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Seismic evaluation and retrofit. of concrete buildings Volume 2-Appendices

Applied Technology Counr:;;i CALIFORf\IIt1. SEISMIC SAFETY COMMISSION Proposition 122 Seisn lie Retrofit Practice8 impr00

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Roor DllpI.CUltDt. d [IDdlel]

Figure II.II·S, Transverse PushDver curve fDr EXisting structure

Pushover Force-Displacement Curve Figures 4.4-2 and 4.4-3 show the pushover curves for the existing (unstrengthened) Escondido Village Midrise buildings, when pushed in the longitudinal and transverse directions, respectively. As can be seen, the first critical events consist of hinging of floor beams throughout the frame. This is considered 4.4.S

A-24

potentially life threatening because of the lack of adequate development of the bottom reinforcing of the beams through the beam column joint. Hinging of the beams - first in positive flexure and on the return cycle in negative flexure - will result in formation of a vertical crack through the beam column joint. Following such behavior the floor systems would rely on the catenary behavior of the

Appendix A, Escondido Village Mldrlse

sh ro po ob ca· tho co aI ex to be, di!

---------

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-----------------------------------------------------------------------------------SEISMIC EVALUATION AND RETROFIT OF CONCRETE BUILDINGS ------------------------------------------------------------------------------------

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compression failure at "toe" ~ ofbaserrent orner walls

/ \

compression failure

Lhing fonnation at bas, frent walls

baserrent stairs #1 a

10

5

/ I ~#2 J

15

20

Roof Displacement, d [inches]

Fll/Ure 4.4·4. Longitudinal Pushover curve For strengthened Building

top reinforcing steel in the beams for vertical support. However, because there are no stirrups in the beams, there is potential for this top steel to pull free of the slabs, resulting in floor collapse. In addition to the hinging of floor beams, shear failure of first floor columns occurs at relatively small roof displacements. This also results in significant collapse hazard. Because the beam hinging and the column shear failure mechanisms form at relatively small roof displacements (3.5" to 4.0"), a performance point as defined by the Methodology cannot be lack of obtained since the demand spectrum and the orcing oI capacity spectrum do not intersect. This indicates . Hinginl' that the structures, as they are, present significant Ion the collapse hazards when subjected to the demands of a large magnitude earthquake. Furthermore, the Iltin existing structure does not present a good example beam to evaluate the procedures of the Methodology e floor 'ior of tIt, because of the high collapse potential at small displacements. Consequently, for the purposes of

Appendix A, Escondido Village Mldrlse

this example building study, it is more instrumental to follow the Methodology using the life-safety retrofit concept. To create a more stable structure and allow the pushover analysis a chance to develop some ductility, the problems of the hinging beams and shear critical columns were initially addressed. The retrofit concept is discussed in Section 5 of this report. For the purpose of continuing our discussion of the pushover curve, assume that the hinging of floor beams and the shear failure of first floor and basement columns are adequately addressed with structural upgrades. Figures 4.4-4 and 4.4-5 present the pushover curves for the strengthened building. Significant events in the progressive lateral response of the building are annotated on the figures, and more fully described in Tables 4.4-1 and 4.4-2. Critical events listed in the tables are indicated in italics.

A-25

SEISMIC EVALUATION AND RETROFIT OF CONCRETE BUILDINGS

2000

rocking oH undation at stair II 1

7

hinge fonmtion at floor bearna J500

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a

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mpression failure at

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ion failure at base_ t elevator core co~res

'-- shear failure of .. emont and 1st floor inteno coluIIIlS

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II>

-----Ie

V-

hin e fonnation at bas e lOnt and 1st floor walls 5

JO

J5

20

25

Roof Dlaplac:ement, d [lnche.]

Figure 4.4·5. Transverse pushDver curve IDr strengthened Building

4 4

SI

11

compression failure at "toe" of basement corner walls

12.84

te

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A-2G

Appendix A, Escondido Village Mldrlse

A

r

-------------------------------------------------------------------------------------

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SEISMIC EVALUATION AND RETROFIT OF CONCRETE BUILDINGS

---- ------------------------------------------------------------------------

I

Table 4.4,2 Transverse Pushover Events

.... ...........

. ·····EVent Chapter 8 of the Methodology. This section ;t with " discusses the results of the analysis and how these :olumns results. were used to construct the required )ped in Capacity Spectrum.

I n shear I 4.4.2

pushover AnalysIs Results I Based on the pushover analysis, the sequence Ich andrei of hinging of beams, column shear failure at the I beam-column connection, and column hinges is I shown in Figure 11. The numbers shown on the i figure correspond to the order in which the beam e 'I hinging, column hinging, or column shear limit need to states occurred, respectively. It can be seen that the hinging generally begins J~tment '[ at the lower floors and progresses upward. Table 6 IS. i presents the base shear and roof displacement !lYSIS. ! associated with the first flexural hinging of a beam

I I

IIday

In~ Appendix D. Holiday Inn

Table 6. Base Shear and Roof Displacement Associated with First Beam and column to Hinge sase Shear at Hinge (kipSJ

Displacemel1t at Hinge (III.)

Beam

155

1,4

Column (Shear!

445

5,6

Column (MOment)

520

8,0

Element " ". , "Name

and column element as well as the first column element to fail in shear. Since the applied shear and roof displacement required for formation of the column shear failure are less than those associated with the flexural limit state in the column it appears that shear, rather than flexure, is the more~obably failure mechanism in columns. This appears to be consistent with the performance of the structure during the Northridge , Earthquake. Over 90 percent of the modal mass participated in the first mode, and from the story drift plot in Figure 12, it can be seen that the initial assumed first mode lateral force distribution is a reasonable assumption for this building. The pushover analysis was terminated after a column shear failure occurred in all columns just below the third level, resulting in a mechanism. This behavior is not entirely consistent with the observed damage from the Northridge Earthquake because the majority of the damage was observed in the floor above. Other studies have demonstrated that it is possible to develop an analytical model that more closely matches the observed damage when ground motion generated by the Northridge Earthquake itself is used. Nevertheless, the significant column shear deficiency appears to be recognized by the analysis and, given the assumed loading distribution, the analytically predicted failure is not unreasonable. Load-displacement results, first yield, major yield and initial deterioration points as defined in the Methodology are shown in Figure 13. As

D·n

SEISMIC EVALUATION AND RETROFIT OF CONCRETE BUILDINGS

shown in the figure, the existing building reaches a mechanism just beyond a total roof displacement of almost 16 in., which corresponds to an overall drift ratio of 2 percent.

capacity Spectrum Load-displacement and modal analysis results were combined to generate the capacity spectrum using the procedure outlined in Chapters 4 and 8 of the Methodology. The steps are: J. Calculate the ratio of base shear versus building weight (V/W). 2. Calculate the modal story participation factor and modal base shear participation factor. 3. Calculate the spectral displacement versus spectral acceleration.

Table 7. Demand RespDnse spectrum parameters seismic zone Factor

Z - .0.40

Near·Source Factor

N - 1.0

seismic Coefficient

c. ~ 0.40 Cv

4.4.8

4.4.4

Demand Response Spectrum The Basic Safety Objective selected for the case study is Building Performance Level "Life Safety" at the Design Earthquake and Building Performance Level "Structural Stability" at the Maximum Earthquake (ME). Descriptions of these performance objectives are found in Chapter 3 of the Methodology and Section 1.3 of this case study. The Design Basis Earthquake was assumed to be described by ground motion with a 10 percent .. chance of being exceeded in a 50 year period. The . Maximum Capable Earthquake was assumed to be described by ground motion with a 10 percent chance of being exceeded in a 100 year period, but not exceeding the maximum single event that can be foreseen within the geologic framework assuming median attenuation. A five percent elastic demand response spectrum, shown in Figure 14, was generated using the procedures outlined in Section 4.4.2.4 of the Methodology with the parameters listed in Table 7 for the Design Earthquake. The Design Earthquake is represented by the 10 percent damped inelastic response spectrum shown in Figure 14 using the spectral reduction factors for the acceleration (SRA) and velocity (SRv) controlled regions of the spectrum calculated using Equations

D·18

= 0.64

8-9 and 8-10 of the Methodology. The building as a whole must be checked for stability, strength degradation, and excessive deformation as described in Section 11.3 of the Methodology. Static inelastic analyses of this building showed no instabilities with respect to gravity loads. All performance point roof displacements in the Design Earthquake are less than the 0.02 x 65.67 ft x 12 inlft = 15.76 in. Life Safety Limit shown in Table 11-2 of the Methodology. Similarly, the Structural Stability Limit is found from the expression 0.33 V;/Pi = 0.33(815/4,661) = 0.058, which translates to Structural Stability Limit of 0.058 x 65.67 ft x 12 inlft = 45.5 in. The resulting demand spectrum in shown in Figure 14. Iterative procedures are needed to find the unique "performance point." The desired performance point is Point B in Figure 14, and it can be seen that the building is not capable of achieving this level of spectral displacement at the given load. For this reason, the rehabilitation scheme discussed in the following section is proposed.

4.5

Time History comparisons

Limited inelastic time-history analyses were executed as an approximate check of the performance point displacements predicted by the Methodology. A group of ten near-field acceleration records, each with components in twO directions, were selected. For each record, the given components were transformed to fault-parallel and fault-normal components. Scale factors were computed so that the average spectral accelerations of the 20 histories would be 0.64g for a structure with a I-second period. That is, the records used as time history input were scaled to

Appendix D, Holiday Inn

mate (unrf

1

DRA to thl push, roof time· very trend J. 1 I, P

2. 1

d b 1 undel oven a pus effec· force

s. 5.1

1 achie 14. 1 progJ and s objec Meth objec stabil p provi to sal inclu, Basel level. struc; each requi was!

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SEISMIC EVALUATION AND RETROFIT OF CONCRETE BUILDINGS

---

ters

g as

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in find Id it f it the

ere y the in two he 5cale ,ectral 64g for he :d to

~ay In"

match a single representative point on the 5 percent (unreduced) spectrum for the Design Earthquake. Time-history analyses were performed using DRAIN -2DX. Five percent damping was assigned to the first two modes. Figure IS shows the pushover curve with combinations of maximum roof displacement and base shear taken from the time-history analyses. It can be seen that there is a very wide scatter in the results; however two trends appear relatively clearly: I. The time histories predict higher shears, at lower displacements, than suggested by the pushover curve. 2. The time histories predict higher maximum displacements, at lower shears, than suggested by the pushover curve. Thus, the pushover analysis appears to underestimate the maximum shear and overestimate the displacements. This suggests that a pushover analysis, in general, may miss critical effects of higher modes that increase component forces without increasing roof displacement.

S.

Rehabilitation Scheme

5.1

Introduction

The subject building is not capable of achieving the performance point shown in Figure 14. This suggests that a seismic rehabilitation program is required to provide the needed strength and stiffness to satisfy the required performance objectives identified in Section 1.3 of the Methodology. Two alternative performance objectives are considered: life safety and structural stability. A number of alternatives are available to provide the needed strength, ductility, and stiffness to satisfy the required performance characteristics including internal shear walls and external frames. Based on a review of the desired performance level, the existing architectural character of the structure, the level of disruption associated with each scheme, and access required to execute the required construction, the exterior frame system Was selected. Alternative analyses are possible

~ppencllx D, Holiday Inn

using the interior shear wall scheme, however, these are not presented in this paper because they do not further explain the application of the Methodology to the analysis and rehabilitation of concrete structures.

5.2

EXterior Frames

The Basic Safety objective requires that for the Life Safety Building Performance Level, that the designers enhance gravity resistance of the frame columns, limit deformation in ,the frame columns, and reduce the vulnerability of the frame columns to shear failures. Figures 16 through 19 illustrate the conceptual distribution and member sizes of the exterior frame concept shown in plan, elevation, and details. Using the methodology outlined in developing the nonlinear model for the existing frame, Section 4 of this case study, a pushover analysis of the structure was undertaken. A preliminary approach to sizing these frames uses hypothetical spectral pushover curves to find performance points within required deformation limits. Spectral values at the hypothetical performance points are then converted back to absolute values, and the required strength and stiffness of additional frame elements can be determined. Assumptions inherent in the new design include: •

The new mode shape matches the existing mode shape. An modal participation factor P = 1.4 was assumed, and an appropriate alpha for the hypothetical performance point was chosen from the evaluation data.

•

Initial and post-yield stiffness of the hypothetical pushover curve match the existing building.

•

For the hypothetical strengthened building, the initial yield point is appropriate.

•

New frames have lower yield displacements than do the existing frames.

•

The effects of new frame weight and material properties can be ignored.

D·'.

SEISMIC EVALUATION AND RETROFIT OF CONCRETE BUILDINGS

---------------------------------------------------------------------------------

The results of the analysis are presented in Figure 20 showing the new capacity spectrum for the rehabilitated structure. A similar analysis was conducted for the structural stability performance goal. As can be seen from Figures 21 and 22. significantly less rehabilitation work is required to satisfy the requirements of this performance goal. Figure 23 illustrates the capacity spectrum for this more modest rehabilitation effort.

G.

Concluding Remarks

This report presented an application of the Seismic Evaluation and Retrofit of Existing Concrete Buildings to the Holiday Inn in Van Nuys, California. The purpose of this example building study was to illustrate the use of the Methodology document as an example for other engineers to follow. The analysis of the existing structure concluded that it could not satisfy the requirements of the assumed level of seismic performance and a

D·20

----

seismic rehabilitation scheme consisting of exterior concrete frames investigated. The resulting rehabilitated structure satisfies the required seismic performance level. The static inelastic analysis appears to do a reasonable job of identifying critical limit states in the structure and provides a simplified design criteria against which the rehabilitation of the building can be undertaken. Although there are a number of other evaluation methods, the guidelines contained in the Methodology appear to offer the design engineer a well-structured approach to evaluating and seismically rehabilitating existing concrete structures. Additional case studies are available that examine the application of the Methodology to other structures. These should be consulted to obtain a broader picture of how this methodology should be applied and to the1\nge of engineering judgment required to evaluate and seismically rehabilitate existing concrete buildings.

APpendix D, Holiday In"

Appe

------

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SEISMIC EVALUATION AND RETROFIT OF CONCRETE BUILDINGS

Iday Inn Appendix D. Holiday Inn

D-21

SEISMIC EVALUATION AND RETROFIT OF CONCRETE BUILDINGS

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North/South Perimeter Frame Clevation Example Building Study Holfday Inn. Van Nuy., CA

D·22

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Appendix D. Holiday .JIII

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3

Holiday Inn, Van Nuy.. CA

' Appendix D, Holiday Inn ,llday In!,

D-21

SEISMIC EVALUATION AND RETROFIT OF CONCRETE BUILDINGS

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D-24

nCUR[

4

Appendix D, HOliday Inn

N,

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SEISMIC EVALUATION AND RETROFIT OF CONCRETE BUILDINGS ~----------------------------------------------------------------------------------

FIGURE 5(a) North Frame Elevation Showing Damage

FIGURE 5(b) Close-up of North Frame Column Shear Damage

FIGURE 5(c) Beam Column Joint Damage at North Frame

Damage Photographs

Example Building Study Holiday Inn. Van HUYSt CA

Iiday 1l1li

Appendix D. Holiday Inn

fIGURE

5

D-25

FIGURE6(a) Column Shear Failure

FIGURE6(b) Column Shear Failure

F/GURE6(c) Beam Column JOint Damage - Note Absence of Specified JOint Reinforcing

Damage Photographs Example Building Study Holiday Inn, Van Nuys, CA

D·26

FIGURE

6 Appendix D. Holiday I"~

SEISMIC EVALUATION AND RETROFIT OF CONCRETE BUILDINGS

ETABS

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Existing Structure

IGURE example BuDding Study

F'lGURE

7

Halldl, Inn. Vln NUYI. CA

6

Appendix D. Holiday Inn

D·27

SEISMIC EVALUATION AND RETROFIT OF CONCRETE BUILDINCS

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D·28

Appendix D. Holiday 1l1li

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Appendix D, Holiday Inn

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SEISMIC EVALUATION AND RETROFIT OF CONCRETE BUILDINGS

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Appendix D. Holiday Inn

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D·:!:!

SEISMIC EVALUATION AND RETROFIT OF CONCRETE BUILDINGS

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D-34

Appendix D. Holiday Inn

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SEISMIC EVALUATION AND RETROFIT OF CONCRETE BUILDINGS

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15

HoIIdoy Inn. Von Nup, CA

~ay

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Appendix D. Holiday Inn

D-35

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Structural Stability Retrofit Example Building Study Holkl8W Inn, V.n Nuy., CA

day Inn

Appendix D, Holiday Inn

21

D·Qt

SEISMIC EVALUATION AND RETROFIT OF CONCRETE BUILDINGS

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South Perimeter Frome Elevation : Structural Stability Retrofit

Ex.mple Building Study Holiday Inn. Van HUYI, CA

..,.. D-42

22

Appendix D. Holiday Inll

Ap~

SEISMIC EVALUATION AND RETROFIT OF CONCRETE BUILDINGS

-

TS a which specifies the fraction of the acceleration of gravity required to begin tilting of the block. The required acceleration in time required to overturn the block is expressed in the equation leral ar

~WR

cosh-t,=l+ 10

(

2~ ~-l ga

mof ts is n to is no k or ction s

igure

om les of lidly ltes lergy

ffeets

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This relationship is illustrated in Figure 4. Housner carefully points out that the analysis for a constant acceleration pulse is not a realistic comparison for earthquake ground motion. This is due to the fact that constant acceleration of finite duration followed by a constant velocity of the ground does not occur during an earthquake. Therefore, it is not meaningful to discuss overturning of blocks in terms of a percent gravity acceleration. Overturning By Sinusoidal Acceleration. Housner continues to develop a theoretical description of the rocking block to a sinusoidal acceleration load. If the variable a represents the maximum acceleration and (i) is the frequency of the sine wave, then the relationship between the two parameters required to overturn the block is

Another version of this equation is:

~= 1 +~(21r)2 WR To

ga

In the second expression, To is the period of the ground acceleration. These relationships are illustrated in Figure 5. Overturning by Earthquake Motion. Overturning can be caused by successive smaller pulses at certain frequencies that may occur during actual earthquakes. Housner illustrates this effect by developing conservation of energy and momentum equations describing the response of a rocking block to earthquake motion. As a result he develops an expression relating the geometry of the block to the spectral velocity which would result in a 50% chance of the block overturning. This expression is:

a- S ,

-.fiR

~MR2

T

For a relatively slender structures, this equation reduces to: S

a=-'-

.fiR

This equation may be interpreted as stating that for a given structural velocity, Sv , a block forming an aspect angle a will have an approximately 50% chance of being overturned. The significance of results of this development is that the stability of the block is dependent on its size, as expressed by the factor R. Thus, when comparing two blocks of the same relative proportions, the larger block is more stable than the smaller. This is explained by the fact that the ground motion is the same for both and the effects of the mass of the block in providing stability is greater for the larger block. This effect is summarized in terms of the half-width of the block by the following three equations

Appendix F, Supplemental Information on Foundation Effects

F-II

SEISMIC EVALUATION AND RETROFIT OF CONCRETE BUILDINGS

Earthquake motion:

b=Svl Square pulse:

Sine pulse: b- a.-,==.;;h== g

l+;(~J

It can be seen from these equations that the half-width of the block required for stability does not increase linearly with its height. The general

conclusion is that tall, slender structures may be more stable than might be supposed intuitively. Housner goes on to study the inverted pendulum water tank structures from the Chilean earthquake. He does some comparative calculations which verify that such structures could have rocked about their foundations during a strong ground shaking. Summary. The key conclusion of this work is that it is misleading to infer stability from considerations of a constant horizontal force acting on a rigid block. In fact, taller slender structures may be more stable than such considerations would imply. It should be noted that this theoretical work was extended with an experimental study by other researchers. This is summarized in Research Summary No. 13.

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Appendix F, Supplemental Information on Foundation Effects

App

-

SEISMIC EVALUATION AND RETROFIT OF CONCRETE BUILDINGS

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Appendix F. supplemental Information on Foundation Effects

F·45

SEISMIC EVALUATION AND RETROFIT OF CONCRETE BUILDINGS

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F-4&

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Appendix F, supplemental Information on Foundation EffectS

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Appendix F. supplemental Information on Foundation Effects

F-S1

SEISMIC EVALUATION AND RETROFIT OF CONCRETE BUILDINGS

Resource Summary 1D Martin, G. R. and Van, L. Modeling Passive Earth Pressure for Bridge Abutments ASCE Conference - Geotechnical Special Publication # 55, Earthquake Induced Movements and Seismic Remediation of Existing Foundations and Abutments, San Diego, CA, October 1995 As a component of a bridge structure, abutments not only act as a retaining wall for backfill soils, but also serve the additional function of providing resistance to deformation to earthquake induced longitudinal inertial loads from the bridge deck. Quantifying an abutment stiffness and ultimate passive capacity is an important issue in modeling bridge structures for earthquake loading. In this paper, design procedures are briefly reviewed and the results of a numerical study modeling the passive earth pressure characteristics of bridge abutments are presented. Although the paper relates to bridge abutments, the results are also applicable to building structures in relation to the lateral passive capacity ability to be mobilized by footings or building basement walls.

F-S2

The paper utilizes a finite difference numerical approach to analyze the load-deformation and passive load capacity of abutments simulated as a rigid wall, (as shown in Figure 1) for both cohesive and cohesionless soil backfill materials. Classical passive pressure solutions are first presented and are followed by numerical parametric studies to examine the influence of wall height and material properties on mobilized passive pressures. The effects of wall friction on results are also examined in the parametric studies. The computer program FLAC used for analysis is shown to provide reasonable numerical results when compared to classical solutions. Overall the paper presents useful charts which can be of value in assessing the problem of lateral passive capacity for building foundation components, such as that shown in Figure 2.

Appendix F, supplemental Information on Foundation Effects

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fects

Appendix F, Supplemental Information on Foundation Effects

F-51

SEISMIC EVALUATION AND RETROFIT OF CONCRETE BUILDINGS

imp SI6

Resource summary"

Dar.

Nakaki, D. K., and Hart, G. C. Uplifting Response of Structures Subjected to Earthquake Motions U. S.-Japan Coordinated Program for Masonry Building Researcb, Report No. 2.1-3, Ewing/Kariotis/Englekirk & Hart, August 1987 In this study, the effect of foundation flexibility and uplift on the response of slender shear wall type structures is investigated. The slenderness ratio (defined as the height divided by half the width) of structures studied has been limited to 3.5. This slenderness ratio is representative of shear wall structures of about 10 story height. Effect of inelastic behavior of the structure on response was also considered. The structure·foundation system considered in this investigation is shown in Figure I. As shown, the flexibility and damping of the soil was modeled by elastic Winkler springs with viscous damping for energy dissipation: The superstructure was represented as an inelastic, single degree of freedom system on a rigid foundation. Relative horizontal displacement between the base of the structure and the Winkler elements was not considered. The vertical Winkler foundation springs were considered effective only for the compressive forces and have zero tensile capacity. The properties of the distributed Winkler springs and dashpots were computed from the rocking spring and dashpot for a rigid foundation resting on an elastic half space. Using this approach the Winkler spring and dashpot constants, ko and Co respectively, are

ko

= 3 Ka/(2 b 3)

Co = 3 Ca/(2 b 3) In the above equations, b is the half width of foundation and Ka and Ca, the stiffness and

F-S4

damping coefficients of a rigid circular massless foundation on an elastic half-space, are Ka = 8 G r 3/[3(I-y)] Ca = a 8 G r4/[3(I-y)v s] where G is the shear modulus of the soil, r is the radius of foundation, y is the Poisson's ratio, Vs is the shear wave velocity and, a is a dimensionless coefficient dependent on the frequency of excitation, the radius of foundation, and the shear wave velocity. The value of ex was taken as 0.2 in this study. The study was aimed at concrete and concrete· masonry shear wall type structures. Therefore, the inelastic behavior of the superstructure was represented by stiffness degrading hysteresis mqdel developed by Newmark and Riddell. Two distinct limit states were defined for the system under consideration. The first limit state is associated with the initiation of uplift and marks the first change in the stiffness of the system. The second limit state corresponds to the yielding of the super structure. P-A effects, since they were considered to be small, were not included. Direct time-history analyses were performed for two types of ground motion: a long duration strong motion and a short duration impulsive type motion. The long duration motion was represented by the SOOE component of 1940 EI Centro earthquake. This record has a peak horizontal ground acceleration (PGA) of 0.35g. The PGA in the vertical direction is 0.2Ig. The short duration,

Appendix F. supplemental Information on Foundation EffectS

of il stud the, eart For pres spec and appl iIlus wid, 30'

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impulsive type motion was represented by the Sl6E component (PGA = l.l7g) of the Pacoima Dam record scaled down to 50 percent. Influence of including vertical ground motions was also studied. Parametric studies were performed to study the effect of foundation flexibility and uplift on the earthquake response and the potential for damage. For this purpose, the results of the analyses were presented both in the form of the ductility demand spectra and time history plots of the input energy and the dissipated and absorbed energy. Practical application of the concepts developed was then illustrated by analyzing a 9-story, 78' high and 27' wide concrete masonry shear wall supported on a 30' long by 4' wide by 3' thick concrete footing. Monte Carlo simulations were also performed to study the influence of yield capacity of the shear wall on response. The key findings of this investigation are summarized below: As shown in Figures 2 and 3, uplift resulted in significant reduction in ductility demands when the rocking frequency of the system was less than the fixed base natural frequency of the structure. When the rocking frequency was greater than the fixed base frequency of the structure, uplift had much smaller effect on ductility demands and, in some cases, allowing uplift produced slightly higher ductility demands. The frequency content of the ground motion had significant effect on the ductility demand. With uplift allowed, the EI Centro motion, which was richer in short period motions, tended to produce higher ductility demands for shorter period structures founded on stiffer soils; whereas, the Pacoima Dam motion, richer in longer period motions, was more severe for longer period structures. When the rocking frequency was less than the fixed base natural frequency of the

structure, including the vertical ground motion, it typically increased the higher mode coupling thus increasing the ductility demands. For cases where the rocking frequency was greater than the fixed natural frequency of the structure, inclusion of vertical ground motion typically had little effect on overall response. Time history energy plots for a system with fixed base natural period of 0.4 sec., see Figure 4, showed that the hysteretic energy loss in a system with uplift permitted is smaller than without uplift thus implying less earthquake damage in the uplifting structure. However, the energy spectra plots, Figure 5, showed that allowing uplift, in most cases, resulted in larger hysteretic energy loss than without uplift. This was especially true for the Pacoima Dam motion which was rich in long period motion and for periods greater than about 0.5 sec. Thus, it was concluded that on the basis of energy dissipated, it can not be conclusively stated that allowing uplift will reduce the damage sustained by the structure and, also, ductility demand alone may not be a true indicator of damageability. Including the vertical ground motion generally increased the energy dissipated by hysteresis. The shear wall studied had a fixed natural period of vibration of about 0.5 sec. The results of the analyses for this case study showed that allowing the structure to uplift from its foundation resulted in an essentially elastic response. The authors, however, cautioned that the reduction in the inelastic deformations in the structure comes at the expense of uplift displacements at the foundation level which must be accounted for in the design. Monte Carlo studies on the variability of yield capacity of the shear wall showed that the foundation rotation and uplift were more sensitive to yield capacity of the wall than the displacement response.

in In,

Appendix F, supplemental Information on Foundation Effects

F-SS

SEISMIC EVALUATION AND RETROFIT OF CONCRETE BUILDINGS

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Appendix F, supplemental Information on Foundation Effects

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F-S7

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SEISMIC EVALUATION AND RETROFIT OF CONCRETE BUILDINGS

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F-S8

Appendix F, Supplemental Information on Foundation Effects

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SEISMIC EVALUATION AND RETROFIT OF CONCRETE BUILDINGS

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F-S!J

Appendix F. supplemental Information on Foundation Effects

---------- _._-

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SEISMIC EVALUATION AND RETROFIT OF CONCRETE BUILDINGS

Figure 5. Input Energy and Hysteretic Energy per unit Mass spectra for the Scaled pacoima Dam Motion, ).=5.S, P =0.9, fJ = 0.7, mv= 161r rad. sec., ~s=O.OS, ~v=0.20

P-60

Appendix F, supplemental Information on Foundation Effects

•

SEISMIC EVALUATION AND RETROFIT OF CONCRETE BUILDINGS

Resource summary 12 »>'>YL»

Pender, M. J. Aseismic Pile Foundation Design Analysis Bulletin of the New Zealand National Society for Earthquake Engineering, Volume 26, No.1, March 1993

This paper presents a comprehensive presentation of methods of assessing, for preliminary design purposes, the stiffness and capacity of pile foundations under seismic forces. Emphasis is placed on expressions for pile stiffness and capacity in the form of simple formulae and illustrations on the use of formulae through a number of worked examples. Comparisons between data from field testing of foundations and analysis methods are also presented. Specific topics covered in the paper include the following: • Observed seismic response and damage to pile foundations during past earthquakes

•

Discussions on the role of kinematic soil-pile interaction and dynamic response of pile groups The case history documentation on the response of pile foundation systems to seismic loading provides a comprehensive overview. One interesting documented case history relates to the response of the Imperial County, California, Services Building (Figure 1) during the 1979 Imperial Valley magnitude 6.3 earthquake. Forced vibration tests on pile caps following building demolition provided the means for earthquake response studies including the effects of foundation interaction. The objectives of the paper are focused heavily on design analysis, particularly preliminary design. The approach presented is suitable for use with spread sheets albeit more sophisticated methods and computer approaches are also discussed. The emphasis on assembling an extensive set of simple formulae and the use with examples make this paper particularly readable for design engineers. Nearly all the methods discussed focus on the common idealization that the soil-pile system will respond in an equivalent linear elastic manner to applied loading. In this respect a useful compilation of correlations between Young's modulus and the coefficient of sub grade reaction with standard penetration blowcount are provided. The reality of nonlinear soil behavior which occurs during strong seismic loading is discussed briefly, and illustrated using the results of field load tests. The presentation also identifies limitations of the various analysis methods and topics requiring

•

Models for pile lateral stiffness including Winkler and elastic continuum models

•

Models for pile vertical stiffness including Winkler and elastic continuum models and discussion on battered piles

•

Methods for evaluating stiffness of pile groups including vertical, rotational and lateral stiffness components

•

Discussions on the influence of nonlinear soil behavior on soil·pile interaction including case studies

•

Discussions on correlations between subgrade soil properties and penetration resistance from field tests

In,

•

Discussions on results of dynamic tests on prototype scale piles and pile groups and

Ffects

APpendix F, supplemental Information on Foundation EHects

F-G'I

SEISMIC EVALUATION AND RETROFIT OF CONCRETE BUILDINGS

further research. A detailed valuation of the relative role of inertial and kinematic interaction of pile foundation subjected to dynamic loading, clarifies the relative importance of the two effects. The significance of pile group effects is also addressed using analytical data and results of field load tests, as for example shown in Figure 2. Questions not addressed in detail in the paper

include the effects of liquefaction and potential degradation in stiffness of soils adjacent to the pile due to cyclic loading. Overall the paper provides good insight as to the mechanics of soil-pile interaction and is perhaps one of the most comprehensive state-ofthe-practice publications available on seismic pile foundation design.

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F-62

Appendix F, Suppiementallnformation on Foundation Effects

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Appendix F, Supplemental Information on Foundation Effects

F·79

SEISMIC EVALUATION AND RETROFIT OF CONCRETE BUILDINGS

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Appendix F. supplemental Information on Foundation Effects

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SEISMIC EVALUATION AND RETROFIT OF CONCRETE BUILDINGS

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Appendix F. Supplemental Information on Foundation Effects

F-B1

SEISMIC EVALUATION AND RETROFIT OF CONCRETE BUILDINGS

Resource Summary ,& Veletsos, A.S., Prasad, A.M., and Tang, Y. Design Approaches for Soil-Structure Interaction Proceedings of the Ninth World Conference on Earthquake Engineering, Tokyo, August, 1988 In this state-of-the-art report, soil structure interaction concep~ expressed in terms of kinematic and inertial interaction are discussed with reference to a simple linear structure of mass, m, and height, h, supported ona rigid mat foundation of mass, mo. at the surface of a homogeneous elastic half space. The authors note that seismic response of a structure is frequently evaluated considering the motion of its base to be equal to the stipulated free-field ground motion at a reference or control point, normally taken at the ground surface. However, an exact analysis requires that the structure be considered to be part of a larger system which includes the foundation and a supporting medium and that spatial variability of ground motion and properties of soils need to be considered. For such an analysis a two step approach is defined. First, the motion of the foundation is evaluated considering the foundation and the structure to be massless. The resulting foundation input motion (FIM) generally includes torsional and rocking components in addition to translational components. Next the response to the FIM of the actual foundation-structure system with mass is evaluated using actual properties of a supporting medium and providing for the dynamic interaction. The difference in the response of a superstructure computed for the FIM and the freefield control point motions represents kinematic interaction effect. The difference of the responses computed with and without regard for the flexibility of the supporting medium is known as the inertial interaction effect. The total soil-

F-82

structure interaction is given by the sum of both effects. For the simplified structure considered, the effects of inertial and kinematic interaction are examined in the paper. Expressions are given for increases in the natural period of the structure on a flexible support system and for the effects of foundation damping, including radiation damping arising from foundation interaction. To address the question as to whether soil-structure interaction increases or decreases the maximum response of the structure, a number of cases are considered where it becomes clear that the answer is a function of the response quantity under examination and the characteristics of the ground motion and the system itself. Kinematic interaction effects are discussed including the effects of wave passage and ground motion incoherence. The relative importance of kinematic and inertial interaction is examined using response spectra plots, such as those shown in Figure I, where the ratios of pseudo spectral velocity divided by peak ground acceleration are shown as a function of the natural frequency of the structure. Because the presented material and analysis results assume a simplified idealized building and a rigid mat foundation system resting on a semiinfinite elastic medium, it is difficult to draw specific quantitative conclusions regarding the significance if kinematic and internal interaction effects for actual building structures, where more complex foundation systems also involve nonlinear or inelastic soil response to earthquake ground motions. However, it is clear that for many

Appendix F, Supplemental Information on Foundation Effects

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SEISMIC EVALUATION AND RETROFIT OF CONCRETE BUILDINGS

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building systems, the effects of kinematic interaction are small in relation to inertial interaction effects and that inertial interaction has the greatest influence on the response of structural systems in the medium and high frequency spectral regions. The authors note that inertial interaction effects are generally more important than that of kinematic interaction and the interaction effects for low frequency highly compliant structures are negligible because such systems "see" the supporting half space as a very stiff effectively rigid medium. The above research and conclusions form the . basis for existing NEHRP Guidelines (for the

seismic design of buildings) on the effects of soilstructure interaction. However, the authors note the limitation of these studies and the approach used, and that additional research is needed to evaluate the behavior of structures for embedded foundation and pile foundation systems. Additionally interaction effects for structures responding in a nonlinear range of deformation are recommended. Clearly, the behavior of individual foundation elements supporting column loads under earthquake loading and nonlinear response can be major factors in determining structural loads, and more research in these areas is needed to formulate improved guidelines.

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Appendix F. Supplemental Information on Foundation Effects

F·BS

SEISMIC EVALUATION AND RETROFIT OF CONCRETE BUILDINGS

Resource Summary 17 Wallace, J.W., Moehle, J.P., and Martinez-Cruzado, J. Implications for the Design of Shear Wall Buildings Using Data from Recent Earthquakes Proceedings of Fourth U.S. National Conference on Earthquake Engineering, Palm Springs, CA, May 1990 This paper presents the results of a study of the measured response and observed seismic performance of reinforced concrete load bearing shear wall buildings during past earthquakes. First, the response of two 10-story concrete shear wall buildings in California during earthquakes was analyzed. Both buildings were designed and built in early 1970s. Figure 1 shows the plan configurations of the two buildings. Both buildings have been instrumented with strong motion instruments by the California Strong Motion Instrumentation Program. Because of the symmetry of the first building, a 2-dimensional computer using SAP-90 computer model was developed; whereas, a three dimensional model of the second building was developed using ETABS computer program. The first building, located in northern California, was analyzed for the motions recorded during the 1984 Morgan Hill (Ms = 6.2) earthquake. The second building, located in southern California was analyzed for the motions recorded during the 1987 Whittier (Ms = 5.9) earthquake. It was observed that when soil flexibility and the effect of initial concrete cracking were ignored in the analysis, the periods of vibration obtained from the computer model were smaller than those measured from recorded response. The correlation between the measured and computed time-history response was also poor, Figure 2. Therefore, the computer model was modified to incorporate these effects. Foundation flexibility was modeled using the relatively simple soil springs approach outlined

F-B4

in the ATC-3-06 document. As shown in Figure 3, good correlation between the recorded motions and the time-history analyses results was observed when the effects of foundation flexibility and cracked section properties were included. Comparison were then made with the response of shear wall buildings during the March 1985 Chilean earthquake (Ms = 7.8) which had a peak acceleration of 0.36 g and duration of strong shaking of more than 60 seconds. Even though the Chilean buildings are designed to similar force levels as California, their ductile detailing and quality control requirements are quite lax by US standards. However, these buildings have performed remarkably well during past earthquakes. To understand the reasons for this good performance, displacement ductility demand spectra were developed from 5 percent damped elastic spectra using the method recommended by Newmark and Hall. These are shown in Figure 4. The calculated base shear strengths and the periods measured from ambient vibrations were then plotted in this figure. It was observed that these data points correspond to a ductility demand of about 3 which corresponds to appreciable local damage. However, when the building strength was plotted as a function of the building period considering soil flexibility, it was noted that several buildings fell on or above the elastic spectra and the largest ductility demand was 2. It was, therefore, concluded that foundation

APpendix F, supplemental Information on Foundation Effects

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SEISMIC EVALUATION AND RETROFIT OF CONCRETE BUILDINGS

flexibility was one of the reasons for the reduced displacement ductility demands in these buildings. The authors also studied the available ductility of the Chilean shear walls. They found that, the available curvature ductility of lightly reinforced walls was about 10 to 12 and was greater than the typical ductility demand of about 3 to 5.

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Therefore, it was concluded that for rectangular, symmetrically reinforced walls, concrete confinement in transverse reinforcement is not necessary for good seismic performance and that the US bearing wall buildings should also perform well during a major earthquake.

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Appendix F, Supplemental Information on Foundation Effects

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SEISMIC EVALUATION AND RETROFIT OF CONCRETE BUILDINGS

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F·8a

Appendix F. Supplemental Information on Foundation Effects

SEISMIC EVALUATION AND RETROFIT OF CONCRETE BUILDINGS

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Appendix F. Supplemental Information an Faundation Effects

F-87

SEISMIC EVALUATION AND RETROFIT OF CONCRETE BUILDINGS

Resource Summary 18 Yim, S. C-S and Chopra, A. K. Simplified Earthquake Analysis of Multistory Structures with Foundation Uplift American Society of Civil Engineers, Journal of Structural Engineering, Vol. 111, No. 12, December 1985. pp. 2708-2731 This investigation is an extension of the approach for the analysis of single degree of freedom systems (Chopra and Yim) to the analysis of IlUIltistory structures with foundation flexibility and uplift. Figure 1 shows the system considered in this investigation. Although, the foundation soil can be represented by the two spring -dashpot model or the distributed Winkler spring and dashpot mode, only the results of analyses with two spring and dashpot system were presented in this paper. Equations of motions were developed for this multistory structure foundation system. It was noted that although the governing equations of motions were nonlinear, the dynamic response of the system under consideration could be obtained as sequential response of three linear systems corresponding to three contact conditions for the foundation mat. The time history response of an idealized 10story structure was analyzed for the north-south component of the 1940 EI Centro earthquake. The idealized structure had uniform stiffness, mass, and inter-story height. The damping was 5 percent in all modes of vibration and the slenderness ratio for the first mode of vibration was 10. The base shear and overturning moment spectra obtained from this analysis are shown in Figures 2 and 3. The beneficial effect of allowing uplift were observed in terms of lowered base shear and overturning moments for periods of vibration less than about 1 sec. The authors also observed that foundation flexibility and uplift have little impact on the higher

F-88

modes of response. Therefore, they concluded that the analysis of a multistory building with foundation flexibility and uplift can be simplified by calculating only the fundamental mode of response considering these effects; the contribution from higher modes can be computed using standard procedures by disregarding the effects of foundation flexibility and uplift. Excellent correlation between the exact solutions and the solutions obtained using this approach was observed, see Figure 4. A simplified approach for estimating the response of uplifting multistory structures was then presented. In this approach, the maximum earthquake base shear for the system is obtained as the SRSS of the modal maxima of individual modes of vibrations. An approximate expression for the maximum base shear in the first mode of vibration considering foundation flexibility and uplift was developed. This equation is analogous to the one developed for the single degree of freedom systems and does not require time history analyses. The modal maxima for the other mod~s of vibration are obtained using the standard procedures for the structure on rigid foundation without uplift. The base shear response spectra using this simplified approach as presented in Figure 5 show reasonable degree of accuracy. Therefore, the simplified approach can be used for practical design or for performing parametric studies on the influence of foundation flexibility and uplift on response of multistory structures.

Appendix F, Supplemental Information on Foundation Effects

A

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F·80

Appendix F. Supplemental Information on Foundation Effects

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SEISMIC EVALUATION AND RETROFIT OF CONCRETE BUILDINGS

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AppenCllx F, Supplemental Information on Foundation Effects

F·91

SEISMIC EVALUATION AND RETROFIT OF CONCRETE BUILDINGS

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F·92

Appendix F. Supplemental Information on Foundation Effects

SEISMIC EVALUATION AND RETROFIT OF CONCRETE BUILDINGS

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Appendix F, supplemental Information on Foundation Effects

SEISMIC EVALUATION AND RETROFIT OF CONCRETE BUILDINGS

AppendixG

Applied Technology Council proJects and Report Information One of the primary purposes of Applied Technology Council is to develop resource documents that translate and summarize useful infonnation to practicing engineers. This includes the development of guidelines and manuals, as well as the development of research recommendations for specific areas determined by the profession. ATC is not a code development organization, although several of the ATC project reports serve as resource documents for the development of codes, standards and specifications. Applied Technology Council conducts projects that meet the following criteria: 1. The primary audience or benefactor is the design practitioner in structural engineering. 2. A cross section or consensus of engineering opinion is required to be obtained and presented by a neutral source. 3. The project fosters the advancement of structural engineering practice. A brief description of several major completed projects and reports is given in the following section. Funding for projects is obtained from government agencies and tax-deductible contributions from the private sector. ATC-I: This project resulted in five papers that were published as part of Building Practices for

Disaster Mitigation, Building Science Series 46, proceedings of a workshop sponsored by the National Science Foundation (NSF) and the National Bureau of Standards (NBS). Available through the National Technical Information Service (NTIS), 5285 Port Royal Road, Springfield, VA 22151, as NTIS report No. COM-73-50188. ATC-2: The report, An Evaluation of a Response Spectrum Approach to Seismic Design of Buildings, was funded by NSF and NBS and was conducted as part of the Cooperative Federal Program in Building Practices for Disaster Mitigation. Available through the ATC office. (Published 1974,270 Pages)

ABSTRACT: This study evaluated the applicability and cost of the response spectrum approach to seismic analysis and design that was proposed by various segments of the engineering profession. Specific building designs, design procedures and parameter values were evaluated for future application. Eleven existing buildings of varying dimensions were redesigned according to the procedures. A TC-3: The report, Tentative Provisions for the Development of Seismic Regulations for Buildings (ATC-3-06), was funded by NSF and NBS. The second printing of this report, which includes proposed amendments, is available through the ATC office. (Published 1978, amended 1982, 505 pages plus proposed amendments)

Appendix C, APplied Technology Council projects and Report Information

G-1

SEISMIC EVALUATION AND RETROFIT OF CONCRETE BUILDINGS

ABSTRACT: The tentative provisions in this document represent the results of a concerted effort by a multi-disciplinary team of 85 nationally recognized experts in earthquake engineering. The provisions serve as the basis for the seismic provisions of the 1988 Uniform Building Code and the 1988 and subsequent issues of the NEHRP Recommended Provisions for the Development of Seismic Regulation for New Buildings. The second printing of this document contains proposed amendments prepared by a joint committee of the Building Seismic Safety Council (BSSC) and the NBS.

ATC-3-2: The project, Comparative Test Designs of Buildings Using ATC-3-06 Tentative Provisions, was funded by NSF. The project consisted of a study to develop and plan a program for making comparative test designs of the ATC-3-06 Tentative Provisions. The project report was written to be used by the Building Seismic Safety Council in its refinement of the ATC-3-06 Tentative Provisions. ATC-3-4: The report, Redesign of Three Multistory Buildings: A Comparison Using ATC-3-06 and 1982 Uniform Building Code Design Provisions, was published under a grant from NSF. Available through the ATC office. (Published 1984, 112 pages) ABSTRACT: This report evaluates the cost and

technical impact of using the 1978 ATC-3-06 report, Tentative Provisions for the Development of Seismic Regulationsfor Buildings, as amended by a joint committee of the Building Seismic Safety Council and the National Bureau of Standards in 1982. The evaluations are based on studies of three existing California buildings redesigned in accordance with the ATC-3-06 Tentative Provisions and the 1982 Uniform Building Code. Included in the report are recommendations to code implementing bodies. ATC-3-5: This project, Assistance for First Phase of ATC-3-06 Trial Design Program Being Conducted by the Building Seismic Safety Council, was funded by the Building Seismic Safety Council

G·2

to provide the services of the ATC Senior Consultant and other ATC personnel to assist the BSSC in the conduct of the first phase of its Trial Design Program. The first phase provided for trial designs conducted for buildings in Los Angeles, Seattle, Phoenix, and Memphis. A TC-3-6: This project, Assistance for Second Phase of ATC-3-06 Trial Design Program Being Conducted by the Building Seismic Safety Council, was funded by the Building Seismic Safety Council to provide the services of"the ATC Senior Consultant and other ATC personnel to assist the BSSC in the conduct of the second phase of its Trial Design Program. The second phase provided for trial designs conducted for buildings in New York, Chicago, St. Louis, Charleston, and Fort Worth. ATC-4: The report, A Methodology for Seismic Design and Construction of Single-Family Dwellings, was published under a contract with the Department of Housing and Urban Development (HUD). Available through the ATC office. (Published 1976,576 pages) ABSTRACT: This report presents the results of an in-depth effort to develop design and construction details for single-family residences that minimize the potential economic loss and life-loss risk associated with earthquakes. The report: (1) discusses the ways structures behave when subjected to seismic forces, (2) sets forth suggested design criteria for conventional layouts of dwellings constructed with conventional materials, (3) presents construction details that do not require the designer to perform analytical calculations, (4) suggests procedures for efficient plan-checking, and (5) presents recommendations including details and schedules for use in the field by construction personnel and building inspectors.

ATC-4-1: The report, The Home Builders Guide for Earthquake Design, was published under a contract with HUD. Available through the ATe office. (Published 1980, 57 pages)

Appendix C, Applied Technology Council projects and Report Information

J

,

1

c c

A

}j

w

A 2

SEISMIC EVALUATION AND RETROFIT OF CONCRETE BUILDINGS

ABS1RACT: This report is a 57-page abridged

version of the ATC-4 report. The concise, easily understood text of the Guide is supplemented with illustrations and 46 construction details. The details are provided to ensure that houses contain structural features that are properly positioned, dimensioned and constructed to resist earthquake forces. A brief description is included on how earthquake forces impact on houses and some precautionary constraints are given with respect to site selection and architectural designs.

I, il

A TC·5: The report, Guidelines for Seismic Design and Construction of Single-Story Masonry Dwellings in Seismic Zone 2, was developed under a contract with HUD. Available through the ATC office. (Published 1986,38 pages)

al

:s

m

d

n

ABS1RACT: The report offers a concise methodology for the earthquake design and construction of single-story masonry dwellings in Seismic Zone 2 of the United States, as defined by the 1973 Uniform Building Code. The Guidelines are based in part on shaking table tests of masonry construction conducted at the University of California at Berkeley Earthquake Engineering Research Center. The report is written in simple language and includes basic house plans, wall evaluations, detail drawings, and material specifications.

A TC·6: The report, Seismic Design Guidelines for Highway Bridges, was published under a contract with the Federal Highway Administration (FHWA). Available through the ATC office. (Published 1981, 210 pages) ABS1RACT: The Guidelines are the

recommendations of a team of sixteen nationally recognized experts that included consulting engineers, academics, state and federal agency representatives from throughout the United States. The Guidelines embody several new concepts that were significant departures from then existing design provisions. Included in the Guidelines are an extensive commentary, an

example demonstrating the use of the Guidelines, and summary reports on 21 bridges redesigned in accordance with the Guidelines. The guidelines have been adopted by the American Association of Highway and Transportation Officials as a guide specification. ATC·6·1: The report, Proceedings of a Workshop on Earthquake Resistance of Highway Bridges, was published under a grant from NSF. Available through the ATC office. (Published 1979,625 pages) ABS1RACT: The report includes 23 state-of-the-

art and state-of-practice papers on earthquake resistance of highway bridges. Seven of the twenty-three papers were authored by participants from Japan, New Zealand and Portugal. The Proceedings also contain recommendations for future research that were developed by the 45 workshop participants. A TC·6·2: The report, Seismic Retrofitting Guidelines for Highway Bridges, was published under a contract with FHWA. Available through the ATC office. (Published 1983,220 pages) ABS1RACT: The Guidelines are the

recommendations of a team of thirteen nationally recognized experts that included consulting engineers, academics, state highway engineers, and federal agency representatives. The Guidelines, applicable for use in all parts of the U.S., include a preliminary screening procedure, methods for evaluating an existing bridge in detail, and potential retrofitting measures for the most common seismic deficiencies. Also included are special design requirements for various retrofitting measures. ATC·7: The report, Guidelines for the Design of Horizontal Wood Diaphragms, was published under a grant from NSF. Available through the ATC office. (Published 1981, 190 pages) ABS1RACT: Guidelines are presented for

designing roof and floor systems so these can

Appendix G, Applied Technology Council proJects and Report Information

GoJ

SEISMIC EVALUATION AND RETROFIT OF CONCRETE BUILDINGS

function as horizontal diaphragms in a lateral . force resisting system. Analytical procedures, connection details and design examples are included in the Guidelines. ATC-7-1: The report, Proceedings of a Workslwp of Design of Horizontal Wood Diaphragms, was published under a grant from NSF. Available through the ATC office. (Published 1980, 302 pages)

ABSTRACT: The report includes seven papers on state-of-the-practice and two papers on recent research. Also included are recommendations for future research that were developed by the 35 workshop participants. ATC-8: This report, Proceedings of a Workshop on the Design of Prefabricated Concrete Buildings for Earthquake Loads, was funded by NSF. Available through the ATC office. (Published 1981, 400 pages)

ABSTRACT: The report includes eighteen stateof-the-art papers and six summary papers. Also included are recommendations for future research that were developed by the 43 workshop partiCipants. ATC-9: The report, An Evaluation of the Imperial County Services Building Earthquake Response and Associated Damage, was published under a grant from NSF. Available through the ATC office. (Published 1984, 231 pages)

ABSTRACT: The report presents the results of an in-depth evaluation of the Imperial County Services Building, a 6-story reinforced concrete frame and shear wall building severely damaged by the October 15, 1979 Imperial Valley, California, earthquake. The report contains a review and evaluation of earthquake damage to the building; a review and evaluation of the seismic design; a comparison of the requirements of various building codes as they relate to the building; and conclusions and recommendations pertaining to future building code provisions and future research needs.

G-4

ATC-IO: This report, An Investigation of the Correlation Between Earthquake Ground Motion and Building Peiformonce, was funded by the U.S. Geological Survey (USGS). Available through the ATC office. (Published 1982, 114 pages)

ABSTRACT: The report contains an in-depth analytical evaluation of the ultimate or limit capacity of selected representative building framing types, a discussion of the factors affecting the seismic performance of buildings, and a summary and comparison of seismic design and seismic risk parameters currently in widespread use.

A

a /;

l' 1

ATC-IO-I: This report, Critical Aspects of Earthquake Ground Motion and Building Damage Potential, was co-funded by the USGS and the NSF. Available through the ATC office. (Published 1984, 259 pages)

ABSTRACT: This document contains 19 stateof-the-art papers on ground motion, structural response, and structural design issues presented by prominent engineers and earth scientists in an ATC seminar. The main theme of the papers is to identify the critical aspects of ground motion and building performance that currently are not being considered in building design. The report also contains conclusions and recommendations of working groups convened after the Seminar.

A J,

R u

A

ATC-ll: The report, Seismic Resistance of Reinforced Concrete Shear Walls and Frame Joints: Implications of Recent Research for Design Engineers, was published under a grant from NSF. Available through the ATC office. (Published 1983, 184 pages)

ABSTRACT: This document presents the results of an in-depth review and synthesis of research reports pertaining to cyclic loading of reinforced concrete shear walls and cyclic loading of joint reinforced concrete frames. More than 125 research reports published since 1971 are reviewed and evaluated in this report. The

Appendix C, Applied Technology Council projects and Report Information

A

SEISMIC EVALUATION AND RETROFIT OF CONCRETE BUILDINGS

preparation of the report included a consensus process involving numerous experienced design professionals from throughout the United States. The report contains reviews of current and past design practices, summaries of research developments, and in-depth discussions of design implications of recent research results. A TC-12: This report, Comparison of United States and New Zealand Seismic Design Practices for Highway Bridges, was published under a grant from NSF. Available through the ATC office. (Published 1982,270 pages) ABSTRACT: The report contains summaries of

all aspects and innovative design procedures used in New Zealand as well as comparison of United States and New Zealand design practice. Also included are research recommendations developed at a 3-day workshop in New Zealand attended by 16 U.S. and 35 New Zealand bridge design engineers and researchers.

F. ~,

ATC-12-1: This report, Proceedings of Second Joint U.S.-New Zealand Workshop on Seismic Resistance of Highway Bridges, was published under a grant from NSF. Available through the ATC office. (Published 1986,272 pages)

d rs y

ABSTRACT: This report contains written

versions of the papers presented at this 1985 Workshop as well as a list and prioritization of workshop recommendations. Included are summaries of research projects being coriducted in both countries as well as state-of-the-practice papers on various aspects of design practice. Topics discussed include bridge design philosophy and loadings; design of columns, footings, piles, abutments and retaining structures; geotechnical aspects of foundation design; seismic analysis techniques; seismic retrofitting; case studies using base isolation; strong-motion data acquisition and interpretation; and testing of bridge components and bridge systems.

i

ts:

3, ts h :ed 1t

on

I

ATC-13: The report, Eanhquake Damage Evaluation Datafor California, was developed under a contract with the Federal Emergency Management Agency (FEMA). Available through the ATC office. (Published 1985,492 pages) ABSTRACT: This report presents expert-opinion

earthquake damage and loss estimates for industrial, commercial, residential, utility and transportation facilities in California. Included are damage probability matrices for 78 classes of structures and estimates of time required to restore damaged facilities to pre-earthquake usability. The report also describes the inventory information essential for estimating economic losses and the methodology used to develop loss estimates on a regional basis. ATC-14: The report, Evaluating the Seismic Resistance of Existing Buildings, was developed under a grant from the NSF. Available through the ATC office. (Published 1987, 370 pages) ABSTRACT: This report, written for practicing

structural engineers, describes a methodology for performing preliminary and detailed building seismic evaluations. The report contains a state-of-practice review; seismic loading criteria; data collection procedures; a detailed description of the building classification system; preliminary and detailed analysis procedures; and example case studies, including nonstructural considerations. ATC-IS: The report, Comparison of Seismic Design Practices in the United States and Japan, was published under a grant from NSF. Available through the ATC office. (Published 1984, 317 pages) ABSTRACT: The report contains detailed technical papers describing design practices in the United States and Japan as well as recommendations emanating from a joint U.S.Japan workshop held in Hawaii in March, 1984. Included are detailed descriptions of new seismic design methods for buildings in Japan

Appendix G, APplied Technology Council projects and Report Information

c-s

SEISMIC EVALUATION AND RETROFIT OF CONCRETE BUILDINGS

and case studies of the design of specific buildings (in both countries). The report also contains an overview of the history and objectives of the Japan Structural Consultants Association. ATC·15·1: The report, Proceedings of Second U.S.Japan Workshop on Improvement of Building Seismic Design and Construction Practices, was published under a grant from NSF. Available through the ATC office. (Published 1987,412 pages) ABS1RACT: This report contains 23 technical

papers presented at this San Francisco workshop in August, 1986, by practitioners and researchers from the U.S. and Japan. Included are state-of-the-practice papers and case studies of actual building designs and information on regulatory, contractual, and licensing issues. ATC·lS·2: The report, Proceedings of Third U.S.Japan Workshop on Improvement of Building Structural Design and Construction Practices, was published jointly by ATC and the Japan Structural Consultants Association. Available through the ATC office. (Published 1989,358 pages) ABS1RACT: This report contains 21 technical papers presented at this Tokyo, Japan, workshop in July, 1988, by practitioners and researchers from the U.S., Japan, China, and New Zealand. Included are state-of-the-practice papers on various topics, including braced steel frame buildings, beam-column joints in reinforced concrete buildings, summaries of comparative U. S. and Japanese design, and base isolation and passive energy dissipation devices.

ATC·lS·3: The report, Proceedings of Fourth U.S.Japan Workshop on Improvement of Building Structural Design and Construction Practices, was published jointly by ATC and the Japan Structural Consultants Association. Available through the ATC office. (Published 1992,484 pages) ABS1RACT: This report contains 22 technical

papers presented at this Kailua-Kona, Hawaii,

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workshop in August, 1990, by practitioners and researchers from the United States, Japan, and Peru. Included are papers on postearthquake building damage assessment; acceptable earthquake damage; repair and retrofit of earthquake damaged buildings; base-isolated buildings, including Architectural Institute of Japan recommendations for design; active damping systems; wind-resistant design; and summaries of working group conclusions and recommendations. ATC·15·4: The report, Proceedings of Fifth U.S.Japan Workshop on Improvement of Building Structural Design and Construction Practices, was published jointly by ATC and the Japan Structural Consultants Association. Available through the ATC office. (Published 1994, 360 pages) ABs1RACT: This report contains 20

technical papers presented at this San Diego, California workshop in September, 1992. Included are papers on performance goals/acceptable damage in seismic design; seismic design procedures and case studies; construction influences on design; seismic isolation and passive energy dissipation; design of irregular structures; seismic evaluation, repair and upgrading; quality control for design and construction; and summaries of working group discussions and recommendations. ATC·16: This project, Development of a 5-Year Plan for Reducing the Earthquake Hazards Posed by Existing Nonfederal Buildings, was funded by FEMA and was conducted by a joint venture of ATC, the Building Seismic Safety Council and the Earthquake Engineering Research Institute. The project involved a workshop in Phoenix, Arizona, where approximately 50 earthquake specialists met to identify the major tasks and goals for reducing the earthquake hazards posed by existing nonfederal buildings nationwide. The plan was developed on the basis of nine issue papers presented at the workshop and workshop working group discussions. The Workshop Proceedings and Five-Year Plan are available through the Federal Emergency

Appendix C, Applied Technology Council ProJects and Report Information

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Management Agency, 500 "C" Street, S.W., Washington, DC 20472.

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ATC-17: This report, Proceedings ofa Seminar and Workshop on Base Isolation and Passive Energy Dissipation, was published under a grant from NSF. Available through the ATe office. (Published 1986,478 pages)

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ABSTRACT: The report contains 42 papers describing the state-of-the-art and state-of-thepractice in base-isolation and passive energydissipation technology. Included are papers describing case studies in the United States, applications and developments worldwide, recent innovations in technology development, and structural and ground motion issues. Also included is a proposed 5-year research agenda that addresses the following specific issues: (1) strong ground motion; (2) design criteria; (3) materials, quality control, and long-term reliability; (4) life cycle cost methodology; and (5) system response. ATC-17-1: This report, Proceedings ofa Seminar on Seismic Isolation, Passive Energy Dissipation and Active Control, was published under a grant from NSF. Available through the ATe office. (Published 1993, 841 pages)

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ABSTRACT: The 2-volume report documents 70 technical papers presented during a two-day seminar in San Francisco in early 1993. Included are invited theme papers and competitively selected papers on issues related to seismic isolation systems, passive energy dissipation systems, active control systems and hybrid systems. ATC-19: The report, Structural Response Modification Factors was funded by NSF and NCEER. Available through the ATe office. (Published 1995,70 pages) ABSTRACT: This report addresses structural response modification factors (R factors), which are used to reduce the seismic forces associated with elastic response to obtain design forces.

The report documents the basis for current R values, how R factors are used for seismic design in other countries, a rational means for decomposing R into key components, a framework (and methods) for evaluating the key components of R, and the research necessary to improve the reliability of engineered construction designed using R factors. A TC-20: The report, Procedures for Postearthquake Safety Evaluation ofBuildings, was developed under a contract from the Califomia Office 'of Emergency Services (OES), Califomia Office of Statewide Health Planning and Development (OSHPD) and FEMA. Available through the ATC office (Published 1989, 152 pages) ABSTRACT: This report provides procedures and guidelines for making on-the-spot evaluations and decisions regarding continued use and occupancy of earthquake damaged buildings. Written specifically for volunteer structural engineers and building inspectors, the report includes rapid and detailed evaluation procedures for inspecting buildings and posting them as "inspected" (apparently safe), "limited entry" or "unsafe". Also included are special procedures for evaluation of essential buildings (e.g., hospitals), and evaluation procedures for nonstructural elements, and geotechnical hazards. ATC-20-1: The report, Field Manual: Postearthquake Safety Evaluation of Buildings, was developed under a contract from OES and OSHPD. Available through the ATC office (Published 1989, 114 pages) ABSTRACT: This report, a companion Field Manual for the ATC-20 report, summarizes the postearthquake safety evaluation procedures in brief concise format designed for ease of use in the field. ATC-20-2: The report, Addendum to the ATC-20 Postearthquake Building Safety Procedures was published under a grant from the National Science

Appendix C, Applied Technology council projects and Report Information

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Foundation and funded by the USGS. Available through the ATC office. (Published 1995.94 pages) ABSTRACT: This report provides updated assessment forms. placards. and procedures that are based on an in-depth review and evaluation of the widespread application of the ATC-20 procedures following five earthquakes occurring since the initial release of the ATC-20 report in 1989.

ATC-20-3: The report. Case Studies in Rapid Postearthquake Safety Evaluation of Buildings, was funded by ATC and R. P. Gallagher Associates. Available through the ATC office. (Published 1996, 295 pages) ABSTRACT: This report contains 53 case studies

using the ATC-20 Rapid Evaluation procedure. Each case study is illustrated with photos and describes how a building was inspected and evaluated for life safety, and includes a completed safety assessment form and placard. The report is intended to be used as a training and reference manual for building officials. building inspectors, civil and structural engineers. architects, disaster workers, and others who may be asked to perform safety evaluations after an earthquake. ATC-20-T: The report. Postearthquake Safety Evaluation of Buildings Training Manual was developed under a contract with FEMA. Available through the ATC office. (Published 1993. 177 pages; 160 slides) ABSTRACT: This training manual is intended to facilitate the presentation of the contents of the ATC-20 and ATC-20-1. The training materials consist of 160 slides of photographs. schematic drawings and textual information and a companion training presentation narrative coordinated with the slides. Topics covered include: posting system; evaluation procedures; structural basics; wood frame, masonry. concrete, and steel frame structures;

nonstructural elements; geotechnical hazards; hazardous materials; and field safety. ATC-21: The report. Rapid Visual Screening of Buildings for Potential Seismic Hazards: A Handbook. was developed under a contract from FEMA. Available through the ATC office. (Published 1988. 185 pages) ABSTRACT: This report describes a rapid visual

screening procedure for identifying those buildings that might pose serious risk of loss of life and injury. or of severe curtailment of community services. in case of a damaging earthquake. The screening procedure utilizes a methodology based on a "sidewalk survey" approach that involves identification of the primary structural load resisting system and building materials. and assignment of a basic structural hazards score and performance modification factors based on observed building characteristics. Application of the methodology identifies those buildings that are potentially hazardous and should be analyzed in more detail by a professional engineer experienced in seismic design. ATC-21-1: The report. Rapid Visual Screening of Buildings for Potential Seismic Hazards: Supporting Documentation. was developed under a contract from FEMA. Available through the ATC office. (Published 1988. 137 pages) ABSTRACT: Included in this report are (1) a

review and evaluation of existing procedures; (2) a listing of attributes considered ideal for a rapid visual screening procedures; and (3) a technical discussion of the recommended rapid visual screening procedure that is documented in the ATC-21 report.

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ATC-21-2: The report. Earthquake Damaged Buildings: An Overview of Heavy Debris and Victim Extrication, was developed under a contract from FEMA. (Published 1988.95 pages) ABSTRACT: Included in this report, a

companion volume to the ATC-21 and

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Appendix C, APplied Technology Council projects and Report Information

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ATC-21-1 reports, is state-of-the-art information on (1) the identification of those buildings that might collapse and trap victims in debris or generate debris of such a size that its handling would require special or heavy lifting equipment; (2) guidance in identifying these types of buildings, on the basis of their major exterior features, and (3) the types and life capacities of equipment required to remove the heavy portion of the debris that might result from the collapse of such buildings.

ATC-21-T: The report, Rapid Visual Screening of Buildings for Potential Seismic Hazards Training Manual was developed under a contract with FEMA. Available through the ATC office. (Published 1996, 135 pages; 120 slides)

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ABSTRACT: This training manual is intended to facilitate the presentation of the contents of the ATC-21 report. The training materials consist of 120 slides and a companion training presentation narrative coordinated with the slides. Topics covered include: description of procedure, building behavior, building types, building scores, occupancy and falling hazards, and implementation.

ATC-22: The report, A Handbookfor Seismic Evaluation of Existing Buildings (Preliminary), was developed under a contract from FEMA. Available through the ATC office. (Originally published in 1989; revised by BSSC and published as the NEHRP Handbookfor Seismic Evaluation of Existing Buildings in 1992, 211 pages) ABSTRACT: This handbook provides a methodology for seismic evaluation of existing buildings of different types and occupancies in areas of different seismicity throughout the United States. The methodology, which has been field tested in several programs nationwide, utilizes the information and procedures developed for and documented in the ATC-14 report. The handbook includes checklists, diagrams, and sketches designed to assist the user.

ATC-22-1: The report, Seismic Evaluation of Existing Buildings: Supporting Documentation, was developed under a contract from FEMA. Available through the ATC office. (Published 1989, 160 pages) ABSTRACT: Included in this report, a companion volume to the ATC-22 report, are (I) a review and evaluation of existing buildings seismic evaluation methodologies; (2) results from field tests of the ATC-14 methodology; and (3) summaries of evaluations of ATC-14 conducted by the National Center for Earthquake Engineering Research (State University of New York at Buffalo) and the City of San Francisco.

ATC-23A: The report, General Acute Care Hospital Earthquake Survivability Inventory for California, Part A: Survey Description, Summary of Results, Data Analysis and Interpretation, was developed under a contract from the Office of Statewide Health Planning and Development (OSHPD), State of California. Available through the ATC office. (Published 1991,58 pages) ABSTRACT: This report, completed in 1991, summarizes results from a seismic survey of 490 California acute care hospitals. Included are a description of the survey procedures and data collected, a summary of the data, and an illustrative discussion of data analysis and interpretation that has been provided to demonstrate potential applications of the ATC23 database.

ATC-23B: The report, General Acute Care Hospital Earthquake Survivability Inventory for California, Part B: Raw Data, is a companion document to the ATC-23A Report and was developed under the same contract from OSHPD. Available through the ATC office. (Published 1991, 377 pages) ABSTRACT: Included in this report, completed in 1991, are tabulations of raw general site and

Appendix C, APplied TeChnology council proJects and Report Information

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SEISMIC EVALUATION AND RETROFIT OF CONCRETE BUILDINGS

building data for 490 acute care hospitals in California. ATC·24: The report. Guidelines for Seismic Testing of Components of Steel Structures. was jointly funded by the American Iron and Steel Institute (AIS!). American Institute of Steel Construction (AISC). National Center for Earthquake Engineering Research (NCEER). and NSF. Available through the ATC office. (Published 1992. 57 pages)

ABSTRACT: This report. completed in 1992. provides guidance for most cyclic experiments on components of steel structures for the purpose of consistency in experimental procedures. The report contains recommendations and companion commentary pertaining to loading histories. presentation of test results. and other aspects of experimentation. The recommendations are written specifically for experiments with slow cyclic load application. ATC·2S: The report. Seismic Vulnerability and Impact of Disruption of Lifelines in the Conterminous United States. was developed under a contract from FEMA. Available through the ATC office. (Published 1991. 440 pages)

ABSTRACT: Documented in this report is a national overview of lifeline seismic vulnerability and impact of disruption. Lifelines considered include electric systems. water systems. transportation systems. gas and liquid fuel supply systems. and emergency service facilities (hospitals. fire and police stations). Vulnerability estimates and impacts developed are presented in terms of estimated first approximation direct damage losses and indirect economic losses. ATC·2S·1: The report. A Model Methodology for Assessment of Seismic Vulnerability and Impact of Disruption of Water Supply Systems. was developed under a contract from FEMA. Available through the ATC office. (Published 1992. 147 pages)

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ABSTRACT: This report contains a practical methodology for the detailed assessment of seismic vulnerability and impact of disruption of water supply systems. The methodology has been designed for use by water system operators. Application of the methodology enables the user to develop estimates of direct damage to system components and the time required to restore damaged facilities to preearthquake usability. Suggested measures for mitigation of seismic hazards are also provided.

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A TC·28: The report. Development of Recommended Guidelines for Seismic Strengthening of Existing Buildings. Phase I: Issues Identification and Resolution. was developed under a contract with FEMA. Available through the ATC office. (Published 1992. 150 pages)

ABSTRACT: This report identifies and provides resolutions for issues that will affect the development of guidelines for the seismic strengthening of existing buildings. Issues addressed include: implementation and format. coordination with otber efforts. legal and political. social. economic. historic buildings. research and technology. seismicity and mapping. engineering philosophy and goals. issues related to the development of specific provisions. and nonstructural element issues. ATC·29: The report. Proceedings of a Seminar and Workshop on Seismic Design and Performance of Equipment and Nonstructural Elements in Buildings and Industrial Structures. was developed under a grant from NCEER and NSF. Available through the A TC office. (Published 1992. 470 pages)

ABSTRACT: These Proceedings contain 35 papers describing state-of-the-art technical information pertaining to the seismic design and performance of equipment and nonstructural elements in buildings and industrial structures. The papers were presented at a seminar in Irvine. California in 1990. Included are papers describing current practice. codes and regulations; earthquake performance; analytical

Appendix G. Applied Technology CounCil Projects and Report Information

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SEISMIC EVALUATION AND RETROFIT OF CONCRETE BUILDINGS

and experimental investigations; development of new seismic qualification methods; and research, practice, and code development needs for specific elements and systems. The report also includes a summary of a proposed 5-year research agenda for NCEER. ATC-3D: The report, Proceedings of Workshop for Utilization ofResearch on Engineering and Socioeconomic Aspects of 1985 Chile and Mexico Earthquakes, was developed under a grant from NSF. Available through the ATC office. (Published 1991,113 pages)

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ABSTRACT: This report documents the fmdings

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of a 1990 technology transfer workshop in San Diego, California, co-sponsored by ATC and the Earthquake Engineering Research Institute. Included in the report are invited papers and working group recommendations on geotechnical issues, structural response issues, architectural and urban design considerations, emergency response planning, search and rescue, and reconstruction policy issues.

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ATC-31: The report, Evaluation of the Peiformance of Seismically Retrofitted Buildings, was developed under a contract from the National Institute of Standards and Technology (NIST, formerly NBS) and funded by the U. S. Geological Survey. Available through the ATC office. (Published 1992, 75 pages) ABSTRACT: This report summarizes the results from an investigation of the effectiveness of 229 seismically retrofitted buildings, primarily unreinforced masonry and concrete tilt-up buildings. All buildings were located in the areas affected by the 1987 Whittier Narrows, California. and 1989 Loma Prieta, California, earthquakes.

ATC-32: The report,lmproved Seismic Design Criteria for California Bridges: Provisional Recommendations, was funded by the California Department of Transportation (Caltrans). Available

through the ATC office. (Published 1996,215 pages) ABSTRACT: This report provides recommended revisions to the current Caltrans Bridge Design Specifications (BDS) pertaining to seismic loading, structural response analysis, and component design. Special attention is given to design issues related to reinforced concrete components, steel components, foundations, and conventional bearings. The recommendations are based on recent research in the field of bridge seismic design and the p.erformance of Caltrans-