservation: Preservation defines all activities that allow keeping the system in a state such that a continuous safe and reliable operation is guaranteed during the entire service life. This is of paramount importance for systems that are subjected to deterioration with usage and age, as well as, for a further extension of lifetime. Preservation encompasses different activities: information updating; reassessment; and, most notably, maintenance, ensuring that the objects remain in the condition assumed in the fitness for purpose assessment (see Chapter 6). If a reassessment has shown an object not to be fit-for-purpose, preservation of other similar objects is important to ensure they do not deteriorate below a safety critical extent. Cost-benefit analysis: The results of a cost-benefit analysis can be used as input to the decision processes. Such decisions have to be made during the whole reassessment process (e.g. should the object be demolished or restored, or what kind of experimental assessments are worthwhile performing). A cost-benefit analysis is a rational decision tool where the optimal decision maximizes the total expected benefits minus the costs in the design or remaining lifetime. All benefits and costs have to be expressed in monetary units and are discounted to, for example, the time of decision. In the decision process, all information and aims should be considered by weighting social, economic, and environmental aspects. The assignment of costs with respect to several factors has been discussed in Chapter 6. Alternatively, a pure cost analysis, like the WLC (whole-life cost) approach suggested in Chapter 6, could be applied.

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8.4 REVIEW OF METHODOLOGIES USEFUL FOR STRUCTURAL REASSESSMENT

8.4

Review of methodologies useful for structural reassessment

8.4.1

Model calibration

147

Model calibration, also called model updating, is a set of numerical tools to calibrate or adjust uncertain model input parameters to increase the correlation between numerically derived model responses and experimentally obtained features. In many cases, the uncertain input model parameters are related to geometry and material parameters of a finite element model. In the context of vibration measurements, for example, typical experimentally obtained features are modal parameters, such as natural frequencies, modal damping ratios and modal displacements. The purpose of model calibration is the generation of a numerical model that represents not only the involved features or measurements, but depending on the intended use, the updated model should also be able, for example, to predict other loading scenarios under different conditions or to estimate the residual lifetime of the realistic structure. A very comprehensive introduction to model calibration can be found in Refs. [6–8]. The most important algorithms for a successful model calibration are the sensitivity analysis to determine the most relevant parameters for the calibration, and the optimization algorithms, such as gradient-based or nature-inspired algorithms, to perform an automatic parameter adjustment. A comprehensive overview of sensitivity analysis methods can be found in Refs. [9–12], with applications in Refs. [13] and [14]. Recommended optimization algorithms are genetic algorithms [15,16], the CMA-ES [17], and particle swarm optimization [18,19] because of their flexibility to be applied to various optimization problems. Examples for the application of a genetic algorithm can be found in Ref. [20]. An important aspect of the optimization is the definition of a suitable objective function, which evaluates the discrepancy between numerically derived and experimentally obtained features. Typical objective functions are based on weighted Euclidean distances. More advanced objective functions based on information theory measures are reviewed in Ref. [6].

8.4.2

Optimal sensor placement

For the planning and execution of experiments, several aspects need to be considered to obtain an experimental set-up that optimally suits pre-defined conditions. If possible, an initial numerical model should be used to investigate the structure in order to design the experiments most suitably. One of the most important aspects is the optimal placement of sensors to increase the benefit from the measured data. For example, in experimental modal analyses, it is important to avoid sensor positions with a low signal-to-noise ratio. In case the structural behaviour is too complex, automatic sensor placement strategies can be applied. A methodology to define optimal sensor positions for vibration measurements is provided in Ref. [21]. Recommendations about measurement set-ups, measurement equipment and the choice of sensors were collected from Refs. [22] and [23]. References [24] and [6] give a general introduction regarding optimal sensor placement.

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8.4.3

CHAPTER 8. STRUCTURAL REASSESSMENT FOR LIFETIME EXTENSION

Uncertainty quantification and propagation methods

If the analysis of standard safety factors is not sufficient or not possible, uncertainties need to be treated directly. Therefore, all uncertain input parameters of a calculation process need to be defined by random variables with statistical properties describing a probability distribution. Such random input variables could be material properties, geometry data, modelling parameters, or loads. By knowing the function or relation between input and output values, it is then possible to derive a set of random variables related to the output parameters of interest, such as stresses and deflections, at certain positions of the structure. This function or relation can be an analytical function or another mathematical description, for instance, a solution obtained from a finite element model. An analytical derivation of the relation between input and output parameters is advantageous to create an analytical probabilistic model. Alternatively, sample-based stochastic structural analysis, as described in Ref. [25], can be applied. This analysis relies on systematic sampling schemes (e.g. D-optimal design, Koshal design, full factorial design [26]) or stochastic sampling schemes (e.g. plain Monte Carlo sampling, Latin hypercube sampling [27][25]) to generate a certain number of samples from the multivariate distributions of input parameters. For each input parameter sample, a sample of output parameters can be determined by using the known relation between input and output parameters. By performing a statistical analysis of the obtained output parameter sets, the statistical properties of the output parameters can be obtained. The effect of randomness on the identifiability of system parameters is discussed in Ref. [28].

8.4.4

System reliability analysis

The system reliability analysis is an advanced numerical assessment method to evaluate structural safety in terms of failure probabilities. Similar to the uncertainty propagation methods described in the previous subsection, the input parameters are random variables of uncertain parameters related to material, geometry, or loading conditions. The random output parameter is the limit state of the structure. Based on this random limit state function and a certain safety margin, the resulting design space can be divided in a domain, where the structure is safe and where the structure fails. Of course, a mathematical or numerical description of the relation between input and output parameters is needed. The calculation of the failure probabilities itself is a numerical integration in the region of the design space, where the structure is unsafe and, therefore, fails. As typically very small failure probabilities are of interest, the application of standard numerical integration techniques is limited due to a high computational effort to reach the required accuracy. Hence, alternative methods have been developed. The first order reliability method (FORM) together with standard optimization procedures assumes a linearization of the limit state function in a certain design point. In addition, advanced sampling schemes, such as importance sampling, directional sampling, and asymptotic sampling, have been developed. An introduction to system reliability analysis can be found in Ref. [25], and in Chapter 6. The probabilistic assessment is a prerequisite for the cost-benefit analysis, discussed below, and also allows to link health monitoring immediately to structural safety evaluation.

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8.5 CONCLUSION

8.4.5

149

Cost-benefit analysis

In addition to the explanations given in Chapter 6 related to the cost analysis, it could be advantageous to analyse the benefits next to the costs of the reassessment, with respect to economical, ecological, and social impact. Finally, the question whether a structure is worthy to be restored or needs to be demolished has to be solved. Of course, each reassessment step causes costs and generates benefits. Therefore, cost-benefit relations should be considered in each step of the reassessment regarding short- and long-term effects in a life cycle cost analysis. General information about cost-benefit analysis related to the reassessment of structures can be found in earlier publications such as Refs. [1] and [2]. Life cycle consideration can be found in Refs. [29] and [30]. Optimal maintenance planning is discussed in Refs. [31] and [32].

8.4.6

Structural health monitoring

Structural health monitoring is a tool to assess the current and to predict the future state of health (condition) of a structure. Such tools are typically fully automated systems with the aim to detect, locate, and quantify current state and predict future damage. In the context of reassessment, these systems can be used to monitor exposure levels and the progress of damage. Therefore, consequences due to rare future events can be controlled, which offers more flexibility to prove the safety of the structures. Damage-tolerant designs too are possible to optimize the use of particular structural parts. A typical example is the incomplete information about previous load histories and high uncertainties about the quality of the material for old steel bridges, which are important for fatigue analysis during reassessment. A structural health monitoring system allows keeping structural parts in place until the remaining true lifetime is reached. An overview of structural health monitoring methods is given in Refs. [33–37]. An example utilizing the experimental results from structural monitoring in a reliability analysis is given in Ref. [38].

8.5

Conclusion

This chapter gave a short review about the general philosophy, current best practice, and new cutting-edge methods for the reassessment of structures. Special emphasis was placed on the differences between the demands on new design, asset management, and reassessment. As shown, binding and comprehensive codes for a general reassessment are not always available. A possible explanation is the interdisciplinarity of the reassessment process, which combines advanced mathematical methods with engineering expertise under consideration of cost-benefit relations. Hence, this review tried to define a general guideline for the reassessment of structures across disciplines and industrial sectors. Of course, this guideline needs to be supplemented by specific codes and guidelines related to the specific objects to be reassessed. In addition, important references for further in-depth investigations were provided. Finally, it is important to note that the extension of serviceability and usability of structures through appropriate reassessment procedures provides most useful leverage to achieve higher levels of sustainability in the built environment.

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References [1]

[2]

[3] [4] [5] [6]

[7] [8] [9] [10]

[11] [12]

[13]

[14] [15] [16] [17]

[18]

[19]

Bucher, C., Brehm, M., Bolt, H. 2010. Framework for assessment and life extension of existing structures and industrial plants. In: Safety and Reliability of Industrial Products, Systems and Structures Soares, C.G. (ed.), CRC Press, 53–62. Diamantidis, D. (ed.) 2001. Probabilistic Assessment of Existing Structures. A Publication of the Joint Committee on Structural Safety (JCSS), RILEM Publications Sarl, Cachan Cedex, France. ISO 2394. 1998. General principles on reliability for structures. ISO 13822. 2010. Bases for design of structures – Assessment of existing structures. ISO International Standard. 2007. Petroleum and Natural Gas Industries – Fixed Steel Offshore Structures. ISO/DIS 19902. Brehm, M. 2011. Vibration-based model updating: Reduction and quantification of uncertainties, PhD Thesis, ISM-Bericht 1/2011, Institute of Structural Mechanics, Bauhaus University, Weimar. Marwala, T. (ed.) 2010. Finite-Element-Model Updating Using Computational Intelligence Techniques: Applications to Structural Dynamics. Springer-Verlag, London, UK. Friswell, M.I., Mottershead, J.E. 1995. Finite Element Model Updating in Structural Dynamics. Kluwer Academic Publishers, Netherlands. Saltelli, A., Tarantola, S., Francesca, C., Ratto, M. 2004. Sensitivity Analysis in Practice: A Guide to Assessing Scientific Models. John Wileys & Sons, Ltd., Chichester, UK. Saltelli, A., Ratto, M., Andres, T., Campolongo, F., Cariboni, J., Gatelli, D., Saisana, M., Tarantola, S. 2008. Global sensitivity analysis. The primer. John Wileys & Sons, Ltd., Chichester, UK. Fellin, W., Ostermann, A. 2006. Parameter sensitivity in finite element analysis with constitutive models of the rate type. Int. J. Numer. Anal. Meth. Geomech., 30(2): 91–112. Oberguggenberger, M., King, J., Schmelzer, B. 2009. Classical and imprecise probability methods for sensitivity analysis in engineering: a case study. Int. J. Approx. Reason., 50(4): 680–693. Brehm, M., Zabel, V., Bucher, C. 2010. An automatic mode pairing strategy using an enhanced modal assurance criterion based on modal strain energies. J. Sound Vibr., 329: 5375–5392. Keitel, H., Dimmig-Osburg, A. 2010. Uncertainty and sensitivity analysis of creep models for uncorrelated and correlated input parameters. Eng. Struct., 32(11): 3758–3767. Holland, J.H. 1992. Adaptation in Natural and Artificial Systems – an Introductory Analysis with Applications to Biology, Control, and Artificial Intelligence. MIT Press, Cambridge, UK. Goldberg, D.E. 1989. Genetic Algorithms in Search, Optimization and Machine Learning. Addison-Wesley Longman Publishing Co. Inc., Boston, MA, USA. Hansen, N., Kern, S. 2004. Evaluating the CMA evolution strategy on multimodal test functions. Proceedings of 8th International Conference on Parallel Problem Solving from Nature PPSN VIII, Springer, Berlin, 282–291. Kennedy, J., Eberhart, R. 1995. Particle swarm optimization. Proceedings of IEEE International Conference on Neural Networks, Volume IV, IEEE Press, Perth, Australia, 1942–1948. He, S., Wu, Q.H., Wen, J.Y., Saunders, J.R., Paton, R.C. 2004. A particle swarm optimizer with passive congregation. BioSyst., 78: 135–147.

BackBack to table ofofcontents to table contents

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REFERENCES

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[20] Ribeiro, D., Calçada, R., Delgado, R., Brehm, M., Zabel, V. 2012. Finite element model updating of a bowstring-arch railway bridge based on experimental modal parameters. Eng. Struct., 40: 413–435. [21] Brehm, M., Zabel, V., Bucher, C. 2013. Optimal reference sensor positions using output-only vibration test data. Mech. Syst. Sig. Process., 41(1–2): 196–225, doi:10.1016/j. ymssp.2013.06.039. [22] Wenzel, H., Pichler, D. 2005. Ambient Vibration Monitoring. John Wiley & Sons Ltd., England. [23] Kuendig, C., Sabathy, M., Biro, T. 2009. System and sensor for monitoring purposes. Proceedings of Final Workshop of European Research Project Details, December 9–11, Lucca, Italy, 118–132. [24] Franchi, C.G., Gallieni, D. 1995. Genetic-algorithm-based procedure for pretest analysis. AIAA J., 33(7): 1362–1364. [25] Bucher, C. 2009. Computational Analysis of Randomness in Structural Mechanics, CRC Press, Taylor & Francis Group, London, UK. [26] Myers, R.H., Montgomery, D.C., Anderson-Cook, C.M. 2009. Response Surface Methodology: Process and Product Optimization Using Designed Experiments, 3rd edn, John Wiley & Sons, Inc., Chichester, UK. [27] Verma, A.K., Ajit, S., Karanki, D.R.. 2010. Reliability and Safety Engineering. SpringerVerlag, London, UK. [28] Bucher, C., Huth, O., Macke, M. 2003. Accuracy of system identification in the presence of random fields. In: Applications of Statistics and Probability in Civil Engineering. DerKiureghian, A., Madanat, S., Pestana, J. (eds.), Millpress, Rotterdam, The Netherlands, 427–433. [29] Frangopol, D.M., Maute, K. 2003. Life-cycle reliability-based optimization of civil and aerospace structures. Comput. Struct., 81: 397–410. [30] Frangopol, D.M., Kallen, M., van Noortwijk, J.M. 2004. Probabilistic models for lifecycle performance of deteriorating structures: review and future directions. Prog. Struct. Engng Mater., 6: 197–212. [31] Macke, M., Higuchi, S. 2007. Optimizing maintenance interventions for deteriorating structures using cost-benefit criteria. J. Struct. Eng., 133(7): 925–934. [32] Bucher, C., Frangopol, D.M. 2007. Optimization of combined lifetime maintenance strategies. Computational Stochastic Mechanics 5, Deodatis, G., Spanos, P.D. (eds.), Millpress, Rotterdam, The Netherlands, 103–107. [33] Carden, E.P., Fanning, P. 2004. Vibration based condition monitoring: a review. Struct. Heal. Monitor. 3(4): 355–377. [34] Farrar, Ch.R, Worden, K. 2007. An introduction to structural health monitoring. Philos. Trans. R. Soc. A, 365: 303–315. [35] Boller, C., Chang, F.-K., Fujino, Y. (eds). 2009. Encyclopedia of Structural Health Monitoring. John Wiley & Sons, Chichester, UK. [36] Wenzel, H. 2009. Health Monitoring of Bridges. John Wiley & Sons, Chichester, UK. [37] Farrar, Ch.R, Worden, K. 2012. Structural Health Monitoring: A Machine Learning Perspective, John Wiley & Sons, Chichester, UK. [38] Bucher, C. 2009. Time-variant reliability analysis utilizing results from nondestructive testing, Proceedings of IABSE Symposium Sustainable Infrastructure, Bangkok, on CD.

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153 Chapter

9 Sustainability through Disaster Risk Reduction

Paul Grundy, Emeritus Professor Faculty of Engineering, Monash University, Melbourne, Australia.

9.1

Introduction

A single disaster can deal a blow to life, livelihood, assets, and the fabric of society from which it can take decades to recover. It can undo improvements in sustainable living gained over many years and indeed set a community as large as a state back behind the starting point of its major developments. The challenge for the structural engineer is to design and build structures and infrastructure such that, in conjunction with other measures of building community resilience, the risk of disaster is minimized. An early definition of sustainable development is given in Ref. [1]: “Sustainable development is development that meets the needs of the present without compromising the ability of future generations to meet their own needs.” By substituting “structures and infrastructure” for “development”, one arrives at a definition suitable for an engineer. However, this substitution makes it clear that the engineer’s contribution to sustainability through disasters is just one component of a multidisciplinary approach. This chapter addresses disasters arising from natural hazards. Disasters arising from human conflict are excluded, although these outweigh those due to natural hazards. We speak of natural disasters, but in reality, natural disasters are man-made. Natural hazards occur only when they overwhelm human communities, which are unprepared for the natural hazard and lack the necessary resilience to reduce the impact to a manageable level.

9.2

The triple bottom line

A valuable enhancement to the concept of sustainability was made in 2006 [2]. While the initial concept focused on ecological issues—environmental degradation and dangerous depletion of resources—in conflict with economic growth, the new concept saw sustainability as the

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Social Bearable

Equitable

interaction of environmental, economic, and social domains with a positive outcome for all three (Fig. 9.1). A development that has a positive outcome in the three domains satisfies the triple bottom line.

Sustainable

Developments are proposed to provide perceived benefits to at least some of the community. Traditionally, proposals have been first evaluated using economic criteria. Environment and social constraints have been seen Fig. 9.1: The three pillars of sustainable as adding to the cost of developments. The development prime objective of the developer has been to minimize the cost, often in the past only the initial cost but more frequently now the life cycle cost. In many parts of the world, legislation allows some environmental or social damage while preventing excesses. This does not comply with the principle of the triple bottom line, where damage is not tolerated in any of the domains. In the triple bottom line, the optimum sustainable development involves a compromise to jointly maximize the environmental, social, and economic gains. Environment

9.3

Viable

Economic

Acceptable risk

There is an uncertainty associated with sustainable design just as there is uncertainty in structural design. Ultimate limit state (ULS) design typically requires that a structure stands (while not necessarily being serviceable) after experiencing a load or operating condition with an annual probability of being exceeded of ~1:500 (equivalent to a return period of 500 years). The load capacity or resistance of the structure is estimated using lower confidence limits for material strength and fabrication and construction imperfections. Combined with the load effect, this modelling results in an annual probability of failure in the range of 1/104 to 1/106. These values are sometimes modified by an “importance factor”. An idea of acceptable risk for disasters can be gained from what is considered acceptable in various industries where human participation is voluntary and in other activities where the victims are innocent bystanders rather than participants. For the former, Ref. [3] is enlightening. For the latter, the acceptable risk for large dams derived by the Australian National Committee on Large Dams [4] provides guidance. (International standards of acceptable risk are similar.) In each case, the acceptable risk is inversely proportional to the number of deaths. These bounds on acceptable risk are shown in Fig. 9.2 [3–6]. While the estimate of deaths is reasonably accurate, the estimate of annual probability of exceedance is a somewhat subjective estimate, strongly affected by the spatial distribution of catastrophic events. Figure 9.2 reveals the huge task of disaster risk reduction. Natural hazards cannot be changed. They might even grow more intense in the future due to climate change. The consequences can be changed. The challenge is to achieve a reduction in loss of lives by, say, two orders of magnitude through the combined actions of community preparedness and education, spatial planning in development, retrofitting of vulnerable structures and infrastructure, and improved disaster management practice. Structural engineers have a significant and cooperative role.

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9.4 BASIC FEATURES OF NATURAL HAZARDS LEADING TO DISASTER Industry bounds acceptable/marginal (Whitman, 1984) 10–1

Annual probability of loss

10–2

10–3

Key to disasters

ANCOLD unacceptable zone Merchant shipping Mobile Natural rigs 4 disasters 6 Fixed 7 rigs 3 8 2 1 5

1 2 3 4 5 6 7

10–4

Indian Ocean Tsunami Wenchuan Earthquake Tropical Cyclone Nargis Victorian bushfires Haiti Earthquake Chile Earthquake New Zealand Earthquake

8 East Japan EQ/Tsunami

Dams

2004 2008 2008 2009 2010 2010 2011 2011

Existing design

10–5 ALARP zone Commercial aviation

10–6

New design ANCOLD acceptable zone

10–7

1

10

103 102 104 Number of deaths

105

106

Voluntary risk Involuntary risk

Fig. 9.2: Acceptable probability of loss versus number of deaths per event (Units: –)

9.4

Basic features of natural hazards leading to disaster

There are two key features of natural hazards leading to disaster: 1. The intensity of the hazard (wind speed, water level, ground acceleration, etc.) can significantly exceed the value assumed for the ULS design. 2. Events can be large scale, with many lives, structures, dwellings, and industries simultaneously at risk of loss—the so-called synchronous failure. These key features require modifications and extensions to conventional structural design methodology in order to partially mitigate their effects.

9.4.1

Excessive hazard intensity

A common feature of many natural disasters is the fact that the peak intensity of the natural hazard exceeds the value used in the ULS design by a large margin. For example: The sea wall at the Fukushima Daiichi Nuclear Power Station was designed for a 5.8 m high tsunami. On 11 March 2011, the tsunami height was 14.0 m. The highest recorded local peak ground acceleration (PGA) due to the East Japan earthquake on 11 March 2011 was 2.99g, whereas the design value was typically 0.4g. The highest PGA recorded in the Canterbury earthquake at Christchurch on 22 February 2011 was 1.99g, whereas the design value was typically 0.2g. Soil liquefaction greatly exacerbated the ground motions with a strong vertical component.

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The highest recorded PGA in the Wenchuan earthquake in the vicinity of the major fault exceeded 1.0g, whereas the design value was typically 0.4g. The design PGAs in the above cases were typically based upon values with a 10% probability of being exceeded in 50 years, which corresponds mathematically to an annual probability of exceedance of 1/475. Similar observations can be made with regard to other natural hazards such as floods, wind, storm surge, and forest wildfires. The apparent frequency with which the design value is exceeded is associated with the many independent locations in a country where the hazard can occur. There are two complementary ways of addressing the problem of excessive hazard intensity. The first is to reduce the probability of exceedance to (say) 1/2500. This is facilitated in a number of structural loading codes by the provision of data with this probability of exceedance, particularly with regard to wind speed, wave height, PGA, velocity, or displacement. In existing loading codes, these more extreme design loads are sometimes applied to buildings with a high importance factor. This is an indirect recognition of potential disaster through failure. Where these data are available, it will be found that the increase in design load is relatively small compared with the amount by which the design load is exceeded in practice, such as the examples cited above. Hence, a complementary action is proposed, described as the “What if?” question: What if the hazard intensity exceeds the design value so that the structure or infrastructure fails? The answer lies in engineering and non-engineering robustness. The engineering robustness leads to structures and systems not leading to loss of life, essential communication, and so on, in spite of failure. Non-engineering robustness means that communities have the emergency response measures effective in preserving life and other essential community operations in spite of the loss of structures or infrastructure.

9.4.2

Synchronous failure

Synchronous failure, a term coined by the United Nations International Strategy for Disaster Reduction (UN ISDR), applies to the simultaneous loss of a group of structures or systems when they are all overwhelmed by the same natural hazard. The loss of 1% of a city’s housing in an earthquake, for example, is a relatively minor disaster, dealt with by insurance and community support. On the other hand, if 90% of the housing is lost, then lives, livelihoods, and governance are lost. The community is in disarray. The social pillar of the triple bottom line (Fig. 9.1) has little weight for an individual home, but is by far the most important component in synchronous loss. The combination of synchronous failure with excessive hazard intensity presents the structural engineer with extreme challenges. Each of the disasters cited in Fig. 9.2 is such a combination. While more conservative design loads combined with element and system robustness will mitigate the disasters, the mitigation will not be enough unless it is complemented by community education and preparedness for disaster impact and post disaster recovery.

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9.5 DESIGN FOR DISASTER RISK REDUCTION

9.5

157

Design for disaster risk reduction

The two principal areas of activity for an engineer in disaster risk reduction are: 1. Reconstruction after a disaster. 2. Retrofitting before disaster strikes. Although the structure or infrastructure is of radically different design according to whether it is an act of reconstruction or retrofitting, the design principles are the same, centred on the concept of the disaster limit state (DLS).

9.5.1

Disaster limit state

The DLS, which is a design limit state more demanding than the ULS, was coined after the devastating Indian Ocean earthquake and tsunami of 2004 [7]. Natural hazards of excessive intensity, the issue of synchronous failure and robustness have to be dealt with for saving lives in spite of structural or system failure and for maintaining post-disaster functionality. The DLS is distinguished from the ULS by a more specific use of importance than is carried by the importance factor, which sometimes appears in codes of practice for structure and infrastructure design. The recommended stages in DLS design are as follows: 1. 2. 3. 4. 5.

Establish the survival category of the structure or infrastructure. Set design parameters according to the survival category. Incorporate robustness measures to minimize loss of life after failure. Review consequences of hazard intensity exceeding design intensity. Identify non-structural measures required to minimize disaster impact.

The last three stages are interactive rather than sequential in the design process. Establish the survival category The survival category is a more detailed way of incorporating the importance factor used in the ULS design. Three categories are defined, as shown in Table 9.1. Examples of structures and facilities in the highest survival category include hospitals; emergency service centres; essential services (power, sanitation); communication links needed for search, rescue and recovery (telecom towers, arterial routes and bridges); and buildings designated for emergency and post-disaster refuges. Examples of structures and facilities in the high survival category include public buildings, places of assembly, schools, dormitories, shopping centres, car parks, housing complexes, and groups of buildings likely to experience synchronous failure. Examples of structures and facilities in the standard survival category include isolated dwellings where occupants can relocate after receiving warnings and light industrial and commercial

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CHAPTER 9. SUSTAINABILITY THROUGH DISASTER RISK REDUCTION

Performance criteria Design probability Additional risk reduction after the event of exceedancea measures

Highest

Fully operational

~1/2500

Early warning response drill; security of equipment and fittings; emergency power supply; emergency communications

High

Limited loss of life and injury

~1/2500

Early warning response drill; security of equipment and fittings; access to refuges; evacuation plan

Standard

Failure acceptable

~1/500

Early warning response drill; access to refuges; evacuation plan

a

Annual probability of exceedance of design hazard intensity

Table 9.1: Definition of survival category buildings typically with a single storey. This category can generally be designed using the ULS design principles. Set design parameters Acceptable risk of loss is determined by the survival category. As indicated in Table 9.1, the design annual probability of exceedance is reduced for the high and the highest survival categories. This is necessary for the dimensioning and equipment of structures and infrastructure, but it is not sufficient for the resilience required when disaster strikes. In some cases, no satisfactory design solution can be found where the post-disaster performance criterion can be met. This can occur where the facility is located in the path of potential landslides, volcanic pyroclastic flows or inundation from floods, storm surge, or tsunamis. In these cases, the solution often lies in relocating the facility out of reach of these hazards. Incorporate robustness measures Robustness is an essential requirement of design regardless of the survival category. The engineering requirements are less stringent for the standard survival category, but all systems require robustness in emergency response. This reveals the two types of robustness required, physical and community based. Physical robustness is achieved where, in spite of significant damage and destruction, lives are not lost, or are reduced to a level where a community can cope with the loss without trauma. Excellent guidelines for structural robustness are provided in Ref. [8]. A simple example of structural robustness is given in Fig. 9.3. Many deaths in major earthquakes have been associated with floors collapsing onto each other, primarily due to inadequate anchorage of the floor slabs to the supporting members on their perimeters. Additional issues created by “strong beam/weak column” construction must also be addressed.

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Carry 100% bottom bars anchor length past support

Slab hangs as a catenary after bending failure

Fig. 9.3: Simple example of structural robustness

Community-based emergency robustness in emergency response is an essential complement to engineering robustness. This is particularly due to the consequences of excessive hazard intensity. Effective disaster resilient engineering of structures and infrastructure requires engagement of the engineer with the community in minimizing risk. Just as redundant load paths are a feature of structural robustness, redundant lines of communication (roads, telecommunications, power supply) are essential features of disaster risk reduction. However, unlike the physical infrastructure, the community requires education and training in the use of lines of communication in an emergency, in acting on early warning, and in evacuation and refuge. Review consequences of excessive hazard intensity Hazard intensity exceeding the design parameters leads to the “What If?” question identified above. The possible actions include higher levels of robustness in the physical environment and in the community preparedness and, if all else fail, the possible relocation of structures and infrastructure to sites less vulnerable to natural hazards. Some of these actions are listed in the risk reduction measures. Identify non-structural measures required to minimize disaster impact Dialogue of engineers with community groups who are risk-aware and with community leaders is essential for taking the necessary risk reduction action. An obvious non-structural measure is the introduction of, and planning for, an early warning system. Science and engineering provide great assistance in the detection of natural hazards and the transmission of early warnings. A striking example from Japan is earthquake detection and the transmission of warnings using sophisticated technology [9]. A warning of 2 seconds delivered through a variety of media is sufficient to save up to 25% of potential lives lost, and a warning of just 5 seconds can save up to 90% of potential lives lost. The community needs education on how to respond to an early warning system. This is as important as the warning system itself. It applies to all natural hazards.

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CHAPTER 9. SUSTAINABILITY THROUGH DISASTER RISK REDUCTION

Reconstruction

The usual slogan after a disaster is “Building Back Better”. In the urgent humanitarian response to a disaster, this is difficult to achieve, especially in developing countries lacking professional and construction skills to adapt traditional construction to resilient forms. This applies particularly to housing. Engagement of the local community in rebuilding is essential for success. Buildings of adobe or fired clay brick masonry are built worldwide with little or no structural performance requirements. Methodologies for earthquake-resistant adobe construction, which can be used by indigenous artisans, have been developed [10]. These have been adopted in many countries, especially in Latin America. Successful implementation requires support from local tertiary institutes and professional engineers. A common methodology for building back better in brick masonry construction is to confine the walls in light reinforced concrete frames [11–13]. An example of this construction, following the Yogyakarta earthquake (27 May 2006), is shown in Fig. 9.4. Figure 9.4a shows the construction method where the columns are progressively concreted and tied into several courses of brickwork at a time. Figure 9.4b shows a typical completed construction, with base course and capping beams tied into the columns. Figure 9.4c shows poor quality concrete placement. A bricklayer could perform all phases of the construction. It is clear that training in best construction practice is needed to achieve the desired quality of construction.

9.5.3

Retrofitting

Retrofitting before disaster strikes is recognized to be more cost-effective disaster risk reduction than rebuilding later. The obstacles to retrofitting are lack of motivation, usually through the community failing to recognize the risk, lack of funding in the face of other economic needs, and lack of suitable economic designs for retrofitting existing structures. Structural engineers have a significant role in overcoming all these obstacles. Retrofitting fragile structures is particularly challenging. Fragile structures are particularly at risk from earthquakes, even if expected ground motions are mild. There have been successful (a)

(b)

(c)

Fig. 9.4: Masonry infilled reinforced concrete frame construction in Yogyakarta. (a) Construction stage, (b) finished product and (c) defective concrete

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achievements in inserting base isolation, sometimes to heritage masonry structures, but brick masonry and adobe structures are not amenable to base isolation. Insertion of a reinforced concrete frame into brick masonry walls is not feasible, but strapping on a frame is. An example of a strapped-on column is shown in Fig. 9.5 [11]. Retrofitting methods such as that shown in Fig. 9.5 need to be backed up by laboratory testing, training in the construction methodology, and engagement of local communities in the endeavour.

9.6

Threaded bar @ 300 mm in hole drilled through brickwork Nut used to clamp form to brickwork

Reusable steel form Rubber seal

Rebar 12 mm diameter

6 mm ties @ 250 mm Nuts may be replaced after stripping form

Fig. 9.5: A proposal for “strapping on” a reinforced concrete column to an existing masonry wall

Obstacles to sustainability in disaster risk

It is obvious from this discussion that the risk of loss of sustainability from the impact of overwhelming natural hazards is much more significant than unsustainable individual construction and operation projects. In the case of natural disasters, the social pillar of the triple bottom line is much more significant than the pillars of environment and economics. A multidisciplinary approach is required. Engineers need to recognize sustainability from the social science perspective. A definition of sociological risk in terms of human vulnerability, and how it is estimated, has been given in Ref. [14]. Hazard × vulnerability – capacity = risk

(9.1)

In this context, risk is defined as social breakdown: loss of hope and meaningfulness in life. There is an analogy between the sociological formula and that used for structural design. In the context of Eq. 9.1, risk is the realization of disaster or loss. In structural engineering, this would be defined as a failure. The two principal factors compromising sustainability in the social context are awareness of risk from natural hazards and the cost of disaster prevention and mitigation.

9.6.1

Awareness of risk

A feature of all the disasters listed in Fig. 9.2 is that in each case, the nation as a whole has suffered from the natural disaster even though the impact is confined to one region of the nation. For those who survived the disaster untouched, the awareness of risk is dimmed by the lack of personal impact. Surviving victims in a region of impact rely on government and foreign aid to build back better to reduce the impact of a future disaster in the same place. Survivors

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in regions outside the area of impact respond variably to the need to increase preparedness, retrofit, and improve emergency response. The variable response corresponds to the variable understanding of disaster risk. Engineers bear a responsibility for raising community awareness of disaster risk.

9.6.2

Cost of disaster prevention measures

It is well known that the benefit to cost ratio of building resilience in a community in surviving natural hazards unscathed is very large compared with the cost of recovery after disaster strikes. Ratios of up to 7:1 have been cited. However, the cost applies to everywhere in the nation at risk, whereas the benefit applies to the local regions where the disaster has impact. Even wealthy nations have difficulty in advancing disaster prevention measures for areas at risk. In countries with developing or weak economies, it is even more difficult to give priority to disaster risk reduction measures over other nation building enterprises, no matter how justified in the long term. The answer to this problem is at the grass roots. Schools need to have disaster risk awareness and reduction measures in their curricula from primary level up. Local government engineers need to be aware of their regional exposure to natural hazards as they go about building and maintaining local infrastructure. Centralized government planning is necessary but not sufficient.

9.7

Conclusion

This chapter addresses the challenge of achieving sustainability where the risk of natural disasters is significant. The main stages in understanding how to achieve sustainability are as follows. − Sustainability must be achieved in the three pillars of the triple bottom line of developments—economic, environmental, and social. − The social dimension is very large in the case of natural disasters compared with individual structure and infrastructure projects, while the environmental and economic impacts remain very large. − Awareness of risk to life, livelihood, social cohesion, and physical infrastructure is key to achieving sustainability in the face of disasters. − A DLS is proposed for design, more stringent than the ULS and with additional community risk reduction strategies. − Structural and non-structural robustness are essential to mitigate disasters. − There are significant technical challenges both for building back better and for retrofitting to annul the impact of future natural hazards.

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REFERENCES

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References [1] [2]

[3] [4] [5] [6] [7] [8] [9]

[10]

[11]

[12] [13] [14]

United Nations. 1987. Our Common Future: The World Commission on Environment and Development. G. H. Brundtland, Ed., Oxford University Press, Oxford, UK, p. 374. Adams, W.M., The Future of Sustainability: Re-thinking Environment and Development in the Twenty-first Century. Report of the IUCN Renowned Thinkers Meeting, January 29–31, 2006. Whitman, R.V. 1984. Evaluating calculated risk in geotechnical engineering. J. Geotech. Eng., ASCE, 110(2): 145–188. ANCOLD, International Commission on Large Dams, Australian National Committee on Large Dams Incorporated. 2003. Guidelines on risk assessment, Hobart, TAS, Australia. Grundy, P. Disaster reduction on coasts. Proc IStructE Centenary Conference, January 24–26, 2008, Hong Kong, 247–263. Grundy, P. 2010. Disaster Risk Reduction and the Structural Engineer (e-lecture). Available at: www.iabse.org/e-learning/L07/player.html. Grundy, P. 2005. Disaster reduction on the coasts of the Indian Ocean. Struct. Eng. Int., 15(3): 193–196. Knoll F. Vogel T. 2009. Design for Robustness. Structural Engineering Document 11. IABSE, Zurich, Switzerland. Homeland Security News Wire. 2011. Early warning system helped save lives in Japanese quake. Available at: http://www.homelandsecuritynewswire.com/early-warning-systemhelped-save-lives-japanese-quake [accessed on 20 July 2015]. Dominic M. 2009. Dowling and Bijan Samali low-cost and low-tech reinforcement systems for improved earthquake resistance of mud brick buildings. Proceedings of the Getty Seismic Adobe Project 2006 Colloquium, The Getty Conservation Institute, Los Angles, CA, USA, April 11–13, 2006. Grundy, P. The Padang earthquake: building back better and retrofitting. Surveys and activities on post-earthquake disaster. UNESCO-IPRED-RIHS International Workshop, Padang, Indonesia, July 6–8, 2010, UNESCO, Paris, France, 121–128. Available at: http:// unesdoc.unesco.org/images/0021/002138/213843e.pdf Grundy, P. Retrofitting for resilience – lessons from the Yogyakarta earthquake 2006. International Disaster and Risk Congress, Davos, August 25–29, 2008, 3 pp. Grundy, P. 2009. The structural engineering challenges following the Wenchuan earthquake. J. Sichuan University (Engineering Science Edition), 41(3): 1–8. Chan, C.L.W., Sun, A., Ho, A., Wang, X.L., Wang, X., Zhang, B., Zhang, X. 2009. IDRC, International Disaster and Risk Conference, Hong Kong University, Chengdu, July 13–15, 2009.

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10 Green Materials for Concrete Production

Jorge de Brito, Full Prof., CERis-ICIST, DECivil, Instituto Superior Técnico, Lisbon, Portugal. Rui V. Silva, MSc. Civil Engineering, CERis-ICIST, Instituto Superior Técnico, Lisbon, Portugal. Contact: [email protected], [email protected]

10.1 Introduction As the world population increases, the use of natural resources and energy grows proportionally, becoming one of the major environmental concerns of our times. Several economic sectors are already pursuing a solution to this problem, by analysing the added-value potential of reusing their own wastes. The conventional methods of constructing and demolishing buildings and concrete structures are implemented in such a way that most of the resulting waste is sent to landfills, instead of being recycled or reused in new constructions. This becomes a serious concern since construction and demolition wastes (CDW) are among the heaviest and bulkier wastes generated by all economic sectors. Numerous studies have shown the feasibility of using recycled aggregates (RAs) in various construction applications, specifically concrete, mortar, and road construction. However, due to the deficient or even inexistent waste separation and sorting techniques, during construction or demolition activities, the RA produced from these CDW often have poor quality and are limited to low grade applications. Indeed, by applying a selective demolition methodology (also known as deconstruction), it is possible to highlight specific components that can be reused in new constructions, as well as to efficiently separate materials by type. This forward thinking allows the production of high quality RAs, which can then be used in high-grade construction applications such as structural concrete. The possibility of using RA in concrete opens a whole new range of possibilities in terms of recycling materials in construction. This could be an important breakthrough for society in its endeavour towards sustainable development, as it is significantly beneficial in terms of environmental protection, as well as preservation of natural resources. There are several studies mainly engaged in the processing of demolished concrete, mix proportion design, mechanical properties, durability aspects, and materials improvement. Recently, the structural and environmental

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performance and economic aspects of using recycled aggregate concrete (RAC) have also been analysed. The current chapter seeks to provide existing knowledge on the effects of using RA on the properties of concrete, in addition to guidelines as to how to make the best use of these materials when producing concrete.

10.2 Background The global construction aggregate market was valued at over €75 billion in 2012 [1]. The largest regional market for aggregates in the world belonged to the Asia-Pacific region, with 42.5%. Europe and North America were the second (26.9%) and third (20.8%) largest regional markets, respectively. Growing economies in the Asia-Pacific, specifically China, India, and Indonesia, are expected to reduce the market shares of Western regions. This is due to the rapid development of infrastructures and other construction markets, which increases the demand for aggregates. Although at a somewhat slower pace, Central and South America, Eastern Europe, and some regions in Africa are also expected to increase consumption of aggregates for construction. Overall, it can be said that the aggregate market for use in construction applications is enormous and worldwide. It is expected to increase 5.2% per year up until 2015 to 48.3 billion metric tons (Fig. 10.1). This represents a slower rate of growth than during the period between 2005 and 2010. Nevertheless, the demand for aggregates still requires a huge amount of natural resources for construction activities. At present, almost all economic sectors have a significant environmental impact, the production of waste. According to Eurostat [2], the total amount of generated waste, in the European Union alone in 2010, was over 2.5 billion tons (Fig. 10.2), of which almost 35% (860 million tons) and 27% (672 million tons) of the total, belonged to construction and demolition activities and mining and quarrying operations, respectively.

50

Other

Western Europe

North America

Asia/Pacific

Aggregate demand (billion tons)

45 40 35 30 25 20 15 10 5 0 2005

2010

2015

Fig. 10.1: World consumption of aggregates for construction [3]

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10.2 BACKGROUND Households

Other economic activities

Construction and demolition activities

Energy and water supply sectors

Manufacturing

Mining and quarrying activities

3000

Waste amount (tons)

2500 2000 1500 1000 500 0 2004

2006

2008

2010

Fig. 10.2: Waste generated by all economic sectors in the European Union [4] The majority of wastes coming from construction and demolition can be considered a mineral waste. Therefore, with proper care, these materials are capable of being recycled and reused in construction. However, there are still several obstacles to the use of RA in construction activities: •

•

•

•

•

Lack of confidence: Clients and contractors still exhibit a great lack of confidence on the positive effects of using RA in construction. It is possible to overcome this issue, by increasing their knowledge on the positive environmental and economic benefits and communicating successful cases in which the feasibility of using these materials has been proven. Uncertain environmental benefits: Some may think that the ecologic footprint of sourcing and processing CDW into RA is greater than that of obtaining NA. This is entirely inaccurate, as the whole point of recycling CDW is to reduce environmental impacts and prevent natural resources’ depletion. In order to eliminate this misconception, seminars and “green” marketing campaigns, including detailed studies on the environmental benefits, are required. Limiting specifications: The lack of standards and specifications, with clauses regarding the use of RA in concrete, is also an alarming barrier to recycling. Since concrete producers follow these codes in a strict manner, only by changing them can a path be built for RA to be used in concrete. Although some standards already contain information on RA use in concrete, they have highly restricting limitations to their use in concrete, which also proves to be an obstacle to the best possible use of these materials. By demonstrating the positive results, obtained by several researchers, that it is possible to use high amounts of some recycled materials, it is possible that specifications will be improved. Quality of final product: Several recycling plants are either unaware of the proper procedure for obtaining RAs with the best possible quality, or simply are not interested in producing RAs with good enough quality for high-grade applications. In either case, the quality of the final product may not be good enough for use in structural concrete. Location of construction and demolition sites: One of the main barriers for recycling CDW is their transportation costs. Indeed, great distances from construction and demolition sites

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to the recycling plant may greatly increase the cost of RAs, reducing their attractiveness to contractors and concrete manufacturers. Supply and demand: These are two main barriers for the recycling of CDW, which are also affected by the aforementioned issues. Considering that most construction and demolition operations are not consistent, it is difficult for recycling plants to have steady streams of raw materials. Additionally, since most wastes are not sorted out at their construction or demolition sites, they come with various types of materials, which may contaminate the final products. As such, there is a serious concern as to obtain sufficient quantities of raw materials with good enough quality to produce RAs for concrete.

10.3 How to make concrete more sustainable According to a conservative estimate, for every kg of cement produced, there is a by-product of 0.9 kg of carbon dioxide (CO2) [4]. This leads to over 3 billion tons of CO2 emissions per year. The main sources of these emissions can be divided into two parts: from the calcination of limestone and from the fuel combustion used in the production of clinker (sintering temperatures of 1400 to 1600°C). The amount of CO2 emissions also depend on the type of fuel used and the processing method. During the sintering process, cement kilns can be ignited using coal, fuel oil, natural gas, petroleum coke, biomass, waste-derived alternative fuels or even mixtures of these fuels [5]. When producing concrete, there are several methods that can be applied in order to manufacture a more sustainable material. Over the course of time, the CO2 quantity emitted in the production of one unit of cement has been decreasing due to simple changes, such as using a dry process, when mixing all the components of the cement, instead of using a wet paste that took longer to dry during the sintering stage. Considering the high temperatures required for its production, cement stores a great amount of emergy. Emergy is defined as the equivalent quantity of solar energy used, directly or indirectly, to obtain a final product or service [6,7]. Therefore, in order to reduce the emergy of cement, apart from some changes in the manufacturing method (such as the use of the dry process), it is also necessary to reduce as much as possible its sintering temperatures, provided that this does not affect the quality of the final product. When producing concrete, the factors with the highest emergy values are the materials required for its production, specifically cement, sand, and gravel [8]. The reduction of concrete emergy is possible by reducing the cement emergy, by optimizing or modifying cement production, by its partial replacement with supplementary cementitious materials [9] and even by using other alternative cement products [10]. However, considering the high emergy of conventional natural aggregates (NA), it is also possible to reduce the emergy of concrete by using RA from CDW. A great number of studies have been performed worldwide on the production of RAC. There are other methods, which may increase the emergy and cost of concrete at the initial stage, but have a higher benefit, in terms of sustainability, over time. When producing concrete, by using better quality materials, lowering the water/cement (w/c) ratio (cement and water contents increase and decrease, respectively) with the assistance of admixtures or additions, it is possible

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10.4 RECYCLED MATERIALS FOR CONCRETE Economies in transition Africa and Middle East Latin America European Union

OECD Pacific India Canada and United States High demand scenario

Other developing Asia China Other OECD Europe Low demand scenario

5000

Cement production (million tons)

4500 4000 3500 3000 2500 2000 1500 1000 500 0 2006

2015

2030

2050

Fig. 10.3: Average estimated cement production in 2006, 2015, 2030 and 2050 [11] to improve the performance of concrete in terms of durability and expand its life span. This will ultimately lead to reduced maintenance, repair, and replacement costs over time. Figure 10.3 presents the current and the average estimated cement production from 2015 to 2050. Throughout this period, a high and a low demand scenario were estimated. Regardless of how low the demand and production of cement can be, it still represents a significant amount of cement produced. For this reason, it is important to find new ways of making cement and concrete more sustainable.

10.4 Recycled materials for concrete There are several types of industries and types of resulting wastes as well. This has led to a rising interest among various researchers in studying the effects of adding these materials on the properties of concrete. This section describes the various types of waste materials which were studied.

10.4.1 Industrial wastes The generation of industrial by-products has been increasing at an alarming rate. Depending on the type of industry, there is a wide range of industrial by-products. One such type of material is ground granulated blast furnace slag (GGBS), which is typically obtained from blast-furnaces of steel industries. GGBS, which is mostly comprised of silicates and alumina, may have binding properties and thus can be used as partial cement replacement. There have been many studies on the use of this material as aggregate and as part of the binder in the production of concrete [12–15]. It is clear that GGBS is most beneficial if it is used as cement replacement, since

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increasing its incorporation may enhance workability. Thus, a smaller amount of water is required in order to maintain the same workability as that of a corresponding ordinary Portland cement concrete mix, leading to mechanical performance improvement. The use of this material has also led to superior resistance to sulphate attack and to chloride ion penetration, in comparison to ordinary Portland cement. Fly ash (FA) or pulverised fuel ash is a by-product obtained from coal burning industries. Similarly to GGBS, it is comprised of silicates and alumina, and when used as partial cement replacement may cause pozzolanic reactions. The effects of using FA in concrete are wellknown [16–21]. A judicious use of this material may lead to improvement of concrete workability, pumpability, cohesiveness, finishing, and mechanical and durability performance. The abundant production and consumption of glass (especially in bottle manufacturing) calls for the need of additional recycling methods for this product. Besides the typical recycling process into new bottles, there are several studies that have assessed its application in the production of concrete [22–30]. Generally, the incorporation of glass waste aggregates causes a decrease in the mechanical performance of concrete. This decrease is mainly attributed to the fragile behaviour of glass waste aggregates and to the difficulty in obtaining proper bond strength between them and the cement paste. However, the use of very fine glass waste aggregates, up to given replacement ratios, may lead to a filler effect, improving some mechanical properties and also durability-related performance (reduced permeability and chloride ion penetration). The use of plastic waste as a NA substitute in concrete is a relatively recent concept. One of the first significant reviews on the use of waste plastic in concrete [31] focused on the advantages and financial benefits of such use, besides their physical and mechanical properties. There have been many studies on the use of plastic aggregates in the production of concrete [32–40]. There is a common ground in that the use of plastic waste aggregate in the production of non-structural concrete is viable, even though the performance of most properties strongly declines. At the end of its life cycle, the final destination of a tyre may vary greatly: from illegal disposal; landfill disposal; energy recovery as fuel; and introduction of ground tyre waste aggregate in hot mix asphalt production. The rising production of rubber-based products has led to a growing interest by several authors [41–46], in alternative recycling methods, specifically in their use as aggregates, fillers, and partial cement replacement, in the production of concrete. The increased use of these materials causes significant losses in mechanical performance. Rubber waste aggregates, which have a very low modulus of elasticity, act as voids in concrete when subjected to loading. There is, however, some improvement in resistance to chloride ion penetration and to abrasion. The use of other unconventional aggregates from industrial by-products, such as stone slurry [47], leather [48], ethylene-vinyl acetate (EVA) [49–51], oyster shells [52], palm tree shell [53–56], and even sewer sludge [57–59], was also considered for the production of concrete. Generally, the use of these materials as NA replacement causes a decrease in the mechanical and durabilityrelated performance of concrete, unless when added in small ratios and as ultra-fine material.

10.4.2 Construction and demolition wastes CDW materials may have different origins and, consequently, different properties. Institutions from several countries have developed standards and specifications [60–74] for the character-

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ization of RA obtained from CDW. Among the various CDW materials, three main classes were identified as best suited for structural concrete production. Although this classification is primarily based on their composition, it is also based on their higher quantity and higher compatibility with cementitious binders, when compared to other waste materials (asphalt, wood, glass, soil, metal, plastic, etc.). Recycled concrete aggregates (RCA): The most common RA, RCA is produced by crushing concrete from prestressed, reinforced, or plain concrete structures and from precast concrete units. This material is made up of a minimum of 90%, by weight of total aggregate, of the sum of cementitious fragments and NA. Recycled masonry aggregates (RMA): This class of materials includes aerated and lightweight concrete blocks, ceramic bricks, blast-furnace slag bricks and blocks, and sand-lime bricks. Rendering mortar and burnt clay materials, such as roofing tiles and shingles, may also be present in RMA [75]. It is composed of a minimum of 90%, by weight, of the sum of any of the aforementioned materials. Mixed recycled aggregates (MRA): This material is an aggregate blend which includes the two previously mentioned RA. It is composed of less than 90%, by weight, of cementitious fragments and masonry-derived debris. After their collection, these materials are then transported to certified recycling plants, where they go through beneficiation or purification processes. The layout of these industrial units is often quite similar to that of conventional NA processing plants. However, there are a few exceptions in these units, in which specific devices are used for the separation of unwanted materials. Before being used as RA, the CDW materials must undergo various processing operations. They must go through a magnetic separator, which extracts ferromagnetic metals. After that, they must undergo several screening processes, to be separated into different sizes. Depending on the size, these may be considered unsuitable for use, or sent to crushers or hand-picking lines. In the latter, trained workers remove contaminants, such as wood, metal, hazardous waste, plastic, paper, glass, among others. Some of the lightweight contaminants (dirt, clay lumps, wood, paper, plastics, and textiles) may also be removed by air sifting processes [75,76]. The resulting materials may again go through some of the previously mentioned recycling processes, in order to ensure maximum decontamination and, only then, they are considered as RA. Steel reinforcement rebars or profiles are a crucial component of concrete or concrete-steel composite structures. When such a structure reaches the end of its service life, all steel elements can be easily recovered, recycled, and/or used again. Using proper equipment, some of these elements (e.g. profiles) can be recovered on site, whereas the removal of other steel components (e.g. reinforcement rebars) is typically done at the recycling plant. This can be done by using electromagnets along the conveyor belts to collect steel between the concrete crushing processes. This is an important step in the recycling process of structural concrete and contributes to the sustainability of this material. The embodied energy of recycled steel elements results from the energy input of the melting and remoulding processes. The energy input to obtain a ton of steel from recycled scrap metal can be less than half of that when producing it from iron ore. Wooden elements, either structural or non-structural, have been recovered, recycled, and/or reused for many centuries. The most valued elements are those with architectural value or made

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of exotic or subsequently rarefied species, which have a good market value. Large structural timber elements also have a big reuse potential and they may also be resized to fit in future applications. However, most of the other wooden elements are either damaged during demolition, degraded by rot or xylophagous or too small to be of any practical future use, and therefore are used for incineration purposes only. Often they act as deleterious elements in mixes of otherwise useful materials for concrete production (such as the inert materials).

10.4.3 Converting CDW into usable aggregates During the demolition of a building structure, two diverging methodologies may be exercised: conventional demolition or selective demolition. In the former, the structure is demolished in such a way that most types of materials are directed to unspecified containers, whilst the latter tends to be more selective when removing each part of the building. Selective demolition, also known as deconstruction, is a relatively new concept in the demolition industry. Processes related to selective demolition are time consuming and have a higher initial cost. However, studies [77–80] have shown that this methodology may lead to lower global costs by selling separated materials to suitable entities and reducing the landfill fees. Naturally, the use of this approach also leads to evident positive effects on the environment, in comparison to the alternative [77,78]. Besides reducing the amount of material sent to landfill, it also reduces the emission of a wide array of substances, which are known to cause nitrification, summer smog, acidification, and increased concentration of heavy metals. There are several types of methods and apparatuses which can be used for obtaining good quality separated materials when demolishing a structure [81,82]. These may vary between simple hand tools (chisels, sledgehammers, crowbars), hand-operated power tools (electrical, hydraulic, pneumatic, gasoline), heavy demolition equipment (impact hammers, wrecking ball, concrete crushers), thermal cutting equipment (cutting torch, thermal lance, powder cutting torch), hydro-demolition devices, mechanical cutting equipment (diamond saws, core drills, stitch drilling) and even expansion-based methods (controlled explosive blasting, gas expansion, solid non-explosive demolition agents). Naturally, the demolition method selection is based on several factors: size and location of the building; allowable levels of noise, dust, and vibration; materials used in that construction; environmental, public, and construction workers’ safety; and time period [83]. CDW recycling plants are not very different from NA production plants. Both are composed of various types of crushers, screens, and transfer equipment. The main difference between them is the existence of apparatuses to remove contaminants. After receiving CDW materials, the degree of processing is determined by a visual examination of the existing level of contamination and of their future application. For instance, when producing RA for high-grade applications, such as structural concrete, CDW must be subjected to extensive processing in order to minimize the existence of contaminants. However, for low-grade applications, such as general bulk fill and subbase layers for road construction, less intensive contaminant removal procedures may be applied, thus reducing their final cost. Figure 10.4 presents a flow chart of a possible recycling procedure capable of producing good quality RA. Depending on the variety of existing types of materials and level of contamination, some steps, such as the manual separation or mechanical removal of contaminants, may be bypassed. This allows energy savings and thus less production costs.

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10.4 RECYCLED MATERIALS FOR CONCRETE Reduce size of individual fragments

Primary screening

Separate storage of different types of materials

Primary crushing

Electromagnetic removal of ferrous materials

Bypass of material with size 10 mm < d < 40 mm

Manual or mechanical removal of contaminants

Secondary crushing

Manual or mechanical pre-crushing separation

Secondary screening

Bypass of material with size d < 40 mm

Washing or air sifting

Final screening and storage of various size fractions

Fig. 10.4: Recycling procedure of CDW (adapted from [75]) It must be understood that recycling plants may produce different batches of RA exhibiting very diverse quality and composition. This is due to variations in the quality, type, and level of contamination of the original materials coming from construction and demolition activities. For this reason, it is important to apply a comprehensive selective demolition, with proper separation and storage of all types of materials. Furthermore, recycling plants have evolved to a point where strict recycling procedures can minimize the contaminant content by using various contamination removal apparatuses. There are two types of CDW recycling plants: stationary and mobile. A stationary recycling plant frequently consists of a large primary crusher, working in combination with a secondary crusher, as well as various contamination removal devices. Some stationary recycling plants operate with a tertiary crushing stage. This extra step, which would certainly produce better quality materials, was found to produce RAs with only slightly better performance than that of the output of a secondary crushing stage [84,85]. Therefore, tertiary or further crushing stages must be considered only in situations in which the RAs are going to be used for structural concrete production. Otherwise, the extra processing stages would render the final product with an unnecessarily high quality and cost. Compared to stationary plants, a mobile recycling plant normally is comprised of fewer processing devices. Tables 10.1 and 10.2 present the main advantages and limitations of using these recycling plants. In order to produce RAs with the best possible quality and free of contamination, in each of the following conditions they must be stored separately whenever possible [83]: • • • •

RAs resulting from CDW debris with different qualities, RAs manufactured from different recycling procedures, RAs of different types, RA with different grading sizes.

Furthermore, it is also necessary that the RAs are kept dry, as much as possible, until they are used, due to self-cementing properties of un-hydrated cement particles.

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Stationary recycling plants Advantages

• Due to the greater size of the plant (economy of scale), it is capable of producing RAs of various grading sizes with improved efficiency and lower cost. • The greater amount of processing stages allows the production of RAs with enhanced quality.

Limitations

• The rate of production and economic viability of this plant depend on the constant supply of CDW from nearby construction and demolition sites, which may be somewhat erratic. • The greater distance between the recycling plant and the construction or demolition sites increases transportation costs. • Due to the greater amount of devices involved in this particular type of recycling plant, a higher initial investment is required.

Table 10.1: Stationary recycling plants: advantages and limitations [86] Mobile recycling plants Advantages

• As the name suggests, this recycling plant can be easily relocated to new construction or demolition sites, capable of sustaining them. • Due to the very close distance between construction or demolition sites and the recycling plant, transportation costs are minimal, especially if the CDW are produced, recycled, and reused on the same site. • The production of RA increases the local supply of aggregates and thus reduces demand and need of NA to be imported to the area.

Limitations

• Due to the typically lower number of contamination removal devices in this type of recycling plant, the final RAs are of lower quality. • This type of recycling plant may only be used in non-urban areas due to its unacceptable high levels of dust and noise. • The economic viability of this recycling plant depends on the amounts of CDW in construction or demolitions sites, which must compensate for the expense of setting up the facility.

Table 10.2: Mobile recycling plants: advantages and limitations [86]

10.5 Early age behaviour of structural RAC The most relevant fresh concrete properties in study are workability, bleeding, and fresh density. In order to encourage the extensive use of RA, it is necessary to know exactly how these materials affect these properties, in comparison to those of the natural aggregate concrete (NAC). Workability, or consistency, being one of the essential properties of fresh concrete, is significantly influenced by various mixing design parameters. When replacing NA with RA, the following main parameters need to be accounted for: replacement ratio, type, size, and moisture content.

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Most studies have shown that increasing RA content leads to decreased workability levels [87–91]. Naturally, this decrease depends on the nature of the RA used. Among the three most suitable RA for concrete production, RCA were found to have lesser impact on the consistency of concrete. This is mainly due to their lower water absorption, in comparison to MRA and RMA, which include materials with greater porosity. All other criteria being equal, as the RA water absorption increases, the consistency levels decrease, due to the absorption of the mixing water. Within each RA type, it is possible for the quality of materials to vary significantly. For example, high strength concrete materials, due to their higher capacity, tend to produce less porous RCA and thus with less water absorption, in comparison to RCA from low strength concrete. However, it was also found that, for the same crushing age, RCA from concrete materials with different compressive strength will not have an influence on the consistency levels of RAC [91–93]. Regarding RA size, the finer fraction generally shows higher water absorption values than that of the coarser fraction. This is mainly due to the recycling process of these materials in which after being subjected to various crushing stages, the finer fraction RA accumulates, increasing crushed fragments of adhered cement paste, which has a relatively high water absorption. Due to this, fine RA usually cause lower consistency levels, when compared to RAC made with coarse RA. There are three methods that allow recovering of the consistency loss, due to RA water absorption: • • •

Use of water reducing admixture (WRA), RA pre-saturation, Water compensation using additional mixing water.

For the same consistency, WRA, or (super) plasticizers, allow reducing the quantity of water. In cases where the amount of water is maintained, these admixtures allow greater consistency levels. The reduction of water may vary between 5 and 30%, depending on the plasticizer’s effectiveness. WRA act as dispersants when introduced in concrete mixes. These prevent the flocculation of fine particles of cement by electrostatic repulsion. In other words, instead of grouping in large clusters, cement particles disperse, allowing a more fluid mix. The second method consists of saturating RA by using a sprinkler system or introducing them in water tanks, for a 24 hour period prior to mixing. One hour before using these aggregates in the production of concrete, they must be dried in air, in order to achieve a saturated and surface dried condition. This allows the production of a concrete mix with the desired slump values and minimal consistency loss over time. The water compensation method is a simple process, which consists of introducing additional water during the mixing stage, corresponding to the extra amount absorbed by RA. In this method, the mixing process requires an extra amount of time for the RA to absorb most of its water capacity. Several researchers [94–98] have used this technique and obtained stable results. Furthermore, one study [98] showed that the use of water-compensated RCA leads to more stable slump values than when using pre-saturated aggregates. In one particular research [99], the authors found that the moisture conditions of the aggregates incorporated had a profound effect on the workability of concrete mixes over time. Figure 10.5

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Air-dried RCA

Oven-dried NA

140

140

120

120

100

100

Slump (mm)

(b) 160

Slump (mm)

(a) 160

80 60

80 60

40

40

20

20

0

Oven-dried RCA

0 0

30

60 90 120 Time (mins)

150

180

0

30

60 90 120 Time (mins)

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180

Saturated and surface-dried NA Saturated and surface-dried RCA

(c) 160 140

Slump (mm)

120 100 80 60 40 20 0 0

30

60 90 120 Time (mins)

150

180

Fig. 10.5: Slump over time of concrete mixes with NA and RCA at different moisture conditions: (a) air-dried; (b) oven-dried; (c) saturated and surface dried [99] presents the slump of concrete mixes over time made with NA and RCA at different moisture conditions and with similar total w/c ratio. As the RCA were introduced at a progressively drier state (oven-dried condition), the initial slump increased, due to a higher amount of mixing water. Concrete mixes made with RCA, in a saturated and surface-dried condition, exhibited initial slump equal to that of control mixes. Over time, concrete mixes made with oven-dried RCA showed the greatest slump loss, while mixes made with saturated and surface-dried RCA presented fairly similar slump levels over time. It was also observed that all RAC mixes, made with non-saturated RCA, exhibited similar slump levels to those of control mixes 15 to 30 minutes after mixing. This period corresponds to the amount of time that RCA take to absorb the additional mixing water, reaching a saturated state.

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Bleeding, referred to the movement of water to the surface of fresh concrete as a result of the settlement of solid particles, is known to have negative effects on the properties of concrete. A high degree of bleeding can significantly increase the near-surface w/c ratio, leading to lower concrete strength of the reinforcement cover. By replacing NA with RA, both positive and negative outcomes were obtained by several researchers [91,100–107]. Some researchers suggested that RA should be pre-wetted or saturated in order to prevent a rapid decrease in consistency of concrete [75,107,108], but others [99] suggested that, when using RAs in saturated and surface dried state, the water within them may cause bleeding during casting. Owing to the lower density of RAs, their increasing use in the production of concrete will lead to progressive density loss. Naturally, this varies according to the RA type. Since RMA normally present lower density values than RCA, for the same replacement ratio, RAC mixes made with RMA will exhibit lower density values than those made with RCA. Full NA replacement with coarse RCA may result in 5 to 10% density loss [109].

10.6 Mechanical behaviour of structural RAC There have been numerous studies on the effect of RA use on the mechanical properties of concrete. In most of these researches, coarse RCA were used in the production of concrete. Although it has been considered as the most compatible RA to be introduced into concrete, with some precautions other RA types and sizes can also be incorporated in relatively high amounts, as will be subsequently explained. As was demonstrated in the fresh concrete section, there are several inherent properties of RA, which differ from those of NA, that need to be accounted for when producing RAC. Since RAs exhibit lower quality, when compared to NA, their increasing use in RAC generally leads to decreased mechanical performance (lower compressive, flexural and tensile strengths and modulus of elasticity, and increased creep and shrinkage). Still, for the same replacement ratio, this decrease may be either minimal or noteworthy, depending on the RA type, size, original material quality, and moisture content. RCA exhibit the closest basic properties (water absorption, density, resistance to fragmentation) to those of NA. Therefore, this aggregate type is more likely to produce RAC with similar or slightly lower strength, in comparison to NAC, than when using the same amount of MRA or RMA. As the RMA content in an aggregate blend increases, the mechanical performance is expected to decline at an even greater rate than for mixes made with RCA alone. This shows that there must be a very strict quality control during the aggregates’ recycling process, in order to separate as much as possible the materials by type. Although the use of coarse RCA may produce RAC with compressive strength losses up to 40% [110], in comparison with corresponding NAC mixes, they may also result in 40% strength gains [111]. Thus far, the existing literature showed that the use of fine RCA resulted in similar [97,112,113] or lower [114–116] compressive strength values, when compared to corresponding control mixes. Therefore, it can be said that coarse RCA are more likely to produce RAC mixes with superior mechanical performance than mixes made with fine RCA. However, this may not

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be the case when producing concrete with RMA. Fine RMA often exhibit similar, or slightly less, density and water absorption to those belonging to the coarser fraction. Moreover, due to their greater surface area, as well as silica and alumina contents, fine RMA are more likely to create pozzolanic reactions with the surrounding cement paste. Consequently, this phenomenon may lead to RAC mixes with increased mechanical performance than when using coarse RMA. The quality of the original material has a vital role on the strength development of RAC mixes. Several studies [85,91,99,117–120] have shown that the use of RCA, from high strength concrete, may produce RAC mixes with marginal strength loss and, in some cases, strength gain. This effect is not exclusive for RCA, as studies [121,122] have shown that the use of RMA, from high strength brick units, resulted in RAC with compressive strength values equivalent to those of corresponding NAC mixes. It is well known that the mechanical strength of concrete mixes improves over time, due to the continuous hydration of cement particles. Researchers [123] have assessed the effects of incorporating coarse RCA contents in the mechanical properties of concrete, over a 10-year period. As expected, the compressive strength decreased as the RCA content increased (Fig. 10.6). However, the relative 28-day compressive strength loss of mixes with 100% RCA was 22%, in comparison to the control NAC, whereas, after 10 years, the relative difference was 7% only. While the relative 28-day splitting tensile strength loss was 8%, after 10 years, mixes with 100% coarse RCA showed a 5% strength gain in comparison to NAC. This phenomenon suggests that the continuous hydration of cement particles allowed a progressive improvement in bond strength between the new cement paste and RCA. An intense study was performed on the effect of exposing RAC, with various replacement ratios, to different environmental conditions [96]. As expected, the mechanical performance of concrete mixes (compressive and splitting tensile strength and modulus of elasticity) declined with increasing coarse

80

NA

50% RCA

100% RCA

NA

50% RCA

100% RCA

4 60 3.5 50

3

40

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30

2 1.5

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4.5

70 Compressive strength (MPa)

5

0.5

0

0 28-day

1-year

3-year

5-year

10-year

Time after demoulding

Fig. 10.6: Compressive (columns) and splitting tensile (lines) strength development of RAC with increasing RCA content [124]

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RCA content. However, in contradiction to a common assumption that RAC is more susceptible to different curing conditions, this research has proven otherwise. Indeed, by comparing the relative loss in performance of concrete specimens exposed to progressively drier environments, the authors found negligible differences between the mechanical performance of RAC and the control NAC. As previously stated, WRA have varying compositions, leading to various levels of effectiveness. Research [97] has set out to determine the effects of adding different kinds of WRA on the mechanical performance of concrete containing fine RCA. In this research, regular and high-range WRA were used in the production of concrete. The results presented in Fig. 10.7 enabled several conclusions. Although increasing the fine RCA content led to a decline of the mechanical performance of concrete, this variation was slight and the specimens presented quality good enough for structural use. Indeed, when producing concrete specimens with fine RCA, the effectiveness of high-range WRA proved to be quite similar to that when used in control NAC mixes. However, the results also indicated that regular WRA had slightly higher sensitivity with increasing fine RCA content. This resulted in concrete mixes with higher relative compressive strength loss, in comparison to mixes made with high-range WRA. The authors argue that the regular WRA act mainly by electrostatic repulsion and partially by steric hindrance, adsorbing onto the surface of the cement particles. Thus, their reduced effectiveness was likely due to their interaction with a greater number of cement particles, as the fine RCA content increased. There have been many studies in which mineral additions were used in the production of RAC. Most have focused on the use of FA [124–128], but there were also studies that used silica fume (SF) [128], GGBS [128,129], and metakaolin (MK) [128]. The results of these studies have shown that, as the RA content increased and regardless of the type of mineral addition, the strength loss of mixes with and without additions was quite similar. In other words, the increasing incorporation of RAs did not influence the expected outcome of adding mineral additions.

Without WRA

Regular WRA

High range WRA

70

Compressive strength (MPa)

60 50 40 30 20 10 0 0

10 30 50 Fine RCA replacement ratio (%)

100

Fig. 10.7: 28-day compressive strength of concrete mixes made with increasing fine RCA content and WRA with different levels of effectiveness [97]

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15% MK

Control

55% GGBS

35% FA

70

Compressive strength (MPa)

65 60 55 50 45 40 35 30 0

50 Coarse RCA replacement ratio (%)

100

Fig. 10.8: 28-day compressive strength of concrete mixes with increasing coarse RCA content and different kinds of mineral additions [128] Figure 10.8 illustrates a good example of this phenomenon, in which the slope, corresponding to the compressive strength loss, is almost similar in all concrete mixes. As previously stated, there are three methods that allow compensation of the consistency loss caused by RA absorption. Various researchers [94–98] using the water compensation method, besides obtaining stable products in terms of workability, have also achieved consistent results in terms of mechanical performance. In one of these studies, the authors [98] compared the effects of using previously saturated coarse RCA, against the water compensation method, on the mechanical performance of RAC. The results were very clear, in that the water compensation method allowed slightly improved performance in the compressive strength and modulus of elasticity. This improvement was even more noticeable in terms of shrinkage. RAC mixes with 100% water-compensated coarse RCA, exhibited close to 25% less shrinkage than corresponding mixes with pre-saturated coarse RCA. Another topic of great interest, which strangely has not been the subject of many investigations, is multiple recycling. In other words, how many times can RCA be used in the production of new concrete before it starts to exhibit a noticeable loss in performance? Researchers [130,131], who studied this theme, performed at least three recycling cycles. In both studies, the resulting RAC mixes exhibited similar or slightly lower compressive strength values to those of the control concrete. This indicates that concrete may endure endless cycles of recycling, without showing a significant loss in mechanical performance. However, this must be verified through further research, in which the durability aspects are also evaluated.

10.7 Durability behaviour of structural RAC Nowadays, engineers look for materials with enhanced durability, which besides improving resistance to external agents also reduce the life-cycle costs of concrete structures. Although less

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10.7 DURABILITY BEHAVIOUR OF STRUCTURAL CONCRETE WITH RAs Debieb and Kenai (2008)

181

Sadek (2011)

Water absorption increase in relation to corresponding NAC (%)

160 140 120 100 80 60 40 20 0 100% fine RMA

100% coarse RMA

100% coarse and fine RMA

Fig. 10.9: Water absorption of RAC mixes with RMA of varying sizes [140,141] frequent in the mechanical performance section, there have been numerous researches that have assessed the effects of adding RAs on the durability-related performance of RAC. Generally, as the replacement ratio increases the performance of concrete declines. The extent of this effect may vary depending on the RA type, size, and quality of the original materials. As stated, RCA’s inherent properties are the most similar to those of NA. Therefore, they are capable of producing RAC mixes with much closer durability-related performance to that of NAC, than RAC mixes made with other RA types [132–136]. This is only natural, considering that the alternative RA (RMA and MRA) may exhibit much greater water absorption than RCA. Regarding the influence of RA size, it was found [137–139] that, for the same replacement ratio, coarse RCA may produce RAC mixes with much less porosity than when using fine RCA. This trend was reversed in the case of RMA (Fig. 10.9) [140,141]. Owing to the greater amount of pozzolanic reactions between the fine RMA and cement paste, these mixes may exhibit less permeability than when using coarse RMA. A significant study [118] assessed the effects of introducing coarse RCA, with varying quality, on the durability performance of concrete. The materials used in this study came from concrete materials with different strength levels and were exposed to a varying number of processing stages. The authors found that the durability factor increased as the strength of the original materials increased. Furthermore, they learned that, as the RCA was subjected to an increasing number of processing stages, the durability-related performance improved. This trend, which is attributed to the use of RCA with progressively lower water absorption, is mainly due to two factors: as the strength of the original material increased, the porosity of the adhered mortar decreased; and as the number of processing stages increased, the amount of adhered mortar decreased, thus exhibiting lower water absorption values. However, this may not be the case in the process of carbonation of concrete. Studies [142–144] reveal that, provided that the incorporated RCA, coming from concrete materials with varying strength levels, exhibit similar water

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absorption values, the strength of the original material and quantity of adhered mortar have little influence on the process of concrete carbonation. In most studies, authors use simple test methods, in a relatively short period of time after casting, to assess the durability of concrete. However, [145] went a step further and determined the performance of RAC mixes over a 10-year period. Figure 10.10 presents the total charge passed and carbonation depth of these RAC mixes, exposed to an outdoor environment, with increasing coarse RCA and FA content. After 10 years, RAC mixes, with no additions and with 100% coarse RCA, showed only 10% higher total charge passed and carbonation depths, in comparison to corresponding NAC mixes. This shows that it is possible to produce RAC, using 100% coarse RCA, with negligible performance loss. Using additions to lower the penetrability of concrete is an effective method to achieve a more durable material. Figure 10.10 shows that incorporating increasing FA content increases the resistance to chloride ion penetration. This, however, does not take happen with carbonation, that is, as the FA content increased, carbonation depths also increased. Apart from the lower calcium hydroxide content in FA, in comparison to cement, high amounts of FA may lead to increased porosity levels [146,147]. Figure 10.11 demonstrates that mineral additions, other than FA, are also able to greatly reduce the chloride ion penetrability of RAC. Although some properties of RAC, when exposed to progressively drier environments, may be more sensitive than those of corresponding NAC [148], the differences are minimal [149]. In other words, the increasing incorporation of coarse RCA has minimal effect on the relative effect caused by exposing concrete to different environmental conditions. Several researches [150–153] have revealed that the increasing use of RAs in RAC mixes may cause a somewhat lower resistance to freezing and thawing cycles. However, this may 28-day

1-year

10-year

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1-year

10-year

8000

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7000 6000 20

5000 4000

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2000 5

1000 0 F5

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00 R1

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00

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0F R5

R0

Rl

0 R5

R0

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Fig. 10.10: Total charge passed (columns) and carbonation depth (lines) of RAC mixes with increasing coarse RCA and fly ash content [145]

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10% SF

15% MK

35% FA

55% GGBS

Total charge passed (coulombs)

6000

5000

4000

3000

2000

1000

0 0

50 Coarse RCA content (%)

100

Fig. 10.11: Total charge passed of RAC mixes with increasing coarse RCA content and different mineral additions [128]

be overcome by introducing air-entraining admixtures. Studies [151,154,155] have shown that after using air-entraining admixtures, very little difference was found between RAC and NAC mixes and that they had the same air content, irrespectively of the RA content.

10.8 Successful case studies using structural RAC As previously mentioned, one of the main barriers to recycling and reuse of CDW materials is the lack of confidence by clients and contractors. It is expected that by presenting various successful case studies, in which structural RAC was used, these players increase their confidence on the use of this sustainable construction material. Table 10.3 presents some of these case studies.

10.9 Concluding remarks This chapter has described several ways of making concrete more sustainable, of which recycling CDW is one of the most important and feasible with the existing technology. For this reason, at the present date, there are no arguments against CDW materials being used for the production of new concrete. The literature, besides providing sufficient evidence of the feasibility of using RA in concrete, it also already covered most aspects in regard to the effects of their incorporation. Many types of wastes were studied as a constituent in concrete production. Although some industrial waste materials (i.e. GGBS and FA) have shown significant improvements in some concrete properties, most were incompatible with concrete. Concerning RA from CDW materials, of the three types identified, RCA are considered the most compatible with concrete. The

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Case Study

Description

Hong Kong Wetland Park (Hong Kong)

Hong Kong Wetland Park is located at the north western part of Hong Kong and is close to the border between Hong Kong and Shenzhen, China. Hong Kong Wetland Park comprises a 10 000 m2 visitor centre with exhibition galleries, theatres, souvenir shops, cafes, children play areas, classrooms and a resources centre. In the construction of the Hong Kong Wetland Park, RA was used to replace part of the NA used in structural concrete. A total volume of around 13 000 m3, and of RAC was used in its construction. The applications of the RAC include pile caps, ground slabs, external works, mass concrete, minor concrete works, and concrete blinding, depending on the strength class of concrete. The replacement levels of coarse RA were of 20 and 100%, for strength classes equal to or above C25 and below C20, respectively. The highest strength class of RAC was C35. The Dutch Concrete Association took the initiative in setting up a demonstration project, called “Delftse Zoom”, to stimulate the use of CDW materials in the production of structural concrete. The purpose was to work with RAC, in which the coarse NA was entirely replaced by RCA and RMA. This project involved the construction of 272 low-rise dwellings and family houses, in which the partitioning walls were made of load-bearing prefabricated concrete elements. Although building specifications limited the use of coarse MRA to a maximum replacement level of 20%, in this project, replacement levels up to 100% were used with caution. In the demonstration project, the partitioning walls were built with C25 RAC. In the first phase of the project, the RAC was only used in relatively simple constructive elements such as unreinforced load-bearing walls. At a later stage, attention was directed towards more high-grade uses, such as pre-stressed facade elements and floors. The Environmental Building is an office and seminar facility at the heart of the main Building Research Establishment (BRE) site in Watford, UK. It was designed to act as a model for low energy and environmentally aware office building of the 21st century. This building incorporates the first-ever use of RA in ready-mixed concrete in the UK. RAs were used under the supervision of structural engineers. RCA was used as coarse aggregate in over 1500 m3 of concrete supplied for foundations, floor slabs, structural columns, and waffle floors. For the foundations, a C25 mix was specified. For floor slabs, structural columns, and waffle floors, a C35 mix was specified. In support of the Singapore government’s goal to achieve sustainable development in the construction industry, the Changi Airport Group has initiated a project using RCA. This material was obtained from the demolition of existing aircraft stand rigid pavement, to reconstruct a new aircraft stand rigid pavement at Singapore Changi Airport.

The “Delftse Zoom” Housing Project (The Netherlands)

The Environmental Building at BRE (United Kingdom)

Singapore Changi Airport (Singapore)

(Continued)

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Case Study

Description

Singapore Changi Airport (Singapore)

The RCA was obtained from the demolition of the aircraft stand rigid pavement, which was processed in a recycling plant. Laboratory tests were carried out on the RCA to ensure that these complied with the requirements before its use in RAC production. A maximum replacement level of 20% RCA was employed. The application of RAC was made similar to NAC, except that special measures were undertaken to ensure that it was properly cured to minimize shrinkage cracking. The first phase of this project involved the construction of an aircraft stand rigid pavement area of about 35 750 m2. The remaining areas, of about 190 000 m2, will be completed by 2019.

Recycled building materials for the Head Office in Osnabrück (Germany)

The German Federal Foundation for the Environment (Deutsche Bundesstiftung Umwelt) erected its new office building in Osnabrück to accommodate its headquarters. With this new structure, the Foundation set an example for the use of environmentally friendly construction materials. When this project started, the existing German standards, for the production of structural concrete, did not yet provide the framework for the use of RA in concrete production. In laboratory investigations, concrete mixes were developed to meet the technical requirements, such as strength and workability. C25 and C35 strength class RAC mixes were used for structural elements.

Table 10.3: Successful case studies using structural RAC [156–158] use of these materials in the production of new concrete has shown considerably less loss in performance, than when using the other two types of RA (MRA and RMA). Of course, due to the varying quality and strength of the original materials, extra precautions must be taken to ensure the use of the best possible materials when producing structural concrete. To ensure that good quality RAs are manufactured, the quality control process must start during construction or demolition activities. By applying a selective demolition methodology, waste materials will then be separated and stored properly, which, besides facilitating the task of recycling plant operatives, will also minimize contamination levels of future RAs. Owing to the similarity between CDW recycling plants and NA manufacturing facilities, it is relatively easy to set up the first one by purchasing currently used technologies or even by converting an existing NA production factory. In either case, the literature review has shown that there is enough information for recycling plants to produce RA with good quality enough to be used in structural concrete production. The recycling procedure and type of recycling plant must adapt to the desired application of the end product. This is important as some processing stages may be bypassed, transportation distances reduced and less energy consumed. This translates into reduced costs and lessens the ecological footprint. Some studies have shown that it is possible to produce RAC mixes, using unsaturated RA, with similar or even improved mechanical performance, when compared to conventional mixes.

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However, in situations in which the consistency of concrete is important, it is recommended that some sort of water compensation method is used. Regardless of the type of RA, the coarser fraction has proved to produce RAC mixes with closer performance to that of a corresponding control mix, than when using the finer fraction. However, it is possible to use fine RA in the production of concrete under special precautions. Since the strength of the original material has a noticeable effect on the properties of RAC, the use of some sort of quality control of materials prior to demolition would increase the potential value of the resulting aggregates. Furthermore, the extra information would also allow a better understanding of the potential effects on the mechanical and durability-related properties of concrete. Although very little information was obtained on the multiple recycling potential of concrete, existing studies have shown that this material is able to endure a significant number of recycling cycles. This aspect is rather significant as it suggests that it is possible to continually produce new concrete from RCA, without significant loss in performance and using minimum amounts of natural resources. However, further research is required on this subject in order to ascertain the effects on the various properties of concrete. Furthermore, as various studies have demonstrated while using a selective demolition approach, significant economic and environmental benefits may be guaranteed. The use of materials from processed CDW results in a dramatic reduction of the use of natural resources as well as the amount of waste sent to landfills. Finally, one of the most important conclusions drawn during this study is that, considering that a proper recycling methodology is used, CDW derived materials should be considered as just another possible aggregate for the production of concrete (i.e. sandstone, granite, limestone, RCA, RMA, and MRA). This forward thinking, in which RA are regarded as an added-value material instead of a poor-quality and unusable material, is a step further into making structural concrete production more sustainable.

References Introduction [1] [2] [3] [4]

[5]

Timetric. 2013. Global Construction Aggregates Market – Key Trends and Opportunities to 2017, Timetric, 225 p. European Commission. Eurostat. http://epp.eurostat.ec.europa.eu/statistics_explained/ -index.php/Waste_statistics, [accessed on 17 July 2013]. Freedonia. 2012. World construction aggregates. Available at: http://www.freedoniagroup. com/brochure/25xx/2564smwe.pdf [accessed on 13 August 2013]. Hendriks, C.A., Worrell, E., de Jager, D., Blok, K., Riemer, P. 1998. Emission reduction of greenhouse gases from the cement industry. Fourth International Conference on Greenhouse Gas Control Technologies, Interlaken, Switzerland, August 1998, Elsevier Science Ltd., 939–944. Imbabi, M.S., Carrigan, C., McKenna, S. 2012. Trends and developments in green cement and concrete technology. Int. J. Sustain. Built Environ., 1(2): 194–216.

BackBack to table ofofcontents to table contents

sed_1410.indd 186

20/08/15 12:32 PM

REFERENCES

187

[6]

Odum, H.T. 1996. Environmental Accounting: Emergy and Environmental Decision Making, Wiley, New York, NJ, USA, 370. [7] Brown, M.T., Buranakarn, V. 2003. Emergy indices and ratios of sustainable material cycles and recycle options. Resour. Conserv. Recycl., 38(1): 1–22. [8] Pulselli, R.M., Simoncini, E., Ridolfi, R., Bastianoni, S. 2008. Specific emergy of cement and concrete: an energy-based appraisal of building materials and their transport. Ecolog. Indicat., 8(5): 647–656. [9] Flatt, R.J., Roussel, N., Cheeseman, C.R. 2012. Concrete: an eco material that needs to be improved. J. Euro. Ceramic Soc., 32(11): 2787–2798. [10] Hasanbeigi, A., Price, L., Lin, E. 2012. Emerging energy-efficiency and CO2 emissionreduction technologies for cement and concrete production: a technical review. Renew. Sustaina. Energ. Rev., 16(8): 6220–6238. [11] International Energy Agency. 2009. Technology Roadmap: Cement - Foldout. Available at: http://www.iea.org/publications/freepublications-/publication/Cement_Roadmap_Foldout_ WEB.pdf [accessed on 21 June 2013].

Industrial wastes Ground granulated blast furnace slag [12] Al-Jabri, K., Hisada, M., Al-Saidy, A., Al-Oraimi, S. 2009. Copper slag as sand replacement of high performance concrete. Cement Concr. Compo., 31(7): 483–488. [13] Dhir, R.K., El-Mohr, M.A.K., Dyer, T.D. 1996. Chloride binding in GGBS concrete. Cement Concr. Res., 26(12): 1767–1773. [14] Oner, A., Akyuz, S. 2007. An experimental study on optimum usage of GGBS for the compressive strength of concrete. Cement Concr. Compo., 29(6): 505–514. [15] Tasong, W.A., Wild, S., Tilley, R.J.D. 1999. Mechanism by which ground granulated blast furnace slag prevents sulfate attack of lime stabilized kaolinite. Cement Concr. Res., 29(7): 975–982. Fly ash [16] Oluokun, F.A. 1994. Fly ash concrete mix design and the water cement ratio law. ACI Mater. J., 91(4): 362–371. [17] Bilodeau, A., Sivasundaram, V., Painter, K.E., Malhotra, V.M. 1994. Durability of concrete incorporating high volumes of fly ash from sources in the USA. ACI Mater. J., 91(1): 3–12. [18] Langley, W.S., Carette, G.G., Malhotra, V.M. 1992. Strength development and temperature rise in large concrete blocks containing high volumes of low-calcium (ASTM class F) fly ash. ACI Mater. J., 89(2): 362–368. [19] Langan, B.W., Weng, K., Ward, M.A. 2002. Effect of silica fume and fly ash on heat of hydration of portland cement. Cement Concr. Res., 32(7): 1045–1051. [20] Siddique, R. 2004. Performance characteristics of high-volume class F fly ash concrete. Cement Concr. Res., 34(3): 487–493. [21] Huang, C.H., Lin, S.K., Chang, C.S., Chen, H.J. 2013. Mix proportions and mechanical properties of concrete containing very high-volume of class F fly ash. Construct. Build. Mater., 46: 71–78.

BackBack to table ofofcontents to table contents

sed_1410.indd 187

20/08/15 12:32 PM

188

CHAPTER 10. GREEN MATERIALS FOR CONCRETE PRODUCTION

Glass [22] Chen, C.H., Wu, J.K., Yang, C.C. 2006. Waste E-glass particles used in cementitious mixtures. Cement Concr. Res., 36(3): 449–456. [23] Ismail, Z.Z., Al-Hasmi, E.A. 2009. Recycling of waste glass as a partial replacement for fine aggregate in concrete. Waste Manag., 29(2): 655–659. [24] Kou, S.C., Poon, C.S. 2009. Properties of self-compacting concrete prepared with recycled glass aggregate. Cement Concr. Compo., 31(2): 107–113. [25] Metwally, I.M. 2007. Investigations on the performance of concrete made with blended finely milled waste glass. Adv. Struct. Eng., 10(1): 47–53. [26] Park, S.B., Lee, B.C., Kim, J.H. 2004. Studies on mechanical properties of concrete containing waste glass aggregate. Cement Concr. Res., 34(12): 2181–2189. [27] Shao, Y., Lefort, T., Moras, S., Rodriguez, D. 2000. Studies on concrete containing ground waste glass. Cement Concr. Res., 30(1): 91–100. [28] Topçu, I.B., Canbaz, M. 2004. Properties of concrete containing waste glass. Cement Concr. Res., 34(2): 267–274. [29] Castro, S., de Brito, J. 2013. Evaluation of the durability of concrete made with crushed glass aggregates. J. Clean. Prod., 41: 7–14. [30] Serpa, D., Santos Silva, A., de Brito, J., Pontes, J., Soares D. 2013.ASR of mortars containing glass. Construct. Build. Mater., 47: 489–495. Plastic [31] [32]

[33]

[34] [35] [36] [37] [38] [39]

[40]

Siddique, R., Khatib, J., Kaur, I. 2007. Use of recycled plastic in concrete: a review. Waste Manage., 28(10): 1835–1852. Akçaözoglu, S., Atis, C.D., Akcaözoglu, K. 2010. An investigation on the use of shredded waste PET bottles as aggregate in lightweight concrete. Waste Manag., 32(2): 285–290. Albano, C., Camacho, N., Hernandez, M., Matheus, A., Gutierrez, A. 2009. Influence of content and particle size of waste PET bottles on concrete behaviour at different W/C ratios. Waste Manag., 29(10): 2707–2716. Choi, Y.W., Moon, D.J., Chung, J.S., Cho, S.K. 2005. Effects of waste PET bottles aggregate on the properties of concrete. Cement Concr. Res., 35(4): 776–781. Saikia, N., de Brito, J. 2012. Use of plastic waste as aggregate in cement mortar and concrete preparation: a review. Construct. Build. Mater., 34: 385–401. Frigione, M. 2010. Recycling of PET bottles as fine aggregate in concrete. Waste Manag., 30(6): 1101–1106. Kou, S.C., Lee, G., Poon, C.S., Lai, W.L. 2009. Properties of lightweight aggregate concrete prepared with PVC granules derived from scraped PVC pipes. Waste Manag., 29(2): 621–628. Soroushian, C. 1999. Experimental investigation of the optimized use of plastic flakes in normal-weight concrete. Magaz. Concr. Res., 51(1): 27–33. Ferreira, L., de Brito, J., Saikia, N. 2012. Influence of curing conditions on the mechanical performance of concrete containing recycled plastic aggregate. Construct. Build. Mater., 36: 196–204. Silva, R.V., de Brito, J., Saikia, N. 2013. Influence of curing conditions on the durabilityrelated performance of concrete made with selected plastic waste aggregates. Cement Concr. Compos., 35(1): 23–31.

BackBack to table ofofcontents to table contents

sed_1410.indd 188

20/08/15 12:32 PM

REFERENCES

189

Rubber [41] [42] [43] [44] [45] [46]

Valadares, F., Bravo, M., de Brito, J. 2012. Concrete with used tire rubber aggregates: mechanical performance. ACI Mater. J., 109(3): 283–292. Marques, A.M., Correia, J.R., de Brito, J. 2013. Post-fire residual mechanical properties of concrete made with recycled rubber aggregate. Fire Saf. J., 58: 49–57. Khatib, Z., Bayomy, F. 1999. Rubberized portland cement concrete. J. Mater. Civil Eng., 11(3): 206–213. Segre, N., Joekes, I. 2000. Use for tire rubber particles as addition to cement paste. Cement Concr. Res., 30(9): 1421–1425. Topçu, I. 1995. The properties of rubberized concretes. Cement Concr. Res., 25(2): 304–310. Pedro, D., de Brito, J., Veiga, R. 2012. Mortars made with fine granulate from shredded tyres, J. Mater. Civil Eng., 25(4): 519–529.

Other wastes [47] [48]

[49] [50]

[51]

[52] [53]

[54] [55] [56]

[57] [58] [59]

Almeida, N., Branco, F., Brito, J., Santos, J. 2007. High-performance concrete with recycled stone slurry. Cement Concr. Res., 37(2): 210–220. Baffa, I., Akasaki, J. 2005. Light-concrete with leather: durability aspects. International Conference on Concrete for Structures, Coimbra, Portugal, July 2005, University of Coimbra, Coimbra, 69–77. Lima, P., Leite, M., Santiago, E. 2010. Recycled lightweight concrete made from footwear industry waste and CDW. Waste Manag., 30(6): 1107–1113. Martins, M., Santos, J., Azevedo, A. 2004. Production of lightweight concrete with E.V.A. residues as recycled aggregate. International RILEM Conference on the Use of Recycled Materials in Buildings and Structures, Barcelona, Spain, November 2004, RILEM, 973–981. Santiago, E., Lima, P., Leite, M., Filho, R. 2009. Mechanical behaviour of recycled lightweight concrete using EVA waste and CDW under moderate temperature. IBRACON Struct. Mater. J., 2(3): 211–221. Yang, E., Yi, S., Leem, Y. 2005. Effect of oyster shell substituted for fine aggregate on concrete characteristics. Part I: fundamental properties. Cement Concr. Res., 35(11): 2175–2182. Chandra, S. 1997. Palm Oil Shell Aggregate for Lightweight Concrete, Waste Materials Used in Concrete Manufacturing. Division of Concrete Structures, Chalmers University of Technology, Sweden, 624–636. Mannan, M., Ganapathy, C. 2004. Concrete from an agriculture waste-oil palm shell (OPS). Build. Environ., 39(4): 441–448. Mannan, M., Ganapathy, C. 2001. Long-term strengths of concrete with oil palm shell as coarse aggregate. Cement Concr. Res., 31(9): 1319–1321. Teo, D., Mannan, M., Kurian, V., Ganapathy, C. 2007. Lightweight concrete made from oil palm shell (OPS): structural bond and durability properties. Build. Environ., 42(7): 2614–2621. Sales, A., Souza F. 2009. Concretes and mortars recycled with water treatment sludge and construction and demolition rubble. Construct. Build. Mater., 23(6): 2362–2370. Tay, J., Hong, S., Show, K. 2000. Reuse of industrial sludge as pelletized aggregate for concrete. J. Environ. Eng., 126(3): 279–287. Mun, K. 2007. Development and tests of lightweight aggregate using sewage sludge for non-structural concrete. Construct. Build. Mater., 21(7): 1583–1588.

BackBack to table ofofcontents to table contents

sed_1410.indd 189

20/08/15 12:32 PM

190

CHAPTER 10. GREEN MATERIALS FOR CONCRETE PRODUCTION

Construction and demolition wastes Specifications [60]

[61] [62]

[63] [64] [65] [66] [67] [68] [69] [70]

[71] [72] [73]

[74]

Building Contractors Society of Japan (BCSJ). 1997. Proposed Standard for the Use of Recycled Aggregate and Recycled Aggregate Concrete. Committee on Disposal and Reuse of Construction Waste, Japan. Building Research Establishment (BRE). 1998. Recycled aggregates, BRE Digest 433, CI/ SfB p(T6), 6 p. Cement and Concrete Association of New Zealand (CCANZ). 2011. Best Practice Guide for the Use of Recycled Aggregates in New Concrete. Cement and Concrete Association of New Zealand, 49 p. CEN/TC 154/SC2. 2005. Proposed Amendments to EN 12620 to Incorporate Clauses for Recycled Aggregates. CEN/TC 154/SC2, Brussels, Belgium, 16. DIN 4226-100. 2002. Aggregates for Mortar and Concrete – Part 100 Recycled Aggregates, DIN 4226-100, Germany. Japan Standards Association (JIS A 5021). 2005. Recycled Aggregate for Concrete-Class H. Japan Standards Association, Japan. Japan Standards Association (JIS A 5022). 2005. Recycled Aggregate for Concrete-Class M. Japan Standards Association, Japan. Japan Standards Association (JIS A 5023). 2007. Recycled Aggregate for Concrete-Class L. Japan Standards Association, Japan. LNEC E 471. 2006. Guideline for the Use of Recycled Coarse Aggregates in Hydraulic Binders’ Concrete (in Portuguese). LNEC E 471, National Laboratory in Civil Engineering, Portugal. NBR 15.116. 2005. Recycled Aggregates from Construction and Demolition Waste: NonStructural Concrete-Requirements (in Portuguese). NBR 15.116, Brazil. DDPS - Département fédéral de la défense, de la protection de la population et des sports (Federal Department of Defence, Civil Protection and Sports). 2006. Ot (Objectif technique) 70085 Instruction technique: Utilisation de Matériaux de Construction Minéraux Secondaires dans la Construction d’abris, Switzerland. Prescriptions Techniques PTV 406 Édition 1.1. 2003. Granulats de Débris de Démolition et de Construction Recycles. PTV 406 Édition 1.1, Brussels, Belgium. RILEM TC 121-DRG. 1994. Specifications for concrete with recycled aggregates, Materials and Structures. Mater. Struct., 27(173): 557–559. Task Force of the Standing Committee of Concrete of Spain. 2004. Draft of Spanish regulations for the use of recycled aggregate in the production of structural concrete. International RILEM Conference on the Use of Recycled Materials in Buildings and Structures, Barcelona, Spain, November 2004, RILEM, 511–525. WBTC No. 12. 2002. Specifications Facilitating the Use of Recycled Aggregates. Works Bureau Technical Circular, Hong Kong.

Converting CDW into RA [75] Hansen, T.C. 1992. Recycling of Demolished Concrete and Masonry, RILEM Report 6, Report of Technical Committee 37-DRC, Demolition and Reuse of Concrete, E&FN Spoon, London, 319 p.

BackBack to table ofofcontents to table contents

sed_1410.indd 190

20/08/15 12:32 PM

REFERENCES

191

[76] Mas, B., Cladera, A., del Olmo, T., Pitarch, F. 2012. Influence of the amount of mixed recycled aggregates on the properties of concrete for non-structural use. Construct. Build. Mater., 27(1): 612–622. [77] Coelho, A., de Brito, J. 2011. Economic analysis of conventional versus selective demolition – a Case Study. Resour. Conserv. Recycl., 55(3): 382–392. [78] Coelho, A., de Brito, J. 2012. Influence of construction and demolition waste management on the environmental impact of buildings. Waste Manag., 32(3): 532–541. [79] Coelho, A., de Brito, J. 2013. Economic viability analysis of a construction and demolition waste recycling plant in Portugal E. Part I: location, materials, technology and economic analysis. J. Clean. Prod., 39: 338–352. [80] Coelho, A., de Brito, J. 2013. Economic viability analysis of a construction and demolition waste recycling plant in Portugal E. Part II: economic sensitivity analysis. J. Clean. Prod., 39: 329–337. [81] ACI Committee 555. 2001. Removal and Reuse of Hardened Concrete. American Concrete Institute, Farmington Hills, MI, USA, Special Publication, 26. [82] Hendriks, C.F., Pietersen, H.S., Fraay, A.F.A. 1998. Recycling of building and demolition waste – an integrated approach. Proceedings of the International Conference on the Use of Recycled Concrete Aggregates, London, UK, November 1998, Thomas Telford, UK, 419–432. [83] Kasai, Y. 1998. Barriers to the reuse of construction by-products and the use of recycled aggregate concrete in Japan. Proceedings of the International Conference on the Use of Recycled Concrete Aggregates, London, UK, November 1998, Thomas Telford, UK, 433–444. [84] Gokce, A., Nagataki, S., Saekic, T., Hisada, M. 2011. Identification of frost-susceptible recycled concrete aggregates for durability of concrete. Construct. Build. Mater., 25(5): 2426–2431. [85] Nagataki, S., Gokce, A., Saeki, T., Hisada, M. 2004. Assessment of recycling process induced damage sensitivity of recycled concrete aggregates. Cement Concr. Res., 34(6): 965–971. [86] O’Mahony, M. 1990. Recycling of Materials in Civil Engineering, PhD. Thesis, University of Oxford, 233.

Fresh behaviour of RAC Consistency [87] Etxeberria, M., Vázquez, E., Marí, A., Barra, M. 2007. Influence of amount of recycled coarse aggregates and production process on properties of recycled aggregate concrete. Cement Concr. Res., 37(5): 735–742. [88] Barra, M., Vazquez, E. 1998. Properties of concretes with recycled aggregates: influence of properties of the aggregates and their interpretation. Proceedings of the International Conference on the Use of Recycled Concrete Aggregates, London, UK, November 1998, Thomas Telford, UK, 19–30. [89] Khatib, J.M. 2005. Properties of concrete incorporating fine recycled aggregate. Cement Concr. Res., 35(4): 763–769. [90] Buyle-Bodin, F., Zaharieva, R. 2002. Influence of industrially produced recycled aggregates on flow properties of concrete. Mater. Struct., 35(8): 504–509. [91] Yang, K.H., Chung, H.S., Ashour, A.F. 2008. Influence of type and replacement level of recycled aggregates on concrete properties. ACI Mater. J., 105(3): 289–296.

BackBack to table ofofcontents to table contents

sed_1410.indd 191

20/08/15 12:32 PM

192

CHAPTER 10. GREEN MATERIALS FOR CONCRETE PRODUCTION

[92] Padmini, A.K., Ramamurthy, K., Mathews, M.S. 2009. Influence of parent concrete on the properties of recycled aggregate concrete. Constr. Build. Mater., 23(2): 829–836. [93] Otsuki, N., Miyazato, S., Yodsudjai, W. 2003. Influence of recycled aggregate on interfacial transition zone, strength, chloride penetration and carbonation of concrete. J. Mater. Civil Eng., 15(5): 443–451. [94] Leite, M. 2001. Evaluation of the Mechanical Properties of Concrete Made With Aggregates From Construction and Demolition Waste, PhD Thesis (In Portuguese), Porto Alegre, Brazil. [95] Evangelista, L., de Brito, J. 2010. Durability performance of concrete made with fine recycled concrete aggregates. Cement Concr. Compos., 32(1): 9–14. [96] Fonseca, N., de Brito, J., Evangelista, L. 2011. The influence of curing conditions on the mechanical performance of concrete made with recycled concrete waste. Cement Concr. Compos., 33(6): 637–643. [97] Pereira, P., Evangelista, L., de Brito, J. 2012. The effect of superplasticizers on the mechanical performance of concrete made with fine recycled concrete aggregates. Cement Concr. Compos., 34(9):1044–1052. [98] Ferreira, L., de Brito, J., Barra, M. 2011. Influence of pre-saturation of recycled coarse concrete aggregates on structural concrete’s mechanical and durability properties. Magaz. Concr. Res., 63(8): 617–627. [99] Poon, C.S., Shui, Z.H., Lam, L., Fok, H., Kou, S.C. 2004. Influence of moisture states of natural and recycled aggregates on the slump and compressive strength of concrete. Cement Concr. Res., 34(1): 31–36. Bleeding [100] Limbachiya, M.C., Leelawat, T., Dhir, R.K. 1998. RCA concrete: a study of properties in the fresh state, strength development and durability. Proceedings of the International Conference On The Use Of Recycled Concrete Aggregates, London, UK, November 1998, Thomas Telford, UK, 227–237. [101] Dhir, R.K., Paine, K.A. 2004. Suitability and practicality of using coarse RCA in normal and high- strength concrete. 1st International Conference on Sustainable Construction: Waste Management, Singapore, June 2004, CPG Laboratories Pte Ltd., Singapore, 15. [102] Kou, S.C., Poon, C.S. 2009. Properties of self-compacting concrete prepared with coarse and fine recycled concrete aggregates. Cement Concr. Compos., 31(9): 622–627. [103] Poon, C.S., Kou, S.C., Lam, L. 2007. Influence of recycled aggregate on slump and bleeding of fresh concrete. Mater. Struct., 40(9): 981–988. [104] Corinaldesi, V., Moriconi, G. 2011. The role of industrial by-products in self-compacting concrete. Construct. Build. Mater., 25(8): 3181–3186. [105] Van Der Wegen, G., Haverkort, R. 1998. Recycled construction and demolition waste as a fine aggregate for concrete. Proceedings of the International Conference on the Use of Recycled Concrete Aggregates, London, UK, November 1998, Thomas Telford, UK, 333–346. [106] Koulouris, A., Limbachiya, M.C., Fried, A.N., Roberts, J.J. 2004. Use of recycled aggregate in concrete application: Case studies. Proceedings of the International Conference on Sustainable Waste Management and Recycling: Construction Demolition Waste, London, UK, September 2004, Thomas Telford, UK, 245–258.

BackBack to table ofofcontents to table contents

sed_1410.indd 192

20/08/15 12:32 PM

REFERENCES

193

[107] Kutegeza, B., Alexander, M.G. 2004. The performance of concrete made with commercially produced recycled coarse and fine aggregates in the Western Cape. Proceedings of the International Conference on Sustainable Waste Management and Recycling: Construction Demolition Waste, London, UK, September 2004, Thomas Telford, UK, 235–244. [108] Sagoe-Crentsil, K.K., Brown, T., Taylor, A.H. 2001. Performance of concrete made with commercially produced coarse recycled concrete aggregate. Cement Concr. Res., 31(5): 707–712. Density [109] CCANZ. 2011. Best Practice Guide for the Use of Recycled Aggregates in New Concrete. Cement and Concrete Association of New Zealand, 49.

Mechanical behaviour of RAC [110] Kou, S.C., Poon, C.S., Chan, D. 2007. Influence of fly ash as cement replacement on the properties of recycled aggregate concrete. J. Mater. Civil Eng., 19(9): 709–717. [111] Ridzuan, A.R., Ibrahim, A., Ismail, A.M.M., Diah, A.B.M. 2005. Durability performance of recycled aggregate concrete. Proceedings of the International Conference on Achieving Sustainability in Construction, Dundee, Scotland, UK, July 2005, Thomas Telford, UK, 193–202. [112] Evangelista, L., de Brito, J. 2010. Durability performance of concrete made with fine recycled concrete aggregates. Cement Concr. Compos., 32(1): 9–14. [113] Sarhat, S.R. 2007. An experimental investigation on the viability of using fine concrete recycled aggregate in concrete production. International Conference on Sustainable Construction Materials and Technologies, Coventry, UK, June 2007, Taylor & Francis, UK, 53–57. [114] Tang, K., Soutsos, M.N., Millard, S.G. 2007. Concrete paving products made with recycled demolition aggregates. International Conference on Sustainable Construction Materials and Technologies, Coventry, UK, June 2007, Taylor & Francis, UK, 77–84. [115] Khatib, J.M. 2005. Properties of concrete incorporating fine recycled aggregate. Cement Concr. Res., 35(4): 763–769. [116] Kenai, S., Debieb, F., Azzouz, L. 2002. Mechanical properties and durability of concrete made with coarse and fine recycled concrete aggregates. Proceedings of the International Conference on Sustainable Concrete Construction, Dundee, Scotland, UK, September 2002, Thomas Telford, UK, 383–392. [117] Kikuchi, M., Dosho, Y., Narikawa, M., Miura, T. Application of recycled aggregate concrete for structural concrete: part 1 experimental study on the quality of recycled aggregate and recycled aggregate concrete. Proceedings of the International Conference on the Use of Recycled Concrete Aggregates, London, UK, November 1998, Thomas Telford, UK, 55–68. [118] Nagataki, S., Iida, K. 2001. Recycling of Demolished Concrete, Recent Advances in Concrete Technology, SP 200, CANMET/ACI, Ottawa, 1–20. [119] Otsuki, N., Miyazato, S., Yodsudjai, W. 2003. Influence of recycled aggregate on interfacial transition zone, strength, chloride penetration and carbonation of concrete. J. Mater. Civil Eng., 15(5): 443–451.

BackBack to table ofofcontents to table contents

sed_1410.indd 193

20/08/15 12:32 PM

194

CHAPTER 10. GREEN MATERIALS FOR CONCRETE PRODUCTION

[120] Wang, Z., Wang, L., Cui, Z., Zhou, M. 2011. Effect of recycled coarse aggregate on concrete compressive strength. Trans. Tianjin Univer., 17(3): 229–234. [121] Khalaf, F.M., Devenny, A.S. 2004. Performance of brick aggregate concrete at high temperatures. J. Mater. Civil Eng., 16(6): 556–565. [122] Khalaf, F.M., Devenny, A.S. 2005. Properties of new and recycled clay brick aggregates for use in concrete. J. Mater. Civil Eng., 17(4): 456–464. [123] Poon, C.S., Kou, S.C. 2010. Effects of fly ash on mechanical properties of 10-year-old concrete prepared with recycled concrete aggregates. 2nd International Conference on Waste Engineering and Management – ICWEM 2010, Shanghai, China, October 2010, RILEM, 46–59. [124] Ravindrarajah, R.S., Tam, C.T. 1987. Recycled concrete as fine aggregate in concrete. Int. J. Cement Compos. Lightw. Concr., 9(4): 235–241. [125] Kou, S.C., Poon, C.S. 2009. Properties of concrete prepared with crushed fine stone, furnace bottom ash and fine recycled aggregate as fine aggregates. Construct. Build. Mater., 23(8): 2877–2886. [126] Kou, S.C., Poon, C.S. 2009. Properties of self-compacting concrete prepared with coarse and fine recycled concrete aggregates. Cement Concrete Compos., 31(9): 622–627. [127] Kou, S.C., Poon, C.S., Chan, D. 2007. Influence of fly ash as cement replacement on the properties of recycled aggregate concrete. J. Mater. Civil Eng., 19(9): 709–717. [128] Kou, S.C., Poon, C.S., Agrela, F. 2011. Comparisons of natural and recycled aggregate concretes prepared with the addition of different mineral admixtures. Cement Concr. Compos., 33(8): 788–795. [129] Berndt, M.L. 2009. Properties of sustainable concrete containing fly ash, slag and recycled concrete aggregate. Construct. Build. Mater., 23(7): 2606–2613. [130] Wang, Z., Huang, X. 2003. Repeated reuse of demolished concrete wastes as aggregates. Proceedings of the International Symposium on the Role of Concrete in Sustainable Development, Thomas Telford, UK, 589–594. [131] de Brito, J.M.C.L., Gonçalves, A.P., dos Santos, J.R. 2006. Recycled aggregates in concrete production. Multiple recycling of concrete coarse aggregates. Rev. Ing. Constr.,21(1) 33–40.

Durability behaviour of RAC [132] Gomes, M., de Brito, J. 2009. Structural concrete with incorporation of coarse recycled concrete and ceramic aggregates: durability performance. Mater. Struct., 42(5): 673–675. [133] Levy, S., Helene, P. 2007. Durability of concrete mixed with fine recycled aggregates. International Conference on Sustainable Construction Materials and Technologies, Coventry, UK, June 2007, Taylor & Francis, UK, 45–51. [134] Levy, S., Helene, P. 2004. Durability of recycled aggregates concrete – a safe way to sustainable development. Cement Concr. Res., 34(11): 1975–1980. [135] Dhir, R.K., McCarthy, M.J., Halliday, J.E., Tang, M.C. 2005. ASR Testing on Recycled Aggregates Guidance on Alkali Limits and Reactivity, DTI/WRAP Aggregates Research Programme STBF 13/14C, WRAP - Waste & Resources Action Programme, Oxon, UK, ISBN: 1-84405-185-4, 31 p. [136] Poon, C.S., Chan, D.X. 2006. Paving blocks made with recycled concrete aggregate and crushed clay brick. Construct. Build. Mater., 20(8): 569–577.

BackBack to table ofofcontents to table contents

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REFERENCES

195

[137] Padmini, A.K., Ramamurthy, K., Mathews, M.S. 2002. Relative moisture movement through recycled aggregate concrete. Magaz. Concr. Res., 54(5): 377–384. [138] Dhir, R.K., Limbachiya, M.C., Leelawat, T. 1999. Suitability of recycled concrete aggregate for use in BS 5328 designated mixes. Proc. Institut. Civil Eng. Struct. Build., 134(3): 257–274. [139] Soutsos, M., Tang, K., Millard, S. 2011. Concrete building blocks made with recycled demolition aggregate. Construct. Build. Mater., 25(2): 726–735. [140] Debieb, F., Kenai, S. 2008. The use of coarse and fine crushed bricks as aggregate in concrete. Construct. Build. Mater., 22(5): 886–893. [141] Sadek, D.M. 2012. Physico-mechanical properties of solid cement bricks containing recycled aggregates. J. Adv. Res., 3(3): 253–260. [142] Ryu, J.S. 2002. An experimental study on the effect of recycled aggregate on concrete properties. Magaz. Concr. Res., 54(1): 7–12. [143] Eguchi, K., Teranishi, K., Nakagome, A., Kishimoto, H., Shinozaki, A., Narikawa, M. 2007. Application of recycled coarse aggregate by mixture to concrete construction. Construct. Build. Mater., 21(7): 1542–1551. [144] Dosho, Y. 2007. Development of a sustainable concrete waste recycling system – application of recycled aggregate concrete by aggregate replacing method. J. Adv. Concr. Tech., 5(1): 27–42. [145] Kou, S.C., Poon, C.S. 2013. Long-term mechanical and durability properties of recycled aggregate concrete prepared with the incorporation of fly ash. Cement Concr. Compos., 37: 12–19. [146] Kou, S.C., Poon, C.S. 2006. Compressive strength, pore size distribution and chloride-ion penetration of recycled aggregate concrete incorporating class-F fly ash. J. Wuhan Univ. Tech. Mater. Sci. Ed., 21(4): 130–136. [147] Sim, J., Park, C. 2011. Compressive strength and resistance to chloride ion penetration and carbonation of recycled aggregate concrete with varying amount of fly ash and fine recycled aggregate. Waste Manag., 31(11): 2352–2360. [148] Amorim, P., de Brito, J., Evangelista, L. 2012. Concrete made with coarse concrete aggregate: influence of curing on durability. ACI Mater. J., 109(2): 195–204. [149] Buyle-Bodin, F., Zaharieva, R. 2002. Concr. Sci. Eng. Mater. Struct., 435(158): 504–509. [150] Moon, D.J., Moon, H.Y., Nagataki, S., Hisada, M., Saeki, T. 2002. Improvement on the qualities of recycled aggregate concrete containing super fine mineral admixtures. Proceedings of the 1st fib Congress, 113–118. [151] Salem, R.M., Burdette, E.G., Jackson, N.M. 2003. Resistance to freezing and thawing of recycled aggregate concrete. ACI Mater. J., 100(3): 216–221. [152] Kimura, Y. 2004. High quality recycled aggregate concrete (hirac) processed by decompression and rapid release. RILEM International Symposium on Environment – Conscious Materials and Systems for Sustainable Development, Koriyama, Japan, September 2004, RILEM, 163–170. [153] Jankovic, K., Nikolic, D., Bojovic, D. 2012. Concrete paving blocks and flags made with crushed brick as aggregate. Construct. Build. Mater., 28(1): 659–663. [154] Teranishi, K., Dosho, Y., Narikawa, M., Kikuchi, M. 1998. Application of recycled aggregate concrete for structural concrete. Part 3: production of recycled aggregate by real scale plant and quality of recycled concrete aggregate. Proceedings of the International Conference on the Use of Recycled Concrete Aggregates, London, UK, November 1998, Thomas Telford, UK, 143–156.

BackBack to table ofofcontents to table contents

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[155] Li, X.P. 2008. Recycling and reuse of waste concrete in China. Part I: material behaviour of recycled aggregate concrete, Resour. Conserv. Recycl., 53(1–2): 36–44. [156] ETN Recycling. 2000. Use of recycled materials as aggregates in the construction industry, ECOserve network. European Thematic Network on Recycling in Construction, 2(3–4), 14. [157] Ho, N.Y., Lee, K.Y., Fwa, T.F., Tan, J.Y., Hon, L.Y., Lim, W.F., How, C.O., Koh, S.Y. 2011. Use of recycled concrete aggregate for the construction of aircraft stand rigid pavement at Singapore Changi Airport. 7th International Conference on Road and Airfield Pavement Technology, Bangkok, Thailand, August 2011, 8. [158] Poon, C.S., Chan, D. 2007. The use of recycled aggregate in concrete in Hong Kong. Resour. Conserv. Recycl., 50(3): 293–305.

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Author Index

Ana Coelho 53 Andrew J. Martin 111 Bruno Gonçalves 93 Christian Bucher 141 Ekasit Limsuwan 9 Frances Yang 69 John E. Anderson 69 Jorge De Brito 165 Jorge M. Branco 53 José C. Matos 93 Jun Kanda 1 Luís Neves 93 Maik Brehm 141 Martin J.D. Kirk 111 Paul Grundy 153 Paulo B. Lourenço 53 Rui V. Silva 165 Tobia Zordan 25

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Dedication

Paul Grundy (1935–2013)

This book is dedicated to the memory of Professor Paul Grundy – A devoted IABSE member, colleague, and friend.

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Structural Engineering Documents Objective: To provide in-depth information to practicing stuctural engineers in reports of high scientific and technical standards on a wide range of structural engineering topics.

SED Editorial Board: J. Sobrino, Spain (Chair); H. Subbarao, India (Vice Chair); M. Bakhoum, Egypt; C. Bob, Romania; M. Braestrup, Denmark; M.G. Bruschi, USA; R. Geier, Austria; N.P. Hoej, Switzerland; S. Kite, Hong Kong; D. Laefer, Ireland; R. Mor, Israel; H.H. (Bert) Snijder, The Netherlands; R. von Woelfel, Germany.

Topics: The International Association for Bridge and Structural Engineering (IABSE) operates on a worldwide basis, with interests of all type of structures, in all materials. Its members represent structural engineers, employed in design, academe, construction, regulation and renewal. IABSE organises conferences and publishes the quarterly journal Structural Engineering International (SEI), as well as reports and monographs, including the SED series, and presents annual awards for achievements in structural engineering. With a membership of some 4,000 individuals in more than 100 countries, IABSE is the international organisation for structural engineering.

Readership: Practicing structural engineers, teachers, researchers and students at a university level, as well as representatives of owners, operators and builders.

Publisher: The International Association for Bridge and Structural Engineering (IABSE) was founded as a non-profit scientific association in 1929. Today it has more than 3900 members in over 90 countries. IABSE’s mission is to promote the exchange of knowledge and to advance the practice of structural engineering worldwide. IABSE organizes conferences and publishes the quarterly journal Structural Engineering International, as well as conference reports and other monographs, including the SED series. IABSE also presents annual awards for achievements in structural engineering.

For further Information: IABSE c/o ETH Zürich CH-8093 Zürich, Switzerland Phone: Int. + 41-44-633 2647 Fax: Int. + 41-44-633 1241 E-mail: [email protected] Web: www.iabse.org Back to table of contents

Structural Engineering Documents

This Structural Engineering Document addresses safety and regulations, integration concepts, and a sustainable approach to structural design. Life-cycle assessment is presented as a critical tool to quantify design options, and the importance of existing structures–in particular cultural heritage structures–is critically reviewed. Consideration is also given to bridge design and maintenance, structural reassessment, and disaster risk reduction. Finally, the importance of environmentally friendly concrete is examined. Consequently, structural engineers are shown to have the technical proficiency, as well as ethical imperative, to lead in designing a sustainable future.

Sustainable Structural Engineering

Sustainability is the defining challenge for engineers in the twenty-first century. In addition to safe, economic, and efficient structures, a new criterion, sustainable, must be met. Furthermore, this new design paradigm–addressing social, economic, and environmental aspects–requires prompt action. In particular, mitigation of climate change requires sustainable solutions for new as well as existing structures. Taking from both practice and research, this book provides engineers with applicable, timely, and innovative information on the state-ofthe-art in sustainable structural design.

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Structural Engineering Documents

14 Sustainable Structural Engineering

14

Sustainable Structural Engineering

John E. Anderson Christian Bucher Bruno Briseghella Xin Ruan Tobia Zordan

International Association for Bridge and Structural Engineering (IABSE)

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