Midas Gen – One Stop Solution for Building and General Structures Construction Stage Analysis and Column Shortening in
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Midas Gen – One Stop Solution for Building and General Structures
Construction Stage Analysis and Column Shortening in Tall Buildings Midas IT Technical Seminar 17th February 2012
Ravi Kiran
Midas Gen – One Stop Solution for Building and General Structures
Contents Construction Stage Analysis
Column Shortening & Related Issues Effects of Column Shortening Procedure for Accounting Compensation at Site Useful Features for Construction Stage Analysis
Project Applications Live Demonstration
Midas Gen – Technical Seminar
Construction Stage Analysis
One Stop Solution for Building and General Structures
Why Construction Stage (CS) Analysis •
In general structures are analyzed assuming that the structure is built and loaded in a moment.
•
Construction of structures is a time taking process and during this period Material Properties, Loads and Boundaries conditions may change. Dead Load + Live Load
LL,WL,EQ Acts
Wind
Other Dead Loads (Partions, Finishes)
Self weight of slab Earthquake
Construction Completed Structure Sequence
Midas Gen – Technical Seminar
Construction Stage Analysis
One Stop Solution for Building and General Structures
Conventional Analysis Vs. Construction Stage Analysis
Stage 1
Case 1 – Conventional Analysis
Stage 2
Case 2 – CS Analysis
Midas Gen – Technical Seminar
Construction Stage Analysis
One Stop Solution for Building and General Structures
Conventional Analysis Vs. Construction Stage Analysis
Case 1 – Conventional Analysis
Case 2 – CS Analysis
Midas Gen – Technical Seminar
Construction Stage Analysis
One Stop Solution for Building and General Structures
Where CS Analysis is Required Long Span Trusses
Long Span Slabs, Beams constructed in multiple stages Prestressed concrete Structures CS analysis should be performed for all structures where there is a change in Support Conditions, Loading and varying material properties (Concrete).
Midas Gen – One Stop Solution for Building and General Structures
Contents Construction Stage Analysis
Column Shortening & Related Issues Effects of Column Shortening Procedure for Accounting Compensation at Site Useful Features for Construction Stage Analysis
Project Applications Live Demonstration
Midas Gen – Technical Seminar
Column Shortening
One Stop Solution for Building and General Structures
Column Shortening and Related Issue When any member is loaded with Axial Load, it undergoes axial deformation
σ
Why is this Important E = (σ / ε) ΔL = (PL/A E)
Midas Gen – Technical Seminar
Column Shortening
One Stop Solution for Building and General Structures
Column Shortening and Related Issue P2, ΔL2
P1, ΔL1
The differential shortening happening between the vertical members may cause additional forces and stress in Beams and Slabs
Midas Gen – Technical Seminar
Column Shortening
One Stop Solution for Building and General Structures
Column Shortening and Related Issue Steel Structures - Linear elastic Behavior
σ
Stress ∞ Strain Strain is constant for a given Stress during loading & unloading
E = (σ / ε) ΔL = (PL/A E)
Midas Gen – Technical Seminar
Column Shortening
One Stop Solution for Building and General Structures
Column Shortening and Related Issue Concrete Structures -
Nonlinear Inelastic Behavior But in general analysis and design behavior of concrete is treated as Linear Elastic Material Neither Stress ∞ Strain Nor Strain is constant for a given Stress During loading & unloading
Elastic Strain + Inelastic Strain
Midas Gen – Technical Seminar
Column Shortening
One Stop Solution for Building and General Structures
Column Shortening and Related Issues Concrete Structures
Elastic Shortening
Inelastic Shortening
σ
Creep Shortening. Shrinkage Shortening.
σ Ei = (σ / ε) ΔL = (PL/A Ei)
Modulus of Elasticity changes with time.
Midas Gen – Technical Seminar
Column Shortening
One Stop Solution for Building and General Structures
Column Shortening and Related Issue
With increased height of structures the effect of column shortening (Elastic & Inelastic) take on added significance and need special consideration in design and construction.
Elastic Shortening of 80 Storey Steel Structure ~ 180 mm to 255 mm.
Elastic Shortening of 80 Storey Concrete Structure ~ 65 mm.
Total Shortening of 80 Storey Concrete Structure ~ 180 to 230 mm.
Inelastic Shortening ~ 1 to 3 times Elastic shortening.
Midas Gen – Technical Seminar
Column Shortening
One Stop Solution for Building and General Structures
Column Shortening and Related Issue Two basic prerequisites for accurately and efficiently predicting these effects are Reliable Data for the creep and shrinkage characteristics of the particular concrete mix Analytical procedures for the inclusion of these time effects in the design of structure.
Some of the popular predictive methods for predicting creep and shrinkage strains are
ACI 209 -92 Bazant – Bewaja B3 CEB – FIP (1978, 1990) PCA Method (Mark Fintel, S.K.Ghosh & Hal Iyengar) GL 2000 (Gardner and Lockman) Eurocode
Midas Gen – Technical Seminar
Column Shortening
One Stop Solution for Building and General Structures
Column Shortening and Related Issue
The total strain at any time t may be expressed as the sum of the instantaneous, creep and shrinkage components:
Where, εe (t) = Instantaneous strain at time t, εc (t) = Creep strain at time t, εsh (t) = Shrinkage strain at time t.
Midas Gen – Technical Seminar
Column Shortening
One Stop Solution for Building and General Structures
Column Shortening and Related Issue
The instantaneous strain in concrete at any time t is expressed by
Where, σ (t) = stress at time t, Ec(t) = Elastic modulus of concrete at time t, given by
fct = Compressive strength at any time t, given by
α & β are constants depending on Type of Cement & Type of Curing
Midas Gen – Technical Seminar
Column Shortening
One Stop Solution for Building and General Structures
Column Shortening and Related Issue Inelastic Shortening = Creep + Shrinkage Creep
Shrinkage
Creep is time-dependent increment of strain under sustained stress.
Shrinkage is the time-dependant decrease in concrete volume compared with the original placement volume of concrete.
Basic creep occurs under the condition of no moisture movement to and from the environment.
Drying Shrinkage is due to moisture loss in concrete.
Drying creep is the additional creep caused by drying.
Drying creep has its effect only during the initial period of load.
Autogenous Shrinkage is caused by hydration of cement. Carbonation shrinkage results as the various cement hydration products are carbonated in the presence of CO
Midas Gen – Technical Seminar
Column Shortening
One Stop Solution for Building and General Structures
Column Shortening and Related Issue Factors affecting the Creep & Shrinkage of Concrete
Concrete Composition
Cement Paste Content Water – Cement ratio Mixture Proportions Aggregate Characteristics Degrees of Compaction
Initial Curing
Length of Initial Curing Curing Temperature Curing Humidity
Environment
Concrete Temperature Concrete Water Content
Geometry
Size and Shape
Loading History
Concrete age at load Application During load Period Duration of unloading Period Number of load Cycles
Stress Conditions
Type of Stress and distribution across the Section Stress/Strength Ratio
Concrete (Creep & Shrinkage)
Member Geometry and Environment (Creep & Shrinkage)
Loading (Creep Only)
Midas Gen – Technical Seminar
Column Shortening
One Stop Solution for Building and General Structures
Column Shortening and Related Issue Inelastic Shortening = Creep + Shrinkage Creep
Shrinkage
As per ACI 209R-92 the creep coefficients are predicted
As per the ACI 209R-92, shrinkage can be predicted by After 7 days for moisture cured concrete
as =
After 1-3 days for steam cured concrete
Where, t = time in days after loading. vu = Ultimate creep coefficient = 2.35 c c = Product of applicable correction factors
Where, t = time in days after the end of Initial Curing (sh)u = Ultimate Shrinkage Coefficient = 780 sh x 10-6 m/m sh = Product of applicable correction factors
Midas Gen – One Stop Solution for Building and General Structures
Contents Construction Stage Analysis
Column Shortening & Related Issues Effects of Column Shortening Procedure for Accounting Compensation at Site Useful Features for Construction Stage Analysis
Project Applications Live Demonstration
Midas Gen – Technical Seminar
Column Shortening
One Stop Solution for Building and General Structures
Effects of Column Shortening
Absolute shortening is rarely of practical interest.
Differential shortening between adjacent vertical elements is the most important factor for engineer.
Axial Shortening of vertical elements will not effect those elements very much,
horizontal elements like beams and slabs and non structural elements are affected.
Midas Gen – Technical Seminar
Column Shortening
One Stop Solution for Building and General Structures
Effects of Column Shortening Structural Effects Slabs may not be truly horizontal after some time. Beams could be subjected to higher bending moments. Load transfer.
Non Structural Effects
Cracks in Partition Walls. Cracks in Staircases Deformation of Cladding. Mechanical Equipment. Architectural Finishes. Built in Furnishings.
These non structural elements are not intended to carry vertical loads and are therefore not subjected to shortening.
Midas Gen – Technical Seminar
Column Shortening
One Stop Solution for Building and General Structures
Effects of Column Shortening
Deformation and breakage of Facades, windows & Parapet walls…
Deformation of Vertical Piping System
Reverse Inclination of Drainage Piping System
Deformation and breakage of internal partitions
Midas Gen – One Stop Solution for Building and General Structures
Contents Construction Stage Analysis
Column Shortening & Related Issues Effects of Column Shortening Procedure for Accounting Compensation at Site Useful Features for Construction Stage Analysis
Project Applications Live Demonstration
Midas Gen – Technical Seminar
Column Shortening
One Stop Solution for Building and General Structures
Movement Related to Construction Sequence •
Pre-slab installation shortenings – Shortenings taking place up to the time of slab installation
•
Post-slab installation shortenings – Shortenings taking place after the time of slab installation
① :Compensation ② : Design Level ③: Pre-slab Installation shortening ④: Post-slab Installation shortening
Midas Gen – Technical Seminar
Column Shortening
Procedure for Accounting Column Shortening
One Stop Solution for Building and General Structures
Midas Gen – Technical Seminar
Column Shortening
One Stop Solution for Building and General Structures
Procedure for Accounting Column Shortening
Climatic Condition
Loading Condition Conditions
Construction Progress
Other Conditions
Pre-Analytical Prediction & Continuous Monitoring
?
Experimental Measurements & Construction Survey
Correctio n
Precise prediction of shortening
Midas Gen – Technical Seminar
Column Shortening
One Stop Solution for Building and General Structures
Procedure for Accounting Column Shortening Analytical Measurement
Using Software or Manually (Manual calculation is almost impossible) Reflection of physical properties in calculation from material experiment: Young’s Modulus, Poisson’s Ratio, Mean Compressive strength, Volume to Surface ratio, Shapes, sizes etc.
Reflection of effects of Climate on shortening: Average Temperature , RH etc. Construction Sequence: Stage duration, Additional Steps, Member Age, Load activation age, Boundary activation age etc. Reflection of the above effects on site masterschedule.
Method has Limitation
Experimental Measurement
Field Measurements
Installation of sensors or gages in members for determining the actual shortening. Understanding and noting the following: Curing procedure / Temperature, Actual Shortening, Change in Ambient Temperature (Important), Actual Humidity, Deviation from Defined Construction Stages, Manipulation of factors in analytical Calculation, Re-Analysis…
Midas Gen – Technical Seminar
Column Shortening
One Stop Solution for Building and General Structures
Procedure for Accounting Column Shortening
Field Measurements
Determination of Installation location
After Installation of Gauge
Installation of Gauge
After Casting of Concrete
After Installation
Field data collection
Midas Gen – Technical Seminar
Column Shortening
One Stop Solution for Building and General Structures
Procedure for Accounting Column Shortening
Engineering Re-Analysis
Manipulation of the construction stage as per site condition
Perform 3D CS Analysis
Activation of Construction stages
Construction stage of each group
Midas Gen – One Stop Solution for Building and General Structures
Contents Construction Stage Analysis
Column Shortening & Related Issues Effects of Column Shortening Procedure for Accounting Compensation at Site Useful Features for Construction Stage Analysis
Project Applications Live Demonstration
Midas Gen – Technical Seminar
Column Shortening
One Stop Solution for Building and General Structures
Compensation at Site 2nd correction 1st correction
1st correction
Column Column
Midas Gen – Technical Seminar
Column Shortening
One Stop Solution for Building and General Structures
Compensation at Site
CON'C Casting face
Height of correction
The order of construction installation of column forms
SLAB THK.
insertion of FILLER Column Rebar
B (= Height of correction
insertion of correcting FILLER
filler
Installation of SLAB forms
securing the thickness of slab.
Midas Gen – One Stop Solution for Building and General Structures
Contents Construction Stage Analysis
Column Shortening & Related Issues Effects of Column Shortening Procedure for Accounting Compensation at Site Useful Features for Construction Stage Analysis
Project Applications Live Demonstration
Midas Gen – Technical Seminar
Useful Features for CS Analysis
One Stop Solution for Building and General Structures
Construction Stage Wizard for Building Strcuture The wizard readily allows us to define the timing of elements created and loadings applied in the construction stages during the erection of a building. You may find it more convenient to first click the [Automatic Generation] button to define the basic construction stages and modify them as necessary.
Midas Gen – Technical Seminar
Useful Features for CS Analysis
One Stop Solution for Building and General Structures
Construction Stage Analysis for Composite Members Define an analytical model for each construction stage by assigning activated or inactivated sections corresponding to each construction stage of a composite section. By using Composite Section for Construction Stage, we can consider the construction sequence with creep and
shrinkage effect.
Midas Gen – Technical Seminar
Useful Features for CS Analysis
One Stop Solution for Building and General Structures
Material Stiffness Changes for Cracked Sections Specific stiffness of specific member types may be reduced such as the case where the flexural stiffness of lintel beams and walls may require reduction to reflect cracked sections of concrete. Section stiffness scale factors can be included in boundary groups for construction stage analysis. The scale factors are
also applied to composite sections for construction stages
Midas Gen – Technical Seminar
Useful Features for CS Analysis
One Stop Solution for Building and General Structures
Spring Supports For Soil Interaction Point Spring Support (Linear, Comp.-only, Tens.-only, and Multi-linear type)
Surface Spring Support (Nodal Spring, and Distributed Spring) Springs can be activated / deactivated during construction stage analysis.
[Nonlinear point spring support]
[Pile Spring Support]
[Surface Spring Support]
[Nodal Spring and Distributed Spring]
Midas Gen – Technical Seminar
Useful Features for CS Analysis
Tendon Loss
Pre-stress load can be considered in construction stage analysis. Tendon primary / secondary forces are provided with pre-stress loss graph
One Stop Solution for Building and General Structures
Midas Gen – One Stop Solution for Building and General Structures
Contents Construction Stage Analysis
Column Shortening & Related Issues Effects of Column Shortening Procedure for Accounting Compensation at Site Useful Features for Construction Stage Analysis
Project Applications Live Demonstration
Midas Gen – Technical Seminar
Project Applications
One Stop Solution for Building and General Structures
Burj Khalifa (Dubai, UAE) CS:1
overview
CS:30
Height No. of floors Location Function / Usage Designer Architect General Contractor
705 m 160 Dubai, United Arab Emirates Office Building & Residential Building Adrian D. Smith Skidmore, Owings & Merrill Samsung Development
Midas Gen – Technical Seminar
Project Applications
One Stop Solution for Building and General Structures
overview
SK S-Trenue (Seoul, Korea)
Area No. of floors Location Function / Usage Structure Type Foundation Type Lateral load resisting system
39,600 m2 36 Seoul, Korea Office Building Composite Structure Mat Foundation RC Core + Steel + RC Composite Frame
Midas Gen – Technical Seminar
Project Applications
One Stop Solution for Building and General Structures
overview
Keangnam Hanoi Landmark Tower (Hanoi, Vietnam)
Height No. of floors Location Function / Usage Structure Type Architect Contractor
345m 70 fl., 49 fl. Hanoi, Vietnam Hotel, Office, and Residential building Reinforced Concrete Structure Heerim, Samoo, Aum & Lee, Hellmuth Obata + Kassabaum Keangnam
Midas Gen – One Stop Solution for Building and General Structures
Contents Construction Stage Analysis
Column Shortening & Related Issues Effects of Column Shortening Procedure for Accounting Compensation at Site Useful Features for Construction Stage Analysis
Project Applications Live Demonstration
Midas Gen – Technical Seminar
Live Demonstration
One Stop Solution for Building and General Structures
Structural Plan
Storey's :- 40 Storey Height :- 3.15 m Total Height :- 126.85 m
Typical Floor Plan
Midas Gen – Technical Seminar
Live Demonstration
One Stop Solution for Building and General Structures
Material and Sectional Properties
Size Level
fck
C1
C2
Wall Thk.
1st to 10th
50
1200 x 1200
900 x 900
500
11th to 20th
40
1000 x 1000
800 x 800
500
21st to 30th
35
800 x 800
700 x 700
500
31st to 40th
30
600 x 600
600 x 600
500
Girder
30
900 x 600
-
Link Beam
30
700 x 500
-
Midas Gen – Technical Seminar
Live Demonstration
One Stop Solution for Building and General Structures
Construction Schedule Partition Load : 5 weeks after first slab casting. Finish Load : 5 Weeks after Partition Wall Construction.
Stage 1
Stage 4
Final Stage
Midas Gen – Technical Seminar
Live Demonstration
Procedure Time Dependant Material Properties •Define Creep and Shrinkage Properties . •Define time Dependant Material Properties. •Define Time Dependant Material Link. •Change Element Dependant Material Property
Define Construction Stage •Define Construction stages using Building Wizard for CS analysis •Create LL group and add LL to LL group. •Define CS for LL
Perform Analysis
Results •BMD’s and SFD’s for different CS. •Deformations for different CS. •Column Shortening Graph.
One Stop Solution for Building and General Structures
Midas Gen – One Stop Solution for Building and General Structures
Q&A