REPORT NO.

UCB/EERC·88/05

MAY 1988

PB91-217968

EARTHQUAKE ENGINEERING RESEARCH CENTER

EXPERIMENTAL EVALUATION OFSEISMIC ISOLATION OF A9-STORYBRACED STEEL FRAMESUBJECT TO UPLIFT

by

M. C. GRIFFITH

J. D. AIKEN

J.M. KELLY

~~~..... Report to the National Science Foundation

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For sale by the National Technical InformationService, U.S. Department of Commerce,Springfield, Virginia 22161

See back of report for up to date listing ofEERC reports.

DISCLAIMERAny opinions, findings, and conclusions orrecommendations expressed in this publica­tion are those of the authors and do not nec­essarily reflect the views of the NationalScience Foundation or the Earthquake Engi­neering Research Center, University of Cali­fornia at Berkeley

50272-101

REPORT DOCUMENTATION 11. REPORT NO•.PAGE NSF/ENG-88042 I~

3. PB91""!217968

4. Title and Subtitle

Experimental Evaluation of Seismic Isolation of a 9-storyBraced Steel Frame Subject to Uplift

7. Author(s)

M.C. Griffith, I.D. Aiken, and J.M. Kelly9. Performing Organization Name and Address

Earthquake Engineering Research CenterUniversity of California, Berkeley1301 S 46th St.Richmond, CA 94804

12. Sponsoring O...anizatlon Name and Address

National Science Foundation1800 G. St. NWWashington, DC 20550

15. Supplementary Notes

!S. Report Date

Mav 1988

S. Performlna O....nlzatlon Rept. No.

UCB/EERC-88/0510. ProJect/Task/Work Unit No.

11. Contrad(C) or Grant(G) No.

(C)

(G) ECE-8414036

13. Ty~ of Report & Period Covered

14.

16. Abstract (Limit: 200 words)

In the second phase of an exper~tal study of base isolation of medium-rise buildingssubject to column uplift, earthquake simulator tests were performed on a 1/4-scale 9­story braced steel frame structure with height to width ratio of 1.59,·for two types ofbase isolation bearings, neoprene and natural rubber with lead plug, against a wide rangeof earthquake ground motions.

The study found that base isolation of medium-rise structures provides significant reduc­tions in base shear and story accelerations. Both the neoprene and lead-plug bearingsproved to be effective isolators. The neoprene bearings did not provide as much dampingas the lead-plug bearings, but did not experience any significant change in stiffnesswhile the lead-plug bearing shear stiffness decreased by 50% after many cycles of dis­placement. The lead-plug bearings also tended to excite more higher mode response inthe structure than the neoprene bearing isolators.

Comparison of the test results with response spectrum analysis showed that the latteris an effective technique for determining the maximum responses of a base-isolated struc­ture. The accuracy of the technique is limited by the accuracy of the computer modelof the structure and, more important, it is limited by the accuracy of the response (ordesign) spectrum. .

The SEAONC design formula for calculating bearing displacements in base-isolated struc-tures was shown to be, in general, conservative when using the velocity related coefficients ~

17. Document Analysis a. Descriptors

isolation bearingsneoprenenatural rubber

b. Identifiers/Open.Ended Terms

response spectrumstiffnessshear stiffness

c. COSATl Field/Group

21. No. of Pages

lLi<S:18. Availability Statemen~

Release Unlimited

19. Security Class (This Report)

unclassified.-====.:==.::.::'-------+---------20. Security Class (This Page) 22. Price

unclassified(See ANSI-Z39.18) $ .. Instruct/ons on R........

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OPTIONAL FORM 272 (4--77)(Formerly NTIS-35)Department of Commerce

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EXPERIMENTAL EVALUATION OF SEISMIC ISOLATION

OF A 9-STORY BRACED STEEL FRAME

SUBJECT TO UPLIFT

by

M. C. Griffith

I. D. Aiken

. J. M. Kelly

Report No. UCB/EERC-88/05

Earthquake Engineering Research Center

College of Engineering

University of California, Berkeley

May 19S8

I'

-/l-e-

ABSTRACT

This report presents the results of the second phase of an experimental study of

base isolation of medium-rise buildings subject to column uplift. This phase of the

research consisted of earthquake simulator tests on a 1/4-scale 9-story braced steel

frame structure with height to width ratio of 1.59. The main objectives of this study

were to:

(1) evaluate the feasibility of base isolation for medium-rise structures subject to

column uplift during severe seismic loads;

(2) evaluate the relative effectiveness of two types of base isolation bearings,

neoprene and natural rubber with lead plug, against a wide range of earthquake

ground motions; and

(3) evaluate the effectiveness of the response spectrum method for predicting max­

imum bearing displacement and base shear.

The test results were compared with values given by the tentative base isolation

design provisions proposed by the seismology committee of SEAONC.

The study found that base isolation of medium-rise structures provides

significant reductions in base shear and story accelerations. Both the neoprene and

lead-plug bearings proved to be effective isolators, however, the neoprene bearings did

not provide as much damping as the lead-plug bearings. On the other hand, the

neoprene bearings did not experience any significant change in stiffness while the lead­

plug bearing shear stiffness decreased by 50% after many cycles of displacement. The

lead-plug bearings also tended to excite more higher mode response in the structure

than the neoprene bearing isolators.

Comparison of the test results with the response spectrum analysis showed that

the response spectrum method is an effective technique for determining the maximum

- ii -

responses of a base-isolated structure. However, the accuracy of the technique is lim­

ited by the accuracy of the computer model of the structure and, more important, it is

limited by the accuracy of the response (or design) spectrum.

Finally, the SEAONC design formula for calculating bearing displacements in

base-isolated structures was shown to be, in general, conservative when using the velo­

city related coefficient Av • The acceleration related coefficients are less conservative,

nonconservative in fact for low frequency ground motions, because they are poor indi­

cators of ground motion magnitude for structures with periods in the constant velo­

city region of the ground motion spectra.

- iii -

ACKNOWLEDGMENTS

The research reported herein was supported by the National Science Foundation

under Grant No. ECE-8414036 and was conducted at the Earthquake Simulator

Laboratory of the University of California at Berkeley. The views and conclusions

expressed in this report are those of the authors and not necessarily those of the

National Science Foundation. Professor James Kelly was the principal investigator for

this project.

The authors would like to thank the National Science Foundation for its support,

especially Dr. Eggenberger, and Oil States Industries in Texas for providing the base

isolation bearings.

The staff of the Earthquake Engineering Research Center, especially Messrs. D.

Clyde, I. Van Asten and Drs. J. Dimsdale, C. Dang, and B. Bolt provided invaluable

assistance and advice over the course of the experimental work.

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Table of Contents

ABSTRACT .ACKNOWI.-EDGMENTS iiiTABLE OF CONTENTS ivLIST OF TABLES viLIST OF FIGURES vii

1. INTRODUCTION 1

2. E:x:PERIMENTAL MODEL 22.1 Model Details 2

3. BASE ISOLATION BEARINGS 43.1 Neoprene Bearings 43.2 Lead-Plug Bearings 4

4. TEST PROGRAM FOR BASE-ISOLATED MODEL 64.1 Dynamic Test Program 64.2 Earthquakes used in Dynamic Test Program 8

5. TEST RESULTS FOR MODEL ON NEOPRENE BEARINGS 105.1 Free Vibration Test Results 105.2 Harmonic Vibration Test Results 105.3 White Noise Vibration Test Results 115.4 Discussion of the Preliminary Test Results 115.5 Earthquake Motion Test Results 12

6. TEST RESULTS FOR MODEL ON LEAD-PLUG BEARINGS 166.1 Free Vibration Test Results 166.2 Harmonic Vibration Test Results 166.3 White Noise Vibration Test Results 176.4 Discussion of the Preliminary Test Results 176.5 Earthquake Motion Test Results 186.6 Performance During Column Uplift 19

6.6.1 Bucharest Tests 196.6.2 EI Centro Tests 206.6.3 Mexico City Tests 21

- v-

7. RESPONSE SPECTRUM ANALYSIS 227.1 Experimental and Theoretical Frequencies and Mode Shapes 227.2 Response Spectrum Analysis 24

8. SEAONC BASE ISOLATION DESIGN FORMULA 258.1 Summary of SEAONC Design Procedure 258.2 Comparison of Experimental and Design Displacements 26

9. IMPLICATIONS OF THE TEST RESULTS 30

REFERENCES 33TABLES 35FIGURES 48

- vi -

List of Tables

Table Page

2.1 Similitude Scale Factors 362.2 Instrumentation and Model Responses 37

4.1 Preliminary Tests of Steel Model on Neoprene Bearings 384.2 Earthquake Tests of Steel Model on Neoprene Bearings 394.3 Preliminary Tests of Steel Model on Lead-Plug Bearings 404.4 Earthquake Tests of Steel Model on Lead-Plug Bearings 414.5 Earthquake Signals Used in Tests 42

5.1 Preliminary Shaking Tests, Neoprene Bearings 435.2 Comparison of Results at 100% Shear Strain 43

6.1 Preliminary Shaking Tests, Lead-Plug Bearings 43

7.1 Cross-Section Properties for Steel Frame 447.2 Comparison of Experimental and Analytical Results 457.3 Response Spectrum Analysis and Experimental Results 46

8.1 Design Code and Experimental Bearing Displacements 47'

- vii -

List of Figures

Figure Page

2.1 Base-Isolated 9-Story Steel Frame 492.2 Loading Conditions for Steel Frame 502.3 Steel Model Instrumentation Diagram ,. 51

3.1 Neoprene Bearing Design 533.2 Dynamic Shear Stiffness vs. Shear Strain for Neoprene Bearings 543.3 Lead-Plug Bearing Design 553.4 Dynamic Shear Stiffness vs. Shear Strain for Lead-Plug Bearings 56

4.1 Plot of White Noise Table Displacement Motion 574.2 Normalized Real-Time Earthquake Record

and its Fourier Amplitude 58

5.1 Free Vibration Test Log-Dec. Curve, Neoprene Bearings 665.2 Fourier Amplitude of Roof Acceleration

for Free Vibration Test, Neoprene Bearings 665.3 Sine Test Transmissibility Plot, Neoprene Bearings 675.4 Sine Test Hysteresis Loops, Neoprene Bearings 685.5 Fourier Amplitude of Roof Acceleration

for White Noise Test, Neoprene Bearings 695.6 Fourier Amplitude of Bearing Displacement

for White Noise Test, Neoprene Bearings 695.7 Peak Acceleration Profiles, Neoprene Bearings 705.8 Story Accelerations, Neoprene Bearings 725.9 Isolation System Hysteresis Loops During

Earthquake Tests, Neoprene Bearings 80

6.1 Fourier Amplitude of Roof Accelerationfor Free Vibration Test, Lead-Plug Bearings 88

6.2 Sine Test Transmissibility Plot, Lead-Plug Bearings 886.3 Sine Test Hysteresis Loops, Lead-Plug Bearings 896.4 Fourier Amplitude of Roof Acceleration

for White-Noise Test, Lead-Plug Bearings 906.5 Fourier Amplitude of Bearing Displacement

for White-Noise Test, Lead-Plug Bearings 906.6 Peak Story Accelerations, Lead-Plug Bearings 91

- viii -

6.7 Story Accelerations, Lead-Plug Bearings 936.8 Isolation System Hysteresis Loops During

Earthquake Tests, Lead-Plug Bearings 1016.9 Effect of Earthquake Tests on Lead-Plug Bearing

Dynamic Shear Stiffness 1096.10 Peak Acceleration Profiles for Bucharest Tests,

Lead-Plug Bearings 1106.11 Column Uplift Displacement Time Histories

for Bucharest Tests, Lead-Plug Bearings 1116.12 Fourier Amplitude of Roof Acceleration During

Bucharest Tests, Lead-Plug Bearings 1126.13 Individual Bearing Hysteresis Loops With Column Uplift

for Bucharest Test, Lead-Plug Bearings 1136.14 Isolation System Hysteresis Loops With Column Uplift

for Bucharest Test, Lead-Plug Bearings 1146.15 Peak Acceleration Profiles for EI Centro Tests,

Lead-Plug Bearings 1156.16 Column Uplift Displacement Time Histories

for EI Centro Tests, Lead-Plug Bearings 1166.17 Individual Bearing Hysteresis Loops With Column Uplift

for EI Centro Test 1176.18 Isolation System Hysteresis Loops With Column Uplift

for EI Centro Test 1186.19 Peak Acceleration Profiles for Mexico City Tests,

Lead-Plug Bearings 1196.20 Column Uplift Displacement Time Histories

for Mexico City Tests, Lead-Plug Bearings 1206.21 Individual Bearing Hysteresis Loops With Column Uplift

for Mexico City Test 1216.22 Isolation System Hysteresis Loops With Column Uplift

for Mexico City Test 122

7.1 Finite Element Model for Braced Steel Frame 1237.2 Experimental and Analytical Mode Shapes 124

8.1 Response Spectrum of ATC Modified Taft Ground Motion 125

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1. INTRODUCTION

Base isolation is a strategy for reducing the effects of earthquake ground motions

on a building by uncoupling the building from the two horizontal components of

earthquake ground motion while simultaneously supporting the vertical weight of the

structure. This technique is becoming widely accepted for providing additional struc­

tural strength against earthquake ground motions for short, stiff buildings up to

about 5 stories in height [1]. However, the feasibility of base isolation for taller, less

stiff buildings has only recently begun to be investigated (2). It has generally been

accepted that the longest feasible period for a base-isolated structure is about 2 to 3

seconds and that the increase in period due to base isolation should be at least 1

second. Thus, taller structures are, in general, less practical to base isolate.

Two factors which must be considered when studying the feasibility of base isola­

tion for taller structures are: (1) the fixed-base period of the structure and (2) the pos­

sibility of column uplift due to the overturning moment caused by horizontal ground

motion. Column uplift is not accommodated by the usual base-isolation device [3].

The main purpose of this research was to investigate the feasibility of base isola­

tion for structures which tend to experience column uplift and to study the behavior

of elastomeric bearing pads used to base isolate a medium-rise structure during such

loadings. In order to do this earthquake simulator tests were performed on a 1/4-scale

model of a nine-story braced steel frame structure. The base-isolated model was

found to uplift off the outer bearings under extreme earthquake loadings even though

the isolation scheme significantly reduced the peak values of base shear and accelera­

tion from those seen in fixed-base tests. The response of the base-isolated structure

was nearly that of a rigid body supported on a horizontally flexible system of bear­

ings, thereby providing a fairly simple problem to model analytically.

- 2 -

2. EXPERIMENTAL MODEL

2.1 Model Details

The earthquake simulator experiments were carried out on a nine-story three bay

welded steel frame model (Figure 2.1). The lowest story of the model was 4 feet high

and the others were 3 feet high. The top of the model was approximately 29 feet

above the top of the isolation bearings and the width of the model was 18 feet. The

aspect ratio (height-to-width) was sufficiently large (1.59) that the model experienced

uplift in the corner columns with moderate accelerations in the structure.

The model was not specifically designed for this test series but was adapted from

that of a previous series of uplift tests [4J. The model represented a section in the

weak direction of a typical steel-frame building at approximately 1/4-scale. The addi­

tional mass necessary for similitude requirements (Table 2.1) was provided by concrete

blocks at each floor level. The total weight of the structure and the concrete blocks

was 122 kips, but the loading was rearranged after the structure was tested on the

neoprene bearings (Figure 2.2). This was done to raise the center of gravity to

encourage column uplift with the subsequent tests since no uplift had occurred with

the neoprene bearings. The two rows of columns were bolted to stiff wide flange sec­

tions (W8x31) which ran the length of the base of the model, and with cross beams

these represented the base mat of a prototype structure. The base isolators were

placed between these W8x31 beams and the shaking table.

The test structure was instrumented with a combination of accelerometers, linear

potentiometers (LPs), direct current linear voltage differential transformers (DeDTs),

and force transducers to record the response of the structure to all input loads. The

force transducers were used to record axial force, shear force and moment immediately

below the rubber bearings. Thus, the support reactions were measured by the force

transducers.

- 3 -

A total of 83 channels of data were recorded for each test; 12 channels recorded

shaking table response and 71 channels recorded model response. Figure 2.3 shows the

instrumentation and Table 2.2 lists the instruments and the corresponding model or

table response. One accelerometer was placed on each floor to measure the horizontal

acceleration of that floor. An accelerometer was also placed on top of each end of the

steel frame to measure vertical acceleration and an accelerometer was placed at the

top of each of column NOI and SOl to measure horizontal accelerations of the roof

perpendicular to the direction of table shaking. In addition, an accelerometer was

placed at each corner of the model above the bearings to measure the vertical accelera­

tion of the model at its base. These accelerometers helped determine when the model

uplifted from its bearing supports. Two DCDTs were located at each corner of the

model (NOl, N02, SOl & S02); one between the shaking table and the top of the

model, the other between the W8X3l wide flange section and the top of the model.

These also helped to detect column uplift. Thirteen LPs were used to measure dis­

placement of the model. Two LPs were used to record the relative displacement of the

rubber bearings under columns 801 and 802. One LP on each floor recorded the

total horizontal displacement at those levels and two LPs were used to record the rela­

tive displacement of the model perpendicular to the direction of input motion of the

shaking table.

Each bearing was supported by a force transducer [5], from which time series

records of the forces acting on the bearing were collected. The shear force at the base

of the model structure was calculated for all excitations using the data acquired from

these force transducers.

- 4 -

3. BASE ISOLATION BEARINGS

The isolation system consisted of eight elastomeric bearings of multilaminate con­

struction with a bearing located under each column of the steel frame. Two types of

elastomers were used for the bearings in this study: neoprene and natural rubber.

Damping in the isolation system was enhanced by additives to the neoprene rubber

compound while the natural rubber bearings provided for the addition of a lead core.

3.1 Neoprene Bearings

The neoprene bearings were 6-inches square in plan with 6 layers of 3/8-inch

thick neoprene, 5 steel reinforcing shims of l/8-inch thickness, and I-inch thick top

and bottom end plates (Figure 3.1). The bearings were designed with 4 dowel holes

on the top and bottom end plates to provide shear connections between the isolation

system and the structure. The dowel holes were fitted by 3/4-inch long tapered pins

to accommodate column uplift while still providing a transfer of shear force.

The high nonlinearity of the neoprene bearing shear stiffness is illustrated by Fig­

ure 3.2. The neoprene bearings had a shear stiffness of about 2.1 kipslinch at 50%

rubber shear strain. The shear stiffness at 2% shear strain was approximately twice

as large as the 50% shear strain stiffness. Large stiffness at small shear strain is

desired in isolation systems so that isolated structures will perform similarly to con­

ventional structures under wind or small earthquake loads.

3.2 Lead-Plug Bearings

The lead-plug bearings were geometrically similar to the neoprene bearings except

that each lead-plug bearing had a 1.25-inch diameter hole through its center (Figure

3.3). This hole was filled by pressing a cylinder of lead into it. The natural rubber

compound used in these bearings is designated EDS 39 [6] by the Malaysian Rubber

Producers Research Association (MRPRA). It is a high-strength lightly-filled rubber

which has a shear modulus of approximately 100 psi at 50% shear strain. The damp­

ing of the rubber is relatively low; the equivalent viscous damping ratio at 50% shear

- 5 -

strain is in the range of 5-7%. However, with the addition of a lead plug the

equivalent viscous damping ratio for a bearing at 50% shear strain is in the range of

20-25%.

The lead-plug bearings had the shear stiffness properties shown in Figure 3.4.

Note the increased stiffness due to the presence of the lead plug. In the absence of the

lead plug these bearings had a stiffness of about 1.6 kips/inch at 50% shear strain

which provided an isolation frequency for the model of about 1 Hz. This frequency

was too low to generate uplift forces at the corner columns for this model since the

isolation system did not transmit enough acceleration to the model to generate tension

in the corner columns. In order to increase the likelihood of uplift, lead plugs were

inserted in the central holes of the four bearings under the center columns. Lead

yields at a stress of approximately 1500 ksi which corresponds to 1.8 kips shear load

in the lead plug, and at 50% shear strain the effective contribution of each lead' plug

to the stiffness was 1.6 kips/inch. With four bearings filled with lead the isolation fre­

quency at 50% shear strain rose to 1.24 Hz. Another step taken to encourage column

uplift was the shifting of some of the concrete blocks upward in the structure (Figure

2.2 - Loading Condition No.2). This raised the center of gravity and increased the

overturning moments for similar levels of shaking table input.

- 6 -

4. TEST PROGRAM FOR BASE-ISOLATED MODEL

4.1 Dynamic Test Program

The test program for the structure on each set of isolation bearings consisted of

free vibration tests, harmonic base input tests, white noise input tests, and earthquake

input tests. The first three types of tests were performed to determine the dynamic

characteristics of the model and to evaluate the effectiveness of existing analytical

methods for predicting these quantities.

The free vibration test was performed to determine the fundamental frequency

and the approximate equivalent viscous damping ratio of the model. This test was

performed by enforcing an initial lateral displacement in the bearings and releasing

the structure from this position. A shear force of approximately 5 kips was applied to

the model just above the top of the bearings by pulling the structure there. This load

was applied with a cable and a turnbuckle connected by shackles to the cable. In line

with the cable was a short length of 5/8-inch diameter threaded rod which, after the

lateral load was applied, was cut using bolt cutters. This instantly released the struc­

ture from its displaced position. Story accelerations and displacements, bearing dis­

placements and column forces of axial, shear, and moment were monitored as the

structure went through its transient response ending in static equilibrium.

An approximate value for the equivalent viscous damping ratio was estimated

from the column shear force measurements taken just above the rubber bearings. The

natural frequency of the model was estimated directly from the shear force time his­

tory by counting the number of zero crossings and it was also estimated by taking the

fast Fourier transform (FFT) of the shear force time history and noting the frequen­

cies associated with the peaks in the Fourier spectra.

The harmonic vibration test determined the fundamental frequency and the

approximate viscous damping ratio of the structure. The model was loaded dynami­

cally with sinusoidal base input of a fixed frequency. The model was subjected to this

- 7 -

input and once the model reached a steady-state harmonic motion, data from the

table and the model were monitored for three seconds. This test procedure was

repeated for a range of frequencies around the expected natural frequency of the struc­

ture. The peak story acceleration normalized to peak table acceleration was plotted

against frequency, and from these plots the fundamental frequencies were estimated.

These quantities were also estimated by taking FFTs of the story acceleration and

bearing displacement time histories.

The white noise vibration test determined the modal frequencies of the structure.

The test consisted of subjecting the isolated model to white noise base displacement in

the frequency range of 0-20 Hz. This motion was applied for 30 seconds during

which the response quantities of floor accelerations and displacements, relative bearing

displacements and column forces of axial, shear, and moment were monitored.

The FFT of ideal white noise input over the range of frequency of 0-20 Hz

should have a constant Fourier amplitude for that range of frequency. Note that in

Figure 4.1, which shows the actual table displacement time history and the FFT of

the table displacement time series, the frequency content is reasonably constant only

for the frequency range of 0-10 Hz. Although the input base displacement was nqt

true white noise input, for the purposes of these tests it was sufficient to enable esti­

mation of the modal frequencies below 10 Hz by taking FFTs of the model roof

acceleration and relative bearing displacement time histories.

The test program for each set of bearings concluded with extensive testing of the

model for eight different earthquake inputs (described in Section 4.2) in order to evalu­

ate the effectiveness of the different bearings in isolating the structure from earthquake

ground motions. The earthquake inputs were varied in amplitude (with respect to

peak horizontal base acceleration) to study the effect of bearing displacement and

column uplift on the effectiveness of the base isolation system. The test programs for

each set of bearings are given in Tables 4.1 to 4.4. The table span refers to the

- 8 -

amplitude of shaking table displacement. A span setting of 1000 corresponds to ±5

inches of table displacement (the maximum possible). Fractions of span 1000 setting

vary approximately linearly so that a span setting of 500 corresponds to a peak input

table displacement of approximately 2.5 inches.

4.2 Earthquakes Used in Dynamic Test Program

The isolated models were tested for response to eight different earthquake input

motions. The types of earthquakes varied from those with predominantly low fre­

quency content, like the 1985 Mexico City Earthquake, to earthquakes with predom­

inantly high frequency content, like the 1957 San Francisco Earthquake. The follow­

ing earthquake ground motions were used for input [7,8,9,10]:

(1) Imperial Valley Earthquake (EI Centro) of May 18, 1940 - SOOE component

(2) Kern County Earthquake (Taft Lincoln School Tunnel) of July 21, 1952 - S69E

component

(3) San Francisco Earthquake (Golden Gate Park) of March 22, 1957 - S80E com­

ponent

(4) Parkfield Earthquake (Cholame, Shandon, Calif. Array No.2) of June 27, 1966 ­

N65E component

(5) San Fernando Earthquake (Pacoima Dam) of February 9, 1971 - S14W com­

ponent

(6) Bucharest Earthquake (Building Research Institute) of March 7, 1977 - EW com­

ponent

(7) Miyagi-Ken-Oki Earthquake (Tohoku University) of June 12, 1978 - SOOE com­

ponent

(8) Mexico City Earthquake (Mexico City Station SCT) of September 19, 1985 ­

S60E component

- 9 -

The records were time scaled by a factor of the square root of four to satisfy

similitude requirements for the 1/4-scale model. For example, an earthquake record

which lasted 60 seconds in real time would have lasted 30 seconds during the earth­

quake simulator tests on the 1/4-scale model. A list of the earthquakes used in the

testing program and the symbols subsequently used to refer to each earthquake in the

rest of this report are given in Table 4.5.

Plots of the real-time earthquake ground motions normalized to 19 peak accelera­

tion and their FFTs are given in Figure 4.2. As can be seen in the FFT plots for each

earthquake, there is a wide range of earthquake characteristics represented by this

group. The real-time Mexico City has a frequency content concentrated almost

entirely in the region of 0.5 Hz. The real-time Bucharest signal has a significant

amount of iow frequency content which gradually decreases to near zero at a fre­

quency of about 5 Hz. The real-time EI Centro record has most of its frequency con­

tent between 1 Hz and 3 Hz and the Miyagi-Ken-Oki record has most of its frequency

content around 1 Hz. Parkfield has a frequency content ranging between 0.5 Hz and 3

Hz while the frequency content of the Pacoima Dam record ranges between 1 Hz and 4

Hz. The frequency of the San Francisco record has a peak near 4 Hz and another at

about 7 Hz. The Taft earthquake record has a broad range of frequency (0.5 Hz to 5

Hz).

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5. TEST RESULTS FOR MODEL ON NEOPRENE BEARINGS

5.1 Free Vibration Test Results

Free vibration tests were conducted on the steel model isolated with the neoprene

bearings. An initial displacement of 0.25 inch was a result of the force applied to the

stiffeners directly above the bearings. Recognizing the strong nonlinearity of the bear­

ings, it is important to note the shear strain in the bearings when comparing fre­

quency results with those obtained from other tests. Thus, the 1.5 Hz natural fre­

quency indicated by this test was at an initial shear strain level of 11%. The approxi­

mate equivalent viscous damping obtained from the log decrement curve (Figure 5.1)

was 11% of critical and the second lateral mode frequency, obtained from the Fourier

amplitude plot of the roof acceleration time history, was 5.7 Hz (Figure 5.2).

5.2 Harmonic Vibration Test Results

The model was then subjected to harmonic base motions at a variety of frequen­

cies ranging from 1.0 Hz to 6.0 Hz. The input frequencies are given in Table 4.1.

Peak lateral floor acceleration for each level of. the model was normalized to peak

lateral table acceleration at each frequency of input and was plotted against frequency

(Figure 5.3). From these plots the fundamental lateral frequencies were estimated.

These frequencies were confirmed by taking FFTs of the story acceleration and bear­

ing displacement time histories. The fundamental lateral frequency was estimated to

be 1.05 Hz at a peak shear strain of 65%. The same test conducted at a shear strain

level of 8% gave a fundamental frequency of 1.4 Hz and a second mode lateral fre­

quency of 5.2 Hz.

The approximate equivalent viscous damping ratio was determined by plotting

hysteresis loops (Figure 5.4) for bearing shear force versus relative horizontal bearing

displacement from which the loss angle (8) of the rubber bearing was obtained and

from which the approximate equivalent viscous damping ratio (€) was calculated using

the equations:

- 11 -

4Ac0= sin-1 -- and e= 0.5 tan 0,1rAr

where Ac is the area of one cycle of the hysteresis loop and Ar is the area of the cir­

cumscribing rectangle. From these equations, the equivalent viscous damping was

estimated to be 9.9% at 8% maximum shear strain and 7.6% at 65% maximum shear

strain.

5.3 White Noise Vibration Test Results

The base-isolated structure was then subjected to the white noise base input

motion described in Section 4.1. By taking FFTs of the 9th story horizontal accelera­

tion and the bearing shear force time histories (Figures 5.5 and 5.6), the modal fre-

quencies were estimated. The peak magnitude of bearing displacement during this test

corresponded to a peak shear strain in the rubber of 6%. From this test, the funda­

mental lateral frequency was estimated to be 1.53 Hz and the 2nd mode frequency to

be 5.26 Hz.

5.4 Discussion of Preliminary Tests

The preliminary test results are summarized in Table 5.1, but the decrease in

stiffness with increasing shear strain that the rubber experienced made direct com­

parisons between the free vibration, harmonic vibration and white noise vibration

tests difficult. However, as a first step, the relation

(5.1)

was assumed between the resonant frequency (fres) and the shear stiffness of the rubber

(kh). The term Cp is a proportionality constant which depends on the mass of the

system. The shear stiffness was taken as that given by Figure 3.2 at the maximum

shear strain (Emax) during the test.

Following this simple approach, the free vibration test which gave a fundamental

frequency of 1.5 Hz at 11% shear strain implied a frequency of 1.18 Hz at 100% shear

- 12-

strain. The harmonic test gave a fundamental frequency of 1.05 Hz for a 65% shear

strain and a fundamental frequency of 1.4 Hz at 8% shear strain which implied funda­

mental frequencies of 1.02 Hz and 1.06 Hz, respectively, at 100% shear strain. The

white noise test gave a fundamental frequency of 1.53 Hz at 6% shear strain and this

implied a frequency of 1.13 Hz at 100% shear strain. Thus, the three tests gave

results which were reasonably consistent - assuming Equation 5.1 and the test data for

the bearings given in Figure 3.2. This result is unlike that found during previous

tests on the reinforced concrete structure [2], however, this was probably due to the

higher level of shear strain achieved in these free vibration tests.

Af3 a first order estimation of the natural frequency of the model on the neoprene

bearings the single degree-of-freedom equation:

f=_l~ ~211" V ~

(5.2)

was used; where m = the mass of the structure = 122 kips and the value for kh at

100% shear strain is given by Figure 3.2. The results are presented in Table 5.2.

The results indicate that the natural frequency of the isolated structure deter­

mined by the free-vibration test was about 6% higher than that given by the simple

rigid body theory, the harmonic test frequency was about 6% lower, and the white

noise test result was about 2% higher than the rigid body result.

5.5 Earthquake Motion Test Results

The model supported on the neoprene bearings was designed primarily to be a

1/4-scale model of a building isolated against strong ground motion in firm soil condi­

tions. The isolated natural frequency of the model was approximately 1 Hz for large

bearing displacements - corresponding to approximately 0.5 Hz (T = 2 sec) for the

full-scale building represented.

- 13 -

The isolated model was subjected to the time-scaled earthquakes listed in Table

4.2. Each earthquake was input at a level of peak table acceleration sufficient to cause

maximum bearing shear strains greater than 50%. It was particularly hoped that the

response of the structure be observed during column uplift, especially since the design

of the bearing connections used in these tests differed from the design used in the pre­

vious study [2}. The connections used in these tests were designed to accommodate up

to 0.75 inch of uplift before the base of the column would disengage from the top of

the bearing.

The key points of interest which are discussed in the riext section include:

(1) the effectiveness of the neoprene bearings at reducing the levels of acceleration

from those of the table acceleration;

(2) the degree to which the isolated structure responded in its first mode;

(3) the performance of the bearing connections near or during column uplift; and

(4) the effect of vertical ground motions on the response of the structure.

By studying the acceleration profiles presented in Figure 5.7 for each of the

different earthquakes, the effectiveness of the isolation system for the different ground

motions was seen. The profiles are plots of maximum horizontal story acceleration for

each level divided by the maximum horizontal table acceleration versus the story

height. The peak story acceleration values used for these plots did not necessarily all

occur at the same time. However, subsequent analysis showed that the peak values

occurred at times very close to each other. The values used were the maximum

accelerations for each floor over the duration of the earthquake motion. Thus, the

profiles are really envelopes defining the maximum value of the acceleration at each

story for the earthquake signal.

The effectiveness of the isolation system depended greatly on the frequency con­

tent of the earthquake signal. That is, for an earthquake signal rich in frequencies

- 14 -

near the resonant frequency of the isolated structure, the isolation system's

effectiveness was limited and, in fact, if sufficient damping had not been provided in

the isolation system then a significant increase in structure acceleration over ground

acceleration would have resulted. It was also clear that for earthquake signals with

the dominant portion of their frequency content well away from the isolated fre­

quency, the isolation system provided significant reductions in structure accelerations

over ground accelerations, on the order of 1/4 in some cases (San Francisco, for exam­

ple).

Figure 5.8 shows the acceleration time histories of all nine stories superimposed

for each earthquake signal used in this set of tests. For all but the San Francisco sig­

nal, generally, all the stories were moving in phase. This is important since the use of

simple design formulae based on site design response spectra for design of base­

isolated structures implies an assumption of single degree-of-freedom behavior, which

in-phase floor accelerations would help justify.

The performance of the neoprene bearings at all levels of shear strain tested (up

to 114%) was studied and felt to be excellent. The bearings displayed no tendency to .

roll out [11], even at shear strains exceeding 100%, and the shear force versus shear

displacement plots (Figure 5.9) for the combined system of bearings at large shear

strains do not indicate any significant changes in the stiffness properties of the bear­

ings even though the bearings were subjected to a large number of displacement cycles

which exceeded 50% shear strain. It should be noted that the hysteresis loops in Fig­

ure 5.9 are for the entire system of bearings, not an individual bearing. The presence

of the relatively thick top and bottom plates of these bearings was felt to be primarily

responsible for the favorable performance.

In order to ascertain whether the horizontal response of the model structure was

affected by vertical ground motions, the El Centro ground motion was used to excite

the model twice at the same levels of input. For both runs the horizontal table

- 15 -

control was set at a span of 300. In the first case (860627.04) only horizontal motion

was supplied to the shaking table. The peak horizontal acceleration for the table was

0.645g and the peak horizontal acceleration in the model was 0.407g.

In the second case (860627.13) both horizontal and vertical motions were input to

the table. The peak horizontal accelerations in the table and model were O.650g and

0.434g, respectively. It appears from these tests that the addition of vertical motion

had little influence on the horizontal response of the model.

- 16 -

6. TEST RESULTS FOR MODEL ON LEAD·PLUG BEARINGS

After testing was completed on the steel structure isolated with neoprene bearings, the

structure was base isolated with eight natural rubber bearings. The four bearings located

under the interior columns each contained a solid lead core while the central cores of the

four bearings located under the comer columns were hollow. As was done for the struc­

ture on the neoprene bearings, the model was subjected to a set of preliminary dynamic

tests before being tested with earthquake ground motions. The results of these tests are

presented in the following sections.

6.1 Free Vibration Test Results

The free vibration tests indicated that the fundamental frequency of the isolated model

was 2.85 Hz and the second mode lateral frequency was 9.1 Hz (Figure 6.1). The high

shear stiffness of this isolation system meant that the approximate equivalent viscous

damping ratio could not be found from the free vibration tests, The maximum pull-back

force that could be generated resulted in less that 1% initial shear strain, and this strain

was insufficient to allow an analysis of the log-decrement curve for the damping ratio.

6.2 Harmonic Vibration Test Results

The model was then subjected to harmonic base motion at a variety of frequencies

ranging from 1.0 Hz to 1.7 Hz (Table 4.3 lists the input frequencies). The model

responses of peak lateral floor acceleration normalized to peak table acceleration at each

input frequency were plotted against frequency (Figure 6.2). The fundamental frequency

was determined from this plot and also by taking FFTs of the 9th story acceleration time

history and the relative bearing displacement time history.

The fundamental lateral frequency indicated by this test was 1.15 Hz at a peak shear

strain of approximately 26% in the rubber, and the second mode frequency was 5.85 Hz.

Hysteresis loops for bearing shear force versus relative bearing displacement are shown in

Figure 6.3. The equivalent viscous damping for the bearings was calculated directly from

the area of the hysteresis loops and was found to be 6.7% of critical for the bearings

- 17 -

without a lead core and 24% of critical for the bearings with a lead core.

6.3 White Noise Vibration Test Results

The isolated model was then subjected to white noise base motion. By taking FFfs of

the 9th story acceleration time history and the relative bearing displacement time history

and observing the frequencies associated with the peaks in the Fourier spectra plots the

modal frequencies were estimated (Figures 6.4 and 6.5). The first mode frequency was

2.42 Hz and the second mode frequency was 7.5 Hz. The level of peak shear strain in the

rubber for this test was very low, 0.4%.

6.4 Discussion of Preliminary Tests

As was found for the preliminary tests performed with the neoprene bearings, the non­

linearity of the bearing shear stiffness with respect to horizontal bearing displacement made

comparisons of preliminary test results difficult. However, for these tests, the results were

not adjusted for comparison at 100% shear strain since insufficient shear stiffness data

existed for the lead-plug bearings below strain levels of 5%. This problem, however, illus­

trates one of the advantages of a lead-plug isolation system; extremely stiff behavior of the

bearings at small shear strains. This would cause a structure isolated with lead-plug bear­

ings to perform similarly to a fixed-base structure. Unfortunately, the magnitudes of load

which could be applied in the free vibration and white noise tests were insufficient to cause

significant deformation in the lead core so that minimal amounts of information could be

obtained from these two tests.

The bearings were, however, displaced sufficiently during the harmonic vibration test

and those results were adjusted to give an estimate of the isolated frequency at 100% shear

strain. This value was 0.97 Hz and compared favorably with the value of 1.06 Hz given

by Equation 5.2 using the known mass and the stiffness at 100% shear strain.

- 18 -

6.5 Earthquake Motion Test Results

The 1{4-scale steel frame and the lead-plug bearings were subjected to the earthquake

tests listed in Table 4.4. The following discussion is limited to the sequence of tests which

caused maximum rubber shear strains in excess of 50% but did not cause any significant

column uplift (860707.09-860707.16). Structural and bearing behavior during column

uplift will be discussed separately in Section 6.6.

The key points of interest here are:

(1) the effectiveness of the lead-plug isolation system for the variety of earthquake

motions used in these tests;

(2) the degree to which the isolated building responded in the 1st mode; and

(3) the performance of the bearings at large shear strains.

The effectiveness of the isolation system at reducing the accelerations transmitted to

the structure can be seen by studying the story acceleration profiles (Figure 6.6) for each of

the earthquake signals. In general, the isolation system performed best against the highest

frequency ground motions. This is consistent with previous shaking table test results [2].

The acceleration profiles also indicated that the structure responded predominantly in the

first mode, and the plots of the story acceleration time histories were superimposed to help

verify this (Figure 6.7). As was seen previously, all the stories were, in general, moving in

phase with each other and the story acceleration amplitudes were similar for all levels.

The San Francisco signal was the only earthquake motion for which this was not the case.

The San Francisco signal had a significantly higher frequency content than the other signals

so it was most able to excite some higher mode response in the structure.

The performance of the isolation bearings is illustrated by the plot of the shear force

hysteresis loops for the combined system of bearings (Figure 6.8) for each earthquake sig­

nal. Note that the shear force plotted in these loops is the sum of the shear forces in all

the bearings, and this was the structure base shear. It was apparent that, as with the

- 19 -

neoprene bearings, the lead-plug bearings performed extremely well at large shear strains

but in this case, deterioration of the stiffness properties of the bearings containing lead

plugs became evident as testing continued. This is most clearly shown in Figure 6.9 where

the effective stiffness for a lead-plug bearing is plotted versus the number of earthquake

tests which caused at least one cycle of shear strain in excess of 25%. The lead-plug bear­

ing shear stiffness after 36 earthquake tests decreased to approximately 33% of its initial

stiffness. This is not considered to be a problem, however, since in practice an isolation

bearing would not be expected to undergo such a large number of significant displacement

cycles.

6.6 Performance During Column Uplift

In order to study the effect of column uplift on the structure and the isolation system

the Bucharest, El Centro, and the Mexico City earthquake motions were selected and each

was input at increasing magnitudes until significant column uplift was induced. These

ground motions were selected because column uplift could be generated at modest levels of

table input using them.

6.6.1 Bucharest Tests

The sequence of tests using the Bucharest earthquake ground motions had peak table.

accelerations of 0.241g, 0.296g, 0.343g, and 0.348g. Two observations can be made from

the story acceleration profiles (Figure 6.10) for these tests. First, the amplitude of the

profile increased modestly as the input magnitude increased and secondly, the shape of the

profile became more curved with increased input. Significant amounts of column uplift

occurred during the tests with input accelerations of 0.343g and 0.348g and a small amount

of uplift occurred during the 0.296g test (Figure 6.11).

The principal effect of column uplift on the structure appeared to be to increase the

higher mode responses in the structure. This was due to impact of the column base on top

of the bearings when the column came back down after uplifting. Figure 6.12 illustrates

this point. The high frequency responses of the structure were greatest for the earthquake

- 20-

tests during which column uplift occurred (Bucharest 0.348g). This would appear to have

some serious implications for buildings with contents sensitive to high f~quencies.

The effect of column uplift on the bearings was evaluated from individual bearing

hysteresis loops (Figure 6.13) and the combined isolation system hysteresis loops (Figure

6.14). The hysteresis loops for the individual bearings subject to column uplift show that

column uplift affected shear hysteresis loops in two ways. When the column lifted, the

axial force on the bearing was reduced to zero from the static dead load compressive force.

This resulted in a slight change in the shear stiffness of the bearing and shows up in the

extreme left side of the hysteresis loop for bearing NO1. The right hand side of the hys~

teresis loop shows what happened when the axia110ad on the bearing increased dramati~

cally during the extreme lateral bearing displacement associated with column uplift. The

hysteresis loop for bearing NO1 appears temporarily to become unstable and start to roll

over. However, because there was a bearing at the other end of the structure which was in

an axially unloaded state while bearing NOt was experiencing its peak compressive load,

the effect of column uplift was barely felt on the isolation system as a whole. This is

shown.by the stability of the hysteresis loop plot for the complete isolation system (Figure

6.14). Clearly, the action of the bearings in parallel prevented a localized instability from

causing a failure of the isolation system.

6.6.2 El Centro Tests

Unlike the story acceleration profiles for the Bucharest test sequence, the story

acceleration profiles for the EI Centro test sequence did not change significantly in magni­

tude or shape (Figure 6.15). This was probably due to the fact that the effect of the fre­

quencies associated with column uplift was masked by the effect of the higher frequencies

of the El Centro ground motion. The magnitude of column uplift during this test sequence

varied from no uplift for the O.313g test to 0.75 inch for the O.842g test (Figure 6.16). The

effect of column uplift on the bearings is best shown by hysteresis loops for the individual

bearings (Figure 6.17). The E1 Centro earthquake motion caused uplift only at one end of

- 21 -

the structure so the hysteresis loops do not have the symmetric shape of those for the

Bucharest tests (Figure 6.13), although at their extreme left end the same shape occurs.

The shape of the hysteresis loop for the total isolation system again illustrates the stable

nature of the bearings when acting in unison (Figure 6.18).

6.6.3 Mexico City Tests

The story acceleration profiles for the Mexico City sequence of tests are shown in

Figure 6.19. The profiles are similar to those for the Bucharest test sequence, although the

change in profile magnitude is more dramatic for the Mexico City test sequence. It is

worth noting that both the Mexico City and Bucharest ground motions are predominantly

low frequency motions and that only with column uplift would any higher frequency input

be introduced to the base of the structure. The amount of column uplift generated by the

Mexico City 0.219g test was 0.42 inch (Figure 6.20); no significant uplift occurred during

the other tests in this sequence. The effect of column uplift on the structure and isolation

system was identical to that for the Bucharest and El Centro test sequences, and is shown

by the hysteresis loop for a bearing subject to uplift (Figure 6.21) and by the hysteresis

loop for the entire isolation system (Figure 6.22).

- 22-

7. RESPONSE SPECTRUM ANALYSIS

7.1 Experimental and Theoretical Frequencies and Mode Shapes

The 1/4-scale braced steel frame structure was analyzed using the commercial

finite element program IMAGES-3D [12]. The structure was modeled as a two dimen­

sional frame. Beam-column elements were used to model the columns and beams

while truss elements were used to model the bracing. Spring elements were used to

model the bearing shear stiffness and axial stiffness. No rotation was assumed to

occur at the base of the model. The computer model is shown in Figure 7.1 and

Table 7.1 lists the element cross-section properties which were used in the analysis.

The first loading condition (Figure 2.2) was applied to the neoprene bearing base­

isolated structure and the second loading condition was used for the model of the

lead-plug base-isolated structure.

The spring stiffness used to model the bearings corresponded to the axial and

shear stiffness of the bearing system. For this analysis, an axial stiffness of 600

kips/inch was used. Since the shear stiffness of the bearings was sensitive to the

amount of shear strain in the rubber, the effective shear stiffness of the entire isolation

system was divided by four and used for each of the spring stiffnesses in the horizon­

tal direction. The effective stiffness of the neoprene bearing system varied between

14.9 kips/inch and 16.4 kips/inch. The effective shear stiffness of the lead-plug system

varied more; between 9.7 kips/inch and 14.0 kips/inch. The larger variation of

stiffness for the lead-plug system was due in part to degradation of the lead core.

The first three natural frequencies and mode shapes for the horizontal modes

were calculated; the results are presented in Table 7.2. Only the first two modes were

determined experimentally. The analytically determined first and second mode fre­

quencies compare quite closely with the experimental frequencies: the theoretical fre­

quencies slightly overestimate the experimental values. Comparison of the experimen­

tal and analytical mode shapes (Figure 7.2) reveals that the theory gave results which

- 23-

compare well with the experimental results, however, the first mode shape determined

experimentally indicates that the superstructure was more flexible than the theory

predicted _. a result not consistent with the result of analytical frequencies lower than

experimental frequencies.

The modal participation factor for each mode 'i' is defined by

l/JiT M r

PF·=--­I M

1

where

l/Ji = the mode shape vector for mode 'i' ;

M = the mass matrix;

r = the load influence vector; and

M j = the modal mass = l/J? M l/Ji .

The load influence vector is a vector of l's and O's, with the rows corresponding to

horiwntal displacement degrees-of-freedom being 1's, all other rows being O's.

From these equations the modal participation factors for the first three modes

were determined to be 1.08, -0.09, and 0.01, respectively. These values indicate that

the first mode was the predominant mode of response for the base-isolated structure.

This was confirmed by calculating the effective modal weight for each mode 'i I. The

effective modal weight is defined as

where g is the acceleration of gravity. The effective modal weights were determined to

be 199 kips, 0.310 kips, and 0.008 kips, respectively, for the first 3 modes. Thus, the

effective modal weight for the first mode was approximately 99% of the total weight

of the structure. This again suggests that the predominant response of the structure

was in the first mode, and agrees with the experimental results presented in Chapters

- 24-

5 and 6. On the basis of these results it was concluded that only the first mode

needed to be considered in a linear elastic response spectrum analysis for this struc­

ture.

7.2 Response Spectrum Analysis

A linear elastic analysis using the response spectrum method was performed to

estimate the maximum bearing displacements and maximum base shear for each of

the earthquake tests conducted on both of the isolation systems tested. The spectra

used for input were the 10% damped linear elastic spectra of the actual shaking table

acceleration time history recorded from each test. Only the first mode was included in

each analysis. The analytical results for the model isolated on both sets of bearings

were found to compare reasonably well with the test results (Table 7.2). Only for the

Mexico City test did the experimental results differ significantly from the analytical

values. The difference between the analytical and experimental results for the Mexico

City test signal shows that the response spectrum technique can underestimate the

maximum bearing displacements significantly for ground motion spectrums which

vary greatly in amplitude near the fundamental frequency of the structure. It should

be remembered that the unsmoothed spectra from the actual shaking table motions

were used for this analysis. Unless a smoothed spectrum is used for analysis, it is pos­

sible to use a value from the spectrum which may be in either a trough or peak and

this could cause a large difference between the experimental and analytical results.

On the basis of these results, it was concluded that. structures which remain elas­

tic can be reliably analyzed using the response spectrum method to give estimates for

maximum base shear and bearing displacement. This assumes, of course, that the

spectrum used for the analysis is a reasonable representation of ground motion that

could be expected for the particular site.

- 25-

8. SEAONC BASE ISOLATION DESIGN FORMULA

The Structural Engineers Association of California (SEAOC) has recognized the

"need to supplement existing codes with design requirements developed specifically for

seismically isolated buildings. This need is shared by the public which requires

assurance that seismically isolated buildings are safe and by the engineering profession

which requires a minimum standard upon which design and construction can be

based.n [13] Out of this need the "Tentative Seismic Isolation Design Requirements,

September, 1986" were developed by the Base Isolation Subcommittee of the Seismol­

ogy Committee of the Structural Engineers Association of Northern California

(SEAONC). These requirements were intended to supplement the SEAOC "Tentative

Lateral Force Requirements, October, 1985" document [14]. The seismic isolation

design requirements are tentative and at the time of writing have not been adopted by

the SEAOC Seismology Committee. The basic design philosophy and design formulae

recommended by this document are discussed here and experimental results from the

tests discussed in Chapters 5 and 6 are compared with values given by the proposed

design formulae.

8.1 Summa.ry of SEAONC Design Procedure

The general design philosophy requires that: (1) the base-isolated structure

remain stable for required design displacements; (2) the isolation system should pro­

vide resistance which increases with increases in displacement; (3) the system should

be capable of repeated cyclic loads without any significant degradation; (4) the isola­

tion system should have quantifiable engineering parameters.

Either of two design procedures are permitted under the proposed design guide­

lines. The first uses a set of simple equations to prescribe design values of displace­

ment and base shear. These formulae are similar to the seismic lateral force formula

now in use for conventional building design. The second procedure requires a dynamic

analysis to determine the peak responses of the base-isolated structure pertinent to

- 26 -

design. This procedure would be required of any structure with geometric irregulari-

ties or of any especially flexible structures.

The tentative design provisions are based on a level of earthquake ground motion

that corresponds to a 500-year return-period earthquake as described by the ATC 3-06

recommended ground motion spectra [15]. The provisions require the base-isolation

system and all structural components at or below this level to withstand the full force

and effects of this ground motion without damage. Structural elements above the iso­

lation level are not, however, required to be designed for the full force of this motion.

A small amount of inelastic damage is allowed above the isolation level if sufficient

ductility is provided. The overall philosophy is that base-isolated structures should be

at least as safe as conventional buildings during extreme earthquake loadings. The

inelastic factor of 2.76 for the 500-year return-period earthquake is meant to ensure

elastic response of the structure for ground motions less severe than those of the 50- to

100-year earthquake.

The purpose of the following comparisons between the test results and the values

for bearing displacement given by the simple design equations is to evaluate the relia­

bility of the design formulae for this particular structural system. Further work is

being conducted in this area for a wide range of isolation systems.

8.2 Comparison of Experimental and Design Displacements

The shaking table test displacements for the 1/4-scale test structure were com­

pared with the displacements predicted by the SEAONC Tentative Seismic Isolation

Design Requirements. The SEAONC base-isolation code formula for displacement, D,

is given by equation (1) from section B.2:

D = 10 Z N S TB

where the terms are defined as follows:

(8.1 )

D = minimum displacement for which the isolation system must be designed;

- 27 -

Z = earthquake zone factor (0.3 or 0.4 for California) ;

N = coefficient to modify displacement due to distance from fault ;

S = soil factor, ranging between 1.0 and 2.7 ;

T = period of the isolated structure;

W = weight of isolated structure above and including the isolation surface;

g = acceleration of gravity;

kmin = minimum effective stiffness of the isolation system; and

B = damping coefficient, ranging between 0.8 and 2.0 .

The period for the prototype isolated structure is calculated from the single degree-of-

freedom equation

T=21rYkW

.mill g

(8.2)

In order to compare the experimental displacements and values given by the pro­

posed code equation (Equation 8.1) the experimental displacements had to be con­

verted to full-scale values. This required that the experimental displacements be mul­

tiplied by the scale factor of 4 (Table 2.1).

The values for Sand B used in the calculations are explained below. A value for

S of 2.7 was used for the Mexico City earthquake since the soil condition at the data

collection site for that signal fell into the S4 category. A value of 2.0 was used for S

for the Bucharest earthquake signal since that signal also consisted mostly of low fre-

quency motion although not as low as the Mexico signal. A value of 1.0 was used for

the San Francisco signal comparisons since that motion was comprised of high fre­

quency content. A value of 1.5 was used for all the other earthquake signals. The iso­

lated period for the scale model was calculated from Equation 8.2 using values from

Figure 3.2 and Figure 3.4 for the stiffness term kmin based on the shear strain which

- 28-

corresponded to the maximum experimental displacement, Dexp, for the particular test.

For use in Equation 8.1, the scale-model period was multiplied by the square root of

the scale factor (Table 2.1). A value of 1.2 was used for B since each isolation system

had a damping ratio of about 10%. Three different types of values were used for Z N

in Equation 8.1. They were:

(1) the peak shake table acceleration, PGA;

(2) the coefficient Aa based on the effective peak acceleration (as defined by ATC 3­

06) for each of the table signals; and

(3) the coefficient Av based on the effective peak velocity (as defined by ATC 3-06)

for each of the table signals.

Displacement values were calculated for the different tests using Equations 8.1

and 8.2 and the ratios Dcode/Dexp were computed for the series of tests and are given

in Table 8.1.

The use of the design formula with Z N = PGA gave conservative results for all

the earthquake test signals except Bucharest, Mexico City, and Miyagi-Ken-Oki.

These signals contained significant low frequency motion and therefore the model

responses were more velocity dependent than acceleration dependent. The use of the

effective peak acceleration coefficient Aa was less conservative than the use of the PGA

coefficient for all the signals except San Francisco. San Francisco contained very little

low frequency motion so the difference between the results using the PGA and Aa

coefficients was negligible. Results using the effective peak velocity coefficient Av were

generally more conservative than when using either the PGA or Aa coefficients for the

test signals containing significant low frequency content. A less conservative result

was obtained for the high frequency San Francisco motion using the coefficient Av

than when using either the PGA or Aa coefficients, however this result was still conser­

vative relative to the experimental results.

- 29 -

The comparison of test results with the design formula was extended to include

two modified earthquake signals. These signals are referred to here as ATC-81 EI

Centro, ATC-82 EI Centro, ATC-81 Taft, and ATC-82 Taft. The 81 and 82 terms

refer to the soil conditions, 81 being firm and 82 soft. These signals have been

modified to represent ground motions which would have response spectra similar in

shape to the ATC design spectra for 81 and 82 soil types. The response spectrum for

the normalized ATC-81 EI Centro shaking table motion is shown in Figure 8.1. The

structure isolated with the lead-plug bearings was tested with these signals and the

results were compared to the 8EAONC design formula values as described above.

Only the procedure using the velocity based coefficient Ay gave results consistently

more conservative than the experimental results. The ATC modified signals were

clearly more severe to low frequency structures than the unmodified Taft and EI Cen­

tro signals.

On the basis of the test results using both the modified and unmodified shaking

table motions, it was concluded that the velocity based coefficient Ay is the most reli­

able coefficient for use in the design formula and that with use of a reliable velocity

based design coefficient the simple design formula can be expected to yield reliable

estimates for the maximum bearing displacements.

- 30-

D. IMPLICATIONS OF THE TEST RESULTS

On the basis of the earthquake simulator tests of the scale model, conclusions

were drawn in several areas. The test results show that base isolation can be effective

for medium-rise structures if an adequate shift in the fundamental period of the struc­

ture is provided by the isolators. For the 1/4-scale model tested, the fundamental

fixed-base frequency was 2.82 Hz (with the 2nd loading distribution) and the isolated

first mode frequency was about 1 Hz. The two isolation systems tested provided

reductions of acceleration levels of up to 1/4 (for the San Francisco signal).

Column uplift was shown to have a significant effect on both the performance of

the bearings and the response of the structure. The large variations in axial load,

which were present when column uplift occurred, had an effect on the shear stiffness of

the bearings. While the bearings at one end of the model became unloaded axially

they were still displaced in shear, and the stability of bearings has been shown [11] to

be highly dependent upon axial load. Simultaneously, the bearings at the opposite

end of the structure experienced axial loads approximately double their static dead

loads while being displaced laterally, and thus they also experienced a momentary'

change in horizontal stiffness. However, if the amount of column uplift exceeds the

height of the bearing shear connection the bearing will become detached from the base

of the structure. This is, of course, unacceptable. A further complication of column

uplift is that the pounding which occurs when the building comes back into contact

with the foundation excites higher mode responses in the structure. This would be a

problem for any structure or internal components sensitive to high frequency motions,

especially vertical motions.

The effect of uplift was especially evident in the story acceleration profiles for the

Bucharest and Mexico City test sequences. The tests conducted on the steel frame

with the two kinds of isolation system were quite extensive and consisted of a large

number of earthquake tests which caused several cycles of shear displacement in excess

- 31 -

of 25% shear strain. The cumulative effect of the large strain displacement cycles on

the shear stiffness was quite dramatic for the lead-plug bearings. This was in contrast

to the effect on the neoprene bearings or the natural rubber bearings without a lead

core. Only the bearings which contained a lead core showed any signs of decreased

stiffness. The shear stiffness of the lead-plug bearings was seen to decrease from 7.9

kips/inch to 2.6 kips/inch after 36 earthquake tests each of which caused at least one

displacement cycle exceeding 25% shear strain.

The shaking table tests also showed that the lead-plug isolation system tended to

excite more high mode responses in the structure than did the neoprene isolation sys­

tem. There was not, however, as dramatic a difference between the responses for the

two isolation systems as there was when column uplift occurred.

The response spectrum method of analysis was shown to be effective for calculat­

ing values of the maximum model responses of bearing displacement and base shear.

The analysis used the unsmoothed response spectra of the actual table acceleration as

input for each of the earthquake signals. Comparisons between the test results and

the response spectrum analysis showed that the results agreed best for the higher fre­

quency earthquake signals. This was felt to be due to the unsmoothed nature of the

response spectra and the sensitivity of the method to change in the spectral values for

the range of period around the period of the isolated model. The lower frequency

earthquake signals (such as Bucharest and Mexico City) had greater variations in the

spectral acceleration ordinates in the region of the fundamental period of the isolated

model than the higher frequency motions. Thus, a slight difference between the

analytical and experimental periods could result in a large difference in the spectral

accelerations used for the analyses. While the response spectrum method was found

to give results comparable with the experimental results, it should be noted that the

accuracy of the method is highly dependent on the accuracy, or reliability, of the spec­

tra.

- 32-

Finally, the proposed SEAONC code design formula for bearing displacement was

found to be most accurate, and in general conservative, if the velocity based coefficient

Av was used to represent the earthquake ground motion magnitude. The proposed

formula was not conservative for the low frequency motions when the coefficients

based on peak acceleration or effective peak acceleration were used. The design values

compared most closely to the experimental values when the term Av ' which is based

on the effective peak velocity, was used to represent the product Z N in the design for­

mula. This is because the period of a base-isolated structure is in the constant velo­

city region of the response spectra for most earthquake motions.

- 33-

REFERENCES

[1] J. M. Kelly, "Aseismic Base Isolation: Review and Bibliography," Soil Dynamicsand Earthquake Engineering, Vol. 5, No.3, (1986).

[2J M. C. Griffith, J. M. Kelly, V. A. Coveney and C. G. Koh, "ExperimentalEvaluation of Seismic Isolation of Medium Rise Structures Subject to Uplift,"Report No. UCB/EERC-88/02, Earthquake Engineering Research Center, Univer­sity of California, Berkeley, (1988).

[3] J. M. Kelly, M. C. Griffith and 1. D. Aiken, "A Displacement Control and UpliftRestraint Device for Base Isolated Structures," Report No. UCB/EERC-87/03,Earthquake Engineering Research Center, University of California, Berkeley,(1987).

[4] Arthur A. Huckelbridge, "Earthquake Simulation Tests of a Nine Story SteelFrame with Columns Allowed to Uplift," Report No. UCB/EERC-77/23, Earth­quake Engineering Research Center, University of California, Berkeley, (1977).

[5J R. Sause and V. V. Bertero, "A Transducer for Measuring the Internal Forces inthe Columns of a Frame-Wall Reinforced Concrete Structure," Report No.UCB/EERC-83/05, Earthquake Engineering Research Center, University of Cali­fornia, Berkeley, (Hl83).

[6] C. J. Derham and H. G. Thomas, "The Stability of Rubber/Steel LaminatedBuilding Bearings," Natural Rubber Technology, Vol. 14, No.3, (1983).

[7] "Earthquake Catalog of California, January 1, 1900 to December 31, 1974,"Charles R. Read et. al., California Division of Mines and Geology, Special Publi­cation No. 52, 1st Edition and Cal. Tech. Report No., EERL 80-01, D.M. Lee,P.C. Jennings, G.W. Housner, (January 1980).

[8] N. Ambraseys, "The Romanian Earthquake of March 4, Hl77," PreliminaryReport of UNESCO Earthquake Reconnaissance Mission, (1977).

[9] Bruce Ellingwood (Ed.), "An Investigation of the Miyagi-Ken-Oki, Japan, Earth­quake of June 12, 1978," National Bureau of Standard Center for Building Tech­nology, Washington, D. C., (1980).

[10] S. Suzuki and A. S. Kiremidjian, "The Mexico Earthquake of September 19,1985, A Preliminary Report," The John A. Blume Earthquake EngineeringCenter, Dept. of Civil Engineering, Stanford University, Report No. 77, (1986).

- 34 -

[11] J. M Kelly, I. G. Buckle and H. C. Tsai, "Earthquake Simulator Testing of aBase-Isolated Bridge Deck," Report No. UCB/EERC-85/09, EarthquakeEngineering Research Center, University of California, Berkeley, (1985).

[12] "IMAGES-3D User Manual," Celestial Software, Berkeley, California (1983).

[13] "Tentative Seismic Isolation Design Requirements," Report prepared by the BaseIsolation Subcommittee of the Seismology Committee of the Structural EngineersAssociation of Northern California, (1986).

[14] "Tentative Lateral Force Requirements: October 1985," Report prepared by theSeismology Committee of the Structural Engineers Association of California,(1985).

[15] "Tentative Provisions for the Development of Seismic Regulations for Buildings,"ATC Publication No. ATC 3-06, prepared by the Applied Technology Council,(1978).

- 35 -

TABLES

- 36-

PARAMETER 1/4-SCALE MODEL/PROTOTYPE

Length L 1/4

Time VL 1/2

Mass L2 1/16

Displacement L 1/4

Acceleration 1 1/1

Stress 1 1/1

Strain 1 1/1

Force L2 1/16

Area L2 1/16

Table 2.1 Similitude Scale Factors for Prototype Responses

- 37 -

Channel Instr. Variable Channel Instr. Variable

1 DCDT hor. table dis. 43 FT Column N01 shear2 DCDT ver. table dis. 44 FT Column N01 mom.3 ACCL hor. table ace. 45 DCDT Column N01 tvdisp4 ACCL ver. table ace. 46 DCDT Column N01 rvdisp5 ACCL pit. table ace. 47 DCDT Column N02 tvdisp6 ACCL roll table ace. 48 DCDT Column N02 rvdisp7 ACCL twi. table ace. 49 DCDT Column S02 tvdisp8 DCDT vI table dis. 50 DCDT Column S02 rvdisp9 DCDT v2 table dis. 51 DCDT Column SOl tvdisp10 DCDT v3 table dis. 52 DCDT Column SOl rvdisp11 DCDT vI table span. 53 LP Column N01 pdisp12 DCVT hor. table vel. 54 LP Column SOl pdisp13 FT Column N01 axial 55 LP Bearing SOl rdisp14 FT Column N01 shear 56 LP Bearing S02 rdisp15 FT Column N01 mom. 57 LP 1st floor hdisp16 FT Column N01 axial 58 LP 2nd floor hdisp17 FT Column N01 shear 59 LP 3rd floor hdisp18 FT Column N01 mom. 60 LP 4th floor hdisp19 FT Column N02 axial 61 LP 5th floor hdisp20 FT Column N02 shear 62 LP 6th floor hdisp21 FT Column N02 mom. 63 LP 7th floor hdisp22 FT Column N02 axial 64 LP 8th floor hdisp23 FT Column N02 shear 65 LP 9th floor hdisp24 FT Column N02 mom. 66 ACCL Column N02 vaee25 FT Column S02 axial 67 ACCL Column N01 vaee26 FT Column S02 shear 68 ACCL Column S02 Yaee27 FT Column S02 mom. 69 ACCL Column SOl yaee28 FT Column S02 axial 70 ACCL base floor haee29 FT Column S02 shear 71 ACCL 1st floor haee30 FT Column S02 mom. 72 ACCL 2nd floor haee31 FT Column SO1 axial 73 ACCL 3rd floor haee32 FT Column SOl shear 74 ACCL 4th floor haee33 FT Column SOl mom. 75 ACCL 5th floor haee34 FT Column SOl axial 76 ACCL 6th floor haee35 FT Column SOl shear 77 ACCL 7th floor haee36 FT Column SOl mom. 78 ACCL 8th floor haee37 FT Column NI2 shear 79 ACCL 9th floor haec38 FT Column NI2 mom. 80 ACCL Frame NO vaee939 FT Column S12 shear 81 ACCL Frame NO paee940 FT Column S12 mom. 82 ACCL Frame SO yaee941 FT Column SIl shear 83 ACCL Frame SO paee942 FT n, STl mom

DCDT - Direct Current Displacement Transducer

ACCL - Accelerometer FT - Force Transducer

DCVT - Direct Current Velocity Transducer

LP - Linear Voltage Displ. Transducer

Table 2.2 - Instrumentation and Model Responses

- 38-

PK. TABLE PK. MODEL REL. BEARING UPLIFTFILE NO. RUN

ACCELJe:'s) ACCELJe:'s) DISPL.(in.) (YIN)

860624.02 1.0hz Sine .053 .038 .068 N

860624.03 1.2hz Sine .039 .050 .112 N

860624.04 1.4hz Sine .029 .066 .181 N

860624.05 1.5hz Sine .028 .060 .154 N

860624.06 1.6hz Sine .032 .060 .137 N

860624.07 1.8hz Sine .032 .058 .101 N

860624.08 2.0hz Sine .043 .058 .097 N

860624.09 3.0hz Sine .076 .070 .066 N

860624.10 4.0hz Sine .120 .091 .045 N

860624.11 5.0hz Sine .155 .252 .036 N

860624.12 5.2hz Sine .116 .248 .053 N

860624.13 5.4hz Sine .162 .224 .097 N

860624.14 5.5hz Sine .163 .214 .086 N

860624.15 5.6hz Sine .152 .202 .076 N

860624.16 5.8hz Sine .180 .149 .076 N

860624.17 5.0hz Sine .213 .126 .082 N

860624.18 12hz Sine na na na N

860625.01 1.32hz Sine .078 .129 .447 N

860625.02 1.32hz Sine .141 .212 .946 N

860625.03 1.30hz Sine .142 .208 .942 N

860625.04 1.25hz Sine .130 .210 .945 N

860625.05 1.20hz Sine .126 .218 1.083 N

860625.06 1.l5hz Sine .115 .204 1.088 N

860625.07 1.l0hz Sine .114 .220 1.289 N

860625.08 1.05hz Sine .109 .236 1.454 N

860625.09 l.oohz Sine .106 .216 1.377 N

Table 4.1 Preliminary Tests of Steel Model with Neoprene Bearings

- 39-

PK. TABLE PK. MODEL REL. BEARING UPLIFTFILE NO. RUN SPAN

ACCEL.(e:'s) ACCEL.(e:'s) DISPL.(in.) (YIN)

860624.19 Random Noise 30 1.101 .466 N

860624.20 Random Noise 30v NA NA NA N

860625.11 Random Noise 200 .036 .038 .103 N

860627.04 Y4 ee2 300 .645 .407 2.249 N

860627.05 y4mko 400 .300 .423 2.117 N

860627.06 Y4 taft2 350 .739 .424 1.938 N

860627.07 Y4 pac2 300 .495 .307 1.954 N

860627.08 Y4 park2 350 .417 .356 2.082 N

860627.09 Y4 sf2 230 1.400 .494 1.223 N

860627.10 Y4 sf2 300 1.609 .619 1.571 N

860627.11 Y4 buel 250 .236 .328 2.118 N

860627.12 Y4 mex2 150 .168 .306 2.570 N

860627.13 Y4 ec2 300 h&v .650 .434 2.378 N

860630.01 Y4 ec2 300* .578 .392 2.223 N

860701.01 Y4 ec2 300** .592 .753 2.247 N

860701.02 Y4 mex2m 100 .162 .152 .824 N

860701.03 Y4 mex2m 150 .187 .284 1.913 N

Table 4.2 Earthquake Tests of Steel Model with Neoprene Bearings

- 40-

FILE NO. RUNPK. TABLE PK. MODEL REL. BEARING UPLIFT

SPANACCEL.£g's) ACCEL.£g's) DISPL.£in.) (YIN)

860702.01 pull-back NA NA .330 .022 N

860702.02 pull-back NA NA .418 .020 N

860702.03 Random Noise 100 .016 .044 .022 N

860702.04 Random Noise 500 .083 .122 .128 N

860702.05 Random Noise 750 .115 .167 .204 N

860702.06 Random Noise 1000 .170 .197 .298 N

860703.01 1.40hz Sine 20 .092 .189 .500 N

860703.02 1.35hz Sine 15 .080 .183 .541 N

860703.03 l.30hz Sine 15 .077 .168 .560 N

860703.04 1.25hz Sine 15 .066 .145 .496 N

860703.05 1.20hz Sine 20 .068 .143 .551 N

860703.06 1.10hz Sine 25 .079 .132 .552 N

860703.07 1.15hz Sine 26 .068 .154 .592 N

860703.08 1.05hz Sine 20 .089 .128 .523 N

860703.09 l.OOhz Sine 40 .106 .180 .900 N

860703.10 1.50hz Sine 40 .099 .198 .509 N

860703.11 1.70hz Sine 60 .158 .176 .528 N

Table 4.3 Preliminary Tests of Steel Model With Lead-Plug Bearings

- 41 -

RUNPK. TABLE PK. MODEL REL. BEARING UPLIFT

FILE NO. SPANACCELJu's) ACCEL(p"s) DISPL(in.) (YIN)

860707.01 \/4 ee2 150 .296 .258 .806 N

860707.02 \/4 miyagi 200 .174 .220 .930 N

860707.03 \/4 taft2 220 .428 .334 1.048 N

860707.04 \/4 nae2 220 .338 .290 1.252 N

860707.05 \/4 park2 220 .243 .226 1.105 N

860707.06 \/48f2 230 1.411 .467 1.183 N

860707.07 \/4 bucl 300 .199 .242 1.348 N

860707.08 V4 mex2m 150 .173 .231 1.317 N

860707.09 V4 mex2m 200 .191 .325 2.337 N

860707.10 V4 bucl 275 .251 .323 2.207 N

860707.11 V48f2 300 1.590 .488 1.519 N

860707.12 \/4 park2 350 .425 .337 1.942 N

860707.13 V4 pae2 350 .562 .463 1.985 N

860707.14 V4 taft2 400 .848 .407 2.259 N

860707.15 V4 miyagi 400 .310 .343 2.404 N·

86070716 V4 ee2 300 .633 .463 2.797 y

860707.17 V4 ee2 150 .338 .202 .991 N

860708.03 V4 ee2 150 .313 .244 .904 N

860708.04 V4 ee2 225 .460 .288 1.712 N

860708.05 V4 ee2 300 .604 .453 2.648 y

860708.06 V4 ee2 400 .842 .607 3.784 y

860708.07 V4 ee2 150 .328 .205 1.014 N

860709.01 V4 bue1 275 .241 .293 1.825 N

860709.02 V4 bucl 350 .296 .444 2.729 y

860709.03 V4 bucl 400 .343 .537 3.259 y

860709.04 V4 mexZm 175 .146 .254 1.898 N

860709.05 \/4 mexZm 250 .194 .425 3.063 N

860709.06 \/4 mex2m 275 .219 .586 3.372 y

860709.07 V4 mexZm 275 .217 .520 3.416 y

860709.08 V4 buc1 400 .348 .767 3.723 y

860709.09 V4 ee2 375 .723 .579 3.603 y

860709.10 V4 eeZ 150 .353 .213 1.054 N

Table 4.4 Earthquake Tests of Steel Model With Lead-Plug Bearings

- 42-

SYMBOL EARTHOUAKE DATE PGA (g)

ec1,ec2Imperial Valley May 18,1940

0.35EI Centro Site SOOE

taft1,taft2Kern County, Calf. July 21,1952

0.18Taft Lincoln School Tunnel S69E

sf1,sf2San Francisco March 22,1957

0.10Golden Gate Park S80E

park1,park2Parkfield, Calf. June 27,1966

0.49Cholame Shandon CA array =#!2 N65E

pac1,pac2San Fernando Feb. 9,1971

1.08Pacoima Dam. Calif. S14W

miyagiMiyagi-Ken-Oki June 12th 1978

0.24Tohoku University SOOE

buc1Bucharest March 7th, 1977

0.21Building Research lnst. EW

mex2Mexico City September 19, 1985

0.20SCT Site S60E

Note: In this report, if the symbol for the earthquake has a suffix of "1", then noadditional filtering was applied to the signal. A suffix of "2" means that the un-time­scaled signal was high pass filtered at 0.1 Hz. For example, "eel" is unfiltered, "ec2"was high pass filtered. All are digitized records at the EERC of the University ofCalifornia at Berkeley.

Table 4.5 Earthquake Signals Used In Tests

- 43 -

Rubber Damping Fund. 2nd

TestShear

RatioHoriz. Horiz.

Strain Freq. Freq.(%) (%) (Hz.) (Hz.)

Free11 11.5 1.55

!

5.74Vibration

Harmonic8 9.9 1.40 5.23

Vibration

Harmonic65 7.6 1.05

Vibrationn.a.

White6 1.53 5.26

Noisen.a.

Table 5.1 Preliminary Shaking Tests, Neoprene Bearings.

Fund. Horiz. Rigid BodyTest Frequency Theory

(Hz.) (Hz.)

Free1.18 1.11

VibrationHarmonic

1.04 1.11Vibration

White1.13 1.11

Noise

Table 5.2 Comparison of Results at 100% Shear Strain

Rubber Damping Fund. 2nd

TestShear

Ratio Horiz. Horiz.Strain Freq. Freq.

(%) (%) (Hz.) (Hz.)

Free1 2.85 9.1

Vibrationn.a.

Harmonic26 15.3 1.15 5.85Vibration

White0.4 2.42 7.5Noise

n.a.

Table 6.1 Preliminary Shaking Tests, Lead-Plug Bearings.

- 44-

ELEMENT SECTIONAREA INERTIA(inches2) (inches4)

BOTTOM BEAM W8X31 18.26 220.0

COLUMN W4X13 7.66 22.6

GffiDER W6X9 5.36 32.8

BRACING (1,5-9) db L's l.!- X II X .!- 2.82 n.a.2 2 4

BRACING (2-4) db L's 1 X 1 X .!- 1.88 n.a.4

Note- The AREA and INERTIA are doubled to account for the stiffness of the two

frames since the total mass was used in the analysis.

Table 7.1 Cross-Section Properties for Braced Steel Frame

- 45 -

FREQUENCIES

FREQUENCY

f 1 f2 f~

Test 1.15 Hz 5.85 Hz ll.a.

Theory 1.03 Hz 5.82 Hz 15.5 Hz

MODE SHAPES

1st 2ndMode Shape Mode Shape

Story Theory Test Story Theory Test

9 1.00 1.00 9 1.00 1.00

8 0.99 0.98 8 0.85 0.81

7 0.98 0.98 7 0.66 0.63

6 0.97 0.91 6 0.45 0.44

5 0.95 0.91 5 0.24 0.23

4 0.94 0.84 4 0.01 0.01

3 0.92 0.82 3 -0.21 -0.22

2 0.90 0.79 2 -0.42 -0.44

1 0.88 0.74 1 -0.60 -0.62

G 0.86 0.71 G -0.75 -0.81

B 0.00 0.00 B 0.00 0.00

Table 7.2 Comparison of Experimental and Analytical Results

- 46 -

Neoprene Bearing Isolation System

EARTHQUAKE MAXIMUM RESPONSE SPECTRUM SHAKING TABLESIGNAL TABLE ANALYSIS RESULTS

ACCEL.Maximum Maximum Maximum Maximum

Bearing Base Shear Bearing Base ShearDisplacement Displacement

(inches) (kips) (inches) (kips)

Bucharest 0.236J( 1.71 25.8 2.12 30.8

El Centro 0.6502 2.16 33.3 2.38 35.0

Mexico City 0.168J( 1.61 24.0 2.57 27.9

Miyagi-Ken-Oki 0.300g 2.18 33.1 2.12 32.1

Pacoima Dam 0.495J( 1.90 29.8 1.95 28.6

Parkfield 0.4172 1.92 29.2 2.08 30.3

San Francisco 1.609J( 1.55 25.4 1.57 24.3

Taft O.739J( 2.29 35.2 1.94 29.5

Lead-Plug Bearing Isolation System

EARTHQUAKE MAXIMUM RESPONSE SPECTRUM SHAKING TABLE

SIGNAL TABLE ANALYSIS RESULTS

ACCEL.

Maximum Maximum Maximum

Bearing Base Shear Bearing Base Shear

Displacement Displacement

(inches) (kips) (inches) (kips)

Bucharest 0.348g 3.73 36.2 3.73 35.2

El Centro 0.842g 3.55 41.6 3.78 39.5

Mexico City 0.219g 3.44 34.8 3.38 32.3

Miyagi-Ken-Oki 0.310g 2.25 29.8 2.40 30.0

Pacoima Dam 0.562g 2.16 28.6 1.99 26.0

Parkfield 0.425g 1.89 25.0 1.94 25.3

San Francisco 1.590g 1.40 19.6 1.52 20.1

Taft 0.848g 2.25 29.8 2.26 28.8

Table 7.3 Response Spectrum Analysis and Experimental Results

- 47 -

Neoprene Bearing Isolation System

Earthquake Dexp DpGA Da Dy

SignalPGA Aa Av (in.) Dexp Dexp Dexp

Bucharest .236g .175 .440 2.12 0.82 0.61 1.53

El Centro .650g .471 .647 2.38 1.52 1.10 1.51

Mexico .187g .160 .251 1.91 0.96 0.82 1.29

Miyagi .300g .198 .486 2.12 0.79 0.52 1.27

Pacoima Dam .495g .387 .385 1.95 1.39 1.08 1.09

Parkfield .417g .263 .418 2.08 1.11 0.70 1.11

San Francisco 1.400g 1.387 .431 1.22 4.03 3.99 1.24

Taft .739g .531 .550 1.94 2.09 1.50 1.55

Lead-Plug Bearing Isolation System

Earthquake Dexp DpGA Da Dy

SignalPGA A.. Ay (in.) Dexp Dexp Dexp

Bucharest .241g .157 .477 1.83 0.97 0.63 1.92

Bucharest .296g .194 .603 2.73 0.86 1.54 1.75

Bucharest .343g .217 .684 3.26 0.86 0.54 1.70

EI Centro .460g .348 .486 1.71 1.48 1.12 1.56

EIOentro .604g .434 .640 2.65 1.31 0.94 1.38

EIOentro .842g .553 .849 3.78 1.37 0.90 1.38

Mexico .146g .132 .271 1.90 0.77 0.70 1.43

Mexico .194g .160 .383 3.06 0.68 0.56 1.35

Mexico .219g .165 .418 3.37 0.71 0.54 1.35

Miyagi .31Og .198 .488 2.40 0.73 0.47 1.16

Pacoima Dam .562g .451 .449 1.99 1.58 1.27 1.26

Parkfield .425g .261 .416 1.94 1.22 0.75 1.20

San Francisco 1.590g 1.595 .559 1.52 3.70 3.72 1.30

Taft .848g .600 .629 2.26 2.12 1.50 1.57

ATO-S1 (ec) .433g .327 .590 1.98 0.81 0.61 1.11

ATC-S1 (taft) .428g .352 .649 2.76 0.62 0.51 0.93

ATO-S2 (ec) .331g .240 .528 2.01 0.92 0.67 1.47

ATO-S2 (taft) .378g .287 .658 3.19 0.71 0.54 1.24

Table 8.1 Design Code and Experimental Bearing Displacements

- 48-

FIGURES

- 49 -

Figure 2.1 Base Isolated 9-Story Steel Frame

LO

AD

ING

CO

ND

ITIO

NN

O.1

LO

AD

ING

CO

ND

ITIO

NN

O.2

78

"6

0"

78

"I..

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.1-

.1

0"1 o

'/S

hak

ing

Tab

le////////

Ela

sto

mer

ic

J!

Ir

Ix

I'f

II

IB

eari

ng

s

Sh

akin

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Unl

oade

dM

odel

wei

ghs

10ki

ps

Fig

ure

2.2

.Lo

ad

ing

Co

nd

itio

ns

for

Ste

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ram

e

::: 00 ~;:: 00 00 ~ II ~ ~ @ 00

~ IQI

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0­

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P's

~D

CD

T's

01~

Fig

ure

2~3

Ste

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od

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stru

men

tati

on

Dia

gra

m

Fo

rce

Tra

nsd

ucer

Lo

cati

on

Dia

gra

m

N0

2 (19-

24)

(13

-18

)

N0

1

(37

-38

)

(43-

44)

NI2

Nil

812

8Il

(39

-40

)

(41-

42)

80

2

(25

-30

)

(31

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)

SO

l

~ ~

Th

en

um

bers

inb

rack

ets

refe

rto

the

chan

nel

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sed

tore

co

rdax

ial,

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an

dm

om

en

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ata

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he

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ucers

un

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or

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Co

nti

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ed

- 53-

PLAN VIEW

6". I

6"

I-0-

I+

r---------------,I I: -0-: III

dowel holes ~" dia. I8 I

I

II -0-: IL ...J

1IIIZZZ? IIZZZII}17!//l'

rubber layers l"_-+lI_z 7 7 7 7 Z Z 7 Z Z Z Z Z Z 7 Z Z Z Z Z ZI

8

steel shims .!." --~cz:."X:2::z:r:z.::z:z:::::z:..:::::z::::::;cz:."X:2::z:r:z.::z:z::::z::J8

4.875"

end plates 1,,1-it- ~" t---------. 8

1" --.J L

3.5" II

SECTION VIEW

Figure 3.1 Neoprene Bearing Design

- 54 -

1---------

~\4.5

140120100806040

- I

.......-.,.-..... -.

,..........-.......". ...............

~' ......._----- -----......_- --,- ~-~_._-._~._------.~-

-~- -----------,,---_.

2,5 ,,

2.0 i-

1.5 L

0 20

:? 4.0Co)

~....";;;- 3. 5P-....~"-" 3. 0

enenQ)

~....~

00J",c!jQ)

..d00

Shear Strain (%)

Figure 3.2 Neoprene Bearing Dynamic Shear Stiffness

- 55-

PLAN VIEW

6"f··f

r--------------...,I I II ~ II -\.±;- II I

: I I:5 '- + Q_I 6"

dowel holes -" dia. I I \::J

1

I8 I I

I II II -0- II I II IL ..J

1'1steel shims ~"---+t1::t:::2~t::t:::;tz:l

1.25" dia.I'" ·1

3rubber layers -"--1-

8 cz:::z:::z:z:z:::r;.:z:::z:f4.875"

end plates 1'1--1l-1." ~--------t

8 3.5"

SECTION VIEW

Figure 3.3 Lead-Plug Bearing Design

- 56-

10 r------- -------------1

Bearing WithLead Plug

_811lQ,....C6

aJ~ Bearing Without~ 4 ~ Lead Plug

j 2 l"-----~--~Ul 0 l "

o 20 40 60 80Shear Strain (%)

100

Figure 3.4 Lead-Plug Bearing Dynamic Shear Stiffness

-.

l1J Q)

.J::

(,) c:: .... '-'

0.2

0f

0.1

5

0.1

0

~0

.05

Q)

0.0

I.~II\]~~h.Ultn.lri'1j~Y~i\h~)

E-0

.05

Q) (,)

-0.1

0

~-0

.15

~-0

.20

I,,I

60

W~

~

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e(s

econ

ds)

Con

0...1

Q)

"t:l ::l -+J

0.0

14

.... -0

.01

2Po

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<0

.00

8~

0.0

06

Q) ....

0.0

04

~ ::l0

.00

20 r..t

0.0

01

020

Fre

qu

ency

(Hz)

30

40

Fig

ure

4.1

Wh

ite

No

ise

Dis

pla

cem

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Tim

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ry

1.0

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0.5

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89

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11

12

13

14

15

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17

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!

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c.n 00 I

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30

< ~2

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0

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23

45

67

89

10

12

14

16

18

20

Fre

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(Hz)

Fig

ure

4.2

Nor

mal

ized

Rea

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rth

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45

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89

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12

14

16

18

20

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(Hz)

Fig

ure

4.2

Co

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1.0

--­l1.l

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) - ~-0

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40

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20

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45

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(Hz)

Fig

ure

4.2

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67

8

~ .......

25

20

10

15

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Ken

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(Hz)

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16

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ure

4.2

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67

89

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12

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(Hz)

Fig

ure

4.2

Co

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14

16

18

20

1.0

.- ...r1l tID

0.5

- l:l 0.~

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~ t -Q)-0

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~~~

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12

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(Hz)

Fig

ure

4.2

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16

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20

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(l)

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4~ ~ 0

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01

23

45

67

89

10

12

14

16

18

20

Fre

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(Hz)

Fig

ure

4.2

Co

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1.0

...-

II,

Ta

ft{J

) ...0

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j 0 ~0

01

23

45

67

89

10

12

14

16

18

20

Fre

qu

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(Hz)

Fig

ure

4.2

Co

nti

nu

ed

- 66 -

Free-Vibration Test, Neoprene Bearings

i--

I

rf 1 = 1.55 Hz

0.02 ~-... e= 11.5%

00 0.01r- Ibtl........I:: 0.00.....

.+J(lj --'0.01l-o \ iQ) \ I-Q) -0.02 ~

\ /(,) I

(,) I

i< ,

-0.03 f- \;

L __-L- ,I-0.04

0 1 2 3 4 5 6 7 8

Time (seconds)

Figure 5.1 Log-Decrement Plot of Roof Acceleration

.004 r

I f} = 1.55 HzQ)

"'0 .003='.+J.....-0.

~ .002

l-oQ).....l-o=' .001o~

0.0

II

I I

l II I

i )il'II I

I

\ /\ j\r~_/

f;2 = 5.74 Hz

~

o 1 2 345 6 7 8 9 11 13 15 17 19

Frequency (Hz)

Figure 5.2 Fourier AInplitude Plot of Roof Acceleration

- 67-

2,5 If t = 5.2 Hz

2.0 (8% Max. Shear Strain)

~~....-.~.,tJ 1.5 r....T1J(/) !....e ; IT1J \ !

~/ \

r:: 1.0 1--1

"'--. / \1C'Q i /~ I; -"---.J~

I.I

L ,I0.5

1 2 3 4 5 6

Frequency (Hz)

f 1 = 1.05 Hz

(65% Max. Shear Strain)

1.301.251.10 1.15 1.20

Frequency (Hz)

1.05

1.9

1.8

Figure 5.3 Transmissibility Plot for Roof Acceleration

Harmonic Vibration Test, Neoprene Bearings

- 68-

Harmonic Vibration Test, Neoprene Bearings

1.0

Q)(J 0.0J..o~J..

~ -0.5~00

e= 9.9% at 8% Max. Shear Strain

0.20.10.0

Displacement (inches)

-0.1

I

i---1.0

-0.2

4 ---r--- ------

l ,

3 e= 7.6% at 65% Max. Shear StrainI

f-.. 21110.....

1~-..-Q)

1(J 0 ,-----------J..0

~~ -1J.. J

~ -2 IQ)i~

~ I I00 -3 L .JI, .___.-L I --4

-1.5 -1.0 -0.5 0.0 0.5 1.0 1.5

Displacement (inches)

Figure 5.4 Bearing Shear Hysteresis Loops

- 69 -

White Noise Vibration Test, Neoprene Bearings

.006 ,--------

,001

II

Q) .005 r"'0~;~ .004-0..8-< .003J".

.2:l . 002J".~o~

0.0

f) = 1.53 Hz (6% Max. Shear Strain)

I

,

191715o 1 2 3 4 5 6 7 8 9 11 13

Frequency (Hz)

Figure 5.5 Fourier Amplitude Plot of Roof Acceleration

~D20-- ---------------------------;-

f) = 1.53 Hz (6% Max. Shear Strain)

0.0

o 1 2 3 4 5 6 7 8 9 11 13

Frequency (Hz)15 17 19

Figure 5.6 Fourier Amplitude Plot of Bearing Displacement

BucharestO.236g

- 70-

EI CentroO.650g

9

8

7

6

4:

3

2

1

G

.ii

;i

*J

*:i~:,!''*I1*

\1*

1\1*It

9

8

7

6

5

4

3

2

1

G

x

(

~iIi'i1'*~Ii

II

II

\

,---o .L 2 o 1 2

9

8

7

6

~ 5~

0 4:~

00.3

2

1

G

Mexico CityO.168g

.i

j

~!III*'II'*!I:il

*\

\

~-

9

8

7

6

5

4:

3

2

1

G

Miyagi-Ken-OkiO.300g

o 1 2 o 1 2

Story AccelerationShaking Table Acceleration

Figure 5.7 Story Acceleration Profiles, Neoprene Bearings

Pacoima DamOA95g

- 71 -

ParkfieldOA17g

9

8

7

6

5

4

3

2

1

G

lI*

II,I<III'"

:*i~

~ ,

\II

1* ____

9

8

7

6

5

4

3

2

1

G

"

1I*I

II<

!;.,II

*Ii*I*\*

l-----

o 1 2 o 1 2

1I*I*II

'"Ii~,i*\*\*\\*-----

9

8

7

6

~ 5~

0 4~

003

2

1

G

o

San Francisco1.609g

1 2

TaftO.739g

9I~

8

l7

6i i

5 *!I ~

4 '",II

3 *\

2 *\

1 *\

\G *----. ~

0 1 2

Story AccelerationShaking Table Acceleration

Figure 5.7 Continued

0.6

1 I

0.4

Bu

cha

rest

O.2

36g

I

.......... lI)

...0

.2bO

'-" d 0 .....

,I~

tAJ

1f"

P\

tW6

JbI'

~'I

:1~

!II

1.'-:1

J,., OJ -

0.0

OJ c,)

c,) <

-0.2

>-

-0.4II!

I!

II

o1

23

45

67

89

10

11

12

Tim

e(s

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s)

Fig

ure

5.8

Su

per

imp

ose

dS

tory

Acc

eler

ati

on

Tim

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lots

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Fig

ure

5.8

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g

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Fig

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5.8

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ure

5.8

Co

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00

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Pa

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g

I I

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89

10

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15

Tim

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Fig

ure

5.8

Co

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0.6

r-

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45

67

89

10

11

12

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Tim

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Fig

ure

5.8

Co

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ed

0.6,

I

0.4

IT

aft

'O

.73

9g

-. rn ... b.O '-'

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89

10

11

12

13

14

15

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Tim

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Fig

ure

5.8

Co

nti

nu

ed

- 80-

30 f= 1---------------,i - //)1I

I Bucharest j // / I20 I _ p'-7

...-(1J

~O.236g

0-s .....

10~"""""='"~Q 0~

0~ -10 /~.- ~~ I <;/ (./jYcd ;Q) /l /~...c:: -- 20 r00

-30 ~. (/I-40

-3 -2 -1 0 1 2

Displacement (inches)

30r-----. "--1

I 1!IKelT = 15.1 kips/inch /,/ II

20 r // . I...- c= 10.2%

(1J

0. 10.....~

'-"~ 0 IQ~

~I

0 -10 / I/ I~

I / //~ I /// icd -20 f··

;////i

Q)

II

..c:: iI

00 i II

-30 r L./

~-40 I

-3 -2 -1 0 1 2

Displacement (inches)

Figure 5.9 Isolation System Hysteresis Loops During

Earthquake Tests, Neoprene Bearings

- 81 -

40 rI /7EI Centro

--. O.650g1110.. 20.~

..:c::-~u~

0 0~

~

// /~cO~

..d -20 ,/ ! :/00 ./ :=://

, V/i

II

-40 L

-3 -2 -1 0 1 2 3

Displacement (inches)

,-//

./.. //,/

(//-40

-3 -2 -1 o 1 2 3

Displacement (inches)

Figure 5.D Continued

- 82 -

21

-L . .. .JJ

o-1

Mexico CityO.168g

,.._.. _-_..__.._ _. _ _-_. __ ._-.- ---_ .•............-.--.----- __ ._- ._ _---_.._. ---_.. _---_ _ _-,

30

--. 20 t-r:tJ~

,~ :-ol

~...'¥:: 10'......~...... :Q,; IC,) I~ 0 "-0 I

I

~ ii

~

~ -. 1 (\~

."'-v

..c:00

-·20

-30

-2

Displacement (inches)

~__----;?L _

I ...-'y"'---.,;-'~ I

./" :..-

./,.~

e= 9.2%

K eff = 14.9 kips/inch

//./

/! // ///! i'~- , '

~ ~ .L L L ~

30

10 rI

0 IIII

--10

-30

-2 -1 o 1 2

Displacement (inches)

Figure 5.9 Continued

- 83-

40 --------------- -- ----- ------: i ---- ---------------------------1

l ".-.,./r

~ (_//

l__ --_.- .. L . .L.. L .l. i. J

.30

-.C11 200..-.~ 10~

~ 0o~

-1.0~

~Q)

..d -2000

.- 30

-40

ir··iiI

I-I

~I

!

Miyagi-Ken-Okio.aOOg

-3 -2 -1 o 1 2 3

Displacement (inches)

40j ' . "•..... ,. - ..• ...•. '•. •..•._•.•.• __.• " ._••__.. -- .• • "_",,.__•. ~. __ . ._. .. ,. __. ·w __"_.••••_. __• __.__ "_

!

f1---------------------II

// /---. 1.-"

~ C--/ - iI I I

L -------L. .. J. L ..1. . ----1.- J

....... -/,/

l_

-40

30

-3 -2 -1 o 1 2 3

Displacement (inches)

Figure 5.9 Continued

- 84 -

Pacoima Dam0.495g

-30

-2.0 -1.5 -1.0 -0.5 0.0 0.5 1.0 1.5 2.0

Displacement (inches)

30

20-..tl.lP......~ 10...-;

~~~ 00~

!

~i

,,10 L-eO !~

..d00 !

-20 r-

30

2.0

--II

1.51.00.50.0

././

Kefi' = 15.7 kips/inch

~ = 9.9%

r-

~-'---------'------r'--+--

I

-30

-2.0 -1.5 -1.0 -0.5

Displacement (inches)

Figure 5.9 Continued

- 85 -

I i

~ L L.... j

r~-- -------~--.----.- .----.. -- --",------- ---- --".._--..-_.-'1'--------- .. -- -' ..-._-----.-... ,.----..----.. ----- ----""'==-"1////,; II

~/ /

". iI

30

L Parkfield20 ! O.417g

j-. I00~

I.... 10 [~~

~ 0C) IJ..0 !

~i

,//~:~,;;;f--10 f-

r..~ / ..../' ../ /~ ~- /// <:>/..c -20 i00 /

/ //

iV/-30 ~----------- I

-2 -1 o 1 2

Displacement (inches).

~--------_.----.-..-._------.--- .------ -------'1-··---------····-·---------------------··--- '---'-----1,!

.-",­

.",~.,..

//

,,/'

I

!-

. ./"

l~~~:~:____ __1 J L J

! K eff = 15.2 kips/inch!

f €~ 9.2%

r

20

-30

-2 -1 o 1 2

Displacement (inches)

Figure 5.9 Continued

- 86-

30

20i San J;....ranciscor 1.609gI

...--., IrtJ0. 10 r....~

~---"->'"

Q.i 0t;.l~ I0 !~ -10 L

//'/

~

~ (::&2./-,.-"'-

Q)

..= -20 !-.00.

_.--,--------- --- -- ---------- _. ------- ---------l

l------ l ..L. l ..L ...L j--30

-1.5 -1.0 -0.5 0.0 0.5 1.0 1.5

Displacement (inches)

----lI

I

1.0 1.50.50.0

_/

-0.5

/./

-1.0

"/'/]

/,/~~;~~,///I l.-/ !

L I ,L j __

1---------------------------T------, I

l K etr = 16.4 kips/inch I~ , • !

I e= 10.4% l

~ii~--_--_----------------~-+---:?L:.,

! /--' !//! //- /-1

_/

30

20

-30

-1.5

Displacement (inches)

Figure 5.9 Continued

- 87 -

r-:--------...---.--.----.-.--., --.-..-----'-- -- -----·-----r-·--·-·- --.-.----.--- ---- ·-·----'--~·_-'------··_-'·_·-·l

/;~7i i

~/ '/ ITaft ,//' r/ i

! O.739g ,/ I

l------!o

20

30

10

,

-10 ,-

-20

-30

-2 -1 0 1 2

Displacement (inches)

2.01.5

,/-7~...,~. ,/////E= 9.5%

K eff = 15.4 kips/inchI­i

r1-----------

i!

20

30

-30

-2.0 -1.5 -1.0 -0.5 0.0 0.5 1.0

Displacement (inches)

-..en~....~ 10--Q)

c,)~ 00~~ -10~Q)

~00 -20

Figure 5.9 Continued

- 88 -

0.003

F

I---------------------------------

f 1 = 2.85 Hz

CI)

"'0=';,;l

0.002....-Po.S<

J,.,

0.001CI)....J,.,

='0~

0.0

a 2 4 6 8 10 12 14 16 18 20

Frequency (lIz)Figure 6.1 Fourier Amplitude Plot of Roof Acceleration

Free-Vibration Test, Lead-Plug Bearings

1.7

~1III

26% Max. Shear Strain

f} = 1.15 Hz

1.2 1.3 1.4 1.5 1.6

Frequency (Hz)1.1

~ I""-',,- I

------ ~ i

lD..-__..l..-__..l..-__...L.-__..L- 1 I I.

3.0

2.8

~ 2.6;,;l....-.... 2.4..0....fIJfIJ 2.2....SfIJ 2,0=CI;l IJ,., 1.8E-4 l1,6

1.4

1.0

Figure 6.2 Transmissibility Plot for Roof Acceleration

Harmonic Vibration Test, Lead-Plug Bearings

- 89 -

!!

1~, Ii, I

L ---L- ----l...- L -----L ---L J

1 0 i-----------------r ------------------------------------

I e= 6.7% at 26% Max. Shear StrainI Bearing Without Lead Core

-1.0

-.ll)

.90 0.5~~

-0.6 -0.4 -0.2 0.0 0.2 0.4

Displacement (inches)

0.6

3i e= 24% at 26% Max. Shear Strain

2 ~ Bearing With Lead Core

I1

C--- -----L- L.... .L--_------L _-3

-0.6 -0.4 -0.2 0.0 0.2 0.4 0.6

Displacement (inches)

Figure 6.3 Bearing Shear Hysteresis LoopsHarmonic Vibration Test, Lead-Plug Bearings

- 90-

O006 p------------------------------.------------------------'

. I - II I f} = 2.42 Hz lmax = 0.4% i

0.005 r-

7.5 Hz

42o 6 8 10 12 14 16 18 20

Frequency (Hz)

Figure 6.4 Fourier AInplitude Plot of Roof Acceleration

White Noise Vibration Test, Lead-Plug Bearings

0.0014 r-----------------------------------------------------------------1

~ O.0012~ f} = 2.42 Hz lmax = 0.4% I"'0 : I::l

;:;; 0.0010-0.8 0.0008<~

.~ 0.0006 iI

~ ! I

~ :.:::iM I ~ .!

o.o~~_,~642o 8 10 12 14 16 18 20

Frequency (Hz)

Figure 6.5 Fourier AInplitude Plot of Bearing Displacement

White Noise Vibration Test, Lead-Plug Bearings

9

8

7

6

5

4:

3

2

1

G

- 91 -

BucharestO.251g

"

11

I IUII*II

*\~

\

9

8

7

6

5

4

3

2

1

G

EI CentroO.633g

1,

fJ

~ I;

i\'

I

\

*

\*

o 1 2 o 1 2

9

8

7

6

5

4:

3

2

1

G

Mexico CityO,191g

"

11

I,

~1j j, .

*I*I*

1*

9

8

7

6

5

4:

3

2

1

G

Miyagi-Ken-OkiO.310g

I*I*

II*J I~

I*I*I*

l*

o 1 2 o 1 2

Story AccelerationShaking Table Acceleration

Figure 6.6 Story Acceleration Profiles, Lead-Plug Bearings

Pacoima DamO.562g

Parkfield0.425g

9

8

7

6

5

4

3

2

1

G

.11I

ILI

1,III i

*\*\

**

9

8

7

6

5

4

3

2

1

G

"

1I*I, I

I *I I*t

*

\**

o 1

San Francisco1.590g

2 o 1

TaftO.848g

2

9

8

7

6

5

4

3

2

1

G

(I*I

I*I*l j

II*I*\*

L*

9

8

7

6

5

4

3

2

1

G

1I*I*I*I*I*\*\*

~o 1 2

Story Acceleration

o 1 2

Shaking Table Acceleration

Figure 6.6 Continued

0.6

,--------------------------

----.:B~

U~C:h~a~

r~e~s:t-

--------

--1O

.348

g0

.4

,-....

.0

.2rt

l'" bO '-

' r:: 0 .....

ft--

i00l-'~-,·1lftt-1tI1t-rJt-1~m-l----I-h-t--~-\----I--~,,-"=

-'-

11<:

0I:,

I;l

<-0

.2. I I

-0.4

13

54

32

1o

-0.6

III

II

II

II

I--'-

67

89

10

11

12

Tim

e(s

eco

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s)

Fig

ure

6.7

Su

per

imp

ose

dS

tory

Acc

eler

ati

on

Tim

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erie

sP

lots

,L

ead

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s

0.6

!

El

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tro

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42g

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0.0

..... ~I

~fMl

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o1

23

45

67

89

10

11

12

13

14

15

16

17

18

Tim

e(s

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Fig

ure

6.7

Co

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nu

ed

0.4

II

Mex

ico

Cit

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g

0.2

--.

_rtl bfl -- =

0.0

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Fig

ure

6.7

Co

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c:o ~

15

14

13

12

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Miy

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Ken

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.--L_

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23

45

67

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Fig

ure

6.7

Co

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0.4

~,---------------------------1

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62g

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--III0

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Fig

ure

6.7

Co

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0.4

1--------------------------

o3l

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0.2

,,-...

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23

45

67

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101

112

13

14

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Fig

ure

6.7

Co

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---------------------------------------------------------l'

0.6

I

Sa

nF

ran

cisc

o1

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0g

0.4

0.2

-.

u.l

... bf) - ~

0.0

0 ....I

'9''.~J~lIlf~i~_'

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r''"

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II-0

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23

45

67

89

10

11

12

Tim

e(s

econ

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Fig

ure

6.7

Co

nti

nu

ed

0.4

"---------------------------------------------,

~T

aft

O.8

48g

0.2

-.

Ul

...0

.0bO '--'

" = 0 .... -+J

IU~

'W

i\WJ

'I,.,

m,

'~.

II-

'ce

0~

0Q

)~

-0.2

() () <-0

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-06

III

!I

II

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•I

,I

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I,

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o~

23

45

67

89

10

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U1

31

41

51

6~7

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Tim

e(s

econ

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Fig

ure

6.7

Co

nti

nu

ed

- 101 -

I

I

._---'-- .-'--__ ._--'-- l-~

Bucharest

O.251g

o II

l.-IIr- ;.I I .

l . ....l--30

-20

30 I--. 20

r1.l0..

.1"'4

~ 10"-

-3 -2 -1 0 1

Displacement (inches)

2 3

30

20-..rJl0..

.1"'4 10~"-

Q)Co)

0~

0~r.. -10~Q)

~00 ~20

-30

'-.- -_ ..-.- --.-.--.-.------------.--------.--,--.-----------------------------1r K eff = 13.2 kips/inch I //1 I

I <~ 12.1% i / /

-3 -2 -1 o 1 2 3

Displacement (inches)

Figure 6.8 Isolation System Shear Hysteresis Loops

During Earthquake Tests, Lead-Plug Bearings

- 102 -

30 r---------

IL El Centro

20 O.633g-..

00

.90 10~'-"

Q) 0Co)~

o~ -10~

~Q) -20

..c:00

-30

-40

rr-

~_V~,/_~~ L----I---l.--

-3 -2 -1 0 1

Displacement (inches)

2 3

30K eff = 12.8 kips/inch

20 c= 16.2%-..00Co

10....~'-"

Q)c.> 0~

0~ -10~c;l

~ -2000

-30 I-

-40

-3 -2 -1 0 1 2 3

Displacement (inches)

Figure 6.8 Continued

- 103-

40

30-..rJ),

~20....

~--Q,J 10C)~

0~ 0

""ro0 -10..d

00

-20

-30

Mexico CityO.191g

---_._----~~

i~..

~l

~;.-c----_.---------I

III

i

JL-__'---_---L-__

-3 -2 -1 0 1

Displacement (inches)

2 3

-..rJ),

Q...... 20~-- 10

-20

-30

--------

-3 -2 -1 o 1 2 3

Displacement (inches)

Figure 6.8 Continued

- 104-

32

~~"""::"------'-----------i

1

Displacement (inches)

40 i-------------l

30Miyagi-Ken-Oki

O.310g..-r1.lPo. 20....~--Q) 10

to)~

0 -----~ 0

&olcd -10 r-Q>

..c::00

-20

-30

-2 -1 0

l

2 3

Displacement (inches)

Figure 6.8 Continued

- 105-

30

-.. 20r1.lc......~"- 10

Q)(,,)~

0 0~

lo<~Q) -10

..c:l00.

-20

-30

-2

KetT = 13.3 kips/inch

e= 11.6%

-1 o 1 2

Displacement (inches)

Figure 6.8 Continued

- 106-

30 I -Ii Parkfield

20 ~-OA25g-.. ,

II)

0.....~ 10--Q)

C,)~ 00~~

~ -10Q)

...dI

00

~-20

-30 L-2 -1 0 1 2

Displacement (inches)

30 j-------·------------------------------T-----

l Keff = 13.2 kips/inch I'00' 20 I e= 13.5%0.....~ 10--

-30

I

J-2 -1 a

Displacement (inches)

1 2

Figure 6.8 Continued

- 107-

1.51.0-0.5 0.0 0.5

Displacement (inches)

-1.0

San Francisco1.590g

o

20

~~-20 I,

- 30 -L.-__-----L- -L.- ----'-.----'----

-1.5

o

-1.0 -0.5 0.0 0.5

Displacement (inches)

1.0 1.5

Figure 6.8 Continued

- 108 -

30

Taft20 O.848g-..

l1.l~....

10~--Q)C)

0l-40

r..l-4 -10~

lQ)

..dr.I'1 - 2 0 I

-30 l-3 -2 -1 0 1 2 3

Displacement (inches)

30 r K eff = /1 1

I13.2 kips/inch // I

// I

20 €= 12.1% I

-.l1.l~....~ 10--Q)

C)l-4 00~~ -10 //~Q)

I'..d /

1-r.I'1 -20 ~

l-30

-3 -2 -1 0 1 2 3

Displacement (inches)

Figure 6.8 Continued

10 r.-..c::

(,,)

l:: 80.-1

..........l1.l0.

0.-1

6~'-'"

l1.ll1.lCl)

4tE0.-1

i~

rn 2 r~

~ lCl)

..c::rn 0

0 10

- 109-

20

---- -- ~- .._--

30

!,I

Ii

II40

Number of earthquake tests which caused at leastone cycle of bearing shear strain in excess of 25%

Figure 6.9 Effect of Earthquake Tests on Lead-Plug

Bearing Dynamic Shear Stiffness

BucharestO.241g

- 110-

BucharestO.296g

9

8

7

6

5

4

3

2

1

G

K

11/

I*II*.II*I*\*\*

\

9

8

7

6

5

4

3

2

1

G

IJ

I•~

*\*

l*

o 1

BucharestO.343g

2 o 1

BucharestO.348g

2

9

8

7

6

~~ 50

-+oJ 400

3

2

1

G

II

LI, '; i

'"\

*\*

l*

9

8

7

6

5

4

3

2

1

G

Ij

*I iI I*l

II

I\*

*\*

l*

o 1 2 o

Story Acceleration

1 2

Shaking Table Acceleration

Figure 6.10 Bucharest Story Acceleration ProfilesLead-Plug Bearings

- 111 -

1098456 7

Time (seconds)32

Bucharest0.251g

1

0.0

0.05

~ - 0.05 f~-0.10 t-a -0 . 15 l..L!__-'--_---'---_--'--__L-.-_---'--_---'-__'---_-'--_-"-'

rn....~

,-.~ 0.10

..dCo)

l:::....'-'

,-.rnQl 0.20~ 0.15.5 0.10'-'~ 0.05~ 0.08 - 0.05~ -0.10~ - 0.15-~ -0.20....~

tBUcharest0.296g

1 2 3

0.17"

456Time (seconds)

7 8 9

! I

10

9 1045678

Time (seconds)

321

f Bucharest --- ---L\-m--ax--0-.6-O-,,---­

0.348gI

,-.rnQl

..d~ 0.6....

'-' 0.4~

~ 0.2

8 0.0 I~ -0.2 ri -0 . 4 u..1! __.1--__-'--__-'---_--'---

....~

Figure 6.11 Column Uplift Displacement Time Histories,Lead-Plug Bearings

Bu

cha

rest

O.2

96g

Bu

cha

rest

O.3

48g

-----

Bu

cha

rest

O.2

51

g

"""' """'J:-:)

10

98

........

,""

.-----

7

"I

/\ ;"'

Ii i 45

6

Fre

qu

ency

(Hz)

32

1~' ~ Iii Il ,i Ii Ii~

I:II

\i Ii ,I

1\I

I:I

Ii \

I\! ,

IIi,

I\:

II',

II

i j

1/I1 III

\ "I

IV

\i!

I'

"\

/-

,,

/'

",

\!'"

~/\';

\

§1

.0

1.... +

l.

~-

~:

rl'i

00

.8

~~

<-

I~

~o

>I

..saS

~::l

0.6

~S

+l

....

=><

c.-.

~

o~

Q,)

"'0

00

.4::l

+l

~"'O

-Q,

)C1

.N

S~

<S

0.2

~~

.~

0~

Z::

l"-'

o ~0

.0

o

Fig

ure

6.1

2F

ou

rier

Am

pli

tud

eP

lots

of

Ro

of

Acc

eler

ati

on

Du

rin

gB

uch

are

stT

ests

,L

ead

-Plu

gB

eari

ng

s

- 113-

6

Bucharest

~4 O.348g

-..IIIQ.,.... 2~-.-

CDt) 0J.c0~r.. -2 I~ ICD

..c:: I

00 -4 ~

L-6

-4 -2 0 2 4

Displacement (inches)

6Kefi' = 1.15 kips/inch

1 4 ~ e= 5.9%....C 2

CDC)r..o 0~

42o-2

I, /--;-?1/

~: l_V_'__-"-- ---1..- _

-4

Displacement (inches)

Figure 6.13 Individual Bearing Hysteresis Loops With

Column Uplift, Lead-Plug Bearings

- 114-

40Bucharest

,-. 0.348g000.. 20.....~-.-Q)t)f-o0 0~

f-o~

t

Q)

..c: -2000

-40

-4 -2 0 2 4

Displacement (inches)

40K eff = 9.70 kips/inch

€ = 10.2%

-40

-4 -2 o 2 4

Displacement (inches)

Figure 6.14 Isolation System Hysteresis Loops WithColumn Uplift, Lead~PlugBearings

- 115-

EI CentroO.313g

EI Centro0.460g

"

L~

i

j I'III !

*, Ii I~I Ii i i;*

\*\

I~

*

i

I*I I

*l\*\~

\*

9

8

7

6

5

4

3

2

1

G

o 1

El CentroO.604g

9

8

7

6

5

4

3

2

1

G

2 o 1

EI CentroO.842g

2

9

8

7

6

5

4

3

2

1

G

"

ii

~~I'I

*

t*

9

8

7

6

5

4

3

2

1

G

~

LII

L II I

* Il I

I

\ I*\

*

\**

o 1 2

Story Acceleration

o 1 2

Shaking Table Acceleration

Figure 6.15 EI Centro Story Acceleration Profiles,

Lead-Plug Bearings

-.~ 0.06

..d~ 0.04r:::

C 0.02~r::: 0.0Q,)e -0.02

~ -0.04~

0..-0.06lIJ....~

- 116-

~Illax = 0.04"

1 2 3 4 5 6 7 8 9 11

Time (seconds)

13 15 17

1 2 3 4 5 6 7 8 9 11

Time (seconds)

-.

~ 0.15 fr:::.... 0.10--~ 0.05

SO.O~ -0.05!l-0.100-lIJ....~

15 17

-.IIIQ,) 0.8

..d ~Illax = 0.75" El Centro~

r::: 0.6 0.842g....--~ 0.4r:::Q,)

0.2eQ,)

0.0~

~-0- -0.2III....~ 1 2 3 4 5 6 7 8 9 11 13 15 17

Time (seconds)

Figure 6.16 Column Uplift Displacement Time Histories,Lead-Plug Bearings

- 117-

6 ----EI Centro

4 O.842g

-.l1.l 20.-....~--Q) 0

cJ

I~

0~ -2

I~

~Q) I..d -4 I00

~.-6

-4 -3 -2 -1 0 1 2 3

Displacement (inches)

4KefF = 1.44 kips/inch

E= 8.5%2

-.l1.l0.-.... 0~-Q)cJ~ -20~

~

~ -4Q)

..d00

-6

-4 -3 -2 -1 0 1 2 3

Displacement (inches)

Figure 6.17 Individual Bearing Hysteresis Loops With

Column Uplift, Lead-Plug Bearings

- 118-

40

---~ 20....~--

El Centro

O.842g

-4 -3 -2 -1 0 1

Displacement (inches)

2 3

I~ ~. ~

Ic/ ·1

II

-4 -3 -2 -1 0 1 2 3

4 0 ,------·---------·---------lI Ketr = 11.7 kips/inchI I€ = 16.8%

-60

--- 20III0.....~--(l) 0to)r..0~ -20c..~(l)

..d00 -40

Displacement (inches)

Figure 6.18 Isolation System Hysteresis Loops WithColumn Uplift, Lead-Plug Bearings

Mexico CityO.146g

- 119 -

Mexico CityO.191g

9

8

7

6

5

4

3

2

1

G

iI I*I I*l II*I*I*

l*

9

8

7

6

5

4

3

2

1

G

~

11

I~{~

I*I*

1*

o 1

Mexico CityO.194g

2 o 1

Mexico CityO.219g

2

9

8

7

6

C 5o

.+J 4r.J)

3

2

1

G

~

111I*

iI*III*

{*

9

8

7

6

5

4

3

2

1

G

jI

I

fII

I

I \1*

III

II

II

o 1 2 o 1 2

Story AccelerationShaking Table Acceleration

Figure 6.19 Mexico City Story Acceleration Profiles,Lead-Plug Bearings

- 120-

-..111 0.10Q)

Mexico City Ll max = 0.07"..c:lv 0.05 0.146gI::.....-- 0.0~

I::8-0.05

~ -0.10~

0. -0.15111..... 0 10 20 30~

Time (seconds)

-..111Q) 0.10..c:l Mexico City Ll = 0.00"v max

I:: 0.05 O.lOlg.....--~ 0.0I::Q)8 -0.05Q)

~ -0.10-~ -0 .15.....~ 0 10 20 30

Time (seconds)

-..111Q) 0.5

..c:l0.4 Mexico City Ll max = 0.42"v

I:: 0.3 0.210g.....--~ 0.2I:: 0.1Q)

8 0.0~ -0.1~ -0.2~ -0.3.....~ 0 10 20 30

Time (seconds)

Figure 6.20 Column Uplift Displacement Time Histories,Lead-Plug Bearings

- 121 -

4321o-1-2-3

Mexico CityO.219g

o

I~

- 4 1'------_-----'-__---"---__'------ .L--__-L__-l.-_--------'

-4

4

-- 2ell0.....~--

Displacement (inches)

4 i-

Kefi' = 1.14 kips/inch

e= 5.2% I

-- 2ell0.....~--Q) 0~,.,0~,.,~ -2Q)

--'=r:n

-4

-3 -2 -1 o 1 2 3 4

Displacement (inches)

Figure 6.21 Individual Bearing Hysteresis Loops WithColumn Uplift, Lead-Plug Bearings

- 122 -

Mexico City0.219g

40

30".-.....

rnCo. 20....~--C> 10

Co)l-40 0~

f,., -10~~

C>~ -20 e-rn

t-30

-40

-4 -3 -2 -1 0 1 2

Displacement (inches)

3 4

40

-. 30rnCo..... 20~--C>

10Co)l-40~ 0

l-4~

~ -1000.

-20

-30

~----------------i--------------------------------------------.. -.-

~ KetT = 10.1 kips/inch I /~~ €~ 9.0% .

f--- -~-----------_ ..-I ~/I _/~ I

~ I _---'----'--------'-_

-3 -2 -1 o 1 2 3 4

Displacement (inches)

Figure 6.22 Isolation System Hysteresis Loops WithColumn Uplift, Lead-Plug Bearings

- 123 -

00- W8X31

® - W4X13

@-W6X9

f'1'. _ db L's 11. X 1.!. X .!.~ 2 2 4

® - db L's 1 X 1 X ~

Figure 7.1 Finite Element Model for Braced Steel Frame

- 124-

- -- -

Figure 7.2 Experimental and Analytical Mode Shapes

- 125-

EI Centro ATC-S1 Linear Elastic Response SpectraNormalized to 1.0gPeak Acceleration(0,2 and 5% Damped Curves)

500

-."t'

=0 100t)Q)f1J

...........f1J

50Q)

At)

=....-~

-+0:>....t)

0-Q) 10>0

"t':; 5Q)rn~

10.01 0.05 0.1 0.5 1

Period (seconds)

5 10 50

Figure 8.1 Response Spectrum of Modified EI Centro

Ground Motion (Time-Scaled)

- 127 -

EARTHQUAKE ENGINEERING RESEARCH CEI'IiTER REPORT SERIES

EERC reports are available from the National Information Service for Earthquake Engineering(NISEE) and from the National Technical InformationService(NTIS). Numbers in parentheses are Accession Numbers assigned by the National Technical Information Service: these are followed by a price code.Contact NTIS. 5285 Port Royal Road. Springfield Virginia. 22161 for more information. Reports without Accession Numbers were not available from NTISat the time of printing. For a current complete list of EERC reports (from EERC 67-1) and avaliablity information. please contact LlniversllY of California.EERC, NISEE, l301 South 46th Street, Richmond. California 94804.

VCB/EERC-80/01

VCB/EERC-80/02

LlCB/EERC-80/03

UCB/EERC·80/04

UCB/EERC-80/05

UCB/EERC-80/06

UCB/EERC-80/07

UCB/EERC-80/08

UCB/EERC-80/09

UCB/EERC-80/l 0

UCB/EERC-80/11

UCB/EERC-80/l2

UCB/EERC-80/l3

UCB/EERC·80/14

UCB/EERC-801l5

UCB/EERC·80il6

UCB/EERC-80/17

UCB/EERC-80/l8

UCB/EERC-80/19

UCBJEERC·80J20

UCB/EERC-80121

UCB/EERC-SO/22

UCB/EERC-80/23

UCB/EERC-80/24

UCB/EERC-80/25

UCB/EERC-80/26

UCB/EERC-80/27

UCB/EERC-80128

UCB/EERC·80/29

UCB/EERC-80/30

UCB/EERC-80/31

VCB/EERC-80/32

"Earthquake Response of Concrete Gravity Dams Including Hydrodynamic and Foundation Interaction Effects. - by Chopra, A.K.•Chakrabarti, P. and Gupta, S.. January 1980. (AD-A087297)AIO.

'Rocking Response of Rigid Blocks to Earthquakes." by Yim. C.S.. Chopra. A.K. and Penzien. J.. January 1980. (PBSO 166 002)A04.

"Optimum Inelastic Design of Seismic-Resistant Reinforced Concrete frame Structures.' by zaga]eski. S. W. and Bertero, V. V.. January1980. (PB80 164 635)A06.

'Effects of Amount and Arrangement of Wall-Panel Reinforcement on Hysteretic Behavior of Reinforced Concrete Walls.' by Iliya. R.and Bertero. V.V.. February 1980. (PB81 /22 525)A09.

'Shaking Table Research on Concrete Dam Models." by Niwa. A. and Clough. R.W.. September 1980. (PB81 122 368)A06.

"The DeSIgn of Steel Energy-Absorbing Restrainers and their Incorporallon into Nuclear Power Plants for Enhanced Safety (Valla):Piping WIth Energy Absorbing Restrainers: Parameter Study on Small Systems.' by Powell. G.H.. Oughourlian. C. and Simons. J.. June1980.

"Inelastic Torsional Response of Structures Subjected to Earthquake Ground Motions." by Yamazaki. Y., April 1980. (PB81 122327)A08.

'Study of X-Braced Steel Frame Structures under Earthquake Simulation." by Ghanaat. Y., April 1980. (PB81 122 335)Al1.

'Hybrid Modelling of Soil-Structure InteractlOn,' by Gupta. S.. Lin. T.W. and Penzien. J., May 1980. (PB81 122 319)A07.

"General Applicability of a Nonlinear Model of a One Story Steel Frame." by Sveinsson, B.I. and McNiven. H.D., May 1980. (PB81124 877)A06.

"A Green-Function Method for Wave Interaction with a Submerged Body," by Kioka. W., April 1980, (PB81 122269)A07.

"Hydrodynamic Pressure and Added Mass for Axisymmetric Bodies.," by Nilrat, F.. May 1980, (PB8l 122 343)A08.

'Treatment of Non-Linear Drag Forces Acting on Offshore Platforms," by Dao. B.V. and Penzien. 1.. May 1980, (PB81 153 413)A07.

"2D Plane/Axisymmetric Solid Element (Type 3-Elastic or Elastic-Perfectly Plastic)for the ANSR-II Program," by Mondkar. D.P. andPowell. G.H.. July 1980. (PB81 122 350)A03.

"A Response Spectrum Method for Random Vibrations." by Der Kiureghian. A., June 1981. (PB81 122301)A03.

"Cyclic Inelastic Buckling of Tubular Steel Braces," by zayas. V.A., Popov. E.P. and Mahin. S.A.. June 1981. (PB81 124885)AIO.

"Dynamic Response of Simple Arch Dams Including Hydrodynamic Interaction." by Poner. C.S. and Chopra. AX., July 1981, (PBSI124000).'\13.

"Experimental Testing of a Friction Damped Aseismic Base Isolation System with Fail-Safe Characteristics," by Kelly, J.M.• Beucke,K.E. and Skinner. M.S., July 1980. (PB81 148 595)A04.

"The Design of Steel Energy-Absorbing Restrainers and their Incorporation into Nuclear Power Plants for Enhanced Safety (VoUB):Stochastic Seismic Analyses of Nuclear Power Plant Structures and Piping Systems Subjected to Multiple Supported Excitations," byLee. M.e. and Penzien.J.. June 1980. (PB82 201 872)A08.

-The Design of Steel Energy-Absorbing Restrainers and their Incorporation into Nuclear Power Plants for Enhanced Safety (Va! IC):Numerical Method for Dynamic Substructure Analysis," by Dickens. J.M. and Wilson. E.L., June 1980.

"The Design of Steel Energy-A.bsorbing Restrainers and their Incorporation into Nuclear Power Plants for Enhanced Safety (Vol 2):Development and Tesllng of Restraints for Nuclear Piping Systems," by Kelly. J.M. and Skinner. M.S.. June 1980.

'3D Solid Element (Type 4-Elastic or Elastic-Perfcctly-Plastic) for the ANSR-I1 Program." by Mondkar. D.P. and Powell. G.H., July1980. (PB8l 123242)A03.

"Gap-Friction Element (Type 5) for the Ansr-II Program." by Mondkar. D.P. and Powell. G.H., July 1980. (PB81 122285)A03.

"V-Bar Restraint Element (Type II) for the ANSR-I1 Program." by Oughourlian, C. and Powell. G.H.. July 1980, (PB81 122293)A03.

"Testing of a Natural Rubber Base Isolation System by an Explosively Simulated Earthquake." by Kelly. J .M.• August 1980. (PB8] 201360)A04.

"Input Identification from Structural Vibrational Response,' by Hu, Y.. August 1980, (PB8l 152 308)A05.

"Cyclic Inelastic Behavior of Steel Offshore Structures." by Zayas. V.A., Mahin. S.A. and Popov, E.P.• August 1980. (PB8! 196180)AI5.

-Shaking Table Testing of a Reinforced Concrete Frame with Biaxial Response.' by Oliva. M.G.• October 1980, (PB81 154 304).'\ 10.

"Dynamic Properties of a Twelve-Story Prefabricated Panel Building," by Bouwkamp, J.G., Kollegger. J.P. and Stephen, R.M.. October1980. (PB82 138 777)A07.

"Dynamic Properties of an Eight-Story Prefabricated Panel Building," by Bouwkamp. J.G.. Kollegger, J.P. and Stephen, R.M., October1980, (PB81 200313)A05.

"Predictive Dynamic Response of Panel Type Structures under Earthquakes: by Kollegger. J.P. and Bouwkamp, J.G.. October 1980.(PB81 152 316)A04.

"The Design of Steel Energy-Absorbing Restrainers and their Incorporation into Nuclear Power Plants for Enhanced Safety (Vol 3):Testing of Commercial Steels in Low-Cycle Torsional Fatique.· by Spanner. p.. Parker. E.R., Jongewaard, E. and Dory, M., 1980.

Preceding page blank

- 128 -

UCB/EERC·SO/33 "The Design of Steel Energy"Absorbing Restrainers and their Incorporation into Nuclear Power Plants for Enhanced Safety (Vol 4):Shaking Table Tests of Piping Systems with Energy-Absorbing Restrainers: by Stiemer, S.F. and Godden, W.G., September 19S0,(PBS2 201 SSO)A05.

UCBlEERC-SO/34 "The Design of Steel Energy-Absorbing Restrainers and their Incorporation into Nuclear Power Plants for Enhanced Safety (Vol 5):Summary Report; by Spencer, P., 19S0.

UCB/EERC·SO/35 -Experimental Testing of an Energy-Absorbing Base Isolation System," by Kelly, J.M., Skinner, M.S. and Beucke, K.E., October 19S0,(PBSI 154072)A04.

UCB/EERC-SO/36 "Simulating and Analyzing Artificial Non-Stationary Earth Ground Motions: by Nau, R.F., Oliver, R.M. and Pister, K.S., October19S0, (PBS I 153 397)A04.

UCB/EERC-SO/37 "Earthquake Engineering at Berkeley - 19S0: by, September 19S0, (PBSI 205 674)A09.

UCB/EERC-SO/3S "Inelastic Seismic Analysis of Large Panel Buildings: by Schricker, V. and Powell, G.H., September 19S0, (PBSI 154 33S)A13.

UCB/EERC·SO/39 "Dynamic Response of Embankment, Concrete-Gavity and Arch Dams Including Hydrodynamic Interation," by Hall, J.F. and Chopra,A.K., October 19S0, (PBS I 152 324)AII.

UCB/EERC·SO/40 "Inelastic Buckling of Steel Struts under Cyclic Load Reversal.," by Black, R.G., Wenger, W.A. and Popov, E.P., October 19S0, (PBSI154312)AOS.

UCB/EERC-SO/41 "Influence of Site Characteristics on Buildings Damage during the October 3,1974 Lima Earthquake: by Repetto, P., Arango, I. andSeed, H.B., September 19S0, (PB81 161 739)A05.

UCB/EERC·SO/42 "Evaluation of a Shaking Table Test Program on Response Behavior of a Two Story Reinforced Concrete Frame: by Blondet, J.M.,Clough, R.W. and Mahin, S.A., December 19S0, (PBS2 196 544)AII.

UCB/EERC·SO/43 "Modelling of Soil-Structure Interaction by Finite and Infinite Elements: by Medina, F., December I9S0, (PBSI 229 270)A04.

UCB/EERC·SIIOI "Control of Seismic Response of Piping Systems and Other Structures by Base Isolation; by Kelly, J.M., January 1981, (PB81 20073S)A05.

UCB/EERC-SII02 "OPTNSR- An Interactive Software System for Optimal Design of Statically and Dynamically Loaded Structures with NonlinearResponse: by Bhatti, M.A., Ciampi, V. and Pister, K.S., January 1981, (PBS I 218 851)A09.

UCB/EERC·SII03 "Analysis of Local Variations in Free Field Seismic Ground Motions: by Chen, J.-c., Lysmer, J. and Seed, H.B., January 19SI, (AD­A09950S)A13.

UCB/EERC-SII04 "Inelastic Structural Modeling of Braced Offshore Platforms for Seismic Loading: by Zayas, V.A., Shing, P.-S.B., Mahin, S.A. andPopov, E.P., January 19SI, (PBS2 13S 777)A07.

UCB/EERC·SII05 "Dynamic Response of Light Equipment in Structures: by Der Kiureghian, A., Sackman, J.L. and Nour-Omid, B., Aprill9SI, (PBSI21S 497)A04.

UCB/EERC-SlI06 "Preliminary Experimental Investigation of a Broad Base Liquid Storage Tank: by Bouwkamp, J.G., Kollegger, J.P. and Stephen, R.M.,May 19SI, (PB82 140 3S5)A03.

UCB/EERC-81107 "The Seismic Resistant Design of Reinforced Concrete Coupled Structural Walls: by Aktan, A.E. and Benero, V.V., June 19SI, (PBS2113 35S)At 1.

UCB/EERC-SI/OS "Unassigned: by Unassigned, 19SI.

UCB/EERC-SI/09 "Experimental Behavior of a Spatial Piping System with Steel Energy Absorbers Subjected to a Simulated Differential Seismic Input," byStiemer, S.F., Godden, W.G. and Kelly, I.M., July 19S1, (PB82 201 S98)A04.

UCB/EERC-SIIIO "Evaluation of Seismic Design Provisions for Masonry in the United Slates: by Sveinsson, B.!., Mayes, R.L. and McNiven, H.D.,August 1981, (PB82 166 075)AOS.

UCB/EERC-SI/ll "Two-Dimensional Hybrid Modelling of Soil-Structure Interaction: by Tzong, T.-I., Gupta, S. and Penzien, 1., August 19SI, (PBS2 142IIS)A04.

UCB/EERC-SlII2 "Studies on Effects of Infills in Seismic Resistant RIC Construction: by Brokken, S. and Bertero, V.V., October 1981, (PB82 166190)A09.

UCB/EERC·SII13 "Linear Models to Predict the Nonlinear Seismic Behavior of a One-Story Steel Frame: by Valdimarsson, H., Shah, A.H. andMcNiven, RD., September 19SI, (PBS2 13S 793)A07.

UCB/EERC-S1/14 "TLUSH: A Computer Program for the Three-Dimensional Dynamic Analysis of Earth Dams; by Kagawa, T., Mejia, L.H., Seed, H.B.and Lysmer, J., September 19SI, (PBS2 139 940)A06.

UCB/EERC-SI/IS "Three Dimensional Dynamic Response Analysis of Earth Dams: by Mejia, L.H. and Seed, H.B., September 19SI, (PBS2 137 274)AI2.

UCB/EERC-8 11 I 6 "Experimental Study of Lead and Elastomeric Dampers for Base Isolation Systems; by Kelly, J.M. and Hodder, S.B., October 19SI,(PBS2 166 lS2)A05.

UCB/EERC·SI/17 "The Influence of Base Isolation on the Seismic Response of Light Secondary Equipment: by Kelly, I.M., April 1981, (PBS2 255266)A04.

UCB/EERC-SIIIS "Studies on Evaluation of Shaking Table Response Analysis Procedures," by Blondet, 1. M., November 19SI, (PBS2 197 278)AIO.

UCB/EERC-S 1/1 9 "DELIGHT.STRUCT: A Computer-Aided Design Environment for Structural Engineering, - by Balling, R.J., Pister, K.S. and Polak, E.,December 1981, (PB82 21S 496)A07.

UCB/EERC-SII20 "Optimal Design of Seismic-Resistant Planar Steel Frames: by Balling, R.J., Ciampi, V. and Pister, K.S., December 1981, (PBS2 220I79)A07.

UCB/EERC-S2/0 I "Dynamic Behavior of Ground for Seismic Analysis of Lifeline Systems," by Sato, T. and Der Kiureghian, A., January 1982, (PBS2 218926)A05.

UCB/EERC-S2I02 "Shaking Table Tests of a Tubular Steel Frame Model: by Ghanaat, Y. and Clough, R.W., January 19S2, (PBS2 220 161)A07.

UCBIEERC-82103

UCB/EERC-82/04

UCB/EERC-82105

.UCB/EERC-82/06

UCB/EERC-82/07

UCB/EERC-82108

UCB/EERC-82/09

UCB/EERC-82/10

UCB/EERC-82111

UCB/EERC-82112

UCB/EERC-821l3

UCB/EERC-82/14

UCB/EERC-82115

UCB/EERC-82/16

UCB/EERC-821l7

UCB/EERC-82/18

UCB/EERC-82/19

UCB/EERC-82f20

UCB/EERC-82/21

UCB/EERC-82/22

UCB/EERC-S2123

UCB/EERC-82/24

UCB/EERC-82/25

UCB/EERC-S2126

UCB/EERC-S2127

UCB/EERC-83/01

UCB/EERC-83/02

UCB/EERC-S3/03

UCBIEERC-83/04

UCB/EERC-83/05

UCB/EERC-83/06

UCB/EERC-83/07

UCB/EERC-83/08

UCB/EERC-83/09

UCB/EERC-83/10

UCB/EERC-83/11

UCB/EERC-83/12

UCB/EERC-83/13

- 129 -

-Behavior of a Piping System under Seismic Excitation: Experimental Investigations of a Spatial Piping System supported by Mechani­cal Shock Arrestors, - by Schneider, S., Lee. H.-M. and Godden, W. G., May 1982, (PBS3 172 544)A09.

-New Approaches for the Dynamic Analysis of Large Structural Systems,- by Wilson, E.L., June 1982, (PB83 148 080)A05.

-Model Study of Effects of Damage on the Vibration Properties of Steel Offshore Platfonns; by Shahrivar, F. and Bouwkamp, J.G.,June 1982, (PBS3 14S 742)AIO.

-States of the Art and Pratice in the Optimum Seismic Design and Analytical Response Prediction of RIC Frame Wall Structures, - byAktan, A.E. and Bertero, V.V., July 1982, (PB83 147 736)A05.

-Further Study of the Earthquake Response of a Broad Cylindrical Liquid-Storage Tank Model; by Manos, G.c. and Clough, R.W.,July 1982, (PB83 147 744)AII.

-An Evaluation of the Design and Analytical Seismic Response of a Seven Story Reinforced Concrete Frame: by Charney, F.A. andBertero, V.V., July 1982, (PB83 157 628)A09.

"Fluid·Structure Interactions: Added Mass Computations for Incompressible Fluid; by Kuo, J.S.-H., August 1982, (PB83 156 281)A07.

"Joint-Opening Nonlinear Mechanism: Interface Smeared Crack Model," by Kuo, J.S.-H., August 1982, (PB83 149 195)A05.

-Dynamic Response Analysis of Techi Dam: by Clough, R.W., Stephen, R.M. and Kuo, J.S.-H., August 1982, (PB83 147 496)A06.

-Prediction of the Seismic Response of RIC Frame-Coupled Wall Structures; by Aktan, A.E., Bertero, V.V. and Piazzo, M., August1982, (PB83 149 203)A09.

"Preliminary Report on the Smart I Strong Motion Array in Taiwan; by BOlt, B.A., Loh, C.H., Penzien, J. and Tsai, Y.B., August1982, (PB83 159 400)AlO.

"Shaking-Table Studies of an Eccentrically X-Braced Steel Structure; by Yang, M.S., September 1982, (PB83 260 778)AI2.

-The Perfonnance of Stairways in Earthquakes; by Roha, C., Axley, J.W. and Bertero, V.V" September 1982, (PB83 157 693)A07.

"The Behavior ofSubmerged Multiple Bodies in Earthquakes; by Liao, W.-G., September 1982, (PB83 158 709)A07.

"Effects of Concrete Types and Loading Conditions on Local Bond-Slip Relationships," by Cowell, A.D., Popov, E.P. and Bertero, V.V.,September 1982, (PB83 153 577)A04.

-Mechanical Behavior of Shear Wall Vertical Boundary Members: An Experimental Investigation; by Wagner, M.T. and Bertero, V.V.,October 1982, (PB83 159 764)A05.

"Experimental Studies of Multi-support Seismic Loading on Piping Systems," by Kelly, J.M. and Cowell, A.D., November 1982.

"Generalized Plastic Hinge Concepts for 3D Beam-Column Elements; b'J Chen, P. F.-S. and Powell, G.K., Novembet 19'&2, (PB'&~ 2<\1981)A13.

"ANSR-II: General Computer Program for Nonlinear Structural Analysis: by Oughourlian, C.V. and Powell, G.H., November 1982,(PB83 251 330)AI2.

"Solution Strategies for Statically Loaded Nonlinear Structures; by Simons, 1.W. and Powell, G.H., November 1982, (PB83 197970)A06.

"AnalnicalModel of Defonned Bar Anchorages under Generalized Excitations; by Ciampi, V., Etigehausen, R., Bertero, V.V. andPopov, E.P., November 1982, (PB83 169 532)A06.

"A Mathematical Model for the Response of Masonry Walls to Dynamic Excitations; by Sucuoglu, H., Mengi, Y. and McNiven, H.D.,November 1982, (PB83 169 0II )A07.

"Earthquake Response Considerations of Broad Liquid Storage Tanks; by Cambra, F.J., November 1982, (PB83 251 215)A09.

"Computational Models for Cyclic Plasticity, Rate Dependence and Creep; by Mosaddad, B. and Powell, G.H., November 1982, (PB83245 829)A08.

-Inelastic Analysis of Piping and Tubular Structures," by Mahasuverachai, M. and Powell, G.H., November 1982, (PB83 249 987)A07.

-The Economic Feasibility of Seismic Rehabilitation of Buildings by Base Isolation: by Kelly, 1.M., lanuary 1983, (PB83 197 988)A05.

·Seismic Moment Connections for Moment-Resisting Steel Frames.; by Popov, E.P., January 1983, (PB83 195 412)A04.

-Design of Links and Beam-ta-Column Connections for Eccentrically Braced Steel Frames; by Popov, E.P. and Malley, 10., January1983. (PB83 194 811)A04.

-Numerical Techniques for the Evaluation of Soil-Structure Interaction Effects in the Time Domain; by Bayo, E. and Wilson, E.L,February 1983, (PB83 245 605)A09.

"A Transducer for Measuring the Internal Forces in the Columns of a Frame-Wall Reinforced Concrete Structure; by Sause, R. andBertero, V.V., May 1983, (PB84 119 494)A06.

-Dynamic Interactions Between Floating Ice and Offshore Structures; by Croteau, P., May 1983, (PB84 119 486)AI6.

"Dynamic Analysis of Multiply Tuned and Arbitrarily Supported Secondary Systems; by Igusa, T. and Der Kiureghian, A., July 1983,(PB84 118 272)All.

-A Laboratory Study of Submerged Multi-body Systems in Earthquakes; by Ansari, G.R., June 1983, (PB83 261 842)AI7.

-Effects of Transient Foundation Uplift on Earthquake Response of Structures,- by Yim, c.-S. and Chopra, A.K., June 1983, (PB83 261396)A07.

"Optimal Design of Friction-Braced Frames under Seismic Loading,· by Austin, M.A. and Pister, K.S., June 1983, (PB84 119 288)A06.

"Shaking Table Study of Single-Story Masonry Houses: Dynamic Perfonnance under Three Component Seismic Input and Recommen­dations; by Manos, G.c., Clough, RW. and Mayes, R.L, July 1983, (UCB/EERC-83/1I)A08.

"Experimental Error Propagation in Pseudodynamic Testing; by Shiing, P.B. and Mahin, S.A., June 1983, (PB84 119 270)A09.

"Experimental and Analytical Predictions of the Mechanical Characteristics of a 1/5-scale Model of a 7-story RIC Frame-Wall BuildingStructure; by Aktan, A.E., Bertero, V.V" Chowdhury, A.A. and Nagashima, T., June,1983, (PB84 119 213)A07.

- 130-

UCB/EERC-83/14 -Shaking Table Tests of Large-Panel Precast Concrete Building System Assemblages," by Oliva, M.G. and Clough, RW., June 1983,(PB86 110 2IO/AS)A I I.

UCB/EERC-83/15 "Seismic Behavior of Active Beam Links in Eccentrically Braced Frames: by Hjelmstad, K.D. and Popov, E.P., July 1983, (PB84 119676)A09.

UCB/EERC-83/16 'System Identification of Structures witll Joint Rotation: by Dimsdale, J.S., July 1983, {PB84 192 210)A06.

UCB/EERC-83/17 'Construction of Inelastic Response Spectra for Single-Degree-of-Freedom Systems: by Mahin, S. and Lin, J., June 1983, (PB84 208834)A05.

UCB/EERC,83/18 'Interactive Computer Analysis Metllods for Predicting tile Inelastic Cyclic Behaviour of Structural Sections," by Kaba, S. and Mahin,S., July 1983, (PB84 192 012)A06.

UCB/EERC-83/19 "Effects of Bond Deterioration on Hysteretic Behavior of Reinforced Concrete Joints," by Filippou, F.e., Popov, E.P. and Bertero, V. V.,August 1983, (PB84 192 020)A IO.

UCB/EERC-83/20 "Analytical and Experimental Correlation of Large-Panel Precast Building System Performance: by Oliva, M.G., Clough, R.W., Velkov,M. and Gavrilovic, P., November 1983.

UCB/EERC-83/21 "Mecllanical Characteristics of Materials Used in a 115 Scale Model of a 7-Story Reinforced Concrete Test Structure," by Bertero, V.V.,Aktan, A.E., Harris, H.G. and Chowdhury, A.A., October 1983, (PB84 193 697)A05.

UCB/EERC-83/22 "Hybrid Modelling of Soil-Structure Interaction in Layered Media," by Tzong, T.-J. and Penzien, J., October 1983, (PB84 192 178)A08.

UCB/EERC-83/23 "Local Bond Stress-Slip Relationships of Deformed Bars under Generalized Excitations," by Eligehausen, R., Popov, E.P. and Bertero,V.V., October 1983, (PB84 192 848)A09.

UCB/EERC-83/24 "Design Considerations for Shear Links in Eccentrically Braced Frames: by Malley, J.O. and Popov, E.P., November 1983, (PB84 192I86)A07.

UCB/EERC-84/01 "Pseudodynamic Test Method for Seismic Performance Evaluation: Theory and Implementation: by Smng, P.,S.B. and Mahin, S.A.,January 1984, (PB84 190 644)A08.

UCB/EERC-84/02 "Dynamic Response Behavior of Kiang Hong Dian Dam: by Clough, RW., Chang, K.-T., Chen, H.,Q. and Stephen, R.M., April 1984,(PB84 209 402)A08.

UCB/EERC-84/03 "Refined Modelling of Reinforced Concrete Columns for Seismic Analysis: by Kaba, S.A. and Mahin, S.A., April 1984, (PB84 234384)A06.

UCB/EERC-84/04 "A New Floor Response Spectrum Method for Seismic Analysis of Multiply Supported Secondary Systems," by Asfura, A. and DerKiureghian, A., June 1984, (PB84 239 417)A06.

UCB/EERC-84/05 "Earthquake Simulation Tests and Associated Studies of a 1I5th-scale Model of a 7-Story RIC Frame-Wall Test Structure: by Bertero,V.V., Aktan, A.E., Charney, FA. and Sause, R., June 1984, (PB84 239 409)A09.

UCB/EERC,84/06 "RIC Structural Walls; Seismic Design for Shear," by Aktan, A.E. and Bertero, V.V., 1984.

UCB/EERC-84/07 "Behavior of Interior and Exterior Flat,Plate Connections subjected to Inelastic Load Reversals," by Zee, H.L. and Moehle, J.P., August1984, (PB86 117 629/AS)A07.

UCB/EERC,84/08 "Experimental Study of the Seismic Behavior of a Two-Story Flat-Plate Structure: by Moehle, J.P. and Diebold, J.W., August. 1984,(PB86 122 553/AS)AI2.

UCB/EERC-84/09 "Phenomenological Modeling of Steel Braces under Cyclic Loading: by Ikeda, K., Mahin, SA and Dermitzakis, S.N., May 1984, (PB86132 1981AS)A08.

UCB/EERC-84/10 "Earthquake Analysis and Response of Concrete Gravity Dams," by Fenves, G. and Chopra, A.I{., August 1984, (PB85 193902/AS)AII.

UCB/EERC-84/ll "EAGD-84: A Computer Program for Earthquake Analysis of Concrete Gravity Dams," by Fenves, G. and Chopra, A.K., August 1984,(PB85 193 613/AS)A05.

UCB/EERC-84/12 'A Refined Physical Theory Model for Predicting the Seismic Behavior of Braced Steel Frames: by Ikeda, K. and Mahin, S.A., July1984, (PB85 191 450/AS)A09.

UCB/EERC-84/13 "Earthquake Engineering Research at Berkeley - 1984: by, August 1984, (PB85 197 341/AS)A10.

UCB/EERC-84/14 "Moduli and Damping Factors for Dynamic Analyses of Cohesionless Soils,' by Seed, H.B., Wong, R.T., Idriss, I.M. and Tokimatsu, K.,September 1984, (PB8S 191 468/AS)A04.

UCB/EERC-84/IS "The Influence of SPT Procedures in Soil Liquefaction Resistance Evaluations: by Seed, H.B., Tokimatstl, K., Harder, L.F. and Chung,RM., October 1984, (PB85 191 732/AS)A04.

UCB/EERC-84/16 'Simplified Procedures for the Evaluation of Settlements in Sands Due to Earthquake Shaking," by Tokimatsu, K. and Seed, H.B.,October 1984, (PB8S 197 887/AS)A03.

UCB/EERC-84/17 "Evaluation of Energy Absorption Characteristics of Bridges under Seismic Conditions: by Imbsen, R.A. and Penzien, J., November1984.

UCB/EERC-84/18 "Structure-Foundation Interactions under Dynamic Loads: by Liu, W.D. and Penzien, J., November 1984, (PB87 124 889/AS)AI \.

UCB/EERC-84119 'Seismic Modelling of Deep Foundations: by Chen, C.-H. and Penzien, J., November 1984, (PB87 124 798/AS)A07.

UCB/EERC,84/20 'Dynamic Response Behavior of Quan Shui Dam: by Clough, R.W., Chang, K.-T., Chen, H.-Q., Stephen, R.M., Ghanaat, Y. and Qi,J.-H., November 1984, (PB86 IIS177/AS)A07.

UCB/EERC-85101 -Simplified Methods of Analysis for Earthquake Resistant Design of Buildings: by Cruz, E.F. and Chopra, A.K., February 1985, (PB86I I 2299/AS)A 12.

UCB/EERC-85/02 "Estimation of Seismic Wave Coherency and Rupture Velocity using the SMART I Strong"Motion Array Recordings: by Abrahamson,N.A., March 1985, (PB86 214 343)A07.

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UCB/EERC-85/03 "Dynamic Properties of a Thirty Story Condominium Tower Building," by Stephen, R.M., Wilson, E.L. and Stander, N., April 1985,(PB86 118965IAS)A06.

UCB/EERC,,85/04 "Development of Substructuring Techniques for On-Line Computer Controlled Seismic Performance Testing," by Dermitzakis, S. andMahin, S., February 1985, (PB86 132941/AS)A08.

UCB/EERC-85/05 "A Simple Model for Reinforcing Bar Anchorages under Cyclic Excitations; by Filippou, F.C., March 1985, (PB86 112 919/AS)A05.

UCB/EERC-85/06 "Racking Behavior of Wood-framed Gypsum Panels under Dynamic Load," by Oliva, M.G., June 1985.

UCB/EERC-85/07 "Earthquake Analysis and Response of Concrete Arch Dams," by Fok, K.-L. and Chopra, A.K., June 1985, (PB86 1396721ASjA I O.

UCB/EERC-85/08 "Effect of Inelastic Behavior on the Analysis and Design of Earthquake Resistant Structures," by Lin, J.P. and Mahin, SA, June 1985,(PB86 135340/AS)A08.

UCB/EERC-85/09 "Earthquake Simulator Testing of a Base-Iliolated Bridge Deck; by Kelly, J.M., Buckle, LG. and Tsai, H.-C., January 1986, (PB87 124I 52/AS)A06.

UCB/EERC-85/10 "Simplified Analysis for Earthquake Resistant Design of Concrete Gravity Dams; by Fenves, G. and Chopra, A.K., June 1986, (PB87124 160/AS)A08.

UCB/EERC-85/11 "Dynamic Interaction Effects in Arch Dams; by Clough, R.W., Chang, K.-T., Chen, H.-Q. and Ghanaat, Y., October 1985, (PB86I35027/AS)A05.

UCB/EERC-85/12 "Dynamic Response of Long Valley Dam in the Mammoth Lake Earthquake Series of May 25-27, 1980; by Lai, S. and Seed, H.B.,November 1985, (PB86 I 42304/AS)A05.

UCB/EERC-85/13 "A Methodology for Computer-Aided Design of Earthquake-Resistant Steel Structures," by Austin, M.A., Pister, K.S. and Mahin, SA,December 1985, (PB86 159480/AS)AIO.

UCB/EERC-85/14 -Response of Tension-Leg Platforms to Vertical Seismic Excitations; by Liou, G.-S., Penzien, J. and Yeung, R.W., December 1985,(PB87 124 871/AS)A08.

UCB/EERC,,85/15 "Cyclic Loading Tests of Masonry Single Piers: Volume 4 " Additional Tests with Height to Width Ratio of 1; by Sveinsson, B.,McNiven, H.D. and Sucuoglu, H., December 1985.

UCB/EERC-85/16 "An Experimental Program for Studying the Dynamic Response of a Steel Frame with a Variety of Infil1 Partitions; by Yanev, B. andMcNiven, H.D., December 1985.

UCB/EERC-86/01 "A Study of Seismically Resistant Eccentrically Braced Steel Frame Systems; by Kasai, K. and Popov, E.P., January 1986, (PB87 124178/AS)AI4.

UCB/EERC-86/02 "Design Problems in Soil Liquefaction; by Seed, H.B., February 1986, (PB87 124 186/AS)A03.

UCB/EERC-86/03 "Implications of Recent Earthquakes and Research on Earthquake-Resistant Design and Construction of Buildings; by Bertero, V.V.,March 1986, (PB87 124 194/AS)A05.

UCB/EERC-86/04 "The Use of Load Dependent Vectors for Dynamic and Earthquake Analyses; by Leger, P., Wilson, E.L. and ClOUgh, R.W., March1986, (PB87 124 202/AS)AI2.

UCB/EERC-86/05 "Two Beam-To-Column Web Connections," by Tsai, K.-c. and Popov, E.P., April 1986, (PB87 124 30IlAS)A04.

UCB/EERC-86/06 "Determination of Penetration Resistance for Coarse-Grained Soils using the Becker Hammer Drill; by Harder, L.F. and Seed, H.B.,May 1986, (PB87 124 210/AS)A07.

UCB/EERC-86/07 "A Mathematical Model for Predicting the Nonlinear Response of Unreinforced Masonry Walls to In-Plane Earthquake Excitations," byMengi, Y. and McNiven, H.D., May 1986, (PB87 124 780/ASjA06.

UCB/EERC-86/08 "The 19 September 1985 Mexico Earthquake: Building Behavior; by Bertero, V.V., July 1986.

UCB/EERC-86/09 "EACD-3D: A Computer Program for Three"Dimensionai Earthquake Analysis of Concrete Dams; by Folc, K."L., Hall, J.F. andChopra, A.K., July 1986, (PB87 124 228/AS)A08.

UCB/EERC-86/10 "Earthquake Simulation Tests and Associated Studies of a 0.3-Scale Model of a Six-Story Concentrically Braced Steel Structure; byUang, C.-M. and Bertero, V.V., December 1986, (PB87 163 564/ASjA17.

UCB/EERC-86/11 "Mechanical Characteristics of Base Isolation Bearings for a Bridge Deck Model Test; by Kelly, J.M., Buckle, I.G. and Koh, C.-G.,1987.

UCB/EERC-86/12 "Effects of Axial Load on Elastomeric Isolation Bearings," by Koh, C.-O. and Kelly, J.M., 1987.

UCB/EERC-87/01 "The FPS Earthquake Resisting System: Experimental Report; by Zayas, VA, Low, S.S. and Mahin, SA, June 1987.

UCB/EERC-87/02 "Earthquake Simulator Tests and Associated Studies of a O.3"Scale Model of a Six-Story Eccentrically Braced Steel Structure; by Whit-taker, A., Uang, C.-M. and Bertero, V.V., July 1987.

UCB/EERC-87/03 "A Displacement Control and Uplift Restraint Device for Base-Isolated Structures; by Kelly, J.M., GrilIith, M.e. and Aiken, LD.. April1987.

UCB/EERC-87/04 "Earthquake Simulator Testing of a Combined Sliding Bearing and Rubber Bearing Isolation System; by Kelly, J.M. and Chalhoub,M.S., 1987.

UCB/EERC-87/05

UCB/EERC,,87/06

UCB/EERC-87/07

UCB/EERC-87/08

UCB/EERC-87/09

UCB/EERC-87/10

UCB/EERC-87/11

"Three-Dimensional Inelastic Analysis of Reinforced Concrete Frame-Wall Structures," by Moazzami, S. and Bertero, V. Y., May 1987.

"Experiments on Eccentrically Braced Frames with Composite floors; by Ricles, J. and Popov, E., June 1987.

"Dynamic Analysis of Seismically Resistant Eccentrically Braced Frames; by Rides, J. and Popov, E., June 1987.

-Undrained Cyclic Triaxial Testing of Gravels-The Effect of Membrane Compliance; by Evans, M.D. and Seed, H.B., July 1987.

"Hybrid Solution Techniques for Generalized Pseudo-Dynamic Testing; by Thewalt, C. and Mahin, S.A., July 1987.

'Ultimate Behavior of Butt Welded.Splices in Heavy RoUedSteel Sections,' by Bruneau., M" Mahin, SA. and Popov, E.,September 1987.

"Residual Strength of Sand from Dam Failures in the Chilean Earthquake of March 3, 1985; by De Alba, P., Seed, H.B., Retamal, E.and Seed, R.B., September 1987.

UCB/EERC-87/12

UCB/EERC-87/13

UCB/EERC-871l4

UCB/EERC-87/15

UCB/EERC-87116

UCB/EERC-87/17

UCB/EERC-87/18

UCB/EERC-87/19

UCB/EERC-87/20

UCB/EERC-87/21

UCB/EERC-87/22

UCB/EERC-88/01

UCB/EERC-88/02

UCB/EERC-88/03

UCB/EERC-88/04

UCB/EERC-88/05

~ 132 -

"Inelastic Seismic Response of Structures with Mass or Stiffness Eccentricities in Plan," by Bruneau, M. and Mahin. S.A., September1987.

TSTRUCT: An Interactive Computer Environment for the Design and Analysis of Earthquake Resistant Steel Structures: by Austin,M.A., Mahin, S.A. and Pister. K.S., September 1987.

"Experimental Study of Reinforced Concrete Columns Subjected to Multi-Axial Loading," by Low, S.S. and Moehle. J.P.• September1987.

-Relationships between Soil Conditions and Earthquake Ground Motions in Mexico City in the Earthquake of Sept. 19, 1985." by Seed.H.B" Ramo. M.P" Sun. J.. Jaime. A. and Lysmer.. J" October 1987.

"Experimental Study of Seismic Response of R. e. Setback Buildings." by Shahrooz, B.M. and Moehle. J.P.. October 1987.

'The Effect of SlabS on the Flexural Behavior of Beams." by Pantazopoulou, S.J. and Moehle, J.P., October 1987.

"Design Procedure for R-FBI Bearings," by Mostaghel, N. and Kelly. J.M., November 1987.

.. Analytical ModelS for Predicting the Lateral Response of R C Shear Walls: Evaluation of their Reliability: by Vulcano, A. and Ber­tero, V.V., November 1987.

"Earthquake Response of Torsionally-Coupled Buildings," by Hejal, R. and Chopra, A.K., December 1987.

"Dynamic Reservoir Interaction with Monticello Dam," by Clough, R.W., Ghanaat, Y. and Qiu, X-F., December 1987.

"Strength Evaluation of Coarse-Grained Soils," by Siddiqi, F.H., Seed, R.B., Chan, e.K., Seed, H.B. and Pyke, R.M., December 1987.

"Seismic Behavior of Concentrically Braced Steel Frames," by Khatib, I.. Mahin, SA and Pister. K.S" January 1988.

"Experimental Evaluation of Seismic Isolation of Medium-Rise Structures Subject to Uplift... by Griffith, M.e., Kelly, J.M., Coveney,V.A. and Koh, e.G., January 1988.

"Cyclic Behavior of Steel Double Angle Connections," by Astaneh-AsI, A. and Nader, M.N., January 1988.

"Re-evaluation of the Slide in the Lower San Fernando Dam in the Earthquake of Feb. 9, 1971: by Seed, H.B., Seed, R.B., Harder,L.F. and Jong, H.-L., April 1988.

"Experimental Evaluation of Seismic Isolation of a Nine-Story Braced Steel Frame Subject to Uplift," by Griffith. M.e., Kelly, J.M. andAiken, I.D., May 1988.