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175133 ''^'^f' OCT I 7 1975

^l^nS BUILDING SCIENCE SERIES 40

Engineering Aspects

of the 1971 San

Fernando Earthquake

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JAN 1 9 1972 , z*^ UNITED STATES DEPARTMENT QF COMMERCE • Maurice H. Stans, Secretary

' T NATIONAL BUREAU OF STANDARDS • Lewis M. Branscomb, Director

1

j

i Engineering Aspects of the

I 1971 San Fernando Earthquake

H. S. Lew, E. V. Leyendecker, and R. D. Dikkers

Building Research Division

Institute for Applied Technology

National Bureau of Standards

Washington, D.C. 20234

Building Science Series 40

Nat. Bur. Stand. (U.S.), Bldg. Sci. Ser. 40, 419 pages, (Dec. 1971)

CODEN: BSSNB

Issued December 1971

For sale by the Superintendent of Documents, U.S. Government Printing Office, Washington, D.C. 20402

(Order by SD Catalog No. C 13.29/40), Price .S3 Stock Number 0303-0940
Library of Congress Catalog Card Number: 70-186531

i i
PREFACE

On February 9, 1971, shortly after an earthquake struck

the San Fernando, California area, the National Bureau of

Standards was requested by the Office of Emergency Preparedness to send a team of engineers to the disaster area for the

purposes of making observations and preparing reports relative to structural damages. A team of structural engineers

from the Building Research Division, Institute for Applied

Technology, National Bureau of Standards, was dispatched

immediately to the disaster area. The NBS team, comprised

of R. D. Dikkers, H. S. Lew, E. V. Leyendecker, and E. 0.

Pfrang, arrived on the scene on February 10. Professors J, E.

Breen and L. C. Reese of the University of Texas at Austin

joined the NBS team on February 11.

This report presents the observations of the NBS on-site

inspection team (most photographs in this report were taken

by the team). The material presented herein is intended to

serve as (1) a documentation of damage resulting from the

earthquake and (2) as a source document for further studies,

research, and recommendations. This is particularly important as necessary remedial work and restoration have resulted

in the removal of evidence that is essential for studies and

eval uati ons .

The authors gratefully acknowledge those organizations

and individuals who assisted in providing necessary information during and after the survey for the preparation of this

report. In particular, the following individuals made direct

contribution to the report and critically reviewed it:

Dr. John E. Breen, Professor of Civil Engineering

The University of Texas at Austin

Dr. William B. Joyner, U. S. Geological Survey

U. S. Department of the Interior

Dr. Lymon C. Reese, Professor of Civil Engineering

The University of Texas at Austin

Mr. Leon Stein, Supervising Structural Engineer

Office of Architecture & Construction

Department of General Services

State of California

Appreciation is also extended to the following individuals

who provided valuable assistance to the NBS on-site survey

team

:

i i i
Office of Emergency Preparedness, Executive Office of

The President

George Grace, Assistant Director for Field Operations,

Washington, D.C.

Ralph D. Burns, Regional Director, Region 7, Santa Rosa,

Cal i f orn i a Terrence S. Mead, Disaster Assistant Coordinator,

Santa Rosa, California

Department of Health, Education, and Welfare

Fred Zimmerman, Assistant Regional Director for

Intergovernmental Relations, San Francisco,

Cal i f orn i a

State of California

Michael J. Colby, Regional Manager, Region I and VI

Office of Emergency Services, Los Angeles,

Cal i f orn i a Clifford Chaffin, Structural Engineer, Office of

Architecture and Construction, Los Angeles,

Cal i f orn i a

County of Los Angeles, California - Department of County

Engineer

Coleman W. Jenkins, Superintendent of Buildings

John F. Lewis, Principal Structural Engineer

The authors also wish to express their appreciation to

the numerous staff members of the National Bureau of Standards

who participated in the preparation of this report. In particular, the staff of the Photographic Services Section who

handled all photographic work and the staff of the Scientific

and Professional Liaison Section who typed the manuscript,

prepared graphic work, and provided other assistance in

completing the report.

This study was funded by the Office of Emergency Preparedness (Executive Office of the President), the Office of

Civil Defense (U. S. Department of Defense), and the National

Bureau of Standards (U. S. Department of Commerce).

i V
SI Conversion Units

In recognition of the position of the USA as a signatory

to the General Conference of Weights and Measures, which gave

official status to the metric SI system of units in 1960, the

authors assist readers interested in making use of the

coherent system of SI units by giving conversion factors

applicable to U. S. units used in this paper.

Length

1 in = 0.0254* meter

1 ft = 0.3048* meter

1 mile = 1609.35 meter

Area

1 in^ = 6.4516* x lO"''^ meter^

1 ft^ = 0.09290 meter^

Force

1 lb (Ibf) = 4.448 newton

1 kip = 4448 newton

Pressure, Stress

2

1 psi = 6895 newton/meter

1 ksi

Mass/ Vol ume

6 2

1 ksi = 6.895 x 10 newton/meter

1 Ib/ft^ (Ibm/ft^) = 16.02 kilogram/meter'

Moment

1 kip-in = 113.0 newton-meter

* Exactly

V
TABLE OF CONTENTS

Page

PREFACE iii

SI CONVERSION UNITS v

1. INTRODUCTION 1

1.1 Seismological Events 1 1.2 Earthquake Measures and Felt Area 3

1.3 Damage and Casualty Statistics 12

1.4 Disaster Relief Act of 1 970 14

1 . 5 References 19

2. SEISMICITY .21

2.1 Seismic History of California 21

2.2 Crustal Deformation in the San Fernando

Earthquake 24

2.3 References 28

3. SEISMIC WAVES AND STRONG-MOTION SEISMOGRAPHS. ... 31

3.1 SeismicWaves 31

3.2 Strong-Motion Records 33

3.3 Strong-Motion Seismograph Data 34

3.4 Summary 37

3.5 References 42

4. GEOLOGY AND SOIL CONDITIONS 83

4.1 Geologic Setting 83

4.2 Types of Soil Movement and Introductory

Remarks 89

4.3 Character of Soil at a Few Sites Affected

by the San Fernando Earthquake 90

4.4 Soil Movements Associated with San

Fernando Earthquake 94

4.5 Comments about Soil Movements '. 99

4.6 References 102

5. DAMAGE TO BUILDINGS 105

5.1 Building Code Seismic Force Requirements . . 105

5.2 Case Histories of Building Damages Ill

Medical Facilities Ill

Commercial Buildings 201

Res i dences 239

Miscellaneous Structures 255

Postal Facilities ... 262

5.3 References 262

vi
6. DAMAGE TO SCHOOLS 267

6.1 Introduction 267

6.2 Laws Governing School Construction 267

6.3 Case Histories of Individual School

Damages 270

Schools Constructed before 1933 270

Reinforced Buildings - Constructed

Prior to 1933 - Reinforced to Resist

Earthquake Forces after 1933 273

Schools Constructed after 1933 in

Accordance with the Field Act 276

Special Institutions with School

Structures 296

6.4 Summary 311

6.5 Recommendations 313

7. DAMAGE TO BRIDGES AND HIGHWAYS 315

7.1 Introduction 315

7.2 Case Histories of Bridge Damages 315

Intersection of Interstate 5 and

California 14 315

Intersection of Interstate 5 and

Interstate 210 325

Foothill Boulevard Unde rc ros s i n g of

Interstate 210 336

Miscellaneous Bridge Damage 341

7.3 Damage to Roads and Streets 344

7.4 Bridge Design Procedures 352

Seismic Design 352

1965 AASHO Specifications 354

California Bridge Planning and Design

Manual 355

Survey of Japanese Design Requirements

for Bri dges 356

7.5 Summary and Recommendations 357

8. DAMAGE TO PUBLIC SERVICES AND FLOOD CONTROL

FACILITIES 365

8.1 WaterSupplies 365

8.2 Electricity 371

8.3 Gas Supplies 384

8.4 Telephone Facilities 387

8.5 Sewers and Storm Drains 389

8.6 Fire Damage and Protection 391

8.7 Flood Control Facilities 394

8.8 References 398

9. CONCLUSIONS AND RECOMMENDATIONS 403

vi i

ENGINEERING ASPECTS OF THE 1971 SAN FERNANDO EARTHQUAKE

Hai Sang Lew, Edgar V. Leyendecker , and Robert D. Dikkers*

Immediately following the San Fernando

,

California earthquake (February 9, 1971), a four-man team from the Building Research Division

of the National Bureau of Standards' Institute

for Applied Technology , surveyed the damage to

buildings and other structures. This report is

based primarily on the data gathered during the

survey but includes some data provided by other

agencies and individuals . Based on study of

these data and observations made during the

survey, recommendations are made pertaining to

the improvement of building and other structural

design and construction practices

.

Key Words: Bridge; building; codes; dams;

earthquakes ; earthquake damage;

foundation geology ; highways

;

housing; hospital; mobile home;

seismic ; standards ; structural

engineering .

CHAPTER 1 INTRODUCTION

1 . 1 Sei smol ogi cal Events

At 6:00:41.6 a.m. (Pacific Standard Time), on February 9,

1971, an earthquake with a magnitude of 6.6 on the Richter

scale occurred, with its epicenter located about 14.5 km (9

miles) east of Newhal 1 -Sauqus , California, at 34° 24.0' N and 118° 23.7' W (fig. 1.1). The initial shock originated

approximately 13.0 km (8 miles) below the earth's surface and

faulting then propagated southward and upward, reaching the

ground surface in the north San Fernando Valley area of Los

*Dr. Lew, Dr. Leyendecker, and Mr. Dikkers are Structural

Research Engineers in the Building Research Division of the

National Bureau of Standards' Institute for Applied

Technol ogy

.

1
118°-30' 118°-15'

Sougus

Newhall

EPICENTER

A' FEB 9, 1971 / M= 6.6 9 TlTArJ '^l

—

1

EPICENTER

MARCH 31, 1971 M= 4.0

Sar Qii,, View

Fetnardo Hoipilol fPocoi

I P°" Res.

34°-15'

o4°-00'

Figure 1.1 Los Angeles, San Fernando Valley, and Newhall,

2
Angeles. Figure 1.2 is an idealized cross sec ti on . whi ch

illustrates the mechanics and orientation of the fault

associated with the San Fernando earthquake. A fault of this

type having an inclined fault plane is known as a dip-slip or

thrust fault. The faulting of this earthquake induced the

north block to move southward and upward about 1.5m (about

4.5 feet) and also westward about 2m (about 6 feet).

Allen et al [1.1]* report that no foreshocks exceeding

magnitude 1.5 had occurred in the San Fernando Valley area

in the preceeding 8 days and no shock exceeding magnitude

2.5 had been identified in the area during the preceding

4 months. The most identifiable event within the area was

a shock of magnitude 2.6 that occurred north of Sylmar (fig.

1.1) on September 20, 1970. In the years prior to 1971, the

San Fernando Valley had been an area of moderate seismic

activity. The only earthquake occurring within this area

which had as much energy release as the 1971 earthquake was

the so-called Pico Canyon earthquake of 1893. Pico Canyon

Is located about 5 km (3 miles) west of Newhall. According

to Townley and Allen [1.2], the Pico Canyon earthquake had

a magnitude of approximately 6 on the Richter scale.

Following the initial shock, more than 200 aftershocks

having a magnitude of 3.0 or greater occurred through

March 1, 1971, including the one that followed immediately

after the main shock with a magnitude of 5.1. The aftershocks for which epicentral locations have been determined

are shown in figure 1.3. The greatest concentration of

aftershocks lies roughly in the shape of an inverted U. It

appears from this figure that the larger shocks are concentrated around the periphery of this inverted U, while smaller

shocks occurred in the interior.

The most damaging aftershock since February 9 occurred

at 6:52 a.m. (Pacific Standard Time) on March 31, 1971 in the

Granada Hills area (fig. 1.1) and was felt over much of Los

Angeles and in eastern Ventura County. This aftershock

registered 4.0 on the Richter scale.

1 . 2 Earthquake Measures and Felt Area

EARTHQUAKE MEASURES

There are two terms which are common'^y used to describe

the size of an earthquake. These are "intensity" and

"magnitude." These two terms are often confused, and it is

^Numbers in brackets indicate literature references listed

at the end of each chapter.

3
•4
Figure 1.3 Location of the epicenter of the main shock

(magnitude 6.6) and of representative aftershocks (magnitudes greater than 3) through

March 1, 1971. Approximate traces of some of the faulting activated during this earthquake

are also shown. Prepared by the Seismological

Laboratory, California Institute of Technology.

5
important to understand the difference.

INTENSITY is an indication of an earthquake's apparent

severity at a specific location, as determined by observers.

It is a measure of the effects of an earthquake determined

through interviews with persons in the quake-stricken area,

damage surveys, and studies of earth movement. Based on this

measure of intensity the seismic risk map of the United

States, such as the one given in the current Uniform Building

Code [1.3], was determined.

The Modified Mercalli Intensity used in the United

States grades observed effects into twelve classes ranging

from I to XII. Description of this scale is given in table

1.1 [1.4]. The older Rossi-Forel Intensity scale has ten

categories of observed effects, and is still used in Europe.

Still other intensity scales are in use in Japan and the

U.S.S.R.

The potential severity of the earthquake at a particular

location can also be determined from the records of a strongmotion seismometer ( accel erome ter ) mounted on a rigid

foundation. The readings from such instruments indicate

the amplitude and frequency of earth accelerations at that

specific site and can be integrated to determine both

velocities and displacement. Such information can be used

by engineers in determining the degree of motion to which

structures have been subjected and to make determinations of

the forces which are exerted on structures. The measure of

potential severity of the earthquake at the recording station

is usually expressed as a fraction of the acceleration due to

gravity. A large number of such strong-motion recorders

were present in the Los Angeles area.

MAGNITUDE, on the other hand, expresses the total amount

of energy released by an earthquake as determined by measuring

the amplitudes produced on standardized recording instruments.

Thus, it is a measure of the absolute size of an earthquake

and does not consider the effect at any specific location.

The Richter scale, which gives the numerical value of

the magnitude, was defined by Richter in 1935 as logarithms

(base 10) of the amplitude in microns of the trace written

by a seismograph at a distance of 100 km from the epicenter.

Observations at distances other than 100 km can be

corrected to convert them to the standard distance. Because

the Richter Scale is expressed in logarithms of base 10, a unit increase in the scale is equivalent to a ten fold

increase in the real trace magnitude. For example, an earthquake of magnitude 8 represents a seismograph amplitude

10 times greater than that of a magnitude 7 earthquake, 100

6
Table 1.1 Modified Mercalli Intensity Scale of 1930

(Abridged and rewritten)

I. Not felt.

II. Felt by persons at rest, on upper floors, or favorably

placed

.

III. Felt indoors . Hanging objects swing. Vibration like

passing of light trucks. May not be recognized as an

earthquake

.

IV. Hanging objects swing. Vibration like passing of

heavy trucks or sensation of a jolt like a heavy ball

striking the walls. Standing motor cars rock.

Windows , dishes , doors rattle. Glasses clink.

Crockery clashes . Wooden walls and frames creak.

V. Felt outdoors ; direction estimated. Sleepers wakened

.

Liquids disturbed, some spi lied . Small unstable

objects displaced or upset. Doors swing, close, open.

Shutters , pictures move.

VI. Felt by all. Persons walk unsteadily. Windows

,

dishes, glassware broken. Knickknacks , books, etc.,

off shelves . Pictures off walls. Furniture moved or

overturned. Weak plaster and masonry D cracked

.

Small bells ring (church , school) . Trees, bushes

shaken visibly, or heard to rustle.

VII. Difficult to stand. Noticed by drivers of automobiles

.

Hanging objects quiver. Furniture broken. Damage to

masonry D, including cracks. Weak chimneys broken at

roof line. Fall of plaster , loose bricks, stones,

tiles, cornices , also unbraced parapets and architectural ornaments . Some cracks in masonry C. Waves on

ponds; water turbid with mud. Small slides and caving

in along sand or gravel banks. Large bells ring.

Concrete irrigation ditches damaged

.

VIII. Steering of automobiles affected . Damage to masonry

C; partial collapse. Some damage to masonry B; none

to masonry A. Fall of stucco and some masonry walls.

Twisting, fall of chimneys , factory stacks, monuments

,

towers , elevated tanks. Frame houses moved on

foundations if not bolted down; loose panel walls

thrown out. Decayed piling broken off. Branches

broken from trees. Changes in flow or temperature

of springs and wells. Cracks in wet ground and on

steep slopes.

7
Table 1.1 Continued

IX. General panic. Masonry D destroyed; masonry C

heavily damaged , sometimes with complete collapse

;

masonry B serious ly damaged . General damage to

foundations . Frame structures , if not bolted, shifted

off foundations . Frames racked . Serious damage to

reservoirs. Underground pipes broken . Conspicuous

cracks in ground. In alluviated area sand and mud

ejected, earthquake fountains , sand craters

.

X. Most masonry and frame structures destroyed with

their foundations . Some well-built wooden structures

and bridges destroyed . Serious damage to dams, dikes,

embankments . Large landslides . Water thrown on

banks of canals, rivers, lakes, etc. Sand and mud

shifted horizontally on beaches and flat land. Rails

bent slightly

.

XI. Pails bent greatly . Underground pipelines completely

out of service

.

XII. Damage nearly total. Large rock masses displaced.

Lines of sight and level distorted. Objects thrown

into the air.

QUALITY OF MASONRY

(BRICK OR OTHER)

Masonry A. Good workmanship , mortar, and design; reinforced

especially laterally , and bound together by

using steel, concrete, etc.; designed to resist

lateral forces.

Masonry B. Good workmanship and mortar; reinforced, but not

designed in detail to resist lateral forces.

Masonry C. Ordinary workmanship and mortar; no extreme

weaknesses like failing to tie in at corners

,

but neither reinforced nor designed against

horizontal forces.

Masonry D. Weak materials , such as adobe; poor mortar; low

standards of workmanship ; weak horizontally.

8
times greater than that of a magnitude 6 earthquake, and so

on. There is no upper limit to the Richter scale. The

largest magnitude ever recorded is 8.9.

The relationship between the magnitude of an earthquake

and the energy which it releases, as given by Richter [1.4],

i s log^Q E = 11 .4 + 1 .5 M,

where M is the Richter magnitude and E is the energy in ergs

which is defined as the unit of work equal to a force of 1 dyne acting through a distance of 1 cm in the centimeter-gramsecond system. A dyne is the force required to accelerate a free-standing gram mass 1 cm per second. A difference of one

degree in magnitude corresponds to a factor of 10^*^ or 31.6

in the amount of energy released. Thus, an earthquake of

magnitude 8 represents an energy release approximately 32

times greater than that of a magnitude 7 earthquake and

almost 1000 times greater than that of a magnitude 6 earthquake. The energy released by an atomic bomb of the Hiroshima

type, for example, is given by the Atomic Energy Commission

as 8 X 10^° ergs, which is equivalent to the energy released

in an earthquake of magnitude 6.3 [1.5].

MAGNITUDE-INTENSITY RELATIONS

Magnitude and maximum intensity of an earthquake are

interdependent to some degree, but there is no close correlation between them. For example, an earthquake might have a low magnitude but because of shallow focus, poor soil

condition, or poor building construction practice, it might

cause a great deal of damage; thus, it would have a very

high intensity. The March 31, 1971, aftershock which occurred

in the Granada Hills area is a typical example. While this

aftershock registered only 4.0 on the Richter scale, it

caused significant damage to residential structures. On the

other hand, an earthquake of very large magnitude might have

a great focal depth, or might occur in an area where there

is very little man-made structure to damage. It would not,

therefore, have a high apparent intensity.

Within a relatively small geographic region, such as within the State of California, an approximate relationship

between magnitude and intensity such as the one shown in

table 1.2 has been suggested. In this table magnitude is

compared with the related energy released, felt area, and

felt distance [1.6]. These relationships were developed

for use with ordinary ground conditions associated with

metropolitan centers in California and were greatly influenced

by the past history and future probability of strike-slip

9
Table 1.2 Approximate Relationship Between Magnitude and Intensity

Magnitude

Energy-Rel ea sed

(Ergs)

Felt Area

(square

miles)

Distance

Felt (St.

miles)

Intensity

(Maximum

Expected

Modified

Mercalli)

15 17

3.0 - 3.9 9.5 X 10 - 4.0 X 10 750 15 II - III

17 18

4.0 - 4.9 6.0 X J-U — Q ft X 10 3,000 30 IV - V

18 20

5.0 - 5.9 9.5 X 10 - 4.0 X 10 15,000 70 VI - VII

20 21

6.0 - 6.9 6.0 X 10 - 8.8 X 10 50,000 125 VII - VIII

22 23

7.0 - 7.9 9.5 X 10 - 4.0 X 10 200,000 250 IX - X

23 24

8.0 - 8.9 6.0 X 10 - 8.8 X 10 800,000 450 XI - XII

faul ti ng

.

The tab 1 e does not seem as applicable to an earthquake of the San Fernando ty p e , which was predominantly

a thrust faulting. For the San Fernando earthquake's

Richter Magnitude of 6.6, table 1.2 would indicate an expected Modified Mercalli (M.M.) Scale Intensity of VII or

VIII, which is quite low when compared to the actual damage.

Qualified observers have indicated that the actual damage

in the vicinity of severely damaged hospital structures

would be closer to a M.M. Scale XI. From table 1.2, this

intensity would correspond to a Magnitude 8 quake, indicating

that the intensity of this particular earthquake was far in

excess of what would have ordinarily been expected.

By using the relationship between the amount of TNT and

associated energy produced by it (one thousand tons of TNT

equal to 4.2 x 10^^ ergs) [1.7], the Richter scale magnitude

versus the energy equivalent in tons of TNT is plotted in

figure 1.4 with several earthquakes indicated on it. It is

seen that the magnitude of the San Fernando earthquake was

moderate compared with others.

FELT AREA

The February 9, 1971, earthquake was perceptible over

approximately 80,000 square miles of California, Nevada, and

Arizona. To establish isoseismals, the National Ocean Survey

(NOS) of the National Oceanic and Atmospheric Administration

(NOAA) conducted a mail survey [1.8]. As of March 4, 1971,

1860 reports had been received from a distribution of 2068

10
RICHTER SCALE OF MAGINITUDE

Figure 1.4 Comparison of Richter Scale Magnitude versus Equivalent Energy of TNT.

n
cards. Of these 784 were distributed to postmasters and

1284 to various other persons, including several hundred

structural engineers. Figure 1.5 shows a preliminary

isoseismal map based on the mail survey, field survey, and

i n tervi ews [1.8].

Based on the catastrophic damage to the San Fernando

Veterans Administration Hospital, the Olive View Medical

Center complex and the Holy Cross Hospital, a maximum

intensity of VIII-XI has been assigned tentatively to a small area in the foothills of the northeastern corner of

the San Fernando Valley. Other severe damages include

collapse of freeway separation and overhead, major damage

to the Van Norman Reservoir dams, severe damage to the San

Fernando Juvenile Hall, the Sylmar Convertor Station, and the

Pacoima Memorial Lutheran Hospital. Severe damage to

structures in the San Fernando Mall and partial collapse of

residences in the City of San Fernando are also included in

this zone.

Zone VII extends to the Newhal 1 -Saugus area to the north

and to downtown Los Angeles to the south. Within this zone,

many houses lost chimneys at roof lines and many unreinforced

masonry walls collapsed. Also observed in this zone were

cracks in masonry shear walls and cracks in lower-story

reinforced concrete columns in highrise buildings.

Outside of the intensity VII zone, only slight-tomoderate damage was reported, principally cracked or fallen

plaster and broken windows.

1 . 3 Damage and Casualty Statistics

DAMAGE STATISTICS

The most severe damage to building structures and

utility systems occurred in the upper San Fernando Valley

area, which encompasses the northern end of the City of Los

Angeles, Sylmar, Pacoima, Granada Hills, and the City of

San Fernando. This area lies five to ten miles south of the

epicenter. The reason why this area suffered more damage

than the immediate epicenter area can be visualized from

figure 1.2. While the rupturing initiated at some 8 miles

below the epicenter, it surfaced at the upper San Fernando

area. As a result, the actual ground displacement was

greater in this area than it was at the epicentral area.

Many damaged structures were either directly on the fault

line or situated near it.

Property damage, both private and public, in the

12
X

<

<

<

>

liJ

/

/

o

o

cno

z.<

13
metropolitan Los Angeles area had been estimated at

$436,600,000 as of March 5, 1971. A partial breakdown of

this estimate related to private and major public property

is listed in table 1.3. A breakdown of building damages is

1 i s ted i n tabl e 1.4.

CASUALTY STATISTICS

The San Fernando earthquake claimed the lives of 64

persons. Of these, 46 persons lost their lives at the San

Fernando Veterans Administration Hospital. Excluding this

concentrated loss of lives, and considering the severity of

structural damage, the number of fatalities from this earthquake was remarkably low. Such a low fatality rate was, as

in several previous earthquakes, due mainly to the time of

day of its occurrence. Had the earthquake occurred a few

hours later, the loss of life would probably have been many

times greater. A list of the number of injuries treated and

the number of deaths is given in table 1.5.

1 .4 Disaster Relief Act of 1970

The San Fernando earthquake is the first disaster to

fall under the coverage of the Disaster Relief Act of 1970

(PL 91-606). This Act gives the President broad powers to

supplement the efforts and resources of State and local

governments in alleviating suffering, hardship, and damage

caused by "major disasters." The Director, Office of

Emergency Preparedness, Executive Office of the President,

has also been given certain authorities and functions under

this Act, including, but not limited to the following:

• The authority to direct Federal agencies to provide

assistance in "major disasters."

t The authority to coordinate the activities of

federal agencies in providing disaster assistance,

and to direct any Federal agency to utilize its

available personnel, equipment, supplies, facilities,

and other resources in accordance with the authority

contained in Public Law 91-606.

• The authority to appoint a Federal Coordinating

Of f i cer

.

• The authority to execute for the Federal Government

a joint Federal -State Disaster Assistance Agreement

with the Governor of a State, for providing supplemental Federal disaster assistance.

14
Table 1.3 Summary of Property Damage Estimates

(As of March 5, 1971)

Private Property :

City of Los Angeles

Building Damage $160 ,000 ,000

Property and Furnishing 50 ,000 ,000

County of Los Angeles

Building Damage 6 ,7 90 ,000

Mobile Home Damage 1 ,120,000

Property and Furnishing No Data

Public Property : Olive View Medical Center $ 35 ,800 ,000

San Fernando Juvenile Hall 6,000,000

Karl Holten Boys Camp 2 ,500 ,000

L.A. County Structures 8,000,000

L.A. County Equipment , Furniture , etc 52 ,000,000

Sylmar Converter S tat ion

(Los Angeles Water and Power only) 30,000,000

Sewage, Water, Electric Distribution 20,000,000

Van Norman Reservoir Dams 34 ,000 ,000

Pacoima Dam 1,500,000

Debris Basin, Disposal Area, Storm Drains . . 800,000

Streets, Roads and Bridges 5 ,000 ,000

Highway Structures 15,000,000

Others : 8 ,090 ,000

TOTAL $436,600,000

15
Table 1.4 Summary of Building Damage

(As of March 5, 1971)

City of Los Angeles

Vacated as Unsafe

Dwellings 415 units

Apartments -54 Commercial and Industrial 382

Major Damage (Structural Damage) 5,405

Minor Damage 17 ,950

24,206 units

County of Los Angeles

Vacated as Unsafe

Dwellings 61 units

Apartments 7

Sheds, Carports , etc 6

Assembly 2

Commercial & Industrial 21

Damaged

Dwellings 2,068 units

Apartments 67

Mobile Homes 1,707

Sheds, Carports , etc 24

Assembly 41

Commercial & Industrial 123

TOTAL 4,128 units

City of San Fernando

Vacated as Unsafe

Dwellings 270 units

Commercial and Industrial 163

Damaged

Dwellings 1,520 units*

Commercial and Industrial No Data

TOTAL 2,953 units

*About 30 percent of the total dwelling units in the City

of San Fernando

16
• The authority to prescribe such rules and regulations

as may be necessary and proper to implement Public

Law 91-606.

Table -1.5 Injury and Life Loss

(As of March 5, 1971)

City of Los Angeles

Dead 13

Injuri es 88 9

Coiinty of Los Angeles : Dead 51

(46 at San Fernando VA Hospital)

Injuries None

Reported

Total Dead 64

Total Injuries 8 89

Under PL 91-606 the Federal Government reimburses to

State and local governments the cost arising from repair,

restoration, reconstruction and replacement of the damaged

public facilities. This law does not directly involve relief

to individuals and families. Thus, the earthquake damage to

facilities such as hospitals, schools, dams, reservoirs,

power distribution systems, sewers, storm drains, highways

and streets are covered by this law.

For reference, several sections related to the restoration of damaged structures, of the Disaster Relief Act of

1970 are excerpted below:

PUBLIC LAW 91-606

91st CONGRESS , S. 1970

December 31, 1970

AN ACT

To revise and expand Federal programs for relief

from the affects of major disasters, and for other

purposes

.

17
Be it enacted by the Senate and House of

Representatives of the United States of America

in Congress assembled , That this Act may be cited

as the "Disaster Relief Act of 1970"

MINIMUM STANDARDS FOR RESIDENTIAL

STRUCTURE RESTORATION

SEC. 243 No loan or grant made by any relief

organization operating under the

supervision of the Director , for repair

,

restoration , reconstruction , or replacement of any residential structure located

in a major disaster area shall be made

unless such structure will be repaired

,

restored, reconstructed , or replaced in

accordance with applicable standards of

safety, decency , and sanitation and in

conformity with applicable building codes

and specifications

.

FEDERAL FACILITIES

SEC. 251 The President may authorize any Federal

agency to repair, reconstruct , restore,

or replace any facility owned by the

United States and under the jurisdiction

of such agency which is damaged or

destroyed by any major disaster if he

determines that such repair, reconstruction, restoration, replacement is of

such importance and urgency that it

cannot reasonably be deferred pending

the enactment of specific authorizing

legislation or the making of an

appropriation for such purposes . In

order to carry out the provis ions of

. this section , such repair, reconstruction

,

restoration , or replacement may be begun

not withstanding a lack or an

insufficiency of funds appropriated

for such purpose , where such lack or

insufficiency can be remedied by the

transfer, in accordance with law, of

funds appropriated to that agency

for another purpose

.

STATE AND LOCAL GOVERNMENT FACILITIES

SEC. 252 (a) The President is authorized to

make contributions to State and local

18
governments to repair, restore,

reconstruct , or replace public facilities belonging to such State or

local governments which were damaged

or destroyed by a major disaster,

except that the Federal contribution

therefor shall not exceed 100 per

centum of the net cost of repairing

,

restoring, reconstructing , or

replacing any such facility on the

basis of the design of such facility

as it existed immediately prior to

such disaster and in conformity with

applicable codes, specifications , and

standards

.

(b) In the case of any such public

facilities which were in the process

of construction when damaged or

destroyed by a major disaster , the

Federal contribution shall not exceed

50 per centum of the net costs of

restoring such facilities substantially

to their prior to such disaster condition and of completing construction

not performed prior to the major

disaster to the extent the increase

of such cost is attributable to changed

conditions resulting from a major

disaster.

(c) For the purposes of this section

"public facility" includes any flood

control , navigation, irrigation

,

reclamation , public power, sewage

treatment and col lection , water supply

and distribution, watershed development

,

or airport facility, any non-Federalaid street , road, or highway , and any

other public building , structure , or

system, other than one used exclusively

for recreation purposes

.

1 . 5 References

1.1 Allen, C. R. et al , "Main Shock and Larger Aftershocks

of the San Fernando Earthquake, February 9 through

March 1, 1971" Geological Survey Professional

Paper 733, U. S. Government Printing Office,

Washington, D. C.

19
1.2 Townley, S. D. and Allen, M. W., "Descriptive Catalog

of Earthquakes of the Pacific Coast of the United

States, 1769 to 1928," Sei smol ogi cal Society of

America Bulletin, v. 29.

1.3 "Uniform Building Code," 1970 Edition, vol. I, International Conference of Building Officials, Pasadena,

Cal i f orn i a .

1.4 Richter, C. F., "Elementary Seismology," W. H. Freeman

and Company, 1958.

1.5 Berg, G. N., "The Skopje, Yugoslavia Earthquake,

July 26, 1963," American Iron and Steel Institute.

1.6 "Earthquakes," National Oceanic Atmospheric

Administration, U. S. Government Printing Office,

Washington, D. C.

1.7 "The Effects of Nuclear Weapons," U. S. Department of

Defense, U. S. Government Printing Office,

Washington, D. C.

1.8 Scott, N. H., "Preliminary Report of Felt Area and

Intensity," Geological Survey Professional Paper

733, U. S. Government Printing Office, Washington,

D. C.

20
CHAPTER 2 SEISMICITY

2 . 1 Seismic History of California

The San Fernando earthquake is only one of a number of

destructive earthquakes that have occurred in California in

the present century (see table 2.1). In terms of magnitude

Table 2.1 Property Damage and Loss of Life from Major California

Earthquakes in the Present Century

Earthquake

San Francisco

April 18, 1906

Magnitude

8,3

Estimated Property Damage

($Millions ) Contemporary

dollars

480

1971

dollars *

4550

Estimated

Loss

of Life

700

Santa Barbara

June 29, 1925

6.3 42 13

Long Beach

March 10, 1933

6.3 40 196 120

Imperial Valley

May 18, 1940

7.1 28

Kern County

July 21, 1952

7.7 60 136 12

San Fernando

February 9, 1971

6.6 440 440 64

*Based on Engineering News-Record Building Cost Index.

it is exceeded by the San Francisco earthquake (1906), the

Kern County earthquake (1952), and the Imperial Valley

earthquake (1940). In terms of property damage measured in

constant dollars it is exceeded only by the San Francisco

earthquake, and in terms of loss of life it is exceeded by

the San Francisco and Long Beach (1933) earthquakes. Sources

for the following account of the seismic history of California

include Richter [2.1], Wood and Heck [2.2], and Tocher [2.3].

The San Francisco earthquake of 1906 was the greatest

earthquake disaster in the history of the United States. It

resulted from movement on the San Andreas fault, a northwest

trending break in the earth's crust along which the coastal

block to the southwest moves northwestward relative to the

21
continental block. At the time of the earthquake the fault

broke over a length of at least 190 miles and the horizontal

displacement reached a maximum of 21 feet (in Marin County).

Shaking accompanying the earthquake caused extensive damage

in San Francisco and other towns near the fault and caused

a fire in San Francisco that destroyed a large part of the

city.

Of the other twentieth century California earthquakes

listed in table 2.1, the Imperial Valley earthquake of 1940

occurred along the Imperial fault, which is a branch of the

San Andreas fault. The rest of the earthquakes were associated with other faults, the White Wolf fault for the Kern

County earthquake of 1952, the Inglewood fault for the Long

Beach earthquake of 1933, and a fault offshore for the Santa

Barbara earthquake of 1925.

There were several major earthquakes in California

during the nineteenth century, but they are difficult to

evaluate because of the lack of instrumental data, the

fragmentary nature of old reports, and the sparse settlement

of the region. An earthquake near Santa Barbara in 1812

damaged missions over a wide area in southern California

and produced a tsunami (tidal wave) in the Santa Barbara

channel. At least two of the nineteenth century earthquakes

are generally considered comparable in magnitude and

destructive potential to the San Francisco earthquake of

1906. They are the Fort Tejon earthquake of 1857 and the

Owens Valley earthquake of 1872. The 1857 earthquake was

accompanied by a break along the San Andreas fault in

southern California that passed within 25 miles of the city

of Los Angeles. The 1872 earthquake occurred in eastern

California near the Nevada border in an area that is still

relatively sparsely populated. Other major nineteenth

century earthquakes occurred in 1838 along the San Andreas

fault near San Francisco and in 1836 and 1868 along the

Hayward fault, a branch of the San Andreas on the east side

of San Francisco Bay.

In analyzing the earthquake risk in California, the

San Andreas fault deserves I'irst attention. A recent

analysis by C. R. Allen [2.4] suggests that the segments of

the fault that broke in 1906 and 1857 (fig. 2.1) are

characterized by relatively infrequent great earthquakes

(magnitude larger than 8) and a comparative absence of

smaller shocks and fault creep. The other segments of the

fault, in contrast, show abundant small and moderate earthquakes accompanied by fault creep without earthquakes.

Allen suggests that this pattern may be stable and typical

of the past and probable future behavior of the fault

system. In this concept, the 1857 and 1906 breaks are

"locked" segments of the fault where strain accumulates to

22
Figure 2.1 Areas of contrasting seismic behavior along

the San Andreas fault zone in California [2.4].

23
a relatively high level before being released in a great

earthquake, whereas strain along the other segments of the

fault is released more often in the form of moderate earthquakes and fault creep. Both the major metropolitan centers

of California, Los Angeles and San Francisco, lie near

segments of the fault that broke during historic great

earthquakes. If the foregoing analysis is correct, those

segments are where great earthquakes should be expected in

the future.

R. E. Wallace [2.5] estimated the possible recurrence

intervals for great earthquakes along the San Andreas fault

by relating geologic data on long-term offset rates with

displacements and lengths of breaks recorded for historic

earthquakes, fault creep rates, and behavior of different

segments of the fault. He arrived at an estimated recurrence

interval of 100 years with an uncertainty of at least a factor of two. In other words, the recurrence interval for

great earthquakes on the San Andreas may lie between 50 and

200 years

.

Although a magnitude 8+ earthquake on the San Andreas

fault seems to represent the most destructive of probable

future shocks in California, the twentieth century earthquake

history of the state of California teaches the lesson that

severe earthquakes with substantial damage and extensive loss

of life must be expected from other faults. The San Fernando

earthquake and three of the other five earthquakes listed in

table 2.1 (Long Beach, Kern County, and Santa Barbara)

occurred on faults that are not included in the San Andreas

system. The San Fernando and Kern County earthquakes occurred

along faults not generally recognized as active before the

earthquakes. This points up the need for the development of

improved methods of characterizing the potential activity

of faults and the application of these methods in geologic

field studies to assess the activity of faults in California

and other seismically active areas.

2 . 2 Crustal Deformation in the San Fernando Earthquake

The crustal movements responsible for the San Fernando

earthquake, like the other earthquakes in California's

history, are part of a pattern ol" deformation that has been

going on for tens of millions of years. An understanding

of this pattern is important for a proper evaluation of the

earthquake hazard in this region and a consideration of

measures to reduce the hazard. The following description

of the geologic setting of the San Fernando earthquake is

summarized from a report by Wentworth and Yerkes [2.6].

The pattern of crustal deformation in coastal California

24
is dominated by the San Andreas fault system. In southern

California, the relative displacement of the two blocks on opposite sides of the fault has amounted to about 130 miles

in the past 30 million years. North of Los Angeles near the

center of the map in figure 2.2, the San Andreas makes a sharp bend from a southeasterly to a more easterly trend. In

the general area to the south of this bend in the San Andreas

lie the San Gabriel Mountains and further to the south and

southwest the San Fernando Valley and the Los Angeles Basin.

As the crustal block to the southwest of the San Andreas

fault moves northwestward, the area to the south of the bend

is compressed against the bend. In response to these

compressive forces the San Gabriel Mountains have been thrust

up and southward relative to the Los Angeles Basin and the

San Fernando Valley, along no rth - di pp i n g faults. As a result

of movements along these faults, mainly in the past 5 to 10

million years, the San Gabriel Mountain block has been

elevated relative to the Los Angeles Basin by some 12,000

feet

.

The San Fernando earthquake represents a single episode

in this continuing process of crustal deformation. The

faulting associated with the earthquake produced a zone of

surface ruptures that trends more or less eastward across

the northern part of the San Fernando Valley (fig. 2.3). The

ruptures in this zone, now named the San Fernando fault zone,

were studied in detail by the U. S. Geological Survey [2.7

and 2.8]. Measurements near the center of the zone indicate

that the block to the north had a relative movement of about

6 feet to the west and 4.5 feet vertically upward. Horizontal

shortening in a north-south direction across the zone amounted

to about 2 feet. Where the orientation could be reliably

determined, the surface ruptures dipped to the north at angles

of about 55° to 65°

Preliminary locations of aftershocks determined by

Wesson, Lee, and Gibbs [2.9] and a fault plane solution by

the same authors for the main shock are consistent with a principal plane of slippage dipping to the north under the

San Gabriel Mountains, with a dip somewhat flatter than

indicated by the ruptures at the surface. Almost all of the

aftershock epicenters lie to the north of the zone of surface

breakage; and, in a north-south cross-section, the aftershock

foci fall into a wedge-shaped zone, the lower boundary of

which dips 30° to 40° north. This lower boundary corresponds

approximately to the fault-plane solution for the main shock

and can tentatively be identified with the principal plane of

slippage.

A substantial amount of building damage was directly

related to ground rupture along the San Fernando fault zone

[2.10]. The breakage of gas and water pipelines and extensive

25
26
Figure 2.3 The San Fernando fault zone. Heavy black lines

show the approximate location of the zone of

surface faulting

.

27
damage to pavements were also the direct result of rupture

along the zone. The spectacular damage at the Olive View and

Veterans Administration hospitals, on the other hand, appears

to be due to ground shaking rather than surface ground

breakage

.

The San Fernando fault zone was not recognized to be

active before the earthquake of February 9. Similarly the

Kern County earthquake of 1952, the largest earthquake in

California since 1906, occurred on the White Wolf fault,

which had not been recognized as active before the earthquake. In view of the severe damage and loss of life caused

by the San Fernando earthquake, it becomes important to

consider whether it would have been possible to recognize

the San Fernando fault zone as active before the earthquake.

The 200-year historical record is too short to provide an adequate basis for evaluating fault activity. Geologic

methods [2.11] have been developed for assessing the

potential activity of a fault zone. These methods include

a consideration of the effects of faulting on alluvial

deposits and on the flow of ground water in alluvium. From

their study of the San Fernando area after the earthquake,

Wentworth and Yerkes [2.6] concluded that an application of

these methods before the earthquake would have suggested

that the fault zone should be considered active, at least

for land uses requiring high safety factors.

2 . 3 References

2.1 Richter, C. F., "Elementary Seismology", W. H. Freeman

and Co. , 1 958.

2.2 Wood, H. 0., and Heck, N. H., "Stronger Earthquakes

of California and Western Nevada", Part II of

Earthquake History of the United States, revised

ed. (through 1963) by R. A. Eppley, U. S. Coast

and Geodetic Survey No. 41-1, 1966.

2.3 Tocher, Don, "Seismic

Region" California

Special Report 57,

History of the San Francisco

Division of Mines and Geology,

1 959.

2.4 Allen, C. R. , "The Tectonic Environments of Seismically

Active and Inactive Areas along the San Andreas

Fault System"; i_n Dickinson, W. R. and Grantz,

Arthur, ed,. Proceedings of the Conference on Geologic Problems of San Andreas Fault System,

Stanford University, published in the Geological

Sciences , Vol . 11 , 1968.

28
2.5 Wallace, R. E., "Earthquake Recurrence Intervals on

the San Andreas Fault", Geological Society American

Bulletin , V. 81 , 1970.

2.6 Wentworth, C. M. , and Yerkes , R. F., "Geologic Setting

and Activity of Faults in the San Fernando Area,

California"; iji^ The San Fernando, California,

Earthquake of February 9, 1971, a preliminary

report: U. S. Geological Survey Professional

Paper 733, 1971

.

2.7 Burford, R. 0., Castle, R. 0., Church, J. P., Kinoshita,

W. T., Kirby, S. H., Ruthven, R. T., and Savage, J.

C, "Preliminary Measurements of Tectonic Movement";

i n the San Fernando, California, earthquake of

February 9, 1971, a preliminary report: U . S.

Geological Survey Professional Paper 733, 1971.

2.8 "U. S. Geological Survey, "Surface Faulting"; iji^ The

San Fernando, California, Earthquake of February 9,

1971, a preliminary report: U. S. Geological

Survey Professional Paper 733, 1971.

2.9 Wesson, R. L., Lee, W. H. K., and Gibbs, J. F.,

"Aftershocks of the Earthquake"; i_n The San

Fernando, California, earthquake of February 9,

1971, a preliminary report: U. S. Geological

Survey Professional Paper 733, 1971.

2.10 Youd, T. L., and Olsen, H. W., "Damage to Constructed

Works Associated with Soil Movements and Foundation

Failures"; ijT^ The San Fernando, California, Earthquake of February 9, 1971, a preliminary report:

U. S. Geological Survey Professional Paper 733,

1971.

2.11 Wentworth, C. W., Ziony, J. I., and Buchanan, J. M.,

"Preliminary Geologic Environmental Map of the

Greater Los Angeles, California", U . S. Atomic

Energy Commission, TID-25363, map scale 1:250,000,

1970.

29

CHAPTER 3 SEISMIC WAVES AND STRONG-MOTION SEISMOGRAPHS

3 . 1 SeismicWaves

Ground motion is excited by the propagation of waves

which emanate from the hypocenter (source) of an earthquake.

There are four basic seismic waves: two preliminary "body"

waves which travel through the earth and two which travel

only at the surface. The total wave propagation pattern is

shown schematically in figure 3.1. Combinations, reflections,

and diffractions produce countless number of waves of other

types. In addition, a large earthquake generates inelastic

waves .The two body waves are the primary (P) wave and the

secondary (S) wave. The P wave travels about twice as fast

as the S wave, and is the first instrumental indication

that an earthquake has occurred.

The P wave is longitudinal, like a sound wave, and

propagates through both liquids and solids. It travels about

4 miles per second or nearly 15,000 miles per hour. As the

compressi onal P wave passes through the earth's crust, an

object embedded in the ground or on the surface is subjected

to a series of sharp pushes and pulls parallel to the wave

path-motion similar to that which the passengers feel when a long train gets under way [3.1].

The S wave is transverse, like a light or radio wave,

and travels barely more than half as fast as the P wave.

As this wave travels, it displaces objects at right angles

to the direction of wave travel. There is hardly any

vertical motion associated with the S wave, as the vertical

component is damped by the opposing force of gravity,

however, side-to-side shaking in the horizontal plane can

be extremely destructive.

Surface waves. Love and Rayleigh, are of much greater

length and period, such as, 30 seconds or more versus less

than one second for P waves. The Love wave produces lateral

shear in the horizontal plane, and the Rayleigh wave induces

a retrograde, elliptical motion, similar to wind-driven

ocean waves. The speed of the Love wave is about 2.5 miles

per second and the Rayleigh wave is about 10 percent slower

[3.1].

Because the waves generated by an earthquake travel at

different speeds, the seismic waves arrive at a given point

at different times. A recording station located at a great

distance could record a single event for days as reflected,

combined, and resonated waves propagate through the earth's

31
Figure 3.1 Elastic earthquake generated waves.

32
mantle and core.

The first indication of an earthquake is signaled by the

arrival of the compress i onal (P) waves. This will be followed

by the shear (S) waves and then the "ground roll" caused by

the surface waves. When compared with the body waves (P and

S) , the surface waves usually have the stronger vibrations

and probably cause most earthquake damage.

The vibrations induced by earthquakes are detected,

recorded, and measured by seismographs. In the region of

strong ground motions near a high-energy source, "strongmotion" seismographs are used. These seismographs are

usually installed in tall and large buildings, in some dams

and bridges, and at nuclear reactor sites. They are triggered

by the earthquake-generated vibration above a given threshold

amplitude, so that the onset of the earthquake motion is

usually lost. However, the lost portion of the record has

little value to earthquake engineering which is primarily

concerned with the earthquake-resistance design of structures.

3 . 2 Strong-Motion Records

The San Fernando earthquake provided a large number of

strong-motion acceleration records. These will undoubtly

supply valuable data on ground and building motions. More

than 250 strong-motion seismographs were in southern

California at the time of the earthquake, of which more than

200 were in the Los Angeles area. These seismographs were

installed primarily in large and tall buildings as a direct

result of the inclusion of provisions in the building codes

of the City of Los Angeles and of other adjoining municipalities requiring the installation of seismographs at three

different levels in these buildings (see Chapter 5 for the

Los Angeles area building code requirements). Most of the

strong-motion seismographs are privately owned but are

maintained by the Sei smol ogi cal Field Survey unit of National

Oceanic Atmospheric Administration's National Ocean Survey as part of a cooperative network [3.2].

A typical strong-motion seismograph measures on paper

or film the duration and amplitude of three acceleration

components, one vertical and two mutually perpendicular

horizontal components. In general, the seismograph at the

basement level of a building provides a reference record of

actual ground motion at a specific site and the two seismographs at the upper stories indicate response of the building.

Both velocities and displacements can be obtained by integration of the acceleration data. They then can be used to

compare actual performance with the performance predicted by

design. In a damaged building, information obtained from

33
such comparison could serve as an aid in locating likely

overstressed members in a building for repair work.

The large number of records obtained in this earthquake

will supply, for the first time, a wealth of data on the

character of the ground motion and the response of structures

to strong ground motion. It is hoped that study of these

data will answer some of the fundamental questions in

earthquake engineering, such as how much the local geology

affects ground motion, and what level of energy induced by

ground acceleration dissipates in buildings.

3 . 3 Strong-Motion Seismograph Data

Strong-motion seismographs located in southern California

outside the Los Angeles area are shown in figure 3.2. The

locations of these seismographs and their recorded accelerations are listed in table 3.1 at the end of this chapter.

The table gives for each location the maximum acceleration

of the vertical component (V) and the two mutually perpendicular horizontal components (HI and H2) , expressed as a fraction of gravity along with approximate periods corresponding to these acceleration components. The Old Ridge Route

station at Castaic (location 6), some 15 miles away from the

epicenter, shows the high value of 0.388g (gravity) in the

horizontal direction and 0.178g in the vertical direction.

Similarly, one station (No. 12) at Lake Hughes (location 7),

some 10 miles east of Castaic, showed peak acceleration values

of 0.371g in the horizontal and 0.178g in the vertical

directions.

The locations of seismographs in the Los Angeles area

are shown in figure 3.3 and recorded accelerations are listed

in table 3.2 at the end of this chapter. Note in figure 3.3

that the nearest seismographs to the City of San Fernando are

locations No. 28 and No. 29. The maximum accelerations at

location No. 28, a Holiday Inn, at the ground floor were

0.276g in the horizontal direction and 0.171g in the vertical

di recti on

.

Preliminary analysis of the acceleration record obtained

at Pacoima Dam (location 29) 5 miles south of the epicenter,

indicates that tDoth horizontal components exceeded 1.25g,

the largest motion ever recorded from an earthquake. The

vertical component had a single peak amplitude of 0.7g. The

acceleration records indicate that during the first 12 seconds,

the ground at the dam was subjected to almost continuous

accelerations ranging from 0.5g to 0.7g. The highest acceleration level ever recorded previously in the United States

was 0.5g, noted during the Parkfield, California earthquake

in 1966 [3.3]. The unexpected magnitude of the ground

34
35
y PACOIMA DAM

29
acceleration at the Pacoima Dam will change the thinking of

many engineers and seismologists who previously thought

0.5g to be a practical maximum that could be transmitted by

an earthquake. It is clearly seen in figure 3.4 that a proposed empirical relationship between the maximum acceleration and the epicentral distance based on measurements made

in previous U. S. earthquakes [3.4] is not applicable to the

San Fernando earthquake.

The ground level accelerations in the Los Angeles area,

measured much farther from the epicenter than the Pacoima

Dam, ranged from O.lOg to 0.23g in the horizontal direction

and from 0.03g to 0.17g in the vertical direction. While

larger values (greater than 0.2g) of acceleration were

noted at stations near or in the San Fernando Valley, a few

locations in downtown Los Angeles also experienced more than

0.2g.

The production of copies of the accelerograms and

digitization of the records were carried out at the California

Institute of Technology. The accelerograms reconstructed from

the digitized records from the Pacoima Dam, the calculated

relative velocity response spectra, and ground displacements

from recorded accelerograms are shown in figures 3.5, 3.6,

and 3.7. Maximum response was in the period of 0.3 - 0.4

second in the east-west direction, 0.4 and 1.6 second in the

north-south direction and 0.2 - 0.4 second in the vertical

direction. It should, however, be pointed out that high

ground accelerations by themselves do not reflect damaging

characteristics of an earthquake. Undamaged Pacoima Dam

clearly points out this fact. As more digitized information

on buildings become available, the response of each structure

to the earthquake as affected by its natural period can be

studied to assist in explaining structural damages sustained

by many buildings in the San Fernando Valley area. The

acceleration records as obtained from a number of field

stations are presented in figures 3.8 through 3.18.

3 . 4 Summary

The San Fernando earthquake provided an opportunity,

for the first time, to collect a wealth of acceleration

records. This is a direct result of the deployment of

strong-motion seismographs in buildings and other large

structures by means of including provisions in building

codes requiring the installation of seismographs. The

acceleration data will undoubtedly serve as the single best

source of scientific information for earthquake engineering

research. The knowledge gained from study of the data will

aid greatly in efforts to reduce hazards from future strong

earthquakes

.

37
6.6 (San Fernando)

1.00

>

<

C9

• 0.10

z

o

I-<

K

UJ

-iUlu

u

<

o

bJo

(to

o

UlK 0.01

3

<

.001

T

-

"I—r"

r T r 1 r r" T f I 1 1 1 1 I 1 I 1 r 1 1 L

-

-

I.I

1 I.I ^"^..^^^

-

-

6.6.

•^•^ -

6.6^ •6.5 •

•

7.1 \

\

- • 7.6

7.6,

-

- 7.3\ -

—

7.3. \

—

•6.4

7.6« -

-

(A t 1 Irf. MAbNI 1 UU • 76

1

1 1 1 III 1

I 1 11 1 1 1

1 1 1 1 10 100

DISTANCE TO EPICENTER - MILES

Figure 3.4 Single-component accelerations recorded from

1933 through 1964 by strong-motion seismographs [3.4]

7.9' 8.4 (

38
SECONDS

NOAA STRONG-MOTION ACCELEOGRAPH NETWORK AND

THE EARTHQUAKE ENGINEERING RESEARCH LABORATORY

CAUFORNIA INSTITUTE OF TECHNOLOGY

Figure 3.5 Ground accelerations at Pacoima Dam.

39
NOAA STRONG-MOTION ACCELEOGRAPH NETWORK AND

THE EARTHQUAKE ENGINEERING RESEARCH LABORATORY CAUFORNIA INSTITUTE OF TECHNOLOGY Figure 3.6 Relative velocity response spectrum at

Pa COima Dam.

40
GROUND DISPLflCEN€NT

2/9/71 0600 PST TOCOIMA DAM CAUFORNIA

S 74° W COMPONENT

SECONDS

NOAA STRONG- MOTION ACCELEOGRAPH NETWORK AND

THE EARTHQUAKE ENGINEERING RESEARCH LABORATORY

CALIFORNIA INSTITUTE OF TECHNOLOGY

Figure 3.7 Ground displacements at Pacoima Dam.

41
The horizontal ground acceleration at Pacoima Dam was

predominantly in a range of 0.5g - 0.7g with a peak in

excess of 1.25g. The vertical acceleration had a single

peak amplitude of 0.7g. Validation of these unexpected

large values may prove to be difficult because the foundation

which supported the seismograph cracked, and might have

caused some distortions in acceleration recordings at this

site. However, a post-earthquake calibration of the seismograph showed that the seismograph performed to specifications.

In addition, physical evidence at the Kagel Canyon Fire

Station some 2 and 3/4-miles south-southeast from Pacoima

Dam indicates that vertical accelerations may have exceeded

l.Og. Morril [3.5] has reported that "A 20-ton fire truck

moved 6 to 8 feet fore and apt, 2 to 3 feet sideways without

leaving visible skid marks on the garage floor." This

movement occurred in spite of the fact that the truck was in

gear and the brakes were set. Rubber marks were found on

the garage door frame three feet above the ground which appear

to have been made by the right rear tire of the fire truck.

The metal fender which extended a few inches beyond the tire

was not damaged.

Ground accelerations in the downtown Los Angeles areas

were, in most cases, less than 0.2g in the horizontal direction and O.lg in the vertical direction. However, larger

values of acceleration were recorded at the top floor of

h i g h r i s e buildings.

In general the systems of accelographs performed well

and obtained much useful data. However, there were cases

where data were not obtained due to a lack of maintenance of

equipment, such as dead batteries, traces too faint to read,

or lack of paper in the instrument.

3 . 5 References

3.1 "Earthquakes," National Ocean Survey, National Oceanic

Atmospheric Administration, U . S. Government

Printing Office, Washington, D. C, 1 969.

3.2 Maley, R. P. and Cloud, W. K., "Preliminary StrongMotion Results from the San Fernando Earthquake

of February 9, 1971," Geological Survey Professional

Paper 733, U. S. Government Printing Office,

Washington , D. C. , 1971

.

3.3 "Earthquake Information Bulletin, March-April 1971,"

National Ocean Survey, National Oceanic

Atmospheric Administration, U. S. Government

Printing Office, Washington, D. C, 1971.

42
Cloud, W. K., "Strong- Mot ion and Building-Period

Measurements: The Prince William Sound, Alaska,

Earthquake of 1964 and Aftershocks," Vol. II, Part

A, National Oceanic Atmospheric Administration,

U. S. Government Printing Office, Washington, D. C.

1 967.

Morril, B. J., "Evidence of Record Vertical Accelerations

at Kagel Canyon during the Earthquake," Geological

Survey Professional Paper 733, U. S. Government

Printing Office, Washington, D. C, 1971.

43
NATIONAL OCEAN SURVEY. NOAA

SEISMOLOGICAL FSELD SURVEY

LOS ANGELES 2/9/71 0600 PST

OLD RIDGE ROUTE

DOWN

g 0

0.5 H

I—'—

r

-1

'—

r

e 9

-1—'—I

'—[—'—I—I—I—I—

r

2 3 4 5 6 10 II 12 13 14 19 seconds

Figure 3.8 Seismograph record, Castaic , California.

44
NATIONAL OCEAN SURVEY, NOAA

SEISMOLOGICAL FIELD SURVEY

LOS ANGELES 2/9/71 0600 PST

LAKE HUGHES ARRAY NO. I

0.5 -

N 21° E

g 0

0 .5 -i

DOWN

0.5

g 0

0.5 H

0.5 -

S 69» E -I

g 0

0.5 i

T '-—T

2 3 T—'

1

'

1

1 1 1 1' 1 '

I 7 e 9 10 II 12 13 14 15 seconds

Figure 3.9a Seismograph record. Lake Hughes, California

,

Station 1

.

45
NATIONAL OCEAN SURVEY, NOAA

SEISMOLOGICAL FIELD SURVEY

LOS ANGELES 2/9/71 0600 PST

LAKE HUGHES ARRAY STATION NO. 9

0.5 -

N 21° E

DOWN

0 5

N 69" W

-1—1—r—f—I—'—I—I—I—I—I—"—I—I—I < I—>—I—'—I—r—1—'—r—'—r"

2 3 4 5 6 7 e 9 10 II 12 13 14 15 seconds

Figure 3.9b Seismograph record. Lake Hughes, California

,

Station 9.

46
NATIONAL OCEAN SURVEY, NOAA

SEISMOLOGICAL FIELD SURVEY

LOS ANGELES 2/9/71 0600 PST

Figure 3.9c Seismograph record. Lake Hughes, California

,

Station 12.

47
NATIONAL OCEAN SURVEY, NOAA

SEISMOLOGICAL FIELD SURVEY

LOS ANGELES 2/9/71 0600 PST

PEARLBLOSSOM PUMPING PLANT

0.5 -

NORTH

g 0

0.5 ^

0.5

DOWN

g 0

WEST

g 0

"T—'—

r

3 4 T—I I

• (

I—I—I—T—'—r—

5 6 7 9 10 II 12 13 14 seconds

Figure 3.10 Seismograph record, Pearlblossom , California

.

48
NATIONAL OCEAN SURVEY, NOAA

SEISMOLOGICAL FIELD SURVEY

LOS ANGELES 2/9/71 0600 PST

100 HOPE ST. BASEMENT

o.s

-

N 50" W

g 0

0.5 i

0.5 -

DOWN

g 0

0.5 -i

T—' I

'—r2 3 4 T—' I'—r5 6 7 T—'

\—I—I—I—I—1—I—I—I—'—r9 10 II 12 13 14 15 seconds

Figure 3.11a Seismograph record, 100 Hope Street, Los

Angel es , basement

.

49
NATIONAL OCEAN SURVEY, NOAA

SElSMOLOGICAL FIELD SURVEY

LOS ANGELES 2/9/71 0600 PST

Figure 3.11b Seismograph record, 100 Hope Street,

Los Angeles, 7th floor.

50
NATIONAL OCEAN SURVEY, NOAA

SEISMOLOGICAL FIELD SURVEY

LOS ANGELES 2/9/71 0600 PST

100 HOPE ST. 15 TH FLOOR

0.5 -

DOWN

g 0

I

'

I ' I

' I' I 1 I 1

I 2 3 4 5 6 7 8 seconds

T—'—I—'—I—"—I—'—I—'—I—I—|—

9 10 II 12 13 14 15

Figure 3.11c Seismograph record, 100 Hope Street,

Los Angeles, 15th floor.

51
0.5 -

DOWN

g 0

NATIONAL OCEAN SURVEY, NOAA

SEISM0L06ICAL FIELD SURVEY

LOS ANGELES 2/9/71 0600 PST

SANTA ANITA RESEVOIR

N 03" E

-

g o

0 .5 -i

7 8 seconds

Figure 3.12 Seismograph record, Santa Anita Reservoir.

52
NATIONAL OCEAN SURVEY, NOAA

SEISM0L06ICAL FIELD SURVEY

LOS ANGELES 2/9/71 0600 PST

3407 SIXTH ST. BASEMENT

0.5-

SOUTH

g 0

0.5 H

0.5 -

DOWN

g 0

0.5 H

7 e seconds

Figure 3.13a Seismograph record, 3407 Sixth Street,

Los Angeles, basement.

53
NATIONAL OCEAN SURVEY, NOAA

SEISMOLOGICAL FIELD SURVEY

LOS ANGELES 2/9/71 0600 PST

54
NATIONAL OCEAN SURVEY, NOAA

SEISMOLOOICAL FIELD SURVEY

LOS ANGELES 2/9/71 0600 PST

3407 SIXTH ST. PENTHOUSE

SOUTH

0.9-

g 0

O S -i

0.9

DOWN

9 0

09 H

EAST

09-

g 0

OA -1

1-

10 IS seconds

Figure 3.13c Seismograph record, 3407 Sixth Street,

Los Angeles, penthouse

.

I 55
NATIONAL OCEAN SURVEY, NOAA

SEISM0L06ICAL FIELD SURVEY

LOS ANGELES 2/9/71 0600 PST

3470 WILSHIRE SUB -BASEMENT

0 5

-

NORTH

g 0

0.5 H

0.5 -

DOWN

g 0 - A'VA\/<*''V'^«"A^\;\^y>/y/Vtfs^ >AvyV~^V/^Vv/S\yw^''W-^

0.5 H

0.5 -

WEST

go

I

' I

'

I

>

I

' 1

• T~-f- 1

I

I I

t

I

*

i t"

'

I

' V I I t

I 0 I 2 3 4 5 6 7 8 9 10 II 12 13 14 15 seconds

Figure 3.14a Seismograph record, 3470 Wilshire , Los

Angeles, sub-basement.

56
NATIONAL OCEAN SURVEY. NOAA

SEISM0L06ICAL FIELD SURVEY

LOS ANGELES 2/9/71 0600 PST

3470 WILSHIRE 5 TH FLOOR

0.5 -

EAST

9 0

0.5 -i

0.5 -

DOWN

g 0-

seconds

Figure 3.14b Seismograph record, 3470 Wilshire , Los

Angeles, 5th floor.

57
NATIONAL OCEAN SURVEY, NOAA

SEISMOLOGICAL FIELD SURVEY

LOS ANGELES 2/9/71 0600 PST

3470 WiLSHIRE -II TH FLOOR

0.5 -

EAST

g 0

OS i

DOWN

g 0

NORTH

g o

T"

7 8 13 seconds

Figure 3.14c Seismograph record, 3470 Wilshire

,

Los Angeles, 11th floor.

58
NATIONAL OCEAN SURVEY. NOAA

SEISMOLOGICAL FIELD SURVEY

LOS ANGELES 2/9/71 0600 PST

4867 SUNSET BASEK^NT

0.5 -

S 89" W

g 0

0.5 H

DOWN

g 0

0.5 H

0.5 -

S 01° E

-

g 0

0 .5 -|

I—'—

r

I I I T ' r

13 seconds

Figure 3.15a Seismograph record, 4867 Sunset,

Los Angeles, basement.

59
0 5 H

NATIONAL OCEAN SURVEY, NOAA

SEISMOLOGICAL FIELD SURVEY

LOS ANGELES 2/9/71 0600 PST

4867 SUNSET 2 ND FLOOR

0.5 -

DOWN

g 0

-I—

r

7 e seconds

10 1—I—T—r—

13

Figure 3.15b Seismograph record, 4867 Sunset,

Los Angeles, 2nd floor.

60
NATIONAL OCEAN SURVEY, NOAA

SEISMOLOGICAL FIELD SURVEY

LOS ANGELES 2/9/71 0600 PST

4867 SUNSET 7 TH FLOOR

seconds

Figure 3.15c Seismograph record, 4867 Sunset, Los

Angeles, 7th floor.

61
NATIONAL OCEAN SURVEY, NOAA

SEISMOLOGICAL FIELD SURVEY

LOS ANGELES 2/9/71 0600 PST

7080 HOLLYWOOD BASEMENT

EAST

0 5 -i

DOWN

g 0

seconds

Figure 3.16a Seismograph record, 7080 Hollywood,

Los Angeles, basement

.

62
NATIONAL OCEAN SURVEY, NOAA

SEISMOLOGICAL FIELD SURVEY

LOS ANGELES 2/9/71 0600 PST

7080 HOLLYWOOD 6 TH FLOOR

Ob -

WEST

g

0.5 -

0.5 -

DOWN

g 0

0.5 -

0.5 -

SOUTH -

g 0

0 .5 -

I—'—I—"—I—'—I—' I

'—I—'—I—'—I—I—I

I—I—'—I—'—I—'—I—'—I—'—I—'—

r

0 I 2 3 4 5 6 7 8 9 10 II 12 13 14 15 seconds

Figure 3.16b Seismograph record, 7080 Hollywood,

Los Angeles, 6th floor.

63
NATIONAL OCEAN SURVEY, NOAA

SEISMOLOGICAL FIELD SURVEY

LOS ANGELES 2/9/71 0600 PST

7080 HOLLYWOOD 12 TH FLOOR

EAST

g o

0 5 -i

DOWN

g 0

T—"—I—'—

r

—I—'—

r

7 e seconds

T—'—r9 10

-1 ' 1 >-

II 12 .

Figure 3.16c Seismograph record, 7080 Hollywood

,

Los Angeles, 12th floor.

64
NATIONAL OCEAN SURVEY, NOAA

SEISMOLOGICAL FIELD SURVEY

LOS ANGELES 2/9/71 0600 PST

1901 AVE. OF STARS

SUB-BASEMENT

0.5 -

N 46" W

0.5 -

0.5 -

DOWN

g 0

0 5

-

0 5

-

S 44" W -

g 0

0 .5 -

1—'—I—'—I—'—I—'—I—'—I—'—I

<—I——I—'—I—'—I—1—I—I

\—'—I—'—I—I—

r

0 I 2 3 4 5 6 7 8 9 10 II 12 13 14 15 seconds

Figure 3.17a Seismograph record, 1901 Avenue of Stars,

Los Angeles, sub-basement.

65
NATIONAL OCEAN SURVEY, NOAA

SEISMOLOGICAL FIELD SURVEY

LOS ANGELES 2/9/71 0600 PST

1901 AVE. OF STARS

9 TH FLOOR

DOWN

g 0

S 44"' W

g 0

1 I

'—I'—r9 10 II 12 1—'—r13 14 seconds

Figure 3.17b Seismograph record, 1901 Avenue of Stars,

Los Angeles, 9th floor.

66
NATIONAL OCEAN SURVEY, NOAA

SEISMOLOGICAL FIELD SURVEY

LOS ANGELES 2/9/71 0600 PST

8244 ORION BLVD. 1ST FLOOR

Figure 3.18a Seismograph record, 8244 Orion Boulevard,

Los Angeles, 1st floor.

67
NATIONAL OCEAN SURVEY. NOAA

SEISM0L06ICAL FIELD SURVEY

LOS ANGELES 2/9/71 0600 PST

8244 ORION BLVD. 4TH FLOOR

' I6 —

r

T—"—T—'—r "

I 7 e 10 II 12 13 seconds

15

Figure 3.18b Seismograph record, 8244 Orion Boulevard,

Los Angeles, 4th floor.

68
NATIONAL OCEAN SURVEY. NOAA

SEISMOLOGICAL FIELD SURVEY

LOS ANGELES 2/9/71 0600 PST

8244 ORION BLVD. 8TH FLOOR

1—'—I—'—I—>—T—'—1—

3 4 5 6 7 8 9 10 II 12 13 seconds

Figure 3.18c Seismograph record, 8244 Orion Boulevaxd,

Los Angeles, 8th floor.

69
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03 -^

c; HS

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•H

u

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CD "t! •H

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fC

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CHAPTER 4 GEOLOGY AND SOIL CONDITIONS

4 . 1 Geologic Setting

The Los Angeles area is both surrounded by and interlaced

with numerous geological faults. Some of the larger welldefined faults are shown on figure 4.1 in relation to Los

Angeles and neighboring cities and geographical landmarks.

The San Andreas fault which has been a dominent influence in

California is seen to be across the mountain range from the

San Fernando Valley and displayed no activity throughout

this earthquake. Major damage was fairly well confined to

the northern portion of the San Fernando Valley, in the

Sylmar-Pacoima-San Fernando area. The predominantly eastwest oriented mountain ranges are referred to by geologists

as the Transverse Ranges.

The following description of geologic setting is

abstracted from material presented by Wentworth and Yerkes

[4.1].

"The faulting associated with the San Fernando

earthquake of February 9, 1971, occurred in the

Transverse Ranges structural province, a region

noted for its strong and relatively young tectonic

def ormati on

.

The Transverse Ranges structural province

trends eastward across southern California and

constitutes a region of late Cenozoic north-south

shortening that lies athwart the north-westerly

regional trend of the dominant San Andreas fault

system.

The Transverse Ranges province consists of

numerous eas t- trendi ng mountain ranges and valleys

typified by late Cenozoic structural deformation

and strike slip, reverse, and thrust faults of

similar trend [4.2 and 4.3]. The most spectacular

development of the structure of this province is

in the Ventura Basin, where an immense Cenozoic

syncline that includes a thickness of 1,500 m of

marine Pleistocene sediments has both limbs

overturned and overridden by thrust [4.2]. Very

young deformation in the Transverse Ranges is not

restricted to the Ventura Basin, however, and late

Quaternary faulting is known to occur from near

Point Conception eastward to the San Andreas

fault.

The February 9, 1971, faulting broke the ground

83
84
surface near the north margin of the San Fernando

Valley opposite the "great bend" in the San

Andreas fault south of the San Joaquin Valley. The

geometry of the crustal blocks in this region is

such that the Transverse Ranges structural block

southwest of the San Andreas fault is constrained

and compressed against the bend as the block moves

northwestward along the fault. During the past 5

to 10 million years this compressive deformation

has thrust the mountain blocks up over adjacent

valleys to the south. The movement has occurred

along north-dipping reverse or thrust-fault

systems such as the Sierra Madre and Santa

Susana, which trend west and northwest along the

southern margins of the mountain blocks. The

most impressive product of this uplift is the

bold southern front of the San Gabriel Mountains,

which stands some 1,500 m above the San Fernando

and Los Angeles areas to the south. Additional

horizontal shortening and uplift of one of the

blocks occurred along the ruptures that accompanied

the San Fernando earthquake.

In the central Transverse Ranges the crystalline

basement rocks are overlain with great unconformity

by Cretaceous and younger sedimentary rocks many

thousands of meters thick. The San Fernando Valley

itself (fig. 4.2) is an asymmetric synclinorium

developed chiefly in Miocene and younger rocks

that have been deformed by late Cenozoic folding

and faulting, especially at the northern margin by

thrusting along the Santa Susana fault and its

eastward equivalents. Based on a gravity-density

model, Corbato [4.4] estimates that approximately

4,500 m of sedimentary rocks are present in the

central part of the valley.

None of the late Cenozoic sedimentary rocks

are particularly hard, and the Saugus Formation

especially is only partially indurated and difficult

to distinguish from alluvium in drill holes.

Precambrian to Cretaceous crystalline rocks of

the basement complex are exposed in the San Gabriel

Mountains in the northeast part of the map area and

in the Verdugo Mountains in the southeast corner.

These dense metamorphic and igneous rocks constitute

the terrane on which the sedimentary sequence was

deposited. Cretaceous and lower Tertiary sedimentary

strata are only exposed locally along the Santa

Susana and San Gabriel faults, although to the

west and south of figure 4.2 they crop out extensively.

85
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87
Within the map area south of the San Gabriel

fault, the oldest sedimentary rocks overlying the

basement are the middle Miocene Topanga Formation,

which includes about 300 m of conglomerate,

marine sandstone, and volcanic rocks.

As much as 1,500 m of marine upper Miocene

Modelo Formation is exposed along the foothills of

the San Gabriel and Verdugo Mountains, in the

Mission Hills, and in the Santa Susana Mountains.

The Modelo is overlain by, and locally interfingers

with, the Towsley Formation of late Miocene-early

Pliocene age. The Towsley ranges in thickness from

zero where it is overlapped by the Pico Formation

just south of the San Gabriel fault zone to about

750 m in the east and west central parts of the

map area.

The Pico grades upward and laterally into the

late Pliocene-early Pleistocene Saugus Formation,

a shallow marine to brackish-water unit that rims

the north side of the San Fernando Valley. The

Saugus Formation thickens westward from essentially

zero at Big Tujunga Canyon to about 1 ,950 m at

Lopez Canyon east of Pacoima Wash. An exploratory

well drilled north of the Olive View fault and about

1 1/2 km west of Olive View Sanitorium penetrated a minimum strati graphi c thickness of 1,200 m of

Saugus Formation, and the California State Water

Rights Board report [4.5] states that the formation

exceeds 1,800 m in thickness in the syncline near

Syl mar

.

The "middle Pleistoce" Pacoima Formation of

Oakeshott [4.6] has been combined with the Saugus

Formation on the map (fig. 4.2). This deformed

f angl omerate-brecci a unit is exposed north of

Sylmar, where it unconf ormably overlies the

Saugus and is unconf ormably truncated by streamterrace and alluvial deposits.

Uplifted erosional remnants of stream-terrace

gravel and sand are widely distributed in the

San Fernando area, but only a few are shown on

the generalized map. No direct evidence for the

age of these deposits is available, although

a late Pleistocene age is inferred on the basis of

their strati graphi c position, lack of deformation,

and unconformable relations with the underlying

Saugus Formation. Oakeshott [4.6] was able to

distinguish five stages of terrace formation

along Pacoima Wash and two in the Lopez-Kagel

88
Canyon area 6 1/2 km northeast of San Fernando.

Some of the late Quaternary history of the

mountain blocks can be obtained from such

geomorphic features.

The relatively flat surface of San Fernando

Valley is underlain by unconsolidated sand,

gravel, and finer sediment ranging in thickness

from zero at the valley edges to greater than

200 m in the east-central part of the valley

near the south margin of figure 4.2. In the

Sylmar area, alluvium is perhaps 6 m thick,

except along Pacoima Wash [4.5].

Sediment west of Van Norman Lakes and along

the southern part of the valley has been supplied

by streams draining areas of sedimentary rocks,

with the result that alluvium in these areas

consists predominantly of clay. In contrast,

larger streams at the north margin of the valley

east of the Lakes drain crystalline rocks of high

relief and have produced deposits of coarser

materials with abundant gravel.

4 . 2 Type of Soil Movement and Introductory Remarks

Soil movements which occur during and subsequent to

earthquakes may be placed in two categories, primary movements associated with the faulting itself and secondary

movements which are triggered by the stress waves generated

by the earthquake. This section presents some brief comments

about the second category of soil movements.

The most common soil movement of the second category is

the landslide. Soil which is on a slope is stressed internally by gravity forces. There is a component of the gravity

force, which may be called a driving force, that is directed

downslope. The driving force is put into equilibrium by an equal and opposite force, the resisting force, which is

derived from the mobilization of the shear strength of the

soil. The accelerations of the surface soils due to an earthquake can cause increases in the driving force and

under some conditions can cause decreases in the resisting

force. When the driving force becomes greater than the

maximum resisting force, instability will result and a landslide will occur. Some massive landslides, both of

natural and man-made slopes, have been associated with

earthquakes in the past. A recent example is the Turnagain

slide which occurred as a result of the earthquake which

struck the city of Anchorage, Alaska, on March 27, 1964. The

slide zone was about 8,000 feet in length along the coastline

89
and extended inwardly approximately 600 feet at one end and

1,200 feet at the other end of the slide zone [4.7],

The analyses of slopes to predict earthquake effects is

a complex problem. Present state-of-the-art is such that a simple model is normally selected to represent the stability

problem. A horizontal seismic force is assumed to be acting

through the center of gravity of the potential sliding mass

and the analysis is performed using principles of static

equilibrium. The seismic force contributes to the driving

force, possibly leading to instability. Most of the current

design procedures presently in use do not take vertical

acceleration into account.

The shear strength of the soil can be affected by the

stresses induced by earthquakes. Normally, this effect is

small or insignificant. However, there are two instances

in which the effect can be catastrophic, disturbance of

quick clays and liquefaction.

Quick clays, or clays which undergo a great loss of

shear strength due to disturbance, exist in some parts of

the world. These clays are rare in the United States, but

in other parts of the world massive slides have been

triggered by such low-level stresses as those induced by a passing railway train [4.8].

Liquefaction accounts for some spectacular soil

behavior during earthquakes. If a loose deposit of saturated

sand is subjected to earthquake stresses, the vibration

induces a tendency toward dens i f i ca ti on of the sand stratum,

reducing the i ntergranul ar pressures to zero, and converting

the sand mass into a liquid. Liquefaction was present at

some of the slides reported at Anchorage and caused some

spectacular failures at Niigata [4.9].

Another type of soil movement which can be associated

with earthquakes is the dens i f i ca t i on and consequent fracturing of the soil due merely to the passage of the stress

waves through the soil. There are many deposits of loose

material which can undergo sizable changes in volume due to

vibrati ons

.

4.3 Character of Soil at a Few Sites Affected by the San

Fernando Earthquake

The surface soils in the San Fernando Valley are alluvial

as a result of erosion of the mountains surrounding the

valley. The character of the surface soils will be described

for a few sites.

90
OLIVE VIEW HOSPITAL [4.10 and 4.11]

The hospital site is on the alluvial fan that has been

formed at the mouth of Wilson Canyon, which flows southerly

out of the San Gabriel mountains. In former times, water

flowed freely across the fan when it rained. The soils at

the site consist of sands and gravels, with a layer of very

large boulders at a depth of about eight feet. The sand

consists of subangular to subrounded grains of quartz,

feldspar, and rock fragments, with abundant biotite. The

granular materials were firm to dense. For the purpose of

foundation design the angle of internal friction which was

recommended was 38 degrees and the recommended density was

113 pounds per cubic foot. Because of the nature of the

material, considerable difficulty was encountered in putting

down borings. The deepest boring penetrated to about 40 feet

below the ground surface. No ground water was encountered

when the test holes were drilled.

SAN FERNANDO JUVENILE HALL [4.12]

The soil conditions at the site are extremely variable;

the natural soils vary from hard, dense conglomerate beneath

the westerly portion of the site to moderately soft silt

and silty sand beneath the southeasterly portion of the site.

The borings were carried to a depth of 30 feet at some

locations. Ground water was encountered in several of the

borings ranging in depths from 12 to 30 feet beneath the

ground surface.

HOLY CROSS HOSPITAL [4.13]

The soils at the site consist of non-uniform alluvial

deposits of sand, silt, and clay in various portions. The

upper soils are primarily fine-grained silts while the

deeper strata are generally more sandy with up to 20 per

cent gravel. The upper soils were found to be low in density,

with low shearing resistance, and they became compressible

upon saturation. The deeper soils are more dense, have

higher shearing resistance, and are more uniform and less

compressible. Borings at the site were carried down to a depth of 50 feet below the ground surface. Ground water

was encountered at the site at approximately 25 feet below

the present ground surface.

SOUTH CONNECTOR OVER- CROSS I NG (Palmdale Interchange-see

fig., 7.2)

Of primary interest from the standpoint of the foundation

91
is Pier 4 (fig. 7.3). The foundation consisted of a 10

foot by 6 foot rectangular section which was placed to a penetration of approximately 45 feet below the ground surface.

The pier was placed on the side of a steep valley (a slope

of approximately 40 per cent).

The soils at the site are an alluvial deposit and are

essentially granular in nature. At the ground surface the

soils are a compact, brown, fine to very fine sand with some

gravel. At a few feet below the ground surface, the soil

becomes more dense and contains more gravel. Occasional

thin layers of sandstone and gravel are encountered. Soil

borings at the site show that very dense, dark gray, silty,

fine to very fine sandstone was encountered at depth in some

of the holes. It is presumed that the bottom several feet of

the foundation penetrated into this sandstone. No information

is available on the depth of the water table at the site.

If good construction techniques were employed, the pier

should have an extremely high capacity to sustain vertical

loads. Insufficient data are available to estimate the

lateral deflection of the pier when subjected to horizontal

loads at the ground surface.

SEPARATION AND OVERHEAD, ROUTE 210/5 (fig. 7.11)

A description of the foundations at the site is given

in table 4.1. It can be noted that a variety of foundation

types were used.

The soils at the site are alluvial deposits and consist

mostly of coarse-grained material. The soils at the ground

surface are generally rather loose and become more dense with

depth. Penetrometer values are given, presumably values

which correlate with those from the standard penetration

tests, in the order of 1 to 10 blows per foot in the top 15

to 20 feet and increasing to perhaps 100 blows per foot at

a depth of 30 feet or less.

A typical boring log at the site is given in table 4.2.

No information is available on the location of the

water table at the site.

NORTHWEST CONNECTOR OVERCROSS I NG , ROUTE 210/5 (fig. 7.11)

The bents of this structure were erected on six foot

outside diameter concrete piles which were cast in drilled

holes which penetrated from 20 to 30 feet below ground

level. The soil is an alluvial deposit consisting

92
Table 4.1 Foundations for Separation and

Overhead , Interstate 210/5

Eleva ti on

of Ground

Surface

( es timated ) , Foundation S tat ion feet

Abutment 1 82+17 1271

Pier 2 83+17 1273

Pier 3 84+21 1276

Pier 4 85+50 1285

Pier 5 86+80 1309

Pier 6 87+88 1309

Pier 7 88+67 1343

Abutment 8 89+88 1375

Description of

Founda ti on

Class 1 concrete piles;

tip elevation of piles

1232; piles have 45 ton

bearing

Footing 17 ft by 19

ft; bottom elevation

1266; supported by

concrete piles; tip

elevation of piles

1235; piles have 45 ton

bear ing

Footing 17 ft by 19

ft; bottom elevation

1267 ; supported by

concrete piles; tip

elevation of piles

1242; piles have 45 ton

bearing

Six-foot outside diameter pile cast in a drilled hole; tip

elevation of pile 1262

Six-foot outside diameter pile cast in a drilled hole; tip

elevation of pile 1262

Six-foot outside

diameter pile cast in

a drilled hole; tip

elevation of pile 127 4

Six-foot outside diameter pile cast in a Drilled hole; tip

elevation of pile 1273

Class 1 concrete piles;

tip elevation of piles

1353; piles have 45 ton

bearing

93
principally of granular materials. The soil conditions

appear to be very similar to those described at the previous

two locations. A typical boring log is given in table 4.3.

4 . 4 Soil Movements Associated with San Fernando Earthquake

There is no evidence that there was any significant

damage to major buildings associated with liquefaction as

a result of the earthquake. The soil at the building sites

described above would not be subject to liquefaction. However, there is considerable evidence of densifi cation and

subsidence of soils which resulted from the vibrations

caused by the earthquakes. There are numerous evidences

of ground cracking and ground distortions. Some of these

ground movements are probably associated with faulting, but

many others are secondary movements due to densi f i cati on of

the soil because of the vibrations.

There was much evidence of landslides in the hills

surrounding the valley. Soil could be seen sliding from

mountains several days after the quake. Morton reported

that "approximately 1,000 landslides, ranging in length from

about 15 to more than 300 meters were mapped from the aerial

photographs" [4.14]. None of the landslides in the hills

appears to have caused major inconvenience or financial

losses. However, it is possible that the numerous areas

where the soil has been weakened by the occurrence of the

earthquake will be highly susceptible to further sliding

in periods of heavy rainfall.

A major landslide of a slope which is substantially

natural occurred in the vicinity of the Van Norman Reservoir

[4.15]. In addition, there was extensive slumping in the

alluvium aroun.d the margins of both the Lower and Upper Van

Norman Reservoirs. Some detail of these movements will be

given in the remainder of this section.

Also described in this section are serious movements

of the man-made slopes at the Upper and Lower San Fernando

Dams (which form the Van Norman Reservoirs).

LANDSLIDES NEAR THE VAN NORMAN LAKES (RESERVOIRS)

Youd [4.15] reports that "extensive slumping occurred

in the alluvium around the margins of both the Lower and

Upper Van Norman Lakes. In some places a nearly continuous

line of scarps formed. The scarp on the west shore of the

lower lake is more than 1 kilometer long." In connection

with these soil movements is the extremely interesting fact

that sand boils commonly formed below the scarps. Youd goes

94
Table 4.2 Boring Log at Separation and

Overhead f Interstate 210/5

Depth (Feet ) Description

0-6 Loose to slightly compact , red-brown silty sand with

scattered cobbles

6-9 Compact , red-brown clayey

sand and sandy, silty clay

9 - 17 Dense to very dense, redbrown and brown, very fine

sand, and silty, very fine

sand with some sandy silt

17 - 38 Dense to very dense, yellow

and tan, very fine sand

38 - 50 Dense to very dense, poorly

sorted sand with scattered

gravel layers

Table 4.3 Boring Log at Northwest Connector

Ove rcros s ing , Interstate 210/5

Depth (Feet ) Description

0-10 Slightly compact to compact

,

brown and ye 1 low-brown sand

and clayey sand with scattered

gravel

10 - 23 Dense, dark brown and grey,

gravelly , clayey sand and

clayey silt

23 - 34 Slightly compact to compact

,

brown, very fine to find sand

with silt and clay binder

34 - 50 Very dense, yellow-brown sand

and clayey sand with scattered

gravel

.

95
on to say

:

"A recently filled and graded area west of the

upper lake was broken up by numerous fissures, which

generally tended to parallel the shoreline and the

contour of the previous surface. This area is

considered here because of the likelihood that

failure in the alluvium below the fill is

responsible for the sliding. Extensional and

vertical displacements in the fill indicate

movement toward the reservoir either in the form

of block gliaes or in slightly rotated slumps.

Sand boils erupted in the southern part of this

fracture zone some 180 meters from the lake and

several meters above the water level at the time

of the shock.

Many fissures formed in the area west of that

described in the previous paragraph. Of those

observed, the most notable were in a schoolyard

in the mouth of Bee Canyon, nearly one kilometer

from the upper lake. These fissures were characterized by vertical displacements of as much

as 50 millimeters and continuous lengths of perhaps

100 meters. They seemingly formed the head of a landslide which had moved down the very mild

slope (about 1.5° or 2.5 per cent) eastward toward

the upper lake" .

i In an excellent study of the soil movements near the

Van Norman Lakes, Youd describes a major slide in the

vicinity of the lakes, called the Juvenile Hall slide.

Located on the slide are much of "the San Fernando Valley

Juvenile Hall, trunk lines of the Southern Pacific Railroad,

San Fernando Boulevard, Interstate Highway 5, the Sylmar

electrical converter station, and several pipelines and

canals". The slide extended for a distance of 1.2 kilometers

from northeast of the juvenile hall to its toe at the shoreline of the Upper Van Norman Lake. The slope of the soil

surface averages about 1.5 degrees with the maximum slope of

about 3 degrees. It is estimated that the total downslope

movements of the slide ranged from 0.5 to 1.5 meters.

Youd also reported that:

"Numerous sand boils erupted on the lake floor,

presumably near the toe of the slide. These were

exposed after the water level was lowered. Sand

boils were also found at the following locations:

Behind the converter station near the base of the

graded fill, in a field south of Juvenile Hall,

96
and along the north edge

in front of the Juvenile

Building".

of the railroad grade

Hall Administration

FAILURES AT UPPER AND LOWER SAN FERNANDO DAMS

Both the Upper and Lower San Fernando Dams were severely

damaged by the earthquake. Most of the news reports about

these failures centered around the Lower San Fernando Dam

where the failure was such that there was a critical danger

that the dam would be breached with consequent severe

f 1 oodi ng

.

The Upper San Fernando Dam was built in 1919-1921 by

hydraulic fill methods [4.16]. During the earthquake this

dam subsided about 0.9 meters and shifted downstream about

1.5 meters [4.16]. Youd and Olsen reported that "extensive

cracking and slumping disrupted the upstream concrete lining

of this dam, and the downstream slope of the embankment also

was cracked. The concrete lining around the Upper Van Norman

Lake was cracked extensively near the high-water line" [4.16].

The Lower San Fernando Dam was constructed in 1913-1915

and it was modified in 1930 and 1940. The construction procedure used in 1913 was a hydraulic fill. The modifications

were made using rolled-fill construction. The new construction added a downstream berm and the dam was raised. There

was an eight-inch concrete rip-rap liner on the upstream face

of the dam. It is estimated that about three million cubic

yards of material are in the dam. The dam impounded the lower

Van Norman Lake which contained 11,000 acre-feet of water at

the time of the earthquake.

The earthquake triggered a massive slide along about

two-thirds of the length of the dam, as shown in figure 4.3.

The material slid into the reservoir. An immediate decision

was made to evacuate about 79,000 people living south of

the Lower Van Norman Lake. A 12-square mile area was

evacuated. The water level had been lowered by 13 feet by

the afternoon of the third day following the quake, and

the people living in that part of the San Fernando valley

were allowed to move back into their homes. The reservoir

contained about 7,000 acre-feet of water at the time the

people moved back.

With regard to the failure of the dams as a result of

the earthquake, there is a possibility that the failure was

due to liquefaction of the material which was placed by

hydraulic methods. In the hydraulic fill technique, a pipeline is used to transport soil-laden water to the dam

site. By appropriate placement of parallel pipelines, the

97
98
mixture is allowed to flow into the fill area, the soil is

deposited and the water returns to the reservoir. The

technique is adjusted so that the coarser-grained materials

are deposited at the upstream and downstream faces with

fine-grained materials being deposited at the core of the

dam. The reason that hydraulic techniques have been

abandoned is that the deposited material is loose and is

subject to densification, hence liquefaction, due to cyclic

stresses such as those from earthquakes.

Aerial views of the Lower Van Norman Dam taken after

several days of pumping to lower the level are given in

figures 4.4, 4.5, 4.6 and 4.7. Figure 4.4 is a view of the

Lower San Fernando Dam taken from downstream and clearly

indicates the degree of collapse of the main fill over a great portion of the width of the dam. Water level was

almost at the height of the lowered crest on the right side

of the dam as viewed in this photo. Figure 4.5 is a similar

photo taken from upstream and shows both the collapsed

concrete liner and the large number of residences in the

downstream flood plain. Figure 4.6 is taken from upstream

and shows a relatively close-up view of the failure near the

east abutment. Original height was at the level of the

roadway on the crest. Figure 4.7 shows the degree of failure

of the earth dam and the concrete liner.

4 . 5 Comments about Soil Movements

The San Fernando earthquake can be judged from the

standpoint of the loss of lives and the property damage.

However, the disaster would have been multiplied many times

had the water from the Lower Van Norman Reservoir plunged

down the San Fernando Valley. This occurrence probably

could not have been prevented had the weakened dam been

overtopped by the water or had piping been initiated due

to seepage through the weakened dam. Either of these

occurrences, of course, was a distinct possibility, if

not probability.

It may be significant to note that hydraulic fill dams

are completely out of vogue in the United States and around

the world. The reason is that the material which is pumped

and placed by the hydraulic methods is in a loose condition

and cannot be compacted and densified and given the appropriate strength with the use of the hydraulic methods.

While some strength increase of a hydraulic fill can be

expected with the passage of time, there is no assurance

that complete stability can be achieved.

No information is at hand regarding the seismic

coefficients which were employed in the design of the Lower

99

Figure 4.6 East abutment of Lower San Fernando Dam.

101
San Fernando Dam. Seed and Martin state that typical United

States practice is to use a seismic coefficient of 0.10

to 0.15 [4.17]. The Bureau of Reclamation states, "In areas

not subjected to extreme earthquake conditions a horizontal

acceleration of 0.10 of gravity and a vertical acceleration

of 0.05 of gravity are generally used" [4.18].

In the analytical methods currently in use for the

stability analyses of earth dams, the effects of vertical

accelerations are not normally taken into account. The

vertical accelerations reported for the San Fernando

earthquake are considerable and serious consideration must

be given in the future to taking the vertical accelerations

into account in analytical procedures.

In many populated regions subject to earthquakes,

reservoirs have been built above the centers of population.

Therefore serious consideration should be given to a careful

study of current analytical methods and to reanalyses of

some earth structures. Such a study is highly recommended

in view of the potential disaster that could have occurred

in the San Fernando valley.

4 . 6 References

4.1 Wentworth, C. M. and Yerkes , R. F., "Geologic Setting

and Activity of Faults in the San Fernando Area,

California," Geological Survey Professional Paper

733, U. S. Government Printing Office, Washington,

D. C. , 1971 .

4.2 Bailey, T. L. and Jahns , R. H., Geology of the

Transverse Range Province, southern California,

i_n Jahns, R. H., ed., Geology of southern

California: California Division of Mines and

Geology Bulletin 170, 1954.

4.3 Jennings, C. W., and Strand, R. G., Geologic Map of

California, Olaf P. Jenkins edition, Los Angeles

sheet: California Division of Mines and Geology,

scale 1 :250 ,000. , 1 969.

4.4 Corbato, C. E., Bouguer Gravity Anomalies of the

San Fernando Valley, California: California Univ.

Pubs. Geol. Sci., v. 46, no. 1, 1968.

4.5 California State Water Rights Board, The City of Los

Angeles vs. City of San Fernando: California

State Water Rights Board, Report of Referee,

No. 650079 , V. I ; v. II , 1 962.

102
4.6 Oakeshott, G. B., Geology and Mineral Deposits of

San Fernando Quadrangle, Los Angeles County,

California: California Division of Mines and

Geology Bull. 172, map scale 1:62,500, 1958.

4.7 "Anchorage Area Soil Studies, Alaska," Shannon and

Wilson, Inc., Seattle, Washington, A Report to U

.

S. Army Engineer District, Anchorage, Alaska, 28

August 1964.

4.8 "The Landslide at Surte on the Gota River," Jakobson,

B., Proceedings , Royal Swedish Geotechnical

Institute, Vol . 5, p. 87 , 1 952.

4.9 "The Niigata Earthquake and Resulting Damage to

Reinforced Concrete Buildings," International

Institute of Seismology and Earthquake Engineering,

Tokyo, Japan, February 1965.

4.10 "Foundation Investigation, Olive View Hospital, Olive

View, California," L. T. Evans, Incorporated.

4.11 "Foundation Investigation, Central Heating and Air

Conditioning Plant, Olive View Hospital, Olive

View, California," Converse Foundation Engineers,

Los Angeles, California, May 20, 1965.

4.12 "Report of Foundation Investigation, Proposed San

Fernando Branch Juvenile Hall, San Fernando Road

and Yarnell Street, Los Angeles, California,"

LeRoy Crandall & Associates, Los Angeles, California,

September 27 , 1 961 . 4.13 "Foundation Investigation, Proposed Holy Cross Hospital,

Mission Hills Road and Indian Hills Road, San

Fernando Valley, Los Angeles, California," Converse

Foundation Engineering Company, Pasadena, California,

July 30, 1958.

4.14 Morton, Douglas M., "Seismically Triggered Landslides

in the Area Above San Fernando Valley," Geological

Survey Professional Paper 733, U. S. Government

Printing Office, Washington, D. C, 1971.

4.15 Youd, T. L., "Landsliding in the Vicinity of the Van

Norman Lakes," The San Fernando, California Earthquake on February 9, 1971, Geological Survey

Professional Paper 733, U. S. Government Printing

Office, Washington, D. C, 1971.

103
4.16 Youd, T. L., and H. W. Olsen, "Damage to Constructed

Works, Associated with Soil Movements and Foundation

Failures," Geological Survey Professional Paper

733, U. S. Government Printing Office, Washington,

1971 .

4.17 Seed, H. Bolton and Martin, Geoffrey R., "The Seismic

Coefficient in Earth Dam Design," Journal of the

Soil Mechanics and Foundations Division , Pro - ceed ings of the American Society of Civil Engineers , Vol . 92 , No. SM3 , May 1966.

4.18 United States Department of the Interior, Bureau of

Reclamation, Desi gn of Smal 1 Dams , U. S. Government

Printing Office, Washington, 1965.

104
CHAPTER 5 - DAMAGE TO BUILDINGS

5 . 1 Building Code Seismic Force Requirements

INTRODUCTION

In the United States, the requirements most used for

the design of buildings to resist earthquake forces are

based on provisions contained in the Uniform Building Code

(UBC) published by the International Conference of Building

Officials. The UBC provisions are closely patterned after

the SEAOC (Structural Engineers Association of California)

recommendations. In order to compare the structural designs

of the various buildings that were subjected to the

February 9, 1971 earthquake, it is necessary to know the

provisions of the building codes under which they were

designed. As more research data are developed and more

accurate design methods become available, the building codes

are revised to incorporate this new information. The Uniform

Building Code is thoroughly revised every three years. Therefore the specific requirements of the particular code in

force at time of design and construction become important in

evaluating the building performance and relating that

performance to the latest lateral force requirements.

Current provisions of the Uniform Building Code are

based on the concept of an equivalent static lateral force

V which represents the base shear induced by the ground

motion. The general code expression is V = ZKCW, where Z is

a coefficient expressing the degree of probable intensity

of an earthquake in various geographical regions (figure 5.1),

K is a coefficient expressing the probable performance of

various types of framing and bracing systems, C is the basic

coefficient for lateral force, and W is the total dead load

and, in some cases, a portion of the live load. There are

no requirements for consideration of vertical forces due to

seismic action.

HISTORY OF CALIFORNIA EARTHQUAKE REQUIREMENTS [5.1 and 5.2]

After the 1906 earthquake, San Francisco was rebuilt

under a code which specified a 30 psf wind force to effect

both wind and earthquake resistance. In the years that

followed, leading structural engineers used the concept

of lateral earthquake forces proportional to masses, but

this simple Newtonian concept did not find its way into

codes until 1927 in the Uniform Building Code and more

extensively in 1933 following the Long Beach earthquake.

The Long Beach earthquake destroyed many buildings in

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that area of California including many public school buildings. Realizing that much of the loss and damage could be

avoided if the buildings had been properly constructed, the

State Legislature adopted the Field Act (see chapter 6 for

discussion)

.

In a study of code provisions, Steinburgge, Manning,

and Degenkolb [5.1] described three "eras" of building code

requirements for earthquake resistant design. Portions of

their description are presented below, along with the description of a fourth "era".

"The first era encompasses the earliest

provisions (1927) through the 1946 edition of the

Uniform Building Code. The essential features

consisted of a constant "C" value, usually 8

percent gravity (g) for all buildings in Zone 3,

although on very poor soil this coefficient would

be doubled. The weight factor "W" included full

dead load plus half of the vertical design live

load. In comparing the magnitude of the "C" factor,

it is important to consider the weight on which it

is based and the allowable material stresses to be

used in the design. Otherwise a direct comparison

of " C" is meaningless."

"This early code seemed reasonable for low

buildings of only a few stories in height. In

taller structures, however, the earthquake

requirements were very restrictive, and experience

in California with the 1906 San Francisco earthquake as well as those at Santa Barbara (1925) and

Long Beach (1933) indicated that the coefficient

may have been much too high for tall framed

structures (usually steel framed)."

"The next era started with the 1949 edition

of the Uniform Building Code, which incorporated

the provisions of the then current City of Los

Angeles Building Code. This used the formula for

C = 0.60/(N + 4.5) where N is the number of stories

above the one under consideration. This coefficient was to be applied to the dead load only,

neglecting all live loads. Since C for a one-story

building worked out to be 13.3 percent, the net

effect, considering both dead and live load requirements, was roughly comparable to the earlier 8

percent in many structures. The provisions of

this formula for C, however, enabled the coefficient

to be reduced for taller structures to a level that

was more consistent with the experience gained on taller framed structures. The empirical formula

107
was to be applicable only up to 13 stories,

since Los Angeles had a 13-story height limitation.

This group of building codes was the first widely

used building codes that recognized the dynamic

effects of an earthquake as related to the flexibility of a building, although the flexibility was

crudely related only to the number of stories in a building."

"The third era was started in 1952 because of

the problem that existed in San Francisco where

there was no height limit, so that the need for

more rational code provisions was recognized. A

committee was formed which resulted in the

"dynamic approach" as exemplified by the 1956 San

Francisco Building Code requirements. Subsequently,

a joint North-South Committee of the Structural

Engineers Association of California (SEAOC) was

formed to achieve a uniform code that could be

used s ta tewi de .

This resulted in the 1960 SEAOC publication, "Recommended Lateral Force Requirements," which introduced a new method

of application of two variables (C and K) used in the base

shear formula (V=KCW). One variable (C) directly introduced

the fundamental period of the structure and defined a method

of determining the period where it cannot be accurately

predetermined. A second variable (K) is dependent on the

type of structural system to be used. Based on research,

seismic experience in the United States, and damage studies,

certain types of construction are assigned bonus considerations

for the seismic factors. The 1960 SEAOC recommendations

appeared in the 1961 and 1964 editions of the Uniform Building

Code, with little change.

"The one change adopted by the International

Conference of Building Officials, in extrapol i ti on

of the SEAOC provisions, concerned the use of zones.

The SEAOC merely stated that all California should

be in Zone 3 and, by inference, recognized that all

areas subjected to major earthquakes of the intensity

to be expected in California should be in Zone 3.

Other zones were not and are not recognized by the

SEAOC.

The fourth era began with the publication of the 1966

SEAOC "Recommended Lateral Force Requirements" which were

subsequently incorporated into the 1967 Uniform Building

Code. Some of the important revisions pertained to the

following provisions:

(1) Qualifying of reinforced concrete moment-resisting

108
frames to the necessary ductility to permit this

construction in buildings more than 160 feet in

height.

(2) A distinction in defining Space Frame-Moment

Resisting and Space Frame- Due ti 1 e Moment Resisting

and the requirement of Ductile Moment-Resisting

Space Frames in buildings over 160 feet in height.

(3) Use of K values of 0.80 or 0.67 requires a Ductile

Moment- Res i s ti ng Space Frame capable of resisting

25 percent or 100 percent, respectively, of the

total required lateral forces for all building

heights. A Moment-Resisting Space Frame is not

required to meet the special ductility requirements

of a Ductile Moment- Res i s ti ng Frame if a K value of

1 . 00 is used in design.

The latest edition (1970) of the Uniform Building Code

contains earthquake provisions based on the 1968 revision of

the SEAOC "Recommended Lateral Force Requirements." After a review of the damage resulting from the earthquake in Caracus,

Venezuela, in 1967, the SEAOC realized that additional consideration should be given to the ductile behavior of tied

concrete columns which receive high over-turning loads but

transmit little seismic shears. Accordingly, the 1968 revision

provides confinement to tied column cores for their full length

unless it can be demonstrated that they will not be subjected

to inelastic strains during an earthquake.

CURRENT EARTHQUAKE REGULATIONS - LOS ANGELES AREA

In the City of San Fernando, the 1967 Edition of the

Uniform Building Code was in effect at the time of the

February 9, 1971 earthquake. The 1970 Uniform Building

Code was adopted by San Fernando on March 29, 1971.

The current City of Los Angeles Building Code became

effective on May 2, 1970. The general earthquake requirements in this code are basically the same as those contained

in the 1970 Uniform Building Code or the 1968 SEAOC "Recommended Lateral Force Requirements." For building permits

issued after July 1, 1965, the City of Los Angeles Code

requires that "every building over six stories in height with

an aggregate floor area of 60,000 square feet or more, and

every building over ten stories in height, regardless of the

floor area, shall be provided with three approved recording

accel erographs . " These instruments are to be located in the

basement, mid-portion and near the top of the building. (See

chapter 3 for a discussion of the strong-motion and buildingperiod measurements obtained in the San Fernando Earthquake.)

109
The current County of Los Angeles Building Code became

effective July 12, 1968, and is based on the 1967 Edition of

the Uniform Building Code. The previous edition of the

County Code was adopted in July, 1965, and was based on the

1964 Uniform Building Code. The 196 5 edition was revised

in November, 1966, to include amendments based on the 1966

SEAOC recommendations. Adoption of a new code edition (1971)

based on the 1970 UBC became effective November 27, 1971, by

the County of Los Angeles.

The earthquake regulations for public schools in effect

as of January 1, 1970, (California Administrative Code,

Title 24 and 21) are based on the 1968 SEAOC recommendations.

Some of the special provisions of the public school earthquake requirements are given below and outlined in Chapter 6.

Section T21 -107 (d) (1

)

.

"The value of KC as used in . . . V=KCW, shall not be less than 0.133 for

all one-story buildings and not less than

0.10 for all 2- and 3-story buildings,

except that the minimum KC may be 0.10 in

one-story buildings with a ductile momentresisting frame having the capacity to

resist the total required lateral force.

"The coefficients, K, as listed . . . are for use under conditions of average

earthquake potential hazard. These

coefficients may be modified by the

Office of Architecture and Construction

upon the advice of seismologists,

engineering geologists, or structural

engi neers

.

"Any building or structure supported

by only a single column or a single row

of columns shall be designed for a minimum

KC=0.30. For the building or structure

with a single row of columns, this

requirement shall apply only to the

lateral force acting normal to the row

of columns. The columns for such

structures shall meet all the requirements for ductile frame design.

"Moment-resisting space frames

used to resist design seismic forces

in any height school building shall

meet ductile frame requirements as defined. . ."

110
5.2 Case Histories of Building Damages

Case histories of buildings are discussed in this

section according to building use. These are medical facilities, commercial buildings, residences, miscellaneous structures, and post offices. Schools, including the San Fernando

Juvenile Hall, are covered in chapter 6. Buildings related to

utilities, are covered in chapter 8.

For the most part, severely damaged buildings are discussed here; although several buildings with moderate or

little damage are described. It is important to note that

many buildings which were subjected to accelerations on the

order of 20 per cent of gravity were not damaged.

Figure 5.2 is a general area map, designated Map 1, which

indicates areas covered by detailed maps 2, 3, 4, and 5.

These detailed maps are shown in figures 5.3a, 5.3b, 5.3c,

and 5.3d. Damaged structures discussed below are referenced

to a map and location number. Locations are numbered in

general geographical order, starting from the Newhal 1 -Saugus

area in Map 2 and moving south.

There were no accel erometers in the immediate vicinity

of the hardest-hit areas. There were accel erometers on the

Pacoima Dam east of location 7 (Map 3), the Holiday Inn at

location 25 (Map 4), the Bank of California at location 28

(Map 4), Crocker Citizens Bank at location 29 (Map 4), and

the Sheraton-Universal Hotal at location 31 (Map 4). The

components of ground acceleration as a fraction of gravity

are shown on the location maps by a set of orthogonal arrows

which indicate direction of horizontal accelerations. Magnitudes are recorded adjacent to the arrow. The value of

the maximum vertical acceleration is recorded between the two

orthogonal arrows. The Holiday Inn, the Crocker Citizens,

and the Bank of California readings were recorded on the

first floor. The Sheraton-Universal readings were recorded

in the basement.

MEDICAL FACILITIES

Los Angeles Olive View Medical Center - Map 3, Location 4

General - The 850-bed Los Angeles Olive View Medical

Center, costing approximately $23.5 million, was dedicated

in November, 1970. The February 9, 1971, earthquake caused

three deaths, evacuation of the structure, and a total loss

of the facility. The Medical Center was constructed generally

of reinforced concrete and was designed during 1965 under

the 1965 Los Angeles County Building code [5.3]. Plan sheets

111
EPICENTER

A/ FEB 9, 1971 / M= 6.6

• fiMOB MAGIC MTN. . r ~ / eEL. 1878 ^( 0 12 3^5

Or-' Miles

Note: All highway numbers shown are Interstate. U.S...

State designatinns

La Canada

Glendale Pasadena

Alhambra

South G£^5/'Downey''

Figure 5.2 Map 1 - Los Angeles, San Fernando Valley

,

and Newhall

.

112
113
114
115
116
are dated January 1966, well before the County Code was

amended (November, 1966). Although the buildings were

"modern", they were not constructed under the latest earthquake design requirements. The County Code as amended in

1966 was significantly different (with respect to column

design and allowable concrete shear stress) from the County

Code used in design. Specific design details are discussed

later in sections describing the separate buildings in the

complex. Plans and design computations for the Medical Center

were provided by the Department of County Engineers, County

of Los Angel es .

A site plan of the Medical Center is shown in figure

5.4. Structures identified are:

1

.

Main Building

2. Stair Towers

3. Assembly Building

4. Exhaust Pavi 1 i on

5. Warehouse

6. Ambulance Port

7. Psychiatric Unit

8. Canopy from Main Building to Psychiatric Unit

9. Power Plant

The main building consists of four wings-A, B, C, and D.

These wings are six stories in height, including the ground

story. Stair towers, separated structurally from the main

building, are located at the outside ends of the four wings.

These wings join to form an interior courtyard. The dotted

line in figure 5.4 shows the outline of the ground story.

On the north and most of the west sides, the ground story is

below grade. Stair towers A, B, and D are located over the

roof slab of the ground story while stair tower C is supported

on footings. General damages are described below. Specific

damages are discussed later in sections describing the separate buildings in the complex.

A photograph taken of the Medical Center, as viewed

from the southeast, before the earthquake is shown in

figure 5.5. The four wings of the main building, the

psychiatric unit, the power plant, the warehouse, and the

ambulance port are identified. Note that the ground story

on the south and east sides is not below grade. However,

the roof of the ground story on these two sides is landscaped

with earth and plants. A photograph taken of the Medical

Center, as viewed from the southeast (as in fig. 5.5), after

the earthquake is shown in figure 5.6. All the buildings

identified in figure 5.5 are also identified in figure 5.6.

Three stair towers at the end of wings A, B, and D are shown

toppled in figure 5.6. Although not clearly visible, the

stair tower at the end of wing C is tipped to the north, but

117
SITE PLAN

THE LOS ANGELES OLIVE VIEW MEDICAL CENTER

FIRST FLOOR

POWER

PLANT

SECOND FLOOR

FIRST FLOOR

WALKWAY CANOPY

STAIR TOWER

1st-5th FLOOR

GROUND FLOOR

ASSEMBLY BUILDING

EXHAUST PAVILION

STAIR TOWER |

STAIR TOWER

STAIR TOWER

NorthFigure 5.4

AMBULANCE PORT

Site plan showing major buildings of the

Los Angeles County Olive View Medical Center.

The main building consists of the four wings - A, B, C, and D. These wings are six stories

in height including the ground floor. The

dotted line surrounding the main building shows

the outline of the ground floor which is below

grade on the north and west sides.

118
119
120
it is still standing. The three toppled towers broke through

the roof of the ground story. The main building is leaning,

mostly in the first story, about two feet to the north. It

may also be noted on the south side of wing D, that the roof

of the ground story is collapsed.

Figures 5.7 and 5.8 are photographs taken before and

after the earthquake, similar to figures 5.5 and 5.6, except

that the view is from the southwest. Note in figure 5.7 that

the ground story is below grade on the north and most of the

west sides. Close comparison of figures 5.7 and 5.8 will show

that the first story of the psychiatric unit collapsed so that

the building now appears to be one rather than two stories in

height. Note also the collapsed ambulance port south of wing

D.

A photograph of the Medical Center as viewed from the

north is shown in figure 5.9. The tipped stair tower at

the end of wing C is clearly visible in this photograph.

The psychiatric unit, the assembly building, the exhaust

pavilion, and the power plant are also shown.

The fact that only three persons lost their lives at

Olive View is fortunate. Two of the three died in their

iron lungs due to power failure. Only one person, a hospital

employee, died as a result of structural failure. This low

life loss was partly due to the early hour of the earthquake.

At some later time the falling stair towers almost surely

would have killed someone. Similarly, no one was occupying

the first floor of the psychiatric unit when the first story

totally collapsed. However, there were some forty to sixty

persons sleeping in the second story who "rode" the building

down without loss of life. Had the earthquake occurred a few hours later, many of these people would have been on the

first floor.

All patients in the main building were brought down

through the interior stairways. Elevators were inoperative

due to both the power failure and the distortion of the

building. The stair towers could not be used due to their

collapse. A fire would have presented a serious problem due

to the minimal evacuation route.

Psychiatric Unit - A photograph taken of the collapsed

psychiatric unit, as viewed from the southwest, is shown in

figure 5.10. As previously indicated and shown in figure

5.7, this was originally a two- story building. A plan view

of the unit is shown in figure 5.11.

The psychiatric unit is discussed before the more

prominent main building because it clearly establishes two

very important considerations: (1) that ground accelerations

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at Olive View exceeded those anticipated by the governing

building code and (2) that column design in the complex was

based on then existing deficient code requirements, as compared with those in use today. Both of these findings will

be discussed in more detail in following paragraphs.

The structure was a lightweight concrete building almost

throughout and was designed as a moment-resisting frame under

the 1960 Structural Engineers Association of Southern

California recommended lateral force requirements. As a moment-resisting frame, a horizontal force factor K=0.67 was

used and as a two-story building a coefficient C=0.10W was

used. These values led to a seismic shear of 0.067W, where

W is the dead load weight of the building.

Evidence of ground motion is shown in the photograph of

the west elevation of the psychiatric unit in figure 5.12.

A close-up of the north entrance indicated in figure 5.12 is

shown in figure 5.13. Figure 5.14 shows an overturned bench

(see fig. 5.9 for location) which was bolted to the sidewalk,

located south of the psychiatric unit. Calculations, which

neglect the bolts, indicate that a horizontal ground acceleration of at least one-half gravity was required to overturn

the bench. Similar calculations made on an overturned tombstone about three blocks south of Olive View indicated that

a horizontal acceleration of one-half gravity or a horizontal

acceleration of one-third gravity accompanied by a vertical

acceleration of one-third gravity might have occurred in that

general vicinity.

The building had an overall height of 27 ft 6 in and

the upper story was 240 ft long in the east-west direction

and 145 ft long in the north-south direction. Appromixate

calculations of the period using the SEAOC formula would

indicate values of around 0.1 sec. Under the Standard

Acceleration Spectrum proposed by Biot [discussed in reference 5.4], the relative shear of a structure with a period

of 0.1 sec would be 60 percent of that experienced by a structure with a period of 0.2 sec. This is the approximate

critical period shown in velocity spectrum from the Pacoima

Dam acceleration records. The SEAOC provisions are specifically drawn up to neglect any possible decrease in base shear

for structures with periods of less than 0.2 seconds. Thus,

the forces experienced by the structure before damping action

would be in the range of 0.6 to 1.0 of the ground accelerations or somewhere between 0.2 and 0.5 gravity. Either of

these combinations indicates that the factor of 0.067 used in

design was far too low for the earthquake intensity which

occurred at this location. The estimated ground accelerations

are not unreasonable in view of the Pacoima Dam acceleration

record

.

127
128
Figure 5.13 Damage to the canopy at the front (north)

entrance to the Psychiatric Unit.

Figure 5.14 This overturned concrete bench, which was bolted to the sidewalk, is located south of

the Psychiatric Unit.

129
The appearance of the structure after failure indicated

that the columns shattered totally and pieces of lightweight

concrete were hurled appreciable distances. All signs point

to shear and compression failures which give virtually no

ductility and so the advantages of nonlinear action and

large amounts of damping in diminishing the magnitude of

lateral forces are minimized.

The second floor was supported by 119 tied columns, of

which 107 were 18 in by 18 in in cross section. The ties

were No. 3 bars usually spaced at 18 in regardless of

column size. In two instances the tie spacing exceeded the

minimum column dimension. Lightweight concrete with a specified compressive strength of 3000 psi was used above

the first floor. Design was based on working stress design

using the general provisions of ACI 318-56 [5.5], which was

the procedure in the Los Angeles County Code during the

period (1965) that this particular structure was designed.

This design basis provides a possible key to the collapse of

the first story.

In order for the column ties to be effective as shear

reinforcement they would have to be spaced at one-half the

effective depth of the cross section. Since the actual ties

were usually spaced at the least member thickness, they were

ineffective in resisting shear. Thus all shear due to

lateral load would have to be carried by the concrete. The

1956 ACI Code allowed a shear stress of 0.03 of the concrete

compressive strength, or 90 psi for the concrete used (without a 33 percent overstress allowance with wind and seismic

forces). The 1963 ACI Code [5.6], which was in effect in

1965 (but not yet adopted in the Los Angeles County Code)

allowed a unit shear stress of 37 psi (for an unknown

lightweight aggregate assuming a splitting factor F =4.0).

This lower stress was to correct the fact that 90 psi was

known (due to several shear failures since the 1956 ACI

Code) to be too high a design value for normal weight and

especially some lightweight concretes. However, it should be

clearly repeated that 90 psi was the legal limit in the Los

Angeles County Code.

As an example of the consequences of this overly large

shear stress, consider the case of column 20Z (see fig. 5.11

for location). This column had computed design shears of

17,500 lb in the north-south direction and 10,600 lb in the

east-west direction for code values of lateral forces.

These shears are complicated by the fact that this is a case of biaxial shear, in that very large simultaneous

accelerations were noted in both the north-south and eastwest directions. Hence, it is quite possible that the column

was under extremely high combined shear stresses. The column

130
is 18 in by 18 in (reinforced with 8 No. 14 bars, 2 in of

clear cover). Assuming an effective depth of 15.2 in, the

shear stress is 64 psi in the north-south direction and 39

psi in the east-west direction. The resultant of these two

gives a shear stress of about 75 psi for the 0.067 acceleration. While this shear stress is below the 1956 ACI Code

allowable value of 90 psi, it exceeds both the 1963 workingstress design value of 37 psi and the ultimate shear stress

of 56 psi for an unknown lightweight concrete. When the

accelerations are scaled up to what they undoubtedly were,

it is no wonder that this column failed completely. In this

same column the calculated axial load was very low and

resulted in only slightly over 150 psi compression in the

column; with the high vertical accelerations that were occurring, the compressive force probably went toward zero and

would have to be disregarded.

An approximate total-story shear capacity may be obtained by multiplying the total column area (about 40,400 sq. in.)

by 0.9 to obtain effective area, and then multiplying this

by the 56 psi that one would obtain from the 1963 ACI Code

using a splitting factor of 4.0, as specified by the Code

for the case where actual values are not known. Through this

procedure the total-story shear capacity would be about 2070

kips, or approximately 20 percent of the 10,327 kips dead

load which the designer calculated. Assuming uniform shear

in one direction and none in the other, this indicates a maximum story shear capacity of about 0.2 gravity. This

analysis neglects torsional shear and biaxial shear, both of

which were almost certainly present. Both of these factors

would lower the maximum story shear capacity even more (note

that compressive stresses were very small and probably were

close to zero with the vertical accelerations which were

probably present). Hence there was no reserve strength in

the ground-story columns since accelerations at least as large

as one-half gravity probably occurred and subsequent shear

failures may have occurred before sufficient ductility was

developed to relieve the acceleration forces. Thus the

probable cause of failure of the structure was the inadequacy

of the columns to take the seismic shears due to (1) the

extremely large accelerations and (2) the inadequate shear

strength of the columns.

It should be pointed out that a proper analysis of the

column strength requires a knowledge of concrete column

behavior under biaxial shear. There is very little research

data available in this area. It should also be noted that

the Los Angeles County Code was amended in 1966, one year

after the plans were dated, lowering the allowable concrete

shear stresses to those in the 1963 ACI Code. The maximum

column tie spacing was also decreased to a maximum of one

half the effective section depth for a ductile frame. Columns

131
were also required to be designed to resist the shears accompanying full moment reversal at the column ends for moments

of a magnitude equal to the column flexural capacity. All

these changes would have improved the column performance

although none would have changed the fact that the County

Code specified horizontal forces were smaller than those

which probably occurred.

Main Building - The main building was of reinforced

concrete construction (with hard rock aggregate) supported

on spread footings. For seismic design the main building was

treated as one complete structure, consisting of wings A, B,

C, and D interconnected around a center courtyard (see fig.

5.4). The ground story (which was about 16.5 ft story height)

and the first story (which was about 14 ft story height) were

considered as moment-resisting space frames with a capacity

to resist the total required lateral force, and hence had a horizontal force factor K=0.67. The four upper stories

(which were about 12.5 ft in story height) were assumed to

have a dual bracing system, consisting of a moment resisting

space frame with a capacity to resist not less than 25 per

cent of the required seismic force and shear walls to carry

the balance. Thus a horizontal force factor K=0.80 was used

above the first story. Using the SEAOC procedure, the structure was designed for a lateral force of approximately 8

percent of gravity. Overturning moment was computed using a

J value of unity (J has since been voted by SEAOC as always

to be taken as unity). A floor plan for the main building

is shown in figure 5.15. The limits of the ground story are

shown dashed. Flat slab construction was generally used

throughout, including the slabs under stair towers A, B, and

D. Stair tower C was supported on spread footings.

The spiral columns in the ground story were supported

on spread footings. Reinforced concrete flat slabs were

used for the ground-story roof. The embankment on the north

and west sides of the ground story was held in place by a retaining wall which was separated from the main building by

a four-inch seismic joint. The seismic joint was intended

to permit the building to move independently of the embankment. However, the width of the joint was inadequate as is

shown in figures 5.16 and 5.17, which show compression ridges

formed above the joint on the west and north sides respectively. Some damage was caused due to the building's colliding

with the retaining wall.

•Most columns in the first story were spirally reinforced

while corner columns were tied. Shear walls from the stories

above were present in the first story although they were

carefully detailed to be ineffective in resisting shear by

cutting them loose from the frame, since the first story was

designed as a moment-resisting frame.

132
Figure 5.15 Floor plan of Main Building

.

133
>

Figure 5.16 Compression ridge

on the west side

of the main building. A toppled

stair tower is

visible in the

background.

134
Most first-story columns were square with round spirally

reinforced cores, except for the tied corner columns. These

latter columns were essentially square with a corner notch

out, giving the appearance of a thick L-shaped column.

The typical floor plan for the stories above the first

story is similar to that of the first floor, except shear

walls were present to carry lateral load. Rectangular tied

columns were used above the first story, except for exterior

columns which were C shaped.

The west face of Wing A is shown in figure 5.18. This

view shows the large lateral displacement of the wing to the

north. Most of the displacement is in the first floor. This

is shown clearly in the photograph of the main entrance in

figure 5.19 (location shown in fig. 5.18).

A typical first-story tied corner column is shown in

figure 5.20. Note that this column was completely shattered

and incapable of resisting load. Vertical bars in some

similar columns actually fractured as shown in figure 5.21.

On the other hand the spiral columns shown in figure 5.20,

although having undergone tremendous lateral displacements,

were still capable of carrying load. However, it is doubtful

that they could have withstood much more strong ground

mot i on

.

The corner column in figure 5.20 had a design shear of

75 kips in the east-west direction and 108 kips for shear in

the north-south direction for building code lateral force

values. The L-shaped column has about 880 sq in of area and

probably 800 sq in effective for shear. The tie spacing of

No. 3 bars at 18 in is so large that the ties cannot count

as shear reinforcement. This means the shear stresses in

the north-south direction are approximately 135 psi and in

the east-west direction 93 psi. These have a vector sum

of approximately 160 psi. This shear stress would compare to

the 1956 ACI allowable value (without a 33 percent overload

allowance) of 90 psi, and 1963 ACI Code allowable value of

approximately 80 psi for working stress and approximately 120

psi for the ultimate shear stress of 5000 psi concrete. This

is based on the relatively low code acceleration coefficient

of about 8 percent which was used in design. This indicates

that this column was on the borderline of adequacy under the

then existing Los Angeles County Code requirements and would

be inadequate if biaxial shear effects are considered. There

is no mention in the code of such biaxial shear effects.

When the more restrictive 1963 ACI Code shear provisions are

considered, the column would be clearly insufficient for the

design lateral forces. Had the County Code been revised to

include the 1963 ACI Code provision, additional lateral reinforcement would have been clearly required in this column.

135
Roof

Figure 5.18 West face of Wing A. Note the extensive

damage at the first floor and the lateral

displacement of the building to the north.

Most glass was intact in windows above the

third floor.

Figure 5.19 Patient evacuation through the main entrance

of Wing A. (Los Angeles Times Photo)

136
Figure 5.20 West end of Wing B. Note the contorted column and the

extent of the northward drift of the building . In the

right foreground is the base of the toppled stair tower.

Note that this stair tower has collapsed through the

roof of the ground story.

Figure 5.21 Close-up view of the first story column in the northeast

corner of Wing B. Note the two fractured main reinforcing bars (arrows) and broken ties.

137
The same column in the basement story had design shears of

83 kips for the east-west direction and 88 kips for the northsouth direction. In general the highest and most critical

shears occurred in the first story rather than the ground

story which had additional and larger sized columns and hence

more capacity for taking shear. For instance, the particular

column discussed above increased to a 32 in by 32 in spiral

column in the ground story below. The reason for the transition from the spiral to a tied column was to provide the

L-shape that was apparently for architectural purposes.

The east face of Wing C is shown in figure 5.22. Again

the lateral displacement of the building to the north in the

first floor can be seen. Note the diagonal cracking in the

second-story C-shaped columns which indicates that the column

was subjected to load reversal.

What appears to be an embankment in the foreground of

figure 5.22 is actually a collapsed garden roof. This type

of failure is shown more clearly in figure 5.23, the south

face of Wing D. The garden roof which is an extension of the

first floor, can be seen in its collapsed position. One hospital employee was killed at this location. Several protruding ground-story columns which originally supported the

garden roof are indicated by arrows. A close-up view of one

of the failed ground-story columns which originally supported

the roof is shown in figure 5.24. A photograph of a groundstory column with the top completely stripped of reinforcement

is shown in figure 5.25. The extensive column damage at the

first floor is typical of column damage found at the first

floor in all wings of the hospital.

The south row of first-story columns in Wing D is shown

in figure 5.26. The first column to the left is the L-shaped

corner column. The remaining columns immediately visible to

the right are spiral columns with a No. 18 bar in each corner

running about two-thirds of the way up the column height.

These bars, which are continued from the story below, have

broken out of the column corners. These bars were not

confined by spirals or ties, contrary to code requirements.

The enclosed first-floor court formed by the four

hospital wings, is shown in figure 5.27. The sagging of the

court was caused by failure of the ground-story columns.

Other interior photographs are shown in figures 5.28, 5.29

and 5.30.

Several points are illustrated by the column shown in

figure 5.31. A spiral column is basically more ductile than

a tied column, but in lateral motion this ductility can only

be achieved if ductility exists at the column-to-beam

connection. In the connection shown, two things happened138
3 - .ALL.

4th Floor

Figure 5.22

HMf^HW^^^' ^^^^^^^^^^^^^^ P"***^***''**^*'—— ifca^ .

Wing C

3rd Floor

apsed Garden Roof-;^

A portion of the

east face of Wing

C. The collapse

of the garden roof

as well as the ex- tensive damage of

the first floor

columns can be

seen. Note the

lateral displacement of the building to the north,

in the first story

and diagonal tension

cracks in the secondstory column.

Figure 5.23 South face of Wing D. Note that the bulk of

major damage suffered by the building is

limited to the ground, first, and second floors.

139
5.24 Close-up view (looking south) of one of the failed

ground-story columns which originally supported the firstfloor garden roof in front of Wing D. This is the same column seen in figure 5.23, the third from the right.

Figure 5.25 A column protruding

through the' garden

roof at the far east

end in front of Wing

D. Note that in

this failure the

reinforcement has

been completely

peeled away from

the upper end of

the column.

140
Figure 5.26 South row of first story columns, in Wing D;

note the lack of ties on the corner bars which

have broken out of the columns.

Figure 5.27 Enclosed court at the first floor level. The

sagging court was caused by failure of the

ground-story columns.

141
Figure 5.28 Damaged main lobby in Wing A. Note the

window mullion distortion . The planted

area seen through the window is a court

enclosed by the four wings.

Figure 5.29 Damaged elevators in the Wing A lobby.

142
Figure 5.30 Violent shaking of the building left the

ground floor hospital kitchen in shambles

.

143
(1) the spiral stopped short of the connection, making it

ineffective where it is needed most in lateral motion, (it

should have been continued into the beam) and (2) the spiral

unwound due to insufficient anchorage. Anchorage was

intended to be achieved by lapping the spiral. This was

not effective since the lap could not work once the covering

concrete had broken away. Positive anchorage by hooks into

the interior of the core is essential.

Stair Towers - A photograph of a typical stair tower

before the earthquake is shown in figure 5.32. The stair

towers were approximately 21 ft by 36 ft in plan with a connecting walkway into the main buildings. The towers were

actually very heavy shear walls through five floors (designed

with a factor K=1.0). Stair towers A, B, and D were supported on ground-story columns with loads being transferred from

the tower, through the first-floor slab and into the columns.

Stair tower C was supported by three columns cast with the

embankment retaining wall and three footings away from the

retaining wall. The towers were structurally separated

from the main building by a four-inch space.

Stair towers A, B, and D overturned leaving the end of

the wings exposed as shown in figure 5.33. Stair tower

C, supported on footings, did not topple as is shown in

figure 5.34. The overturning coefficient J was calculated

as 0.557 and 0.656. Base shears were computed as 0.053 and

0.058 of the structure weight. Applying the J factor to

the base shears means that the structure was designed for

approximately 0.03 gravity when calculating overturning

moment. All evidence indicates that accelerations at Olive

View greatly exceeded this amount.

Examination of the base of stair tower B indicates bars

which seemed to pull out of the first-floor slab (fig. 5.35).

As previously indicated the stair tower walls were dowelled

into the slab, which in turn was dowelled into supporting

beams. These dowels were 36 in long (18 in into the walls

and 18 in into the beams). The dowels matched the wall

reinforcement which was usually No. 4 bars. This means that

the overturning moment was resisted by No. 4 bars embedded

18 in. This is not adequate anchorage for such an important

tensile tie under these load conditions.

Canopy from Main Building to Psychiatric Unit - The

canopy connecting the main building to the psychiatric unit

is shown in figure 5.36; this structure was severely damaged.

The canopy roof was of lightweight concrete, supported on

a pair of stone aggregate concrete columns spaced 9.5 ft

across the width. This pair of columns was spaced at 15 ft

along the canopy length except near the assembly building.

In the latter location the spacing varied. The column

144
Figure 5.32 Typical stair tower before the earthquake.

K

Figure 5.33 Wing D after

stair tower

overturned

.

145
Figure 5.35 Base of stair tower B.

146
147
reinforcing bars extended only a few inches into the canopy

slab and could not offer restraint due to bending at the top

of the columns.

Assembly Building - The assembly building is shown in

figures 5.9 and 5.17. As shown in the latter figure, the

structure is leaning about two feet to the north.

This structure was constructed in reinforced concrete

with a lightweight concrete roof and stone aggregate columns.

Two of its three stories are below grade.

Exhaust Pavilion - The exhaust pavilion is shown in

figures 5.9 and 5.37. This building is surrounded by an

overhanging canopy (originally horizontal) which was severely

damaged, indicating large vertical accelerations.

Power Plant - The power plant is a one-story rectangular

building. The structure was constructed of steel frames

diagonally braced at the north end with steel straps. This

bracing is shown in figure 5.38. The straps on the right

stretched about three feet. One of the two straps on the

left fractured at a weld, as shown in the inset.

The power plant contents were severely damaged, with

boilers shifting as much as four feet.

Ambulance Port - The ambulance port located south of

wing D is rectangular in plan, measuring 27 ft by 117 ft.

The lightweight concrete joist roof is supported on twelve

reinforced concrete columns. The columns were 14 in by 18

in reinforced with No. 9 bars and ties spaced at 12 in on

center

.

The columns failed as shown in figure 5.39. The north

columns were restrained at the base by the pavement and tried

to resist most of the shear. Note the nonshattered portion

of the columns remained vertical. The south columns (originally vertical) rotated about the footings.

Old Buildings - There were a number of pre-1933. buildings

in the old section of the Olive View complex. Many of these

buildings were either totally collapsed or severely damaged.

Figure 5.40a shows a completely collapsed old brick-wall

building and figure 5.40b shows a severely damaged wood-frame

house

.

San Fernando V.A. Hospital - Map 3, Location 7

The San Fernando Veteran's Administration Hospital had

the misfortune of being located near the earthquake epicenter.

148
149
150
151
Figure 5.40a

Figure 5.40b

Totally collapsed old brick building at

the old section of the Olive View Medical

Center. The building was not designed

to resist earthquake forces.

Severely damaged pre-1933 wood-frame

structure at the old section of the

Olive View Medical Center.

152
The Pacoima Dam which is located about one mile east of the

hospital experienced the largest ground accelerations ever

recorded in an earthquake (refer to section 3.3 for its

magnitudes). The hospital is located adjacent to the

community of Sylmar in the northeastern section of the San

Fernando Valley, approximately four miles from the center

of the city of San Fernando. The hospital was built

by the Veteran's Bureau, the predecessor agency of the

Veteran's Administration, in 1925 and opened as a Tuberculosis

Hospital on March 1, 1926. It was redesignated as a General

Medical Hospital on July 1, 1963. As of February 9, 1971,

the hospital consisted of 45 separate buildings and 6 support

facilities which constituted a 420-bed general medical hospital and a 36-bed Nursing Home Care Unit.

Forty-six people, mostly patients, died as a result of

the collapse of two major buildings shown in figure 5.41

(much of the rubble had already been cleared at the time of

the photo). Efforts to obtain rescue aid were hampered by

a general loss of communications, including telephone service

(see chapter 8) and the HEAR System. HEAR (Hospital Emergency

Assistance Radio) is a special emergency communication system

among the hospitals in the Los Angeles area which can operate

from emergency power supplies. Unfortunately the building

which housed the power supply at the V.A. hospital collapsed,

making the system useless. The room containing the transmission equipment was also inaccessible due to debris. Either

of these f'actors alone would have prevented use of the HEAR

system. It was reported that a man was sent by ' automobi 1 e to

obtain help. Once the message was given to the police, the

request for aid was confused with the collapse at the nearby

Olive View Medical Center; thus, there was no response to the

request. It was over an hour before the collapsed V.A. buildings were observed from a passing helicopter and assistance

was sent. Communications were established soon afterwards by

sending a mobile transmitting unit to the hospital.

Once rescue operations (fig. 5.42) were underway, they

were handicapped by difficulty in clearing the rubble, since

all material had to be moved almost by hand in the search

for survivors. Rescue work continued around-the-clock until

the last victim was recovered some four days after the quake.

The intense efforts of rescue workers were partly rewarded

when a survivor was found some 58 hours after the earthquake.

The man survived by sliding under a sink. Structural members

which fell across kitchen equipment apparently supported the

upper f 1 oor s 1 abs . Table 5.1 is a schedule of buildings and ancillary

structures which comprised the existing hospital complex.

Also included in the table is the year in which each unit

was constructed, the general type of construction, and the

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155
degree of damage sustained by the building or structure

during the February 9 earthquake. Figure 5.43 is a general

plan of the 100-acre hospital site showing the location of

the various buildings and structures. These data and the

following information are based on reports prepared by the

Office of Construction, Veterans Administration dated

February 16, 1971, and Brandow and Johnston Associates,

Structural Engineers, dated March 12 and 26, 1971.

As indicated in table 5.1, many of the original hospital

buildings constructed in 1925 and 1927 had reinforced concrete

structural frames with unreinforced clay tile exterior walls.

Quarters buildings and other small shop buildings were

constructed with wood framing. All buildings were four

stories or less in height and many of them were not designed

to resist seismic forces because no recognized standard for

this purpose was in use at that time.

Over the years, several minor buildings were added. The

first major addition to house patients was the three-story

Building No. 41, constructed in 1938. The next additions to

the hospital were the three-story Building No. 43 and a new

boiler plant built in 1949. Since that time other buildings

were erected, including the Chapel (Building No. 52) and a kitchen and dining hall addition (Building No. 2b) in 1950

and a laundry (Building No. 50) in 1951. All buildings constructed at the hospital since 1935 were designed for earthquake forces in compliance with historically applicable Los

Angeler building codes.

Aerial views of the San Fernando Veterans Administration

Hospital complex following the February 9 earthquake are

shown in figures 5.44 and 5.45. Many buildings and their

construction dates are shown in these two photos.

In general, the 26 buildings and additions built prior

to 1933 sustained the greatest structural damage. Four of

these buildings (No. 1 and 2a in fig. 5.44 and No. 8 and 10

in fig. 5.45) totally collapsed during the initial moments

of the main shock. The floor plans showing the typical

beam and column framing of Buildings 1 and 2a are shown in

figures 5.46 and 5.47 respectively. These two pre-earthquake

design buildings (1925) had little or no earthquake resistance and would not have been acceptable by modern standards.

Building No. 6, a two-story building approximately 50

ft by 100 ft in plan, was one of the original 1925 buildings

which was severely damaged (figs. 5.48, 5.49 and 5.50). A

small one-story wood frame building (Building No. T-7)

constructed in 1947 adjacent to Building No. 6 suffered no

apparent damage.

156
i

i

157
Table 5.1: Building Schedule, Veterans Administration Hospital,

San Fernando, California

(a) Building Year

Number Building Name Constructed

1 Semi-Ambulant 1925

2a Infirmary 5 Main 1925

Ki tchen

2b Dining Room & Kitchen

Addn. 1950

3 Mens' Ambulant 1925

4 Recreation 1925

5 Infirmary 1925

6 Infirmary 1925

7 Recreation Supply &

Fiscal 1925

8 Garage & Firehouse 1925

9 Supply Warehouse 1925

10 Engineering Office

and Shop 1925

11 Nursing Home 1925

12 Nurses Quarters 1925

13 Quarters 1925

14 Quarters 1925

15 Quarters 1925

16 Quarters 1925

17 Quarters 1925

18 Quarters 1925

19 Gate house 1925

20 Water Tank 1925

'23 Ground Maintenance 1931

24 Carpenter Shop 1927

25 Plumbing Shop 1927

26 Paint Shop 1947

28 Guest House 1928

29 Paint & Oil Storage 1930

31 Garage 1939

32 Garage 1939

33 Garage 1939

34 Green House 1932

35 Equipment Repair Shop 1927

40 Automatic Valve Chamber 1925

41 Infirmary 1938

42 Pump House 1940

158

Type of

Construction

I

I

II

I

I

I

I

I

I

I

I

I

I

III

III

III

III

III

III

III

IV

IV

IV

IV

III

II

III

III

III

V

IV

II

III

Degree

of Damage

Destroyed

Destroyed

Serviceable

Severe Damage

Severe Damage

Severe Damage

Severe Damage

Severe Damage

Destroyed

Severe Damage

Destroyed

Severe Damage

Severe Damage

Severe Damage

Severe Damage

Severe

Severe

Severe

Severe

Severe

Damage

Damage

Damage

Damage

Damage

Serviceable

Severe Damage

Severe Damage

Severe Damage

Severe Damage

Severe Damage

Serviceable

Severe Damage

Destroyed

Destroyed

Serviceable

Severe Damage

Serviceable

Serviceable

Severe Damage
Table No. 5.1 (continued)

Building

Number Building Name

Year

Constructed

Type of (b)

Construction

Degree

of Damage

43

44

45

47

49

50

52

53

54

55

56

57

58

Main Infirmary 1949

Incinerator 1949

Boiler House 1949

Steel Water Tower 1949

Concrete Chimney 1949

Laundry 1951

Chapel 1950

Pump House 1950

Main Switch House 1950

Wet Salt Storage Basin 1950

Transformer Pad ? Transformer Vault ? Golf Club House 1957

II

II

II

II

II

II

II

II

IV

Serviceable

Severe Damage

Servi ceable

Serviceable

Servi ceable

Servi ceable

Serviceable

Serviceable

Serviceable

Serviceable

Serviceable

Serviceable

Serviceable

Temporary Buildings

T-7

T-8

T-10

T-12

T-13

Patients' Recreation

Room 1947

Canteen 1947

Research Storage 1947

Recreation 1948

Animal House 1947

IV

V

V

V

V

Serviceable

Serviceable

Serviceable

Serviceable

Serviceable

(a) All buildings erected since 1935 were seismic resistive construction.

(b) I-Reinforced concrete frame and diaphragms with unreinforced clay

tile shear walls.

II-Reinforced concrete frame, diaphragms, bearing and shear walls.

Ill-Wood frame and diaphragms with unreinforced clay tile bearing

and shear walls.

IV-Wood frame and diaphragms with wood stud and plaster shear walls.

V-Metal frame and diaphragm and metal bracing.

159
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Buildings constructed since 1935, including the addition

to Building No. 2 (Building No. 2b, fig. 5.44), sustained

relatively minor structural damage with the exception of

Buildings No. 31, 32, 33 (three- and four-car garages) and

Building No. 42 (Pump House). In addition, the boilers in

the Boiler House were severely damaged and there was major

damage to all utilities. The incinerator stack which was

constructed in 1949 collapsed.

Building 41 (fig. 5.44), which was located north of

collapsed Building 2a was constructed in 1938 and is a threestory (plus basement) reinforced concrete frame and bearing

wall building. The structure had some diagonal hairline

cracks in some of the walls but the frame was essentially

intact. Figure 5.51 is a plan of Building 41 showing the

general arrangement of the reinforced concrete bearing walls,

shear walls, and columns. The longitudinal and exterior

walls are 12-in thick and the interior transverse walls are

10-in thick. The foundation consists of interconnected

spread f ooti ngs

.

Building 43, (fig. 5.44), which was located south of

collapsed Building 1, was constructed in 1949 and is also

a reinforced concrete frame and bearing wall building. It

varies in height from 3 to 4 stories (plus basement) and has

a spread-footing foundation. Similar to Building 41, damage

consisted primarily of hairline cracks in some of the walls.

The general arrangement of the structural walls and columns

is shown in figure 5.52. The exterior walls are 12-in thick

and transverse walls are 10-in thick in Unit A and 8-in

thick in Units B and C. As indicated in figure 5.52, the

walls in the end wings (Units B and C) are separated 6

inches from the adjacent parallel walls in the main center

wing of the building (Unit A).

Based on preliminary sei smol ogi cal data reported by the

California Institute of Technology, the building failures

at the San Fernando V.A. Hospital were precipitated by intense

areal ground motion rather than localized earth faulting or

ground movements . Buildings 2b, 41, and 43 provide excellent examples of

the performance of post-earthquake design structures when

they are compared with the pre-earthquake design of Buildings

1 and 2a, all of which were adjacent to each other. This

series of buildings clearly demonstrates the need for

determining the strength of old buildings and strengthing

or demolishing them where required. The V.A. has already

started such a program as a result of this earthquake.

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168
Holy Cross Hospital, Map 3, Location 17

Holy Cross Hospital which opened in June, 1961, is a seven-story building located at Rinaldi Street and Indian

Hills Road. As shown in figure 5.53 the hospital complex

included a boiler plant (service building) and a one-story

Continuing Care Facility, Also shown in the figure is the

Indian Hills Medical Center which is discussed under

Commercial Buildings. A general layout of the buildings is

shown in figure 5.54. Note that the long direction of the

hospital is not quite in the east-west direction, although

it will be considered so-oriented in the discussions which

f ol 1 ow

.

After the earthquake, patients began arriving from the

nearby areas. It was only then that the extent of damage

to Holy Cross was becoming apparent and evacuation of the

building was found necessary. Elevators were inoperative due

to counter weights leaving their tracks and tangling cables.

Steel guides were also bent. About 170 patients were evacuated by means of an exterior stairway at the east end of

the seven-story tower. Rescue workers entered through an interior stairwell near the west end of the tower to avoid

interference with the evacuees. During the evacuation

emergency power supplies and oxygen cylinders were in use.

A strict no smoking or open flame policy was enforced as a safeguard against fire since there was no water available.

Evacuated patients and patients received from nearby areas

were treated on the lawn and in the continuing care facility.

The main building is a reinforced concrete shear wall

structure with normal weight aggregate concrete columns and

lightweight aggregate concrete floors. The floor framing was

comprised of pan-joists and beams. The foundation was drilled

cas t-i n-pl ace friction piles. The building was designed in

the period 1957-1958 under the Los Angeles City Building Code.

A floor plan of the building showing column and shear

wall locations throughout its height is shown in figure 5.55.

The building consists of a seven-story tower (a partial

basement under the tower and a service tunnel running from

the basement and under the north wing are not shown) with

appendages of varying height located around the tower.

An aerial photo of the main building is shown in figure

5.56. The exterior columns on the north and south sides

were extensively cracked, particularly in the third- and

fourth-stories, as shown in figure 5.57. The concrete in

the southeast fourth-story exterior column was crushed as shown in figure 5.58. Close-up views of this same column as viewed from inside are shown in figures 5.59 and 5.60 (note

the splice of the column steel and the widely spaced ties).

169
170
171

Figure 5,56 Aerial view of Holy Cross Hospital. This

2 09-bed , reinforced concrete structure was badly damaged and has been evacuated.

Figure 5.57 Extensi ve col umn cracking is visible

in the third and

fourth stories of

the south face.

173
174
Further extent of damage at the fourth floor can be seen in

figure 5.61. Note the massive failure at the fourth-floor

construction joint.

A west elevation of the tower is shown in figure 5.62.

Note the horizontal cracking at the third-floor construction

joint. A close-up of this damage is shown in figure 5.63.

Interior damage was extensive at the west end of the third

story. Two third-story columns centered between the two end

walls failed in shear. The southernmost of these columns

is shown in figure 5.64. The third floor in this area was

extensively damaged as shown in figure 5.65 (note the base

of one column in the background and the door off to the

right). A closeup of floor displacement is shown in figure

5.66. The room located through the door to the right in

figure 5.65 (northwest corner) is shown in figure 5.67. Note

the cracks in the shear wall, floor, and spandrel. The southwest corner room is shown in figure 5.68. Damage was similar

to that in the northwest corner room.

The interior stairwell near the west end of the building,

which was used by rescue workers to enter the building, is

shown in figure 5.69. Note the diagonal cracking and the

horizontal crack at the third-floor construction joint.

Movement of the building caused concrete to spall and powder

around some reinforcing bars as shown in the inset.

Limited wall cracking was found in the basement and more

pronounced wall cracking was found in the first- and secondstories. Structural damage was not severe above the fourth

story although some did occur as shown in the photograph of

a doorway on the seventh story in figure 5.70. Shaking on

the seventh floor also caused shelves to overturn, dumping

their contents on the floor (figure 5.71).

The three-story north appendage, referred to as the

north wing, is shown in figures 5.72 and 5.73. Note the

portion of the wing supported on the second-story columns

and attached to the third and fourth floors of the tower

section. It was probably this configuration which caused

the extensive damage to the third and fourth stories of the

seven-story tower. The second-story columns shown in the

east elevation were cracked as shown in figures 5.74 and

5.75. The north wing has now separated from the tower by

cracking which occurred at the juncture of the wing and the

tower

.

Some damage, consisting mostly of movement of equipment,

was found in the service building. The Continuing Care

Facility shown in figure 5.76 was undamaged.

175
176
Figure 5.62 West elevation of tower.

177
ffij

Figure 5.64 Reinforced concrete column at the west end

of the third story.

178
Figure 5.65 Floor damage at the west end of the third

floor.

Figure 5.66 Floor cracking at the west end of the third

floor. The floor is concrete pan-joist

construction with a 3-in. slab.

179
Figure 5.68 Damaged southwest

corner room on the

third floor. Note

floor and spandrel

cracking

.

180
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181
Beam over doorway near the west end of the

seventh floor. A duct passes through an opening above the beam.

182
Figure 5.72 West elevation of North Wing.

183
Figure 5.73 East elevation of three-story north wing.

The east row of the second-story columns are

shown in figure 5.74.

Figure 5.74 Torsional cracking of second-story columns in

the north wing.

184
185
Pacoima Memorial Lutheran Hospital, Map 3, Location 22

Pacoima Memorial Lutheran Hospital is located on

Eldridge Avenue. The hospital was built in 1959 and is

shown in figure 5.77 along with the Golden State Mental

Health Center which was under construction but almost complete. The light areas on the hills in the background are

landslide areas.

All patients were evacuated from the 110-bed facility

shortly after the earthquake. It was reported that the

emergency facilities were initially closed but, although

badly damaged, were reopened out of necessity; since this was

the only hospital in this part of the San Fernando valley.

The elevators were inoperative after the earthquake (one

elevator was operative later). Emergency power had to be

used throughout.

The north elevation of Pacoima Hospital is shown in

figure 5.78. The building is a reinforced concrete shear

wall structure with some reinforced masonry shear walls

in the north and south sections. The floor and roof structures are reinforced concrete pan joist and beams. The

foundation consists of drilled concrete piles. The structure

was designed in 1958 under the Los Angeles City Building

Code and was designed to resist horizontal forces of about

10 percent of gravity.

The building consists of three sections. The three

story plus basement center section, the one- and two-story

north section, and a one-story south section (figs. 5.77 and

5.78). A south elevation of the center section which shows

the basement is shown in figure 5.79. A portion of the

south section is barely visible behind the trees in the right

of the figure. The reinforced brick wall behind the trees

was cracked diagonally as shown in figure 5.80. This was

the west wall Df the cafeteria.

The east-end shear wall, a major load resisting element,

was badly damaged as shown in figure 5.81. The portion of

the walls outlined by a distinct rectangular crack pattern

at each of three stories are referred to as "knockout panels"

on the structural drawings. They were apparently provided

for future expansion. An interior view of the first-story

shear wall is shown in figure 5.82.

The stairwell shown in figure 5.83 was located at the

east end of the center section and was damaged extensively.

One of the two elevators (shown in figure 5.84) was badly

distorted and inoperative. The second elevator was functioning.

186
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187
Figure 5.78 North elevation of Pacoima Hospital.

Figure 5.79 South elevation of center section.

188
1,
Figure 5.82 Interior view of damaged reinforced concrete

shear wall at the east end of the center

section of Pacoima Hospital

.

Figure 5.83 Damaged reinforced

concrete beam and

walls in the stairwell at the east

end of Pacoima

Hospital.

190
The walkway shown in figure 5.85 connected the north

section with the mental health center. Relative movement

shown seemed to indicate uplift of the main building.

Further relative movement is shown in figure 5.86 which shows

the north side of the north section. It was not certain at

the time if the displacement was due to building uplift or

soil settlement. Later reports indicated that the pile

caps had "jumped" off the piles.

The west elevation of the new two-story mental health

center is shown in figure 5,87. Interior finishing was being

rapidly completed so that this reinforced brick masonry

building could be used as a general purpose facility. Damage

to shear walls and other structural elements was minor as indicated by the cracking shown in figure 5.88.

Sepulveda V.A. Hospital, Map 3, Location 23

The Sepulveda Hospital (fig. 5.89), which is located

about 2.5 miles south of the lower Van Norman Reservoir, was

built by the Veterans Administration and opened in 1955. It

is a 1000-bed campus-type complex dedicated mainly to psychiatric treatment. As of December 31, 1970, the hospital was

operating at a level of 720 beds. Buildings range from one

to six stories and are designed to resist earthquake forces.

Patient buildings are constructed of reinforced concrete

frames with reinforced masonry walls.

One of the six-story buildings experienced considerable

damage to the seismic (flexible) joints between building

segments. However, it was observed that these joints did

minimize the damage which could have occurred. Another sixstory building sustained minimal cracking in structural

concrete walls and extensive plaster cracking, particularly

on the fifth and sixth floors. Several buildings sustained

visible cracking in reinforced concrete joist and slab floor

systems. A number of elevators sustained damage to the cast

iron counterweight guide shoes and rail brackets. Several

other elevators sustained additional damage to hoisting

machine drive motors.

Overall, there was only minimal structural damage to

the Sepulveda V.A. Hospital. The operation of the hospital

was not interrupted. However, extensive elevator and plaster

repairs were required and a number of seismic joints required

repl acemen t

.

Northridge Hospital, Map 4, Location 24

This hospital is located on Roscoe Boulevard near Reseda

191
Figure 5.84 Buckled steel elevator door frame in the

Pacoima Hospital.

Fi gure 5 . 85 Connecting

enclosed walkway

between Pacoima

Hospital (on the

left) and the

Mental Health

Cen ter , The

structural damage

and ground con- dition ( arrows

)

appeared to

indicate that

the hospital

building had

experienced

several inches

of uplift.

192
Figure 5.86 Relative movement between north section and

ground.
Figure 5.88 Cracking in exterior roof beams of the Mental

Health Center.

Figure 5.89 Aerial view of Sepulveda V.A. Hospital which

opened in 1955.

194
Boulevard, some 15 miles away from the epicentral region.

The epicentral distance of this hospital was about the same

as that of the Holiday Inn (Orion Boulevard and Roscoe

Boulevard, location 25), where ground accelerations were

recorded. Thus, it is reasonable to assume that the ground

accelerations at the hospital might have reached as much as 0.27g in the horizontal direction and 0.17g in the vertical

direction.

The west elevation of this structure is shown in figure

5.90. It is a five-story steel frame structure with reinforced brick masonry shear walls. The exterior cladding

was of brick veneer. Damage to the veneer was extensive on the east and west elevations (fig. 5.91). The shear walls

in the first story were badly cracked at many places. However, it appeared that there was no damage to the steel

frame as all parts of the structure were intact without a sign of significant permanent deformation. All mechanical

and electrical equipment was functioning after the earthquake,

including el evators

.

The aftershock of March 31 (refer to section 1.1) caused

additional damage to the brick veneer. Although the magnitude

of this aftershock was small (4.0 on the Richter scale), because the epicenter was only three and a half miles away from

this structure, the resulting damage to the exterior cladding

was considerably greater than that caused by the February 9

quake. During the aftershock large pieces of the brick veneer

were spalled off from the wall, exposing the reinforcement

in the shear wall (fig. 5.92). The building, however, remained in full use after both the February 9 earthquake

and the March 31 aftershock.

Kaiser Foundation Hospital, Map 4, Location 26

Kaiser Foundation Hospital, 13652 Cantara Street,

Panaroma City, is a 10-story reinforced lightweight concrete

shear wall structure (fig. 5.93). The basement and lower 3

stories have a rectangular plan, approximately 215 ft by

125 ft (fig. 5.94). The upper 7 stories consist of two

circular sections, approximately 90-ft in diameter, connected

by an elevator lobby section (fig. 5.95).

There was severe cracking of the shear walls in the

first, second, and third stories (fig. 5.96). The doors to

the interior stairwell on the second and third floors were

rendered inoperable due to the crushing of the spandrel beam

in the shear wall (fig. 5.97). The fourth-floor slab, which

is the transfer slab between the circular tower shear walls

and the walls below, cracked and displaced vertically. There

195
5.90 Northridge Hospital on Roscoe Boulevard near

Reseda Boulevard.

Figure 5.91 Typical cracks

in brick veneer

over the west

entrance.

196
197
198
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199
Figure 5.96 Crushed reinforced concrete elevator shaft on the first floor. Note the exposed reinforcing

steel. (See fig. 5.94, location 1)

.

200
was no apparent sign of structural damage above the fourth

f 1 oor level . During the February 9 earthquake about 50 glass panels

fell from the building. In addition many windows were blown

out by wind on February 19. The chief engineer for the hospital attributed the wind damage to glass panels which were

loosened in their stops during the earthquake.

All the elevators were out of service after the earthquake and one elevator was still inoperable on March 1. The

emergency power system remained functional. The entire

hospital remained in operation.

COMMERCIAL BUILDINGS

Indian Hills Medical Center, Map 3, Location 18

The Indian Hills Medical Center is a six-story reinforced

concrete structure with a light steel frame penthouse. The

building is located near the previously described Holy Cross

Hospital and is shown in figures 5.53 and 5.54.

A view of the structure taken from Holy Cross is shown

in figure 5.98. A typical floor plan is shown in figure

5.99. The first-story height is 17 ft 6 in, then 13 ft 3 in

is typical for all stories above. The structure is supported

by a concrete pile foundation.

Design was based on the 1966 Los Angeles City Building

Code using K=1.0. The building has eight normal weight

concrete shear walls with integrally cast columns in addition

to a beam-and-col umn frame. Floor slabs are lightweight

concrete

.

There was horizontal cracking at the construction joint

at each floor level as shown in figure 5.100. This was

particularly pronounced at the second, third, and fourth

floors where concrete also spalled at the corners (figs.

5.101, 5.102, 5.103, and 5.104). Note the buckled vertical

reinforcement in figure 5.104. These same shear walls were

also cracked diagonally for the full height of the building

(fig. 5.102). There was also extensive crushing at the base

of the southeast shear wall as shown in figure 5.105.

Interior damage consisted of horizontal cracking at the

f 1 oor- to-wal 1 joint of the third, fourth, and fifth floors

(fig. 5.106). There were also damaged beam-column connections

on these same floors (fig. 5.107). Some damage was also

noted in the stairwell where the connections of metal stairs

201
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Indian Hills Medical Center - Typical floor

plan.

203
Figure 5.100 View of the

northeast corner.

The north and

east shear walls

were cracked horizontally at the

second through

the sixth floors.

Diagonal cracks were also present

between floors

.

Figure 5.101 South elevation of the Indian Hills Medical Center.

Note the horizontal crack and spalling visible on

the left shear wall at the fourth-floor level.

204
205
Figure 5.104 Buckled vertical reinforcement in southeast

shear wall.

Figure 5.105 Cracking at the base of the southeast corner

shear wall. Note the exposed reinforcing

bar.

206
Figure 5.106 Interior view of horizontal cracking at the

northeast corner of the fourth floor.

Figure 5.107 Damaged beamcolumn connection

in the fourth

story. The large

piece of broken

concrete is sus- pended by an electrical cable.

207
pulled away from the concrete wall at the landings. Although

usable, the stairs were "shaky." Elevators were inoperative

immediately after the earthquake but were working at the time

of inspection.

The structure was repaired by attaching new 8-in

gunite walls to the existing shear walls and providing

additional floor-slab support by means of steel angles.

Holiday Inn, Map 4, Location 25

The Holiday Inn at 8244 Orion Street, Panorama City, is

a seven-story (no basement) hotel that is about four years

old. The building is a reinforced concrete frame with two

end shear walls (fig. 5.108),

This building had strong-motion acc el erome ters on the

first and fourth floors and in the roof penthouse. On the

first floor the maximum horizontal and vertical accelerations

were 0.276g and 0.171g, respectively. The maximum horizontal

and vertical accelerations recorded in the penthouse were

0,388g and 0,224g, respectively. These recordings are quite

important since this was the closest instrumented building to

the epicenter and the area of greatest damage.

The most severe damage was to nonstructural elements

such as plaster walls and plumbing fixtures. This damage

is illustrated in figure 5.109. A cracked cast-iron bathtub

which has already been removed from the building is shown in

figure 5.110. This type of damage was greatest on the second,

third, and fourth stories. This evidence together with the

recorded accelerations suggest that this building underwent

severe lateral deformation during the earthquake. There

were apparently some cracks in the structural frame which

were repaired with epoxy.

Union Bank, Map 4, Location 27

The thirteen-story Union Bank Building is located at

15233 Ventura Boulevard across the street from the Bank of

California (fig. 5.111). Accel erome ters were not installed

in the Union Bank; however, maximum horizontal and vertical

ground accelerations of 0.227g and O.lOOg were recorded at

the Bank of California.

The building is constructed of reinforced concrete and

was designed under the 1964 Los Angeles City Code as a moment-resisting frame (K=0.67). A typical floor plan is

shown in figure 5.112. Typically the story height is 11 ft

9 in with a 23 ft 6 in first story. The total building

208
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24 X 32

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Figure 5.112 Typical floor framing plan of the Union Bank

Building.

212
height is 164 ft 6 in. There is a two-level underground

garage and a mechanical penthouse. The foundation is drilled

cast- i n-pl ace friction piles.

An elevation of the bank building is shown in figure

5.113. Principal structural damage was in the first-story

columns, primarily at the second-floor beam-column connections

as shown in figure 5.114. These columns were repaired with

epoxy shortly after the earthquake as shown in figure 5.115.

However, the initial attempt was not successful and two

additional trials were made before the repair was considered

to be acceptable.

Other non-structural damage reported consisted of

inoperative elevators, jammed doors on the 2nd, 3rd, 4th,

and 5th floors, steel stair landings pulled away from supports,

some partition damage, and cracked glass and marble veneer

in the first story.

The parking garage located on the north side of the

bank (see fig. 5.111) is shown in figure 5.116. The garage

was constructed of precast pretensioned hollowcore planks

with a cas t-i n-pl ace topping supported on precast pretensioned

girders. Columns are cas t-i n-pl ace reinforced concrete. Most

damage was limited to the columns which were cracked on the

east-west faces as shown in figure 5.117. Concrete column

corbels were also cracked as shown in figure 5.118.

Bank of California, Map 4, Location 28

The twelve-story Bank of California is located at 15250

Ventura Boulevard across the street from the Union Bank

Building (fig. 5.111). Strong-motion accel erometers were

located on the first floor, on the seventh floor, and on the

roof. Maximum recorded horizontal and vertical accelerations

in the basement were 0.227g and O.lOOg. On the roof the

maximum horizontal and vertical accelerations were 0.261g and

0.131g.

The building is constructed of reinforced concrete and

was designed under the 1964 Los Angeles City Code as a shear

wall building with a 25 percent frame (K=1.0). Shear walls

are present only in the first two stories. The building is

a frame structure for the rest of its height. An elevation

is shown in figure 5.119 and a floor plan in figure 5.120.

There is no basement. The building foundation is on drilled

concrete piles.

There were cracks in the building frame over most of its

height. These were especially pronounced in the connection

of the lightweight concrete beams to the normal weight concrete

213

215
216
217
—5a 12-0 =60-0 30-0 sz ^

No4es: t. Columns not shaded are present only

from the 3rd story up.

2. Shear walls are present only through

the second story.

Figure 5.120 Bank of California - Typical floor plan.

218
columns as shown in figure 5.121. This damage was being repaired with epoxy.

Crocker Citizens Bank, Map 4, Location 29

The fourteen-story Crocker Citizens Bank shown in figure

5.122 is a reinforced concrete frame and shear wall structure

located at 14724 Ventura Boulevard, very near the Union Bank

and Bank of California. A typical floor plan is shown in

figure 5.123. There was little or no damage reported in this

building. This building had strong-motion recorders on the

ground floor (no basement), sixth floor, and penthouse. First

floor maximum horizontal and vertical accelerations were

0.258g and 0.093g. At the roof the maximum horizontal

acceleration was 0.315g. The vertical trace was too faint

to read.

Sheraton Universal Hotel, Map 4, Location 31

The 21-story Sheraton Universal Hotel, figure 5.124, is

a reinforced concrete building located at 3838 Lankershim

Boulevard. This 210- ft building was designed under the Los

Angeles Code using the November 1966 modifications for a ductile moment-resisting frame. The floor plan of the highrise portion is shown in figure 5.125. A cross section

through the main building and a typical beam-to-column

framing detail is shown in figure 5.126a and b, respectively.

Apparent damage to this concrete structure was limited to a cracked mural as shown in figure 5.127.

Strong motion accelero graphs in this building were

installed in the basement, the 11th floor, and the 21st

floor. Maximum horizontal and vertical accelerations of

0.175g and 0.087g were recorded in the basement. Both

maximum accelerations were 0.226g on the 21st floor.

Grant's Department Store, Map 2, Location 2

Grant's Department Store is located on Soledad Canyon

Road in Newhall, some 10 miles directly west of the epicenter.

An exterior view of what appears to be an undamaged building

is shown in figure 5.128. It is a single story, brick-wall

structure with "panelized roofs".

The use of panelized roof systems was found to be common

for commercial and industrial buildings. Roof framing

usually consisted of gl ue- 1 ami na ted wood girders spanning

between interior columns and the exterior wall. Wood joists

spaced at 8 ft on center span between the girders and wooden

219
220

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222
223
See figure 5.126b

Figure 5.126a TypicaJ czoss section of elevation.

224
225
226
ledgers which are fastened to the wall by means of anchor

bolts or drilled-in anchors. Usually these joists are

supported on sheet metal hangers (fig. 5.129). Factory

preassembled panels of 4 ft by 8 ft plywood sheet nailed to

2 in by 4 in wood members with metal hangers attached to the

ends are placed between the joists. The edges of plywood

are nailed to adjacent panels or to wooden ledgers attached

to the exterior wall. With this framing system, the lateral

support to the walls and the continuity of the roof panels

is exclusively dependent upon the nailing of the plywood.

There are no positive anchors at the wall to prevent it from

pulling away from the roof.

When outward forces on the wall are generated by earthquakes, the tension load of the wall pulling away from the

roof is resisted solely by a row of closely spaced nails

pulling across the grain of the wooden ledger. Although the

nailing stresses can be justified under the present building

code, there is a tendency for the ledger to split as well as fail in cross bending caused by the eccentricity between the

position of the anchor bolt and the top of the ledger where

the plywood is attached.

Figure 5.129 shows a collapsed portion of the roof which

spanned between the exterior brick wall and the interior beams.

It is apparent from this photograph that the nailing through

the roof panel did not have sufficient strength to accommodate

lateral movement of the wall. Since the earthquake, the

City of Los Angeles has proposed building code changes which

would not permit the type of anchorage of masonry walls to

the roof as described in this previous paragraph.

Other interior damage consisted of fallen suspended

ceiling and merchandise thrown to the floor (fig. 5.130).

Shopping Center at Glenoaks Boulevard and Hubbard Avenue , Map 3, Location 13

A shopping center located at the corner of Glenoaks

Boulevard and Hubbard Avenue, City of San Fernando, was so

severely damaged that it was later razed. This center was

located in the region of maximum ground movement. A postearthquake survey of ground elevation indicated that the

ground in his area was raised as much as about 5 ft (see

fig. 8.23). Gas, water, and sewer lines were severely damaged

in the immediate area (fig. 8.21).

Considerable ground movement was evident in the parking

lot around the Boy's Market grocery store as shown in figure

5.131. The market experienced considerable damage to windows

and structural elements. The construction was similar to

227
228
Figure 5.130 Interior view of Grants Department Store

showing missing portions of suspended ceiling.

Most of the merchandise which had been thrown

to the floor had been picked up when this

photograph was taken.

Figure 5.131 East elevation of Boy's Market.

229
Grant's Department Store (location 2) except damage was more

severe. At this site the masonry wall supporting wood beams

fell outward, dropping beams to the ground. The laminated

wood girder which supported one end of the roof beams is

visible in figure 5.132.

Another small store in the center was similarly damaged

as shown in figure 5.133. Note that the reinforced brick

masonry wall remained essentially intact even though it fell

against an adjacent building. A view from the opposite end

of the store is shown in figure 5.134. The laminated timber

beam at the left spanned approximately 65 ft from a column

at the front of the store to a rear masonry wall which also

collapsed. Wood joists spanned from this beam to a wood

ledger fastened to the wall on the right. Another view of

this store is shown in figure 5.135.

The construction of the southern portion of the center

shown in figure 5.136 differed from that described above.

This portion had a concrete canopy supported on a light

steel frame and was severely racked during the earthquake.

The des tructi veness of ground shaking can be envisaged by

extensive cracking in the parking lot pavement. Yielding

and fracture of one of the support columns is shown in

figure 5.137.

San Fernando Mall, Map 3, Location 19

The San Fernando Mall, main business district in the

City of San Fernando, is shown in figure 5.138. Most buildings were four stories or less in height and appeared to be

built before 1930.

The hotel shown in figure 5.139 was severely damaged.

The second story and roof are held up by interior partitions.

One of the walls fell through the roof of the adjacent store

causing severe interior damage (fig. 5.140). Fallen parapets,

walls, and bricks were common as shown in figures 5.141,

5.142, and 5.143. The Kress store was severely damaged as shown in figures 5.144, 5.145, and 5.146. The diagonally

cracked wall of Kress shown in figure 5.146 was common in

other buildings in the mall as shown in figure 5.147.

This damage, though severe, was not unexpected considering the type of construction. A similarly constructed

building, the Midnight Mission, as far away as downtown Los

Angeles was damaged as shown in figure 5.148. At this latter

location one man was killed when he ran outside and was struck

by falling masonry. Such falling objects are common and

dangerous with the pre-1933 masonry construction. It is certainly not typical of modern reinforced masonry construction.

230
Figure 5.132 View of the Boy's Market looking east.

Most debris has been cleared.

Figure 5.133 Collapsed side wall of a small store in the

shopping center.

231
Figure 5.134 Collapsed side wall shown in figure 5.133 as viewed from the rear of the store.

Figure 5.135 Another view of the store shown in figures

5.133 and 5.134.

232

Figure 5.138 Main business district (San Fernando Mall) in

City of San Fernando.

Figure 5,139 Total collapse of brick masonry wall surrounding

three-story wood frame building (Mission City

Hotel )

.

234
Figure 5.140 The wall of the building shown in figure 5.139

fell through the roof of this building

.

Figure 5.141 Damaged parapet and wall.
Figure 5.142 Damage to brick masonry parapet wall.

Figure 5.143 Collapsed wall and parapet.

236
237
238
such as the Golden State Medical Center at the Pacoima

Hospital, described previously, and the Sportsmen's Lodge

Hotel, which is described later.

Foothill Medical Center, Map 3, Location 21

The Foothill Medical Center (see fig. 5.149 and fig.

5.150) is located on Van Nuys Boulevard at Dronfield Avenue,

Pacoima. This structural steel frame building (about 65 ft

by 200 ft in plan) had considerable glass breakage as shown

in figure 5.151. There was also some damage to the stucco

covered wood-frame exterior walls as shown in figures 5.151

and 5.152.

The wallboard had been removed near the entrance to

examine the lateral bracing (fig. 5.153). While the bracing

showed no evidence of damage, the exposure revealed local

flange buckling of the steel column as indicated by the

arrow. There was considerable damage to interior partitions

and stairwells (fig. 5.154).

The reinforced concrete masonry wall shown in figure

5.155 was on two sides of the center parking lot. The wall

reinforcement did not always extend to the top of the wall

and reinforced cells were not always grouted. Usually blocks

above the reinforcing cut off were toppled (indicated by

arrows). Walls were usually leaning when reinforced cells

were not grouted.

Sportsmen's Lodge Hotel, Map 4, Location 30

The nine-year old Sportsmen's Lodge Hotel shown in

figure 5.156 is located on Ventura Boulevard near Coldwater

Canyon Avenue. The complex consists of two buildings, one

two-stories (60 ft x 170 ft) and one five-stories (68 ft x 240

ft) high. Construction is reinforced concrete masonry

bearing wall and precast reinforced lightweight concrete

slabs. This structure had only minor damage consisting of

some cracked plaster and one broken window.

RESIDENCES

Essentially all of the dwellings in Southern California

including large two- and three-story apartment complexes are

wood frame construction. Most of the single family residences

are predominantly one-story structures, although some are

two-story. Roofs are wood rafters covered either with plywood or one-inch thick boards. Roof coverings are varied and

239
Figure 5.148 Midnight Mission, 396 South Los Angeles Street, in

downtown Los Angeles. This building , erected in 1896,

provided shelter for about 200 men. One man was killed

when he ran out of the front door and was struck by

falling masonry. (Los Angeles Times Photo).

Figure 5.149 General view of Foothill Medical Center

240

242
Figure 5.154 Wallboard

cracking in

stairwell. The

cracking pattern

reflects the size

of the wallboard

.

Figure 5.155 Reinforced concrete masonry wall around the

Medical Center parking lot. Arrows indicate

the location of vertical reinforcement.

243
include built-up asphalt impregnated asbestos material,

asphalt shingles, wood shingles or shakes, and clay tile,

depending on the slope of roof and cost of the structure.

Walls are constructed with 2 in by 4 in wood studs spaced 16

inches apart and braced at each corner and at 25 feet intervals with a diagonal brace. The exterior of the walls are

covered with cement plaster, wood siding, or plywood while

the interior surfaces and ceilings are generally finished

with plaster on gypsum board lath or with gypsum board

"drywall". Floors are either wood joists with plywood or

concrete slab on grade, and the buildings are generally

supported on spread foundations.

Buildings ranging in cost from modest to very expensive

employ the above construction with minor variations. Most

dwellings are constructed in accordance with specification

code criteria and are therefore not substantiated by engineering computations, unless there are very large rooms (over

25 feet clear span) or other unusual construction. Normally

the rooms are small with enough cross partitions to "brace

themsel ves

.

Fireplaces installed in higher priced homes are usually

masonry with grout and nominal reinforcement placed between

the flue lining and the outer masonry shell. The chimneys

are usually anchored at the roof or upper-story ceiling.

Split-level houses frequently collapsed as in the case

of the house shown in figure 5.157 (map 3, location 5). This

house was similar in appearance to the one shown in figure

5.158 which was not damaged. Other damaged split level

houses (map 3, location 6) are shown in figures 5.159, 5.160,

and 5.161. A similar house located slightly farther south

(map 3, location 12) is shown in figure 5.162. In general,

split-level or irregularly-shaped houses that were not adequately tied at the changes in roof or floor elevation were

severely damaged either by collapse or at the junction of the

wings (fig. 5.161). Collapse frequently occurred due to a wide open-space provided by the garage door in the end wall,

which offered little lateral resistance (fig. 5.162).

Masonry chimneys on many residences collapsed as shown

shown in figure 5.163 (map 3, location 10). Leaning chimneys

were not uncommon as shown in figure 5.164 (map 3, location

11) when they were properly reinforced but inadequately tied

to the house. Note the collapsed masonry fence in front of

the house.

Because of their "self bracing" effect, residences

usually suffered only nominal damage except at locations

close to the zone of ground rupture. The houses shown in

figures 5.165, 5.166, and 5,167 (map 3, location 15) are

244
Figure 5.156 Aerial view of Sportsmen' s Lodge Hotel.

Figure 5.157 Collapsed split-level residence at Fenton

Avenue and Tyler Street.

245
Figure 5.158 Undamaged split-level residence at Fenton

Avenue and Tyler Street.

Figure 5.159 Collapsed split-level residence at Almetz

Street and Leedy Avenue.

246
Figure 5.160 Damaged split-level residence at Aldergrove

Street and Leedy Avenue.

Figure 5.161 Closeup of damaged split-level residence shown

in figure 5.160.

247
Figure 5.162 Split-level residence , Sylmar. Note crushed

car (arrow) . (Los Angeles Times Photo) .

248
Figure 5.164 Leaning reinforced brick masonry chimney.

Figure 5.165 Wood-frame and stucco house on 8th Street, San

Fernando. Horizontal cracking occurred along

the top of the foundation wall. Note ground

cracking in left foreground.

249
Figure 5.166 Damaged single family residence

.

Figure 5.167 Destroyed wood-frame house.

250
typical examples of the damage which occurred near severe

ground rupture.

One group of partially completed residences located

east of and adjacent to the San Fernando Veterans Hospital

(map 3, location 8) was heavily damaged as shown in figure

5.168. The frames and roofs were essentially complete at the

time of the earthquake. The walls of the houses on the left

were covered with wire mesh and paper backing which was to be

covered with stucco (in a few cases decorative plywood panels

were also installed). This covering was essentially the

only difference from the houses on the right which collapsed.

It appears that a very nominal amount of material furnished

considerable lateral support. (The house in the right rear

background which did not collapse was apparently no different

than those which did collapse. The reason it remained standing is not known.) A partially collapsed house is shown in

figure 5.169.

Apartments differ little in construction from houses.

The "Friday USA" Apartments (map 3, location 14) suffered

severe damage as shown in figure 5.170 due to little lateral

resistance provided by large open-garage areas in the first

floor. The Mardette Apartments (map 3, location 16) were

similarly damaged as shown in figures 5.171 and 5.172. The

wide open parking areas and entranceways provide little

lateral resistance as in the case of split-level houses

previously discussed.

Typical damaged mobile homes are shown in figure 5.173

(map 2, location 1) and figure 5.174 (map 2, location 3).

These homes are usually supported on small concrete or metal

base supports. Metal curtain walls around the base were

usually damaged when trailers moved sideways (there is little

to resist lateral movement since these homes are usually not

attached to the base supports). Frequently considerable

damage was caused by the supports subsequently punching

through the floor.

A major change to building code requirements relating to

residential dwellings does not appear to be warranted. However, making proper use of the inherent strength of the

structure and providing adequate ties at corners and chimneys

would improve its behavior. Connections and details should

be carefully considered by the designer and should be clearly

shown on the drawings; it should not be left to the discretion of the builder.

251
252
Figure 5.170 Rear view of damaged three-story "Friday USA'' apartment building.

Figure 5.171 Rear view of damaged two- story Mardette

apartment building

.

253
Figure 5.172 Front view of Mardette apartment building

.

Figure 5.173 Mobile home (Soledad Canyon Road, Newhall)

which was damaged when it fell off its small

concrete and metal base supports.

254
MISCELLANEOUS STRUCTURES

Nethercutt Museum, Map 3, Location 9

The Nethercutt Museum for antique cars, which is

located on Bledsoe Street near Bradley Avenue, Sylmar, is

a reinforced concrete structure approximately 80 ft by 100

ft in plan and 110 ft in height (fig. 5.175). The 3-story

building was designed in accordance with City of Los Angeles

Building Code (K=1.33). The first story is 36 ft in height

and has a partial mezzanine. The second- and third -story

heights are 22 ft. The exterior concrete walls which

extend up beyond the roof level are 8-in thick. Eight-inch

two-way floor slabs span to 4-ft wide by 2-ft deep floor

beams which are carried on columns spaced about 26-ft apart.

The foundation consists of drilled concrete piles.

Damage noted on the building exterior consisted primarily of horizontal cracks and concrete spelling along the

construction joints (fig. 5.176 and 5.177) and at the building corners (fig. 5.178). The penthouse free-standing

cantilever concrete walls were only 12 hours old at the time

of the earthquake but suffered no damage.

A severely damaged light frame store located diagonally

across the corner from the museum is shown in figure 5.179.

San Fernando Industrial Park, Map 3, Location 20

This industrial park comprised of some 30 small

industrial buildings located at the northeast corner of the

City of San Fernando. The complex was located in the region

of strong ground motion with evidence of vertical ground

displacement of as much as three feet. The primary cause of

damage to many buildings, therefore, can be attributed to

permanent ground displacement and faulting (see figs. 5.180

and 5.181)

.

The buildings are single-story structures with wood

"panelized roofs". The exterior walls are either reinforced

grouted masonry or tilt-up concrete panels. The floors

are concrete si ab-on-grade either at the street level or at

truck loading level. The buildings are supported on spread

f oot i ngs .

The type of construction of most buildings in this

industrial park is similar to that of the Grant's Department

Store, described previously, thus similar types of failures

occurred. Structural damage to the buildings in the industrial park consisted of portions of exterior wall pulling

255
Figure 5.174 Mobile home park located along Sierra Highway 14

in Newhall . At the center of the figure are the

remains of a home which was completely destroyed

by fire. Note damaged metal curtain walls around

the bases of the mobile homes (arrows)

.

Figure 5.175 Elevation of Nethercutt Museum.

256
Figure 5.176 Horizontal crack along the construction

joint at the base of the structure.

Figure 5.177 Damage to the exterior surface of the

concrete wall along the construction

joint.

257
Figure 5.178 Cracking and spalling at first floor

Corner of the Nethercutt Museum.

258
259
away from the roof and floor, thereby causing the roof to

collapse. A typical failure is shown in figure 5.182.

The performance of drilled-in anchors can be inferior

to cast-in anchors or to anchor bolts in resisting tensile

forces since the strength is dependent on the quality of

installation. Typical evidence of failure of drilled-in

anchors is seen in figure 5.183. The drilled-in anchors in

the wall, which were used to connect reinforcing dowels at

the floor level, failed thereby contributing to the exterior

wal 1 coll apse

.

Because the buildings in this industrial park were

located in the region of severe ground movement and faulting

the level of acceleration might have been considerably

greater than the code design criteria. Consequently severe

structural damage would be expected. However, it appears

that the addition of positive tension anchors between the

wall and framing members would significantly increase earthquake resistance and could have reduced the extent of damage

Parking Structure in West Los Angeles, Map 5, Location 32

This five-level structure is located at 2215 Purdue

Avenue in West Los Angeles, some 25 miles away from the

epicentral region. Based on acceleration measurements taken

at neighboring structures, it can be estimated that peak

ground accelerations at this location could have been about

0.17g in the horizontal direction and 0.06g in the vertical

di recti on .

An overall view of the structure is shown in figure

5.184. The structure is about 105 ft wide and 147 ft

long. It is of steel frame construction with concrete

end shear walls and diagonal bracings to resist lateral

forces. The floor framing is comprised of steel joists

supported on steel beams. The three-inch concrete slab

was poured directly on corrugated sheet-metal decks which

rest on the steel joists.

The structure was designed in accordance with the 1961

Los Angeles City Building Code using a horizontal force

factor "K" of 1.33. It was designed to support a design

dead load of 38 lb per sq ft and a design live load of 50 lb

per sq ft. At the time of the earthquake the building was

net occupied by cars.

Damage to the structure was confined to web crippling

of some of main floor beams to which diagonal braces were

attached. Positions of damaged beams with respect to

diagonal braces and a close-up view of a damaged beam are

260
Figure 5.182 The roof collapsed when the exterior wall

pulled away.

Figure 5.183 Typical failure of drilled-in anchors.

261
shown in figures 5.185 and 5.186. It is clear from these

photographs that no vertical stiffeners were provided at the

support. Figure 5.187 shows a typical repaired beam. Two

vertical stiffeners were added to the beam and bottom half

of the crippled web and the flange was replaced with a new

section over the support. Initial installation of vertical

stiffeners at a cost far less than the repair cost could

have prevented the web from crippling.

POSTAL FACILITIES

There are over thirty postal facilities in the San

Fernando Valley. These are generally one-story high (in

at least one case leased "mobile homes") of numerous construction types. Damage was usually a function of the age

of the structure more than any other single factor. The

most important findings were damages to nonstructural elements.

The following information was abstracted from a report to the

Assistant Postmaster General, Facilities Department, U. S.

Postal Service.

Suspended light fixtures were the most common source

of injury, primarily by breaking loose at the fixture

connections. Tiles frequently fell from acoustical tile

ceilings. Battery-operated emergency lights were generally

of little value, usually smashing to the floor and leaving

the buildings in darkness. In cases where lights did not

fall there were frequently an insufficient number of lights

or beams were aimed too high to light the floors and exits.

With the loss of power, exit signs and lights were useless.

Fire extinguishers were sometimes thrown from their

brackets or the bracket pulled loose from its support. In

some cases fire extinguishers were not in an area where

emergency lighting existed.

5 . 3 References

5.1 The Prince William Sound Alaska Earthquake of 1964 and

Aftershocks, Volume II, Part A, Publication 10-3

(C&GS), U. S. Department of Commerce, 1967.

5.2 Structural Engineers Association of California,

Recommended Lateral Force Requirements and Commentary, 1968.

5.3 Los Angeles County Building Laws, 1965 Edition,

International Conference of Building Officials.

Pasadena, California, 1965.

262
Figure 5.184 General view of parking structure , located

at 2215 Purdue Avenue in west Los Angeles.

Figure 5.185 Location of damaged floor beams (arrows)

263
Figure 5.186 Close-up of

dcimaged floor

beam . Wood

blocks were

used to provide

temporary support.

Figure 5.187 Repaired floor beam. The bottom half of

the beam near the support was repaired

with a new section and two bearing

stiffeners were added.

264
5.4 Joint Committee on Lateral Forces, "Lateral Forces

of Earthquake and Wind," ASCE Transactions, Vol.

117, 1952.

5.5 American Concrete Institute, Building Code Requirements

for Reinforced Concrete (ACI 318-56) , Detroit,

Michigan, May , 19 56.

5.6 American Concrete Institute, Building Code Requirements

for Reinforced Concrete (ACI 318-63) , Detroit,

Michigan, June, 1963.

265

CHAPTER 6 DAMAGE TO SCHOOLS

6 . 1 Introduction

The majority of the schools in Southern California are

one- and two-story buildings with wood stud walls or reinforced grouted masonry walls and with wood or light steel

roof construction. However, there are some buildings of

every conceivable type of construction. There are also many

temporary or portable classroom buildings, many on "substandard" foundations of wood sills and short cripple studs

directly on the ground. At many school sites, the portable

buildings moved on their support, requiring that they be res et

.

There are approximately 200 public schools within the

area subjected to strong ground motion (ten mile radius of

San Fernando) and at least 25 on or within one mile of the

zone of ground rupture. Although there was structural

damage to modern school buildings (those constructed

according to the requirements of the Field Act of 1933),

only one such school which was within the zone of ground

rupture was damaged to the extent that the school board

considered abandoning it. The school did not collapse, and

after the school board and their structural engineer reviewed

the extent of damage and estimated cost of repairs, the

engineer was commissioned to prepare plans for repairs.

Many schools close to the zone of major disaster reported no damage whatsoever. In contrast, 13 older (pre-Field Act)

buildings at 10 school sites in the Los Angeles Unified

School District, as much as 20 miles from the central disaster

area, were so seriously damaged that they were immediately

vacated and scheduled for demolition.

6 . 2 Laws Governing School Construction

On the evening of March 10, 1933, the Long Beach- Compton

area experienced a severe earthquake (Magnitude 6.3) which

left most of the schools in shambles. Had the quake occurred

during school hours, the loss of life and injury would have

been devastating. The California Legislature took immediate

action to avoid a future disaster and one month later, on April 10, 1933, adopted a bill authored by Assemblyman

Don Field of Glendale, California to amend the Education

Code

.

The new law, usually referred to as the Field Act, as now amended provides the following:

1. All new buildings regardless of cost and additions

267
or alterations costing over $10,000 shall be

constructed under the supervision of the Department

of General Servi ces .

2. The school board shall submit plans and specifications to the Department of General Services for

review and obtain approval prior to awarding a contract for the work, and shall not pay for work

not in accordance with the approval.

3. All plans and specifications shall be prepared by

an architect or a structural engineer licensed by

the state. The construction shall also be supervised by an architect or structural engineer.

4. The school board must provide a qualified full-time

resident inspector who is satisfactory to the

architect or structural engineer and to the

Department of General Services.

5. Verified reports shall be submitted by the architect,

engineer, contractor, and inspector certifying that

all work complies with the approved documents.

6. The Department of General Services shall make such

field inspections during the progress of the

construction as in its judgement is necessary and

proper to enforce the act.

7. The Department of General Services shall make rules

and regulations (building code) to carry out the

provisions of the act.

8. A procedure is established whereby school boards

may have the Department of General Services examine

old schools to determine if they are safe for

occupancy

.

9. Any violation of the Field Act or false statement

on a verified report or affidavit is a f e 1 ony .

The Department of General Services has delegated the enforcement of the Field Act to the State Architect who in turn

delegated the enforcement, except for making the rules and

regulations, to Chief Structural Engineer, Schoolhouse

Section of the Office of Architecture and Construction. The

Schoolhouse Section does, however, act in an advisory capacity to the Building Standards Commission in establishing

the rules and regulations.

The code regulating the design and construction of

268
schools is the Basic Building Regulations (California

Administrative Code Title 24). For those sections of the

Basic Building Regulations not yet finalized, sections of

Chapter 1 of California Administrative Code Title 21 are

still in use.

The requirements for schools set forth in Title 24 and

Title 21 are somewhat more stringent than some of the local

building codes. Some of the more restrictive requirements

of Ti tl e 24 and Ti tl e 21 are :

1. Additional requirements for material testing and

inspections

.

2. Limitation of deflection, drift, and span-depth

ratio.

3. Higher seismic forces for some buildings three

stories or less in height.

4. Lower allowable masonry stresses.

5. Limitations of slope of grain for "machine stress

rated" lumber.

6. Lower allowable stress for wood joists, rafters,

and other members spaced two feet or less.

7. Greater minimum spacing of adjacent concrete

reinforcing bars to reduce congestion.

8. Requirement that steel ties in concrete columns be

spaced at half the normal required spacing (twice

as many ties) within the top and bottom two feet.

9. Lower allowable capacity for shear connectors for

composite (steel beam and concrete slab) construction.

10. Greater minimum thickness of light gage steel used

for structural members.

However, the primary difference between school construction and other work is in the scrutiny given to details and

connections, and in the added job site surveillance by the

architect, engineer, inspector, and a field engineer of the

Schoolhouse Section of the Office of Architecture and

Construction.

Other sections of the Education Code also control the

construction and occupancy of schools.

269
An article entitled Fitness of Buildings for Occupancy , as amended in 1968, provi des for the examination of all

pre-Field Act school buildings prior to January 1, 1970.

Buildings found to be unsafe as defined in the Code must be

reinforced or abandoned not later than June 30, 1975. In

determining the safety of a building, the sole determination

shall be protection of life and the prevention of personal

injury at a level of safety equivalent to that established

by the Field Act and the rules and regulations adopted

thereunder, disregarding insofar as possible, such building

damage not jeopardizing life which would be expected from

one disturbance of nature of the intensity used for design

purposes in said rules and regulations.

A Section relating to Investigation of Prospective

School Sites , added to the statutes in 1967, requires a school district to have a proposed site investigated by

competent personnel to ensure that all factors affecting

public interest are included, not cost alone. "The investigation shall include such geological and engineering studies

as will preclude siting of a school over or within a fault,

on or below a slide area, or in any other location where the

geological characteristics are such that the construction

effort required to make the site safe for occupancy is

economically unfeasible."

6 . 3 Case Histories of Individual School Damages

SCHOOLS CONSTRUCTED BEFORE 1933

Los Angeles High School (Main Building) was constructed

in 1917. The school is located approximately 20 miles southeast of the City of San Fernando (location 1, fig. 6.1). The

building was a four-story concrete frame with unreinforced

brick filler walls and had a 35-ft central tower which had a steel frame (fig. 6.2). The roof and classroom floors were

wood framing and sheathing; the concrete frame was designed

for gravity loads only; the exterior brick filler walls were

unreinforced and laid in lime mortar; the partitions were

hollow clay tile. The building was supported on spread

foundations. A portion of the parapet fell through the roof

of a teacher's work room and came to rest on a table (fig.

6.3). Much of the brickwork fell from the parapet directly

onto the rear exit stairs and into the courtyard (fig. 6.4).

There was serious cracking of the brick filler walls and the

clay tile partitions. The building has been abandoned and

was demolished.

Morningside School (Building #2) in the City of San

Fernando was constructed in 1928. The school was located

adjacent to the area of ground rupture (location 2, fig. 6.1).

270
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271
Figure 6.2 Main building at Los Angeles High School before

demolition

.

Figure 6.3 A portion of the

parapet wall fell

through the roof

and came to rest

on a table, Los

Angeles High School.

Ill
The structure was a two-story double loaded corridor classroom

building 60-ft wide and 100-ft long with unreinforced brick

bearing walls laid in lime mortar. The structure had a wood

framed gable roof covered with heavy slate roofing, wood

framed floors in the classrooms, and concrete slabs in the

corridor. The walls were unreinforced brick with a concrete

bond beam at the roof. The building rested on spread footings.

The structure did not collapse, but sustained serious cracking

of the brick walls (fig. 6.5), brick separated at the bond

beam and was displaced at the gable end (fig. 6.6). The

building has been abandoned and was demolished.

REINFORCED BUILDINGS - CONSTRUCTED PRIOR TO 1933 - REINFORCED

TO RESIST EARTHQUAKE FORCES AFTER 1933

Morningside School (Building #1) in the City of San

Fernando, was constructed in 1915 and is located adjacent to

Building #2 previously described. The building is a two-story

"T"-shaped concrete bearing wall structure (fig. 6.7). The

original construction had a wood framed gabled roof with

heavy slate roofing. Floor framing consisted of wood joists

and sheathing. The exterior walls were concrete having an

ultimate compressive strength of approximately 900 psi. The

partitions were wood studs with plaster on wood strip lath.

The building rests on spread foundations. In 1964, the building was reinforced by removing the heavy slate roofing,

installing new plywood sheathing in the plane of the secondstory ceiling, anchoring the floors and roof to the walls,

installing a plywood shear-resisting element in the attic to

stabilize the gabled roof framing in the longitudinal direction,

and the installation of additional roof supports. New concrete

shear-resisting wall panels were added since Title 21 considers

concrete with a compressive strength below 1500 psi the same

as unreinforced brickwork. There was nominal structural damage. The plywood sheathing on the longitudinal wall in the

attic pulled loose from the studs, and some of the roof-towall anchors were damaged. Most of the interior plaster on

wood strip lath was loosened. All the lath and plaster has

been removed and replaced with drywall.

Hoover High School (Auditorium) in Glendale was

constructed in 1930. The school is located approximately

14 miles southeast of the City of San Fernando (location 3,

fig. 6.1). The original construction consisted of steel

roof trusses and wood joists and sheathing supported on steel

columns encased in exterior unreinforced brick walls laid in

lime mortar. The interior was plastered directly on the brick.

The floor system is wood framing and the building rests on spread foundations. In 1937, the building was reinforced by

removing the wood roof joists and sheathing, the top three

feet of the brick walls, and the outer face of brick on the

273
Figure 6.4 Brickwork fell

from the parapet

into the courtyard, Los Angeles

Hi gh School

.

Figure 6.5 Brick walls sustained serious cracking,

Morningside School Building #2.

11^
Figure 6,6 Brick wall was displaced at the gable end,

Morningslde School Building #2.

Figure 6.7 Morningslde School Building #1 was constructed

in 1915 and strengthened to resist earthquake

forces in 1964.

275
walls. New steel roof joists were then installed. New

reinforced concrete was cast against the remaining brick and

a new concrete roof slab was cast.

There was no structural damage to this building. Some

interior plaster, which was installed at the time of the

original construction, flaked from the wall. Tapping the

surface with a hammer indicated that the plaster is no longer

bonded to the brick at many locations. Newer brick bearing

wall structures at this school suffered only superficial

damage, such as minor plaster cracks and displacement of

structural separation joint covers. The entire school is

occupi ed

.

Franklin High School (Auditorium) in the Highland Park

area of Los Angeles was constructed in 1928. The school is

located approximately 19 miles southeast of the City of San

Fernando (location 4, fig. 6.1). Original construction

consisted of steel roof trusses with wood rafters and

sheathing, wood ceiling joists, and metal lath and plaster.

The walls were unreinforced brick bearing walls laid in lime

mortar. The building rests on spread foundations. The

building was reinforced in 1960 by removing the exterior

face of brick from the wall, cutting chases for stiffening

ribs, placing reinforcing steel near the wall and in the

chases, and applying a blanket of gunite. The walls were

tied to the roof construction and additional bracing was

installed in the plane of the roof.

There was no apparent structural damage. Some of the

decorative plaster on the ceiling, which was installed at the

time of the original construction, has fallen. The ceiling

has been replaced. Other buildings at this site sustained no apparent damage.

SCHOOLS CONSTRUCTED AFTER 1933 IN ACCORDANCE WITH THE FIELD

ACT

Harding Street School in the City of San Fernando was

constructed in 1964. The school is in the area of ground

rupture (location 5, fig. 6.1). The construction is onestory wood frame and stucco. The roof framing is comprised

of wood joists and plywood sheathing. There are plywood shearresisting elements, usually located in the walls. The floor

is a concrete slab on grade and the building rests on spread

f oot i ngs

.

There was minor structural damage to the walls and slab

on grade. The slab cracked in two classrooms, presumably

located directly above ground rupture, with a vertical displacement of approximately 3 1/2 in (fig. 6.8). The walls

276
racked slightly causing some doors to bind in the steel frames

(fig. 6.9). There was also plaster cracking. The two classrooms in which the floor was cracked were repaired. The

entire school is occupied.

Van Gogh Street School , Granada Hills was constructed

in 1968. The school is in an area of ground rupture directly

west of the Upper Van Norman Reservoir (location 6, fig. 6.1).

The construction is a single-story wood frame and stucco.

The roof framing is comprised of wood joists and plywood

sheathing. There are plywood shear-resisting elements, usually

located in the walls. The floor is concrete slab on grade.

The building rests on concrete spread footings. The lunch

shelter is a wooden roof structure supported on 6-in square

steel tube columns can t i 1 everi ng from the foundation. Although

there was no collapse, there was major structural damage which

consisted of buckling of slabs on grade (fig. 6.10), fracturing of concrete foundation walls (fig. 6.11), and displacement

of bearing walls in the zone of cracked foundations (fig.

6.12). The lunch shelter columns were permanently bent

approximately 15 degrees at the base at the point of weakness

created by openings for electrical outlet boxes (fig. 6.1?).

A cantilever concrete block garden wall leaned approximately

ten degrees but remained standing (fig. 6.14). The underground utilities were severely damaged. The school has been

repaired and is fully occupied.

Sylmar High School in Sylmar was constructed in 1961.

The school is in the zone of earth rupture adjacent to the

City of San Fernando (location 7, fig. 6.1). The school

consisted of a complex of single-story wood frame and stucco

buildings. The gymnasium is a concrete structure. The

buildings have wood rafters and plywood sheathing, wood stud

bearing walls with plywood shear-resisting elements. Floors

are slab on grade except for the cafeteria kitchen which has

a raised structural concrete slab and beam with intermediate

concrete piers. The buildings rest on spread foundations.

The gymnasium has a prestressed concrete folded plate roof,

concrete exterior walls, concrete slab on grade and rests on

drilled concrete friction piles. The covered arcades are

wood roof structures supported on pipe columns cant i 1 everi ng

from the foundation.

Principle structural damage was caused by the differential stiffness of the buildings and the covered arcades. The

arcades pulled loose both from the buildings and from each

other and distorted their supporting pipe columns (fig. 6.15

and 6.16). There was a slight spalling of the gymnasium

pres tress ed-concrete roof member where a steel cross beam was

attached to support gymnastic equipment (fig. 6.17). The

ground under the gymnasium subsided approximately 1 1/2 in

leaving a void beneath the slab on grade adjacent to the

277
Figure 6.8 Cracked slab with a vertical displacement of

approximately 3 1/2 inches, Harding Street

School .

Figure 6.9 Plaster cracks over door at Harding Street

School . Racking of wall caused doors to bind

in the steel frames.

I,

278
279
Figure 6.12 Displaced bearing wall. Van Gogh Street School.

Figure 6.13 Lunch shelter columns were permanently bent at

opening for electrical outlet box. Van Gogh

Street School

.

280
Figure 6.14 Cantilever concrete block garden wall leaned

approximately ten degrees, Van Gogh Street

School

.

Figure 6.15 Arcades pulled loose from each other at Sylmar

High School.

281
Figure 6.16 Distorted pipe columns at arcade, Sylmar High

School

.

Figure 6.17 Spalled prestressed concrete roof member at

gymnastic equipment support, Sylmar High School

282
walls. The floor slab sagged down toward the middle of the

room. The gymnasium walls which rested on piles did not

subside. Slabs on grade were extensively cracked and buckled

(fig. 6.18 and 6.19). The interior supporting piers for the

structural floor in the kitchen were severely damaged and

shoring was required to provide for safe occupancy. A

reinforced grouted brick transformer vault, constructed

partially below grade, was extensively damaged. There was

considerable damage to lighting fixtures, acoustical ceilings,

and plaster. The school is presently occupied.

San Fernando High School in the City of San Fernando was

constructed in several i ncremen ts starting in about 1 952. The

school is located adjacent to the area of ground rupture

(location 8, fig. 6.1). The buildings are primarily one-and

two-story concrete bearing wall structures with the classroom

wings hav.ing double loaded corridors. The roof has concrete

beams and slabs except for the auditorium which has metal

decking supported on steel trusses with a horizontal bracing

system in the plane of the lower chord. The gymnasium has a steel sawtooth roof framing system with horizontal rod bracing

in the plane of the lower chord. The walls are reinforced

concrete and the floors are concrete beams and slabs. The

buildings rest on spread footings. In addition there are two

frame and stucco classroom buildings.

There was limited structural damage; in the gymnasium,

the diagonal rods in the horizontal bracing system pulled

out of clevises where oversized clevises were erroneously

installed (fig. 6.20). In the auditorium several 5x3 angles

in the horizontal bracing system buckled (fig. 6.21).

The administration building sustained water damage to

the ceiling caused by a broken fire sprinkler pipe. The twostory classroom buildings suffered damage to plaster at the

junction of the transverse partitions and the concrete

exterior walls. Some of the cabinets along the transverse

classroom partitions were displaced and racked. Several

window panels in the sawtooth roof of the gymnasium fell

onto the roof. The "T"-bar ceiling in the wood framed

classrooms was damaged primarily at the perimeter; however,

no lighting fixtures dropped. The extent of damage was

minimal considering the school's close proximity to the

earthquake

.

Patrick Henry Junior High School in Granada Hills was

constructed in 1959. The school is located approximately

four miles southwest of the City of San Fernando and is

approximately two miles southeast of the epicenter of the

strong aftershock of March 31, 1971 (location 9, fig. 6.1).

The buildings are primarily one- and two-story reinforced

grouted brick and concrete bearing wall structures. The

283
284
285
classroom wings are constructed back-to-back (longitudinal

wall at center of building with rooms on both sides) with an

exit to an exterior walk or balcony on each side. The

buildings have concrete roof and floor slabs (first floor is

concrete slab on grade), and rest on spread footings. Mechanical penthouses on the roof are constructed with a braced

structural steel frame and covered with corrugated cementasbestos board.

The major structural damage consisted of fracturing of

four second-story columns of a two-story covered arcade (fig.

6.22 and 6.23). The concrete roof of the arcade was shored

to prevent collapse. The longitudinal concrete wall in the

classroom buildings, extending the full length of the buildings

sustained some hairline diagonal cracks near both ends of the

building. The cracking can be attributed to shrinkage stresses

that existed prior to the earthquake. A concrete curb at the

corner of the mechanical penthouse fractured under the steel

column at the brace connection (fig. 6.24 and 6.25). Structural damage was minimal; however, a major loss of lighting

fixtures constituted a real hazard. Approximately 1500

lighting fixture stems failed at the ceiling canopy or at

the fixture. All fixtures have been reinstalled. There

was nominal damage to acoustical ceiling tile. Electrical

conduits were damaged at structural separation joints where

they were rigidly connected to both sides (fig. 6.26). The

earthquake aftershock of March 31, 1971, caused little

additional damage. There were a few new plaster cracks, a few damaged ceiling tiles, and some additional flaking of

concrete on the previously damaged arcade columns. It is

possible that the aftershock could have caused collapse of

the arcade if it had not been shored. The damaged arcade has

been removed. The entire school is in use.

Beckford Avenue School in Northridge was constructed in

1966. This school is located essentially over the epicenter

of the March 31, 1971 aftershock and approximately 6 miles

west of the City of San Fernando (location 10, fig. 6.1).

The school is a single-story wood frame and stucco complex.

The roof framing consists of wood joists and plywood sheathing. Ceilings are "T" bar with lay- in acoustical tile.

Lateral bracing is provided by plywood shear-resisting

elements. The floor is concrete slab on grade and the

foundations are continuous footings. There are two temporary classroom buildings on wood mudsills resting on the

asphalt pavement.

There was no damage caused by the main shock of

February 9, 1971; however, the March 31, 1971, aftershock

caused considerable nonstructural damage. Much of the ceiling tile and "T" bars at the perimeter of the rooms fell.

Most of the diffuser lenses on the light fixtures fell. One

286
Figure 6.22 Fractured concrete at second-story covered

arcade columns, Patrick Henry Jr. High

School

.

Figure 6.23 Close up of fractured concrete second-story

covered arcade column, Patrick Henry Jr. High

School

.

287
e 6.24 Corner of mechanical penthouse

fractured under

steel column

(exterior view)

,

Patrick Henry Jr

High School

.

Figure 6.25 Corner of mechanical penthouse under steel

column (interior view) , Patrick Henry Jr.

High School.

288
of the portable classroom buildings moved approximately two

inches. All damaged ceiling sections were removed and the

school was reopened. There was extensive damage and collapse

of chimneys and masonry garden walls in the residential area

directly adjacent to and surrounding the school.

Castlebay Lane School in Northridge is still under

construction but nearing completion. The school is located

approximately two miles north of the epicenter of the

March 31, 1971, aftershock and about six miles west of the

City of San Fernando (location 11, fig. 6.1). The school

is a two-story wood frame and stucco structure. The roof

and second-floor framing consist of wood "T rus - Jo i s ts " and

plywood sheathing. Lateral bracing is provided by plywood

shear- res i s ti ng elements. The first floor is concrete on

grade. The building rests on concrete spread footings.

Exterior finish is stucco with some ceramic tile veneer.

Interior walls are plastered on gypsum board lath. Classroom

ceilings are acoustical plaster, corridors have "T"-bar

acoustical ceilings.

There was no structural damage caused by either the

earthquake of February 9, 1971, or the aftershock of March 31,

1971. However, at the time of the main shock some ceramic

tile veneer fell from the wall (fig. 6.27). The interior

plaster cracked at many locations, the "T"-bar ceiling was

damaged, the structural separation joint covers distorted,

and mechanical equipment located on the roof moved off the

isolation mounts (fig. 6.28). Repairs were underway when the

aftershock of March 31, 1971, occurred causing additional

ceramic veneer to fall from the wall, damage to corridor "T"-

bar ceilings which had already been repaired (fig. 6.29) and

extensive cracking of interior plaster at the joints of the

gypsum board lath (fig. 6.30).

Crescenta Valley High School (Administration Classroom

Building) in La Crescenta was constructed in 1955. The

school is located approximately twelve miles southeast of the

City of San Fernando (location 12, fig. 6.1). The building

is a three-story concrete bearing wall, double loaded corridor,

classroom structure with a one-story and basement administrative office wing at the north end (fig. 6.31). The roof and

upper-story floors are concrete beams and slabs, the lower

floor is a concrete slab on grade. The building is supported

on spread footings. There was major cracking of the piers

in the north wall of the administration wing (fig. 6.32),

which is a continuation of the three-story shear wall of the

classroom section. Since there are only minor cracks in the

three-story portion of the wall, it is difficult to attribute

the pier cracking to horizontal forces; it appears that the

damage was caused primarily by vertical movement of the

administration wing relative to the main classroom area.

289
Figure 6.27 Ceramic tile fell from wall, Castlebay Lane

School

.

290
291
292
There are also transverse cracks near the middle and near

the south end of the classroom portion. There was considerable light fixture damage; in addition, many ventilating

louvers weighing about 40 pounds pulled loose from the

corridor wall above the exit doors and fell to the floor

(fig. 6.33). There was only minimal damage reported on the

rest of the school site. However, the glass in the enclosure

surrounding the exit stairwell of the gymnasium shattered and

fell into the stairwell and could have been a serious hazard.

The entire school is in use.

Clark Junior High School in La Crescenta was constructed

in 1961. The school is located approximately eleven miles

southeast of the City of San Fernando (location 13, fig. 6.1).

The school has two-story brick bearing wall, double loaded,

corridor classroom buildings. The roofs are poured gypsum

on light steel framing; the second floor is concrete slab

and joist; and the first floor is a concrete slab on grade.

The upper-story intermediate transverse shear-resisting

elements are f 1 at-s teel -bar diagonal braces concealed in the

transverse partitions. The end transverse shear elements

in the upper story and all of the elements in the lower

story are reinforced grouted brick masonry. The buildings

rest on spread footings. The major structural damage was

caused by excessive elongation of the steel diagonal braces

(fig. 6.34). This permitted the gypsum roof diaphragm to

deflect excessively and thus greatly increased the bending

stresses near the middle and the shearing stresses at the

ends of the roof diaphragm. Cracks were noted in the roof

diaphragm. The increased shears at the ends of the roof

diaphragm also caused some minor cracking of the end brick

shear walls. There was extensive nonstructural damage

including damage of lighting fixtures (fig. 6.35) and cracked

plaster partitions due to excessive drift of the top story.

The school is in use.

Honby School in Saugus was constructed in 1967. The

school is located in a zone of ground rupture approximately

ten miles northwest of the City of San Fernando (location 14,

fig. 6.1). The school consists of a single-story group of

reinforced grouted brick bearing wall, hexagonal shaped

buildings. The roof construction is wood joists and plywood

sheathing; the walls are reinforced grouted brick with a concrete bond beam at the top; the floor is a concrete slab

on grade and the buildings rest on concrete spread foundations.

There was visible cracking in the concrete bond beam directly

over the cracks in the ground surface and vertically displaced slabs on grade. No other damage was reported, and

the school is fully occupied.

293
Figure 6.32 Cracked pier in

north wall of

administration

wing, Crescenta

Valley High School.

Figure 6.33 Ventilating lou- vers pulled loose

from corridor wall

above classroom

doors (louver

placed on table

for photo)

,

Crescenta Valley

High School

.

294
Figure 6.34 Flat steel bar braces concealed in transverse

partitions , Clark Junior High School. Damage

to partition caused by buckling of brace and

striking the studs.

Figure 6.35 Damage to lighting fixtures at Clark Junior

High School

.

295
SPECIAL INSTITUTIONS WITH SCHOOL STRUCTURES

The school portions of these special institutions were

constructed in compliance with the Field Act; whereas, the

remainder of the structures were constructed under the less

restrictive requirements of the Los Angeles County Building

Code

.

Los Angeles County Juvenile Facility , in Sylmar was

constructed in 1965. This institution is located in a zone

of extreme ground fracture approximately three miles northwest of the City of San Fernando (location 15, fig. 6.1).

The institution is primarily a group of one- and two-story

concrete block bearing wall buildings, some of which are

joined at split levels to accomodate a sloping site (fig.

6.36). The roof and second floor consist of concrete joists

and slabs. Walls are concrete block. The first floor is a concrete slab on grade. The gymnasium has a metal deck roof

supported on steel trusses resting on top of concrete walls

with clerestory windows on four sides. Diagonal rods provide

the lateral bracing of the steel trusses from the roof level

to the top of the walls. All buildings rest on spread footings. The concrete block construction of the school buildings

in this complex is different from that of other buildings.

The rules and regulations for school buildings require uniform

distribution of reinforcement in both horizontal and vertical

directions and all block cells must be fully grouted. On

this project, reinforcement was spaced at two feet on center

in both directions. For other buildings the Code permits the

concentration of horizontal reinforcement in the bond beam

and only the reinforced cell need be grouted.

There was a collapse of a portion of the administration

wing which occurred directly over the area of maximum ground

fracture (fig. 6,37), and there was extensive damage without

collapse at other areas of ground rupture (fig. 6.38 and

6.39). In the area adjacent to the actual ground cracking,

the degree of damage was variable.

The school buildings at this institution survived the

quake very well (fig. 6.40, 6.41 and 6.42). The west end

wall of the boys' school was severely damaged and one window

fell inwardly (fig. 6.43). Some of the perimeter ceiling in

the west classroom was damaged; however, the contents of the

room remained intact and it appears that the classroom would

have been safe (fig. 6.44). There was some minor displacement

of concrete blocks at the tops of transverse partitions (fig.

6.45). The walls at the junction of the boys' school and

the gymnasium were cracked (fig. 6.46). The glass in the

east and west clerestory between the trusses in the

gymnasium fell to the ground and the bracing rods between

the roof and the top of the walls either stretched or broke

296

1
Figure 6.36 Some buildings were constructed with split

levels to accommodate a sloping site at the

Los Angeles County Juvenile Facility

.

Figure 6.37 A portion of the Administration Wing collapsed

at the Los Angeles County Juvenile Facility

.

Note the distortion of the ground surface.

297
fWfc^^ Figure 6.38 Ground crack

\ f-\ adjacent to girls'

i ^ living unit, Los

I ---^ .' Angeles County

I / Juvenile Facility

.

Man standing in

|;

r ^23e crack is

I 6 ft 0 in tall.

298
Figure 6.40 Boys' school and gymnasium, Los Angeles County

Juvenile Facility

.

Figure 6.41 West wall of girls' school, Los Angeles County

Juvenile Facility . Note displacement at left

(north) end of building and severe ground

rupture (see figure 6.48).

299
Figure 6.42 East wall of girls' school, Los Angeles County

Juvenile Facility . Note distress at right

(north) end adjacent to taller (cafeteria)

building and ground rupture.

Figure 6.43 Damage to west wall of boys' school , Los Angeles

County Juvenile Facility . Window fell inward.

300
301
(fig. 6.47). There was damage to the portion of the girls'

school adjacent to the cafeteria at a location of vertical

ground fracture; however, the solidly grouted concrete

block wall resisted the distortion (fig. 6.48), and prevented

collapse. The floor was badly cracked in this area. There

was minimal damage to the rest of the girls' school.

Major damage on other buildings consisted of shattering

of walls at locations of change in roof elevations (fig.

6.49 and 6.50) and fracturing of concrete block walls constructed with "stacked bond", in which the horizontal reinforcing was concentrated only at the bond beam (fig. 6.51 and

6.52). The better behavior of the school buildings can be

attributed to the more restrictive rules and regulations of

the Field Act since the other factors (Architects, Engineers,

Contractors and Inspectors) were the same for both types of

buildings. The school buildings could be economically repaired; however, the entire facility has been vacated and may be

abandoned.

Camp Karl Holton , Los Angeles County Probation Camp,

located in Little Tujunga Canyon was constructed in 1959.

The camp is located in an area of extreme ground fracture

(fig. 6.53 and 6.54) approximately four miles northeast of

the City of San Fernanco (location 16, fig. 6.1). This camp

contains a group of single-story concrete block bearing wall

buildings which include administration, service facilities,

school, living quarters, and a recreation building. Construction consists of wood joists and roof sheathing, concrete

block walls, and concrete slabs on grade. The buildings rest

on spread footings. There is one wooden portable classroom

building near the masonry school. A concrete block security

wall surrounds the institution. Much of the perimeter

security wall has fallen or is severely tilted (fig. 6.55).

As previously noted, concrete block masonry for schools

requires uniform distribution of horizontal and vertical

reinforcement with all block cells fully grouted whereas for

other structures horizontal reinforcement may be concentrated

in the bond beam and only reinforced cells must be grouted.

The recreation building suffered severe structural

damage. The concrete block walls which were grouted only in

the reinforced cells shattered and were displaced as much as four inches laterally at the base (fig. 6.56 and 6.57). The

living unit was undergoing major alterations at the time of

the earthquake. Thus, the damages sustained do not necessarily reflect the condition of the building. The vehicle storage

building has a broken bottom chord at one gabled wooden roof

truss, and the wood sheathing appears to be supporting the

roof by plate action. Approximately six inches of vertical

displacement between the masonry classroom building and the

portable classroom building was noted (fig. 6.58). Either

302
Figure 6.46 Cracked wall at

junction of hoys'

school and gymnasium, Los Angeles

County Juvenile

Facility

.

Figure 6.47 Clerestory windows of gymnasium fell out and

bracing rods stretched , Los Angeles County

Juvenile Facility

.

303
Sh

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0) Sh 0 "-H tr, 0

-uH

^3

(U rO 0 0

qj

•s

304
Figure 6.49 Damage to wall at change in roof elevation

(exterior) , Los Angeles County Juvenile

Facility

.

Figure 6.50 Damage to wall at change in roof elevation

(interior) , Los Angeles County Juvenile

Facility

.

305
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IS

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306
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307
Figure 6.53 Eight-inch vertical displacement in out-door

recreation area. Camp Karl Holton.

Figure 6.54 Extensive cracking of parking lot pavement,

Camp Karl Holton.

308
Figure 6.55 A portion of perimeter security wall has fall

some is severely tilted. Camp Karl Hoi ton.

Figure 6.56 Concrete block wall grouted only in verticall

reinforced cells shattered. Camp Karl Holton.

309
Figure 6.57 Recreation Building at Camp Karl Holton. Fourinch displacement between slab and wall

.

Figure 6.58 Approximately 6 inches of vertical displacement

between masonry classroom building and the

portable classroom building , Camp Karl Holton,

310
the portable building and the ground on which it is supported

dropped or the adjacent area, together with the building

thereon, was raised. The building remained intact although

two covered arcade pipe columns were displaced a few inches

at the base where the slab on grade pulled apart (fig. 6.59).

The stem mounted lighting fixtures in all buildings were

severely damaged and most fell to the floor (fig. 6.60).

Damage to the portable classroom was minimal. A sheet metal

foundation clip was distorted and an interior partition was

offset a quarter of an inch at a joint in the wallboard. The

classroom building could be used in its present condition if

the light fixtures were reinstalled; however, the complex has

been vacated pending a study of the disposition of the camp.

6 . 4 Summary

School buildings as a group survived the earthquake

exceptionally well. It is again noted that, although structural damage was experienced, none of the new buildings

collapsed. It appears that no one would have been seriously

injured as a result of such structural damage. The cost to

repair this damage will be relatively minimal. Fortunately,

there was no total collapse of older pre-Field Act buildings,

but there was partial collapse and extensive damage requiring

extensive repair and reinforcement or replacement prior to

reoccupying these older structures. As previously noted,

thirteen buildings at ten schools in the Los Angeles Unified

School District were vacated immediately; all of the other

old (pre-Field Act) schools within the district were reviewed

by a panel of engineers. Approximately 85 buildings (approximately 900 classrooms) were found to be potentially dangerous

in the event of the reoccurrence of a quake of similar

magnitude closer to these schools. These schools are now

vacated, and depending on cost, will either be strengthened

or replaced prior to July 1, 1975, as required by Article 5

of the California Education Code. Older buildings which were

strengthened in accordance with the intent of the Field Act

suffered relatively minor structural damage.

Structural damage to new schools included displacement

of slabs on grade and foundations at locations of ground

rupture; permanent deformation of cantilever columns

supporting lunch shelters or arcades; cracked arcade columns;

cracked shear wall piers; stretched steel strap bracing with

consequently large deflections and cracking of poured gypsum

roof diaphragm. Damage to concrete and masonry consisted of

minor cracking.

The present code makes no provision for forces caused

by vertical acceleration of an earthquake. When this is

coupled with the present code provision, permitting a one311
Figure 6.59 Arcade pipe columns were displaced at

base where slab on grade pulled apart.

Camp Karl Hoi ton.

(Damaged lighting

fixtures were removed from buildings and stored on walkway .

)

312
third (1/3) increase in the working stresses when seismic

loading is combined with vertical loading, the margin of

safety is reduced to an unacceptable value. Further,

permitting the one-third (1/3) increase of stresses in

steel bracing also increases the elongation of the brace

and therefore the drift of the building, thereby increasing

the amount of nonstructural damage.

Comfort must not be sought in the fact that there was

only minimal structural damage to the new buildings because,

in some instances, these same buildings suffered considerable

nonstructural damage which could have been an extreme hazard

to its occupants. Many of the suspended "T"-bar acoustical

ceiling systems failed, dropping acoustic tile and "T" bars,

principally at perimeters of rooms. Lighting fixtures

attached only to the "T" bars pulled away and in many cases

dropped to the floor. Lighting fixtures with a swivel

connection at the ceiling but not at the fixture fractured at

the stem and dropped to the floor. Glass shattered because

it was tightly set in the frames. Heavy ventilating grilles

dropped from the ceiling or walls. Relative displacement

between structures at separtion joints sheared electrical

conduits which were rigidly connected to both sides of the

joint, thereby causing a failure in the lighting system.

There was plaster and ceramic tile damage primarily at

junctions of rigid to flexible elements.

6 . 5 Recommendati o ns

School structures resisted the earthquake forces very

well, and are in effect a testimonial to good design and

construction procedures within the present state of the art.

The first objective of earthquake resistive design, "prevention of loss of life or personal injury" has been met.

However, the reduction of personal hazard and damage

primarily from nonstructural elements is still a major

consideration. Therefore, the following changes to the

rules and regulations should be considered:

1. Provide for vertical seismic forces as well as lateral seismic forces.

2. Eliminate the permitted one-third (1/3) increase to

the allowable working stresses when considering

seismic loading combined with vertical loading.

3. Apply an occupancy multiplier of perhaps 1.5 for

schools to the seismic shear determined for

ordinary structures.

313
4. Reinforce all concrete column-beam connections as required for a ductile frame.

5. Linrit the drift of structures to be compatible with

contiguous rigid elements, and make provision for

differential movement between buildings or portions

of buildings.

6. Provide for the design and detailing of all

"nonstructural" elements that could fall; such as,

ceiling construction, lighting fixtures and

accessories, mechanical duct and louvers, mechanical

equipment, curtain walls, veneers, glazing, etc.

314
CHAPTER 7 DAMAGE TO BRIDGES AND HIGHWAYS

7 . 1 Intro duct ion

The State of California has been widely acknowledged as

a leader in the development of street, highway, and freeway

nets and the northern San Fernando Valley had a wide variety

of such transportation arteries. Post-quake reports to the

California State Highway Commission indicated that the earthquake damaged approximately 11 miles of multilane freeways

and 6 miles of conventional state highways, in addition to

numerous city and county streets. Estimates of total damage

to roads and highways varied from $27.5 million to $33 million,

with approximately $15 million damage related to the freeway

system shown in figure 7.1. Of this total, approximately

$7 million represented damages to sixty bridges. Approximately 10 percent of these bridges either collapsed or were

so badly damaged that they will have to be removed and

replaced. The remainder varied widely in degree of damage,

but have the possibility of complete restoration.

Two major interchanges in the area were under varying

degrees of construction at the time of the earthquake, so

that the loss represents estimated losses of forms, materials,

and other construction equipment. In addition to the material

loss, two men lost their lives when a freeway overpass fell

on their pickup truck as they passed beneath it during the

quake. Considerable disruption of traffic flow was caused

by the collapses and pavement ruptures but was quickly

brought under control by provision of temporary detours and

alternate routing. The heavily traveled Golden State Freeway

(Interstate 5) was reopened to traffic using emergency

detours within five days after the earthquake.

The major damage to bridge structures was concentrated

in the area shown in figure 7.1, with approximately 80 percent of the reported estimated costs of bridge repairs and

replacements being for structures in this area, which

undoubtedly experienced substantial accelerations and large

earth motions. In addition, several of the aftershocks had

epicenters which apparently bracketed the Interstate 5/210

intersection. This area is immediately adjacent to the

Sylmar Converter Station and the San Fernando Juvenile

Hall (both of which experienced substantial damage), and is

just north of the Van Norman reservoirs.

7 . 2 Case Histories of Bridge Damages

INTERSECTION OF INTERSTATE 5 AND CALIFORNIA 14 (Palmdale

Interchange--Locati on A on fig. 7.1)

315
Figure 7.1 Layout of freeway interchanges.

316
This impressive interchange which linked the Golden

State and the Antelope Valley freeways had been designed

in the latter part of 1968, and was under active construction.

The major damage at the interchange was sustained by the

Southern Connector Overcross i ng , which is labeled Bridge No.

1 in figure 7.2. At the time of the earthquake the superstructure had been essentially completed, as indicated by

the dashed lines on figure 7.2. Two spans with the intermediate supporting column collapsed, and the debris can be

seen in the bottom of the canyon. The two bridges shown with

falsework in the foreground of figure 7.2 were under construction and suffered substantial damage due to shifting and

settling of the falsework, which caused cracking in the

girder soffits and stems. In addition, one of the piers was

damaged by the collapse of the South Connector Overcrossing

(Bridge No. 1), which struck it during its fall.

The South Connector Overcrossing was a nine span,

continuous box girder bridge, as shown in figure 7.3. The

bridge was curved in plan, and consisted essentially of two

cast-i n-pl ace reinforced concrete box girder spans, a short

overhang and hinge, two cas t- i n-pl ace pos t-t ens i oned box

girder spans, another hinge and short overhang, a cast-inplace reinforced box girder span, three cas t-i n-pl ace

pos t- tens i oned box girder spans, and another cas t-i n-pl ace

nonpres tres s ed concrete box girder span. The portion of the

bridge which collapsed was the 354-ft cas t-i n-pl ace

prestressed box girder section which spanned between carefully detailed hinges which were located 14-ft inside piers

3 and 5. The section which collapsed was cast integrally

with a very slender column which was founded on sandstone.

The box girder section had three cells and a 34-ft overall

width, as shown in figure 7.4. The girder dead load was

approximately 9000 lb per ft of span. The girder was 7-ft

deep with a 7- in top slab, 6- in bottom slab, and nominal

1 2-i n webs .

The supporting pier which failed was nominally 10 ft

by 6 ft in cross section, with an octagonal form as shown

in figure 7.4. It was reinforced with 52 No. 18 bars, which

were Grade 60 steel . Most other bars were Grade 40 steel . While all other piers were specified to be Class A concrete,

this pier was specified to have a concrete compressive

strength of 4000 psi. This particular pier was founded at

elevation 1417, with a nominal ground elevation of 1463, and

the bottom of the box girder was at approximately elevation

1604. Therefore, the column had nominal clear height of

142 ft above the ground surface, and the overall pier was

approximately 187 ft in height. Since the earth would not

give full fixity at ground level, the practical unsupported

height of the column would be around 150 ft. This would

indicate a slenderness ratio of 25 in the longitudinal

317
318

320
direction and 15 in the transverse direction. The slenderness

of the column and the nature of the hinge seat can be seen

in figure 7.5, which is a post-failure view of pier 5.

Figure 7.6 shows the hinge cross section immediately adjacent

to pier 3. Reference to the hinge detail as shown in figure

7.4 indicates that each web of the box girder rested on a 2-in thick by 10-in deep by 30-in wide elastomeric bearing

pad and the center bay of the hinge seat had a 1-ft high

raised shear key, which was approximately 5-ft 6-in wide.

The raised cross section of this shear key is visible in

figure 7.6. The only positive ties in the longitudinal

direction were 1 1/2-in equalizing bolts, one of which was

placed in the center of each of the three cells, parallel to

the axis of the bridge.

The box girder had stiffening diaphragms at the center

lines of the span and a 9-ft 6-in wide solid diaphragm

above the pier, with the column reinforcement extending up

into this diaphragm to within 1 ft of the top deck surface.

Figure 7.7 indicates the debris after the collapse. Sections

of the box girder can be seen at the upper right of the

picture (resting against the pier from the other undercross

bridge). The column can be seen lying across the center of

the picture, and additional sections of the box girder can

be seen in the lower left. There were obvious marks along

the upper edge of the column standing in the upper right of

the picture, which indicated that the girder had brushed

against it with substantial force while dropping. Additional

failure detail can be seen in figure 7.8, which shows the

column top as it would be seen from underneath the structure.

It can be observed that the column stub and column bars have

pulled out of the cas t-i n-pl ace diaphragm. This can be seen

with greater clarity in figure 7.9, which shows the top of

the column in the center of the picture, resting on a wrecked

hoisting crane. It is extremely interesting to note that

none of the heavy No. 18 cross bars, which were used as the

main top reinforcement in the wide diaphragm, appear in the

picture. These bars were reported to be in the rubble at

the base of the column.

From the appearance of the failure debris and the

remnants, as well as the reports of large ground motion in

the area, it seems probable that the various sections of

the bridge began to deflect with different magnitudes and

frequencies and the amount of movement exceeded the seating

capacity at the hinge, throwing a tremendous moment on the

single slender pier. It may be significant that the section

which collapsed was the only portion of the bridge which

depended on a single column, as can be seen from figure 7.2.

The other prestressed box girder section was supported on two columns and, hence, had some possibility of further

stiffening if hinge capacities were exceeded. The raised

321
Figure 7.5 Post-failure view of Pier 5 and hinge seat.

322
Figure 7.6 Post-failure view of Pier 3 and hinge seat with

snear key.

323
Figure 7.8 The top of Pier 5 and girder debris from the

South Connector Overcrossing

.

Figure 7.9 The top of Pier 5, which was embedded in the

girder diaphragm, resting on the construction

crane after collapse

.

324
shear key appears to be reasonably effective for preventing

transverse motion at the hinges, as the hinge shear keys at

both ends were visible from ground inspection, although

possibly damaged. In spite of the apparent slenderness of

the columns, very rough checks indicate that the moment

capacity would be adequate for the specified earthquake loads

used with the California Highway Department standard design

procedures. However, the structural system used was vulnerable to the coupling of extremely high accelerations with

large ground motions, since there is no alternate load path

if the deflection capacity of the hinge is exceeded. Cursory

examination of the box girder debris indicated that the

girder section itself had probably performed well. In a number of cases the tendons were still intact although the

girders were ruptured.

INTERSECTION OF INTERSTATE 5 AND INTERSTATE 210 (Golden

State Freeway and Foothill Freeway Interchange--Locati on B on fig. 7.1)

This complex interchange, much of which was completed

and open to traffic, suffered extensive damage and must be

almost completely rebuilt. Figure 7.10 is an aerial view

of the freeway interchange looking north toward San Fernando

Pass and Newhall. The collapsed IS 210/5 Separation and

Overhead caused major damage to the Golden State Freeway

(IS 5), the Foothill Freeway (IS 210), the San Fernando Road

(which paralleled the railroad), and the Southern Pacific

Railroad tracks. The collapse of the Separation and Overhead

resulted in the loss of the lives of two men who were passing

underneath it in a pickup truck. Additional detail can be

seen in figure 7.11. In addition to the collapsed Separation

and Overhead structure (Bridge 2), the Northwest Connector

Overcrossing (Bridge 3) was severely damaged from the impact

of Bridge 2 and must be removed and replaced. The series of

essentially parallel spans carrying IS 5 South and IS 5

North, and the northbound truck routes over the Southern

Pacific Railroad tracks and San Fernando Road (Bridge Group

4) were also destroyed. Some spans of this bridge group

were impacted by the falling IS 210/5 Separation and Overhead,

while one steel girder span collapsed by dropping off its

bearings. This complex represented various types of bridges,

including reinforced concrete box girders, precast prestressed

I-beam girders, and concrete-steel composite girder bridges.

Immediately to the east of this group, Bridge 5 (as shown

in fig. 7.12) was a two span cas t-i n-pl ace prestressed box

girder with a longest span of 122 ft. It was supported by

a single column bent founded on 16-in diameter cas t-i n-pl ace

drilled shaft piles. The structure suffered major column

damage and was removed. Because of the need to rapidly remove

the destroyed and damaged bridges in order to reopen the

325
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326
327
railroad tracks, immediate destruction of the remains of the

bridges was undertaken and very little information was

gathered concerning Bridge Group 4 or Bridge 5.

The epicenters of two of the moderate aftershocks were

reported to have bracketed this bridge interchange and

substantial evidence of ground motion and cracking was

apparent. The closeness of this interchange to other severely damaged modern facilities such as the San Fernando Juvenile

Hall and Olive View Hospital can be seen in figure 7.13.

Because of the absence of recording accel erome ters in the

immediate area, the magnitude of actual accelerations is

unknown. However, based on the general distribution of other

accel erometer records and the extensive damage observed, it

is probable that the site underwent horizontal accelerations

of from one-third to one-half gravity and possible vertical

accelerations of approximately one-half that amount. These

would be substantially above the design values contemplated

as will be seen in a later section. Very severe ground

motion was noted on the Southern Pacific Railroad

tracks adjacent to the San Fernando Juvenile Hall and the

entire area around the Juvenile Hall was suspected to be a portion of a large slide area.

The collapsed IS 210/5 Separation and Overhead structure

(Bridge 2) was a 7-span, nonprestressed , reinforced concrete

box girder structure, carried on single column bents as shown in figure 7.14. This bridge was also curved in plan

and had hinge details generally similar to those described

previously for the bridge at the Palmdale interchange. The

bridge was supported on elastomeric bearing pads on the

pile-supported end abutments shown in the upper left of

figure 7.15. A closeup of the abutment bearings at the

north end is shown in figure 7.16. One of the elastomeric

bearing pads can be seen lying next to the concrete bearing

block. Another of these pads was found in a relatively

undamaged state adhering to the under side of a box girder

web after the girder had fallen approximately halfway down

the slope. The appearance of the concrete pedestals in

figure 7.16 indicates that the girders slid off the pedestals

fairly rapidly.

The girder cross section is shown in figure 7.17, along

with typical pier details. The three-cell girder was 6-ft

6-in deep, with a 7 1/4-in thick top slab, 6 1/4-in thick

bottom slab and 8-in webs. The southernmost columns were

carried on spread footings mounted on Class 2 piles, while

the northern group of columns was mounted on 6-ft diameter

circular concrete shafts which were cast in drilled holes.

As noted in the discussions in the section on soils and

foundations, the foundations for these columns were carried

328
Figure 7.12 View looking northwest at the IS 5 and IS 210

interchange , showing Bridge group 4 and Bridge

5 immediately after the quake and before removal

to restore railroad service

.

Figure 7.13 Aerial view of IS 5 and IS 210 interchange

looking east toward Olive View and Veterans

Administration Hospital

.

329
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330
Figure 7.15 East abutment of IS 210/5 Separation and

Overhead structure

.

Figure 7.16 Close up of east abutment and elastomeric

bearing pad.

331
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332
down to strata of sands and gravels which showed very high

penetration resistance. This differs from the Palmdale

interchange which was founded on sandstone and possibly

explains the more extensive damage occurring in this area.

As can be seen from figure 7.17, the transition from the

octagonal column to the circular cast-i n-pl ace drilled shaft

is essentially a massive splice wherein all of the No. 18

bars in the column are lap-spliced to the No. 11 bars in the

drilled shaft, with a nominal 6-ft lap length. This is

possibly a severe interpretation of what would be considered

a foundation anchorage, but the absence of reasonable

percentages of transverse flexural reinforcement that would

occur in a normal footing and the need for a transition zone

before the earth can give full confinement to the drilled

shaft allow one to visualize the action almost as that of a splice. As can be seen in figure 7.18, the columns both

pulled out from the cas t- i n-pl ace drilled shafts and

developed massive plastic hinges at the col umn -g i rder connection. In some cases the girders appeared relatively

undamaged and uncracked at the column connection (see fig.

7.19) and had shattered through at intermediate span points.

In other cases, as shown in figure 7.20, the reinforcement

in the lower slab of the girder had been completely stripped

out as well as the column having separated from the cast-inplace drilled shaft. In this latter figure, the close

spacing of the No. 18 bars can be seen as well as the almost

total absence of transverse reinforcement at the splice

zone. As shown in figure 7.17, the octagonal columns were

nominally 4 ft by 6 ft in cross section and a typical

column was reinforced with 22 No. 18 bars of Grade 40 steel.

The longitudinal slenderness ratios varied from 11 to 16 and

transverse slenderness ratios from 7 to 11. The tied columns

had No. 4 hoops at 12-in spacing and these hoops were a single

pair of U-bars which overlapped 18 in, as shown in figure

7.17. An extra pair of cross ties was also provided. At

failure, some hoops separated and pulled out, as may be

seen in figure 7.20. The drilled shafts were reinforced

with 36 to 52 No. 11 bars, with No. 4 hoops at 12-in spacing

enclosing the bars. The hoops were lapped 18-in and had

no hooks. The combination of lap splices of No. 18 bars,

splicing at essentially the point of maximum moment, the

absence of large amounts of confining transverse reinforcement, and the splicing of all bars at one section compound

the difficulty of developing this joint and should be avoided

where possible in the future.

As in the case of the Palmdale interchange, it is

extremely difficult to determine whether the bridge came off

its abutments before the column joint failed, but from the

appearance of the collapsed structure it can be concluded

that the bridge was unable to withstand large ground movements

and the column-to-foundation and column-to-girder connections

333
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Figure 7.19 Column-girder

connection with

major distress in

the column. Note

the separated

column hoops.

335
were unable to withstand the combination of seismic and

deflection produced moments. Again, with single columns at

points of support, the column-to-foundation connection became

critical and there was no chance for development of an alternate load path.

The Northern Connector Overcrossing (Bridge 3 in figs.

7.1 and 7.10) was a skewed, curved, 7-cell cast-in-pl ace

reinforced concrete box girder bridge. It had four spans

of 70 ft, 180 ft, 162 ft, and 100 ft, and was carried

on three- and four-columns bents, as shown in figure 7.21.

The columns were octagonal, inscribed in a 4 ft square as shown and were reinforced with 16 to 20 No. 18 bars, which

were surrounded by a No. 5 spiral at a 5-in pitch. Reinforcement was Grade 40 and column concrete was 4000 psi compressive

strength. The columns rested on 6-ft diameter cas t-i n-pl ace

drilled shaft piles which were reinforced with 22 No. 11

bars, which extended approximately 15 ft into the pile. The

columns in all bents were essentially hinged at the base

where they connected to the cas t-i n-pl ace pile using a 2-ft

diameter by 1 5/8-in thick keyway, with only four No. 11 bars

crossing it, as shown in the key detail in figure 7.21.

This structure was struck by the falling South Connector

Overcrossing at its south and east end, as shown in figure

7.18. This impact added to the natural acceleration forced

the structure northward, and because of the skew angle it

slid in a northeast direction at the northern end, as shown

in figure 7.22. The line of columns at bent 2 on the north

edge collapsed with increasing distress from west to east,

as shown in figure 7.23. Note that the columns are virtually

uncracked near their base and over the lower two-thirds of

their height. The action of the No. 5 spirals in holding the

columns together is apparent and can be seen in detail in

figure 7.24. In this same photo the relatively undamaged

appearance of the girder at the col umn- gi rder connection

can also be seen. Because of the damage to the substructure

and in order to expedite the restoration of traffic, the

entire structure is slated for removal and replacement.

FOOTHILL BOULEVARD UNDERCROSS I NG OF INTERSTATE 210 (Location

C on fi g . 7.1)

The Foothill Boulevard Undercross i ng was a pair of four

span continuous reinforced concrete box girder skewed bridges,

which carred IS 210 above Foothill Boulevard. The southernmost bridge of the pair was the more extremely damaged.

A typical cross section is shown in figure 7.25, along with

column and pier details. The intermediate bents consisted

of octagonal columns inscribed in a 4 ft square and reinforced typically with 22 No. 14 bars or 18 No. 18 bars.

336
337
Figure 7.22 Abutment and pier damage at the western end

of the Northwest Connector Overcrossing

.

Figure 7.23 Spiral column failures in bent 2 at the west

end of the Northwest Connector Overcrossing

.

338
339
340I
The columns were provided with No. 4 hoop ties at 12-in

centers and the hoops had an 18-in lap length around the

circumference. There was an important difference in the

types of foundations between the northern or left bridge and

the more heavily damaged southern or right bridge. The less

damaged northern (left) bridge was founded on spread footings

which were placed on top of piles in interior bents 2 and 3

and spread footings without piles in bent 4. In contrast,

the southern or right bridge was carried on spread footings

on all bents with no piles being used. The right bridge was

also narrower in cross section because of the ramp space

provided in the left bridge. The typical base detail at the

bottom of the columns in bents 2 and 4 provided for a 2-ft

square by 1 5/8-in thick keyway, with 4 No. 11 bars extending

from the column into the footing into the center of the key,

thus providing "hinged" bases on these column lines. In

contrast, the middle bent 3 had full dowel splices into the

footings for all bars.

The major damages noted in this bridge was sustained by

the southern or right bridge and were mostly in the columns

and abutments, as can be seen in figure 7.26, which shows

bent 3 of the right bridge in the foreground. The bridge

had apparently twisted in a clockwise direction and it

appeared that it had rotated about the third column from the

right hand side of the photo, which is relatively undamaged.

Severe damage was encountered in the other columns, as can

be seen from the closeup in figure 7.27, which indicates

complete destruction of the core concrete and buckling of

the bars, as well as loss of the relatively light hoops

provided. Note the hoops lying in the rubble in the foreground. The columns of bents 2 and 4 were set in a series

of closure walls and movement could take place only at the

top, so the damage to these columns was fairly well confined

to the very top portion, as shown in figure 7.28. In spite

of the massive damage to the support elements, the girders

appeared to be in surprisingly sound shape, and visual

examination did not indicate any appreciable evidences of

concrete cracks large enough to indicate reinforcement

yielding.

MISCELLANEOUS BRIDGE DAMAGE

Throughout the remainder of the north San Fernando

Valley, numerous bridges were damaged in a much less dramatic

manner. A typical sight was extensive cracking in the

abutments, similar to that shown in figure 7.29. In this

case a major crack ran through the earth fill up to the

bridge abutment, through the abutment and out the other side

of the abutment. The bridge in this case was displaced

341
Figure 7.26 Column failures in bent 3 of Foothill Boulevard

Undercrossing

.

Figure 7.27 Close-up view of

failure of a tied

column in bent 3.

Note hoops on ground in debris.

342
Figure 7.28 Damaged columns in bent 4 with 10-in closure

wall which was separated from the columns by

1/2-in filled expansion joints.

Figure 7.29 Typical abutment damage.

343
both longitudinally and transversely over 6 in, as can be

seen in figure 7.30. This particular structure was a continuous reinforced concrete box girder bridge, located

between the Palmdale and Foothill interchanges.

Bridges supported on tall, slender columns and piers

seemed particularly susceptible to movement and bridges

located several miles north of the Palmdale interchange

indicated substantial movement at hinges, as shown in figure

7.31, and extensive butting of one section against another

causing spalling as shown in figure 7.32. However, these

damages can be classified as minor. Many of the bridges

with heavy abutments came through with relatively light

damage to concrete slope paving and no visible damage to

the structure, as did the single span prestressed box girder

bridge shown in figure 7.33. This bridge was located on the

Foothill Freeway at Glenoaks Boulevard and is only a few

blocks from Olive View Hospital.

7 . 3 Damage to Roads and Streets

Throughout the entire northern San Fernando Valley

ground movement caused extensive damage to roads, streets,

and highways. Only a few examples of damage which occurred

at the locations shown in figure 7.34 are discussed here.

BLUCHER AVENUE, Location 1, Figure 7.34

Blucher Avenue (figs. 7.35 through 7.37) was extensively

damaged due to lateral and vertical movements of several

feet. The extent of ground movement in the area is further

illustrated by the ground cave-in shown in figure 7.38.

HUBBARD AVENUE AND GLENOAKS BOULEVARD, Location 2, Figure

7.34

Many major streets; such as Hubbard Avenue, San Fernando

Road, and Glenoaks Boulevard were badly damaged and total

reconstruction was reported as the only solution.

Some of the most spectacular damage occurred at the intersection of Hubbard and Glenoaks. As shown in figure 7.39,

repair work was underway almost immediately. Considerable

street damage was caused by gas line explosions. Further

evidence of the ground movement is shown in figure 7.40.

ORANGE GROVE AVENUE, Location 3, Figure 7.34

Damage to streets, driveways, and sidewalks is

illustrated is figures 7.41 and 7.42. The ground movements

in this area were on the order of four feet horizontally.

344
Figure 7.30 Longitudinal and transverse movement of castin-place box girders with respect to abutment

sections

.

Figure 7.31 Typical movement at a hinge joint of a slender

box girder bridge.

345
Figure 7.32 Typical movement and spalling at a joint in an elevated box girder bridge, caused by battering

at the joints.

Figure 7.33 Typical damage to wing walls and sloped paving

on a single span prestressed concrete box

girder bridge.

346
347
Figure 7.36 Concrete road slabs were crushed by the ground

motion in this location.

348
Figure 7.38 Ground cave-in (2-ft wide) near the damaged

road slabs shown in figure 7.35.

349
Figure 7.39 Broken gas, water, and sewer lines being repaired

near intersection of Hubbard Avenue and Glenoaks

Boulevard , San Fernando.

Figure 7.40 Considerable ground movement is evident in the

parking lot of the shopping center at the

corner of Hubbard Avenue and Glenoaks Boulevard

.

350
Figure 7.41 Sidewalk along

Knox Street, near

Orange Grove

Avenue, San

Fernando . Hori

zontal ground

movement is

clearly evident.

Figure 7.42 Damaged street and sidewalk along 8th Street,

between Orange Grove Avenue and Fernmont

Street, San Fernando.

351
HARDING ELEMENTARY SCHOOL, Location 4, Figure 7.34

Street damage in Sylmar near the Harding Elementary

School is shown in figure 7.43.

Both Portland cement and asphaltic concrete pavements

were subject to fracture in areas of appreciable ground

movement. Fractures were of both the tensile and compressive

type, depending on the nature and magnitude of the movement.

In a number of cases rupture of the pavement was caused by

breakage in the utility lines underground, or by erosion of

the substrata, due to the flow of escaped liquids. Throughout

the mountain area a number of roads were blocked and in some

cases badly eroded by slide action. However, this type of

damage has been widely seen in previous earthquakes and is

certainly to be expected in view of the large displacements

of soil masses reported in this particular earthquake.

7 . 4 Bridge Design Procedures

In general the major structures which suffered severe

damage or destruction in the earthquake were designed under

the general provisions of the American Association of State

Highway Officials Standard Specifications for Highway Bridges , 9th edition, 1965, with revisions and as supplemented by the

California Highway Department Bridge Planning and Design

Manual. Design live loading was based on HS20-44 and

Alternative. Reinforced concrete design was based on working

stress theory with an allowable concrete compressive stress

in flexure of 1200 psi, based on a concrete compressive

strength of 3000 psi. In a few of the important columns the

concrete strength was increased to 4000 psi. The modular

ratio n was ordinarily taken as 10 and the allowable steel

stresses as 20,000 psi, based on an intermediate grade

reinforcement (Grade 40). In the No. 18 bars used in the

Palmdale interchange. Grade 60 steel was used with an allowable tensile stress of 24,000 psi.

SEISMIC DESIGN

The proper design of bridges in seismic areas is

extremely complex. It is not simply a question of the

adequacy of estimating the seismic force or seismic coefficient, but rather one of the entire design, detailing, and

construction procedures. Any assumptions made in setting

the best estimate of the seismic forces should be integrated

in the design criteria and must be carried out in all

subsequent details and considered for all possible failure

modes. The method of analysis used, the determination of

limit states, and the overall stability of the structure

352
Figure 7.43 Buckled street in Sylmar near Harding Elementary

School. (Los Angeles Times Photo.)

353
must be considered on the same rational basis. Design

considerations should not be limited to questions of strength

but should also consider deformations and deflections since

the inability of a support detail to either restrain deformation or provide positive support under extreme deflections

can cause a precipitous failure. Details concerning the

reinforcement of individual members, joints, and connections

must be developed carefully to ensure that the full ductility

assumed in the analysis can be developed. In special cases

where very slender structures are involved or where differences can exist between centroids of lateral stiffnesses and

lateral forces, comprehensive analyses should be carried out

which consider the dynamic nature of the problem. In

addition, on al 1 uvi al -type soils the interaction of the

foundation with the soil and with the structure should be

examined under both static and dynamic conditions. Where a considerable backlog of experience with a particular type of

design exists in an earthquake area, the design procedures

can be simplified to equivalent static load cases based on satisfactory performance of structures in previous earthquakes. However, the design of new and somewhat unconventional

structures should be carefully checked both analytically and

experimentally for possible weaknesses under earthquake- type

loading.

In the subsequent sections information will be provided

concerning the general provisions for seismic design and

several different guideline specifications. Wherever any

comparisons are made between specifications, it will be on

the basis of earthquake forces only and using as a general

criterion the working stress and yield point values of

Grade 40 reinforcement, which was the type of reinforcement

most widely used in the highway structures in the San

Fernando Valley area.

Most specifications for earthquake forces to be applied

to bridge structures use the concept of the equivalent

static lateral load and are expressed on a force basis with

little written emphasis on the need to check deflections and

deformations, particularly as they might effect stability

of the overall structure. The equivalent static load

expresses the postulated earthquake induced dynamic loadings

as static forces similar to wind loading, using a coefficient

which relates the lateral or vertical acceleration to the

acceleration of gravity. The choices of these coefficients

vary widely under various specifications.

1965 AASHO SPECIFICATIONS

The 1965 AASHO Specifications were basically a working

stress design specification in which Article 1.2.22,

354
governing loading combinations, indicated that in loading

combinations with earthquake loading (Group VII) a one-third

increase in the basic unit stresses would be allowed. The

lateral forces specified by Article 1.2.20 were expressed as

a percentage of the dead load of the structure and the live

load could be disregarded. The values of the lateral force

coefficients range from 2 percent for structures on spread

footings on material rated at less than 4 tons per square

foot to 6 percent for structures founded on piles.

The magnitudes of these coefficients are far less than

the accelerations reported in the San Fernando earthquake

and thus would demand a high degree of dynamic damping and

ductility for structures in severe earthquake regions. The

specification makes no mention of vertical accelerations and

does not include any factor which would reduce or increase

the coefficients according to geographical location and

p r 0 b a b i 1 i ty of seismic a c t i v i ty

.

CALIFORNIA BRIDGE PLANNING AND DESIGN MANUAL

The California State Highway Department has implemented

a somewhat more comprehensive requirement, which was adapted

from the 1960 Structural Engineers Association of California

"Recommended Lateral Force Requirements". This seismic

force computational procedure was outlined in the March 1968

California State Highway Department Bridge Planning and

Design Manual, which is referenced in the plans for a number

of the damaged freeway structures. The California requirement

is as f ol 1 ows : 2-25 Seismic Forces

All structures except underground structures

and retaining walls shall be designed to resist

earthquake forces (EQ) in accordance with the

following equations. A nomograph is available on Page 5-65 of Vol. Ill of the Bridge Planning and

Design Manual for solving equation (2).

(1 ) EQ = KCD

EQ = The force applied horizontally at the

center of gravity of the structure. This

force shall be distributed to supports

according to their relative stiffnesses.

K = Numerical coefficient representing energy

absorption of the structure:

K = 1.33 For bridges where a wall with a height to length ratio of 2.5 or

less resists horizontal forces

applied along the wall.

355
K = 1.00 For bridges where single columns

or piers with a height to length

ratio greater than 2.5 resist the

horizontal forces.

K = 0.67 For bridges where continuous

frames resist horizontal forces

applied along the frame.

(2) C = (Maximum value of C = 0.10)

C = Numerical coefficient representing structure

sti f f ness

(3) T = 0.32-/^ for single story structures only

T = Period of vibration of structure

D = Dead load reaction of structure

P = Force required for one inch horizontal

deflection of structure

The EQ forces calculated above shall never be less

than 0.02D. Special consideration shall be given to

structures founded in soft materials capable of

large earthquake movements, and to large structures

having massive piers.

Very approximate checks were made using these equations for

a bridge similar to the tall overcrossing at the Palmdale

interchange and the lateral force coefficient was found to

be between 3 and 4 percent. Insufficient design detail was

available for a more exact check. Again, the magnitude of

these coefficients would imply extremely large ductility

factors and in view of the reported accelerations during the

San Fernando earthquake would appear to be inadequate. The

California specification does caution the designer to give

special consideration to structures on soft materials and

to large structures with massive piers, but does not specify

any vertical acceleration levels or vertical force coeffici ents .

SURVEY OF JAPANESE DESIGN REQUIREMENTS FOR BRIDGES

The various agencies responsible for the design of

railroad and highway bridges and expressways in Japan have

adopted considerably more severe equivalent static load

coefficients than those outlined for either AASHO or the

California State Highway Department. A direct comparison is

difficult because of the different values for allowable and

ultimate material properties. In addition, in most of the

specifications the Japanese allow a 50 percent increase in

the allowable stresses for both concrete and steel reinforcement for earthquake load in contrast to those for dead and

356
live loads. However, when both the design stresses and the

overload factors are considered, the ratio of allowable

earthquake design stress to yield point for the reinforcement

is of approximately the same magnitude in Japanese practice

and in U. S. practice. Hence, the seismic design coefficients

used by the Japanese highway groups can be compared to those

in use in the United States on an order of magnitude basis

with reasonable dependability.

The 1964 editions of the Japanese Road Association,

"Specifications for the Design of Reinforced Concrete Highway

Bridges," and "Specifications for the Design of Steel Highway

Bridges," specify horizontal seismic coefficients for highway

bridges as a function of probability of earthquake intensity

and foundation conditions as shown in table 7.1. It can be

seen that in areas of high seismic probability the lateral

force coefficients vary from 0.15 to 0.35, or substantially

above the values in the U . S. specifications. In addition,

a value of 0.10 is specified for the standard vertical seismic coefficient in all cases.

The Tokyo Expressway Public Corporation, 1967, "Aseismic

Design Standard," is used for expressways in the Tokyo

metropolitan area and is more closely tied to soil conditions.

The design coefficients are shown in tables 7.2 and 7.3 (In

these tables the value N is defined as the number of blows

necessary to produce a penetration of 30 centimeters when a hammer weighing 63.5 kilograms is dropped onto a standard

sampler from a height of 75 centimeters). Again it can be

seen that the range of seismic coefficients is appreciably

above those called for in the U. S. specifications.

In addition to the increased basic design coefficients,

various Japanese specifications call for an increase in the

design seismic coefficient for those parts of the structure

higher than 10 to 15 meters above the ground surface. Those

increases in coefficients for tall structures can actually

result in total horizontal coefficients of as much as one-half

gravity. Suggested distributions for the application of

seismic coefficients below the ground surfaces are also made.

An excellent summary of the various design provisions is

contained in "Earthquake Resistant Design for Civil Engineering Structures, Earth Structures, and Foundations in Japan,"

compiled by the Japan Society of Civil Engineers in November

1968.

7 . 5 Summary and Recommendations

In spite of evident conscientiousness in design,

detailing, construction, and maintenance, a number of

important highway structures failed completely and catas357
Table 7.1 Japan Road Association^ Horizontal Seismic

Coefficients for Highway Bridges

Ground Condition

Tnr.alitv ~~ . Soft Medi urn Hard

Where strong earthquakes have frequently

occurred

.

0.35

to

0.30

0.30

to

0.20

0.20

to

0.15

Where a strong earthquake is known to

have occurred.

0.30

to

0.20

0.20

to

0.15

0.15

to

0.10

Other localities

.

0.20 0.15 0.10

Table 7.2 Design Seismic Coefficients for

Tokyo Metropolitan Expressways

~~ T'lrC—^^ Ground*

Seismic Coeff. I II III IV

Hori zontal 0.20 0.24 0.27 0.30

Vertical 0.10 0.10 0.10 0.10

*The numbers indicating the types of grounds correspond to the numbers

given in table 7.3.

358
Table 7.3 Classification of Grounds

Ground Conditions of

^"'^'v^,^ Alluvium and Kanto Loam

^^^^^^ Layer

Thickness of

Alluvium and Kanto Loam

Layer

Sand &

Gravel

Sand

,

Clay, & Kanto

Loam

Layer

wi th

N^5.

Soft Ground

2-^N< 5 N < 2

0 - 3 m

I (Foundations must be constructed

after completely removing this thin

layers)

3 - 10 m III (II)* Ill

(II)

IV (III) IV

(III)

10 - 25 m III (II) IV

(III) IV (III)

IV

(IV)

Greater than 25 m IV (III) IV

(III)

IV (IV) IV

(IV)

*The numbers in brackets maybe used as the type of ground if very rigid

foundations such as caissons are used and the length of the foundation is

less than 3 times the diameter or the shorter linear dimension of the

bottom surface.

359
trophically in the San Fernando earthquake. Due to the

fortunate combination of circumstances, in that a number of

the bridges and roads had not been opened to traffic and the

earthquake occurred at a time when very few vehicles were on the highways, the actual loss of life and injury to vehicular

occupants was small. However, in a more extensive earthquake

or in one occurring closer to a built-up region or during a peak traffic period, collapses like those which occurred

in the interchanges could produce large numbers' of casualties

and extensive disruption of vital transportation arteries

required by emergency services. In view of this potential

danger, all lessons which may be learned from failures should

be intensively pursued and design and construction procedures

altered as necessary.

The recurring themes which seem to appear in discussions

of numerous failures of bridges in earthquakes are true in

the bridge failures of the San Fernando earthquake. Generally, superstructures behaved well with major damage to

girders occurring upon impact when they fell to the ground.

Except for such impacts on falling, the superstructures

generally showed only minor damage to joints and near

abutments. Throughout the area extensive damage was incurred

at abutments where large foundation movements took place and

where consolidation and compaction of loose strata produced

large differential movements. Consequent settlement and

both transverse and longitudinal movement of abutments

and piers literally pulled the supports out from under

girders, producing heavy demands on other columns and

abutments to attempt to stabilize the structure. Lack of

restraining devices at bearings, hinges, and joints permitted

the girders to pull free from the supports and fall to the

ground. In a number of other cases the lateral and torsional

forces imposed on the supporting members in addition to the

high rate of vertical accelerations caused column stresses

which were particularly serious in lightly tied columns,

since the poorly confined concrete then failed completely.

Both girder-to-column and column-to-pile connections proved

especially vulnerable because of the large size reinforcing

bars and small amounts of confining reinforcement utilized.

Such failures are catastrophic in single column bents since

no load redistribution possibility exists and the lack of

redundancy or alternate load paths means that loss of a poorly detailed section results in a total collapse.

In view of the extent of serious collapse of important

highway bridges and in view of the extensive reports of

recorded horizontal and vertical accelerations far beyond

those envisioned in formulation of design criteria, it is

recommended that an immediate review be made of the adequacy

of present requirements for seismic design of highway bridges.

This study should not focus completely on the lateral and

360
vertical dynamic or equivalent static design forces, but

should consider the complete seismic design problem.

Assessment should be made of the adequacy of specifications

for ensuring that methods of analysis are capable of correctly

representing important structural variables such as appreciable curvature, skewness of span, variation in mass and

resistance centroids, and effect of typical foundation

condi ti ons . Particular attention must be paid to the overall design

concept to ensure that the structure is provided with an alternate load path or with some type of aseismic connectors

or restrainers, so that in the event of an earthquake of

such a magnitude, if it is not practical to attempt to keep

the structure from being damaged, total collapse will not

ensue. In construction similar to that observed in this

earthquake, increased widths could be provided on abutment

pads and on hinge supports, so that increased longitudinal

displacements would be possible without the girders coming

completely off the supports. Alternatively, types of

connections could be devised which would allow the girder to

travel an amount which would be more than ample to overcome

shrinkage, temperature, or other ordinary volume changes,

but which would then cause additional stiffening and

continuity in the system for displacements of the magnitude

of those occurring with large foundation disturbances. In

the case of the single column bent, where all of the moment

must be taken by a can ti 1 ever- type action, extreme cases

might indicate that the bent will have to be changed to a multiple column design, so that the lateral force moments

can be resisted by a couple, with a substantially enlarged

moment arm. In any case, it will be especially necessary

for tall, slender structures to consider the possibility of

deflection of alternate supports in opposite directions, thus

imposing severe deformation requirements on the girder and

girder seats. The entire structural system must be designed

for the forces required to stabilize such a structural

condi ti on

.

Revised regulations for highway bridge construction

should include a factor which expresses the probability of

the occurrance of an earthquake of high intensity, a factor

which reflects a general soil and foundation condition, a factor which reflects the importance of the structure and the

degree of danger in its collapse, and a factor which is an accurate appraisal of the amount of ductility which can be

expected in the particular type of structural design and

materials. It is not realistic to expect all highway related

agencies in the United States to design all bridges to the

same identical specifications. However, the guideline

specifications should be flexible enough to clearly distinguish between regions and to encourage more accurate

361
microzoning within a particular region. The specifications

should also require material properties and connection

details which are consistent with the assumed amount of

ductility allowed for in dissipation of the seismic energy.

Many of the details of the structures in the San Fernando

region were inadequate for the development of ductility

factors of the order of 4 or more. Specific recommendations

to increase the ductility factor should be studied in detail.

Among these are:

(1) Reassessment of lateral reinforcement requirements

in columns and piers. In many cases the size, spacing, and

volumetric percentage of lateral reinforcement seem to be

only a token contribution when compared to the load-carrying

capacity of the main longitudinal reinforcement. Minimum

percentages for ties or hoops, approximately either a portion

of the volumetric percentage required for spiral reinforcement, or the minimum requirements for shear reinforcement

would be a step in the right direction.

(2) Maximum spacing of column ties and hoops should be

limited to one-half the effective depth of the cross section,

so as to ensure effectiveness as shear reinforcement.

(3) Additional column ties, hoops, or spiral wraps

should be provided in the end sections of all columns and

into the beam column or girder column connections where

possible.

(4) If the column drilled shaft pier is to be considered

as a column-to-footing connection, then additional transverse

reinforcement should be placed in the top of the pier section

to prevent concentration of overlapping splitting stresses

from the column reinforcement. It is probably more logical

to consider this connection as a type of indirect splice

and to follow modified splice rules which would call for

special precautions for the splicing of No. 18 bars, caution

against having a splice at the point of maximum tensile

stress, and call for additional lateral reinforcement in the

splice reg i on .

(5) The use of lapped splices for lateral reinforcement,

such as column hoops, should be discouraged and all hoops or

ties should be positively anchored by hooks or embedment into

the core. Wherever close spacing of multiple, large diameter

reinforcing bars, such as No. 14 or No. 18, are required in

an anchorage zone (as at pier top-girder diaphragm connections) a portion of the bars should be positively anchored

to the main transverse reinforcement in the anchor member.

As a result of the observations made following the

earthquake, it is apparent that additional research and

362
study is needed in the following areas of importance to

bri dge des i gners :

(1) The dynamic behavior of curved and skewed bridges.

It is particularly apparent that these structures are

susceptible to severe transverse and oblique movements and

comprehensive design procedures are required to ensure safe

des i gn .

(2) Behavior of splices of closely spaced and large

bars under dynamic loading conditions.

(3) The general field of bond and anchorage requirements

for large size reinforcing bars under dynamic loading conditions, with emphasis on a study of the anchorage requirements

for column bars in drilled shaft-type footings when subjected

to alternating dynamic loading.

(4) Distribution of dynamic loads to cast-in-place

drilled shafts in alluvium strata and the effective length

of pier-column combinations with various connection details.

(5) Investigation of procedures for developing more

effective hinge details to withstand seismic forces and

restrain large deformations while still allowing service load

1 evel movements . The California State Highway Department and the many

local street and road departments reacted quickly and expertly

in restoring the transportation net in the San Fernando Valley

to a high degree of capacity within days of the earthquake.

Their prompt and efficient action minimized the impact of the

millions of dollars of destruction done to the highway and

bridge systems, and indicated that a certain degree of

damage is certainly acceptable and practical. The goal of

future specifications and code revisions should be directed

at preventing total collapse and to control other damage to

a manageable, repairable degree, minimizing public loss

within an acceptable cost framework.

363

CHAPTER 8 DAMAGE TO PUBLIC SERVICES AND

FLOOD CONTROL FACILITIES

8 . 1 Water Supplies

CITY OF LOS ANGELES

The City of Los Angeles receives water from several

sources: underground wells; High Sierra water through the

two Owen river aqueducts; and the Colorado River through

its aqueducts. As a result of the earthquake, the Los

Angeles water system facilities in the north end of San

Fernando Valley were severely damaged.

Immediately following the earthquake, approximately

five percent of the area of the City of Los Angeles, primarily around the northern part of the San Fernando Valley,

had its water service interrupted (see fig. 8.1). Water

service was restored to most of this area within four to

five days. However, because of extensive damage to water

distribution systems, several areas did not receive water

until eleven days after the quake occurred.

DEPARTMENT OF WATER AND POWER FACILITIES (CITY OF LOS

ANGELES)

Total damages to the water supply and distribution

systems under the Department of Water and Power are estimated

at $48 million. Half or more of this amount will result from

replacement cost of the water storage and related facilities

at the Upper and Lower Van Norman Reservoirs.

Major damage to the water distribution facilities was

confined primarily to the Van Norman Reservoir complex and

trunk lines in the Syl mar-Granada Hills area. The complex

consisted of two major reservoirs formed by the Upper and

Lower San Fernando Dams, a smaller bypass reservoir, a complex of bypass pipelines, penstock for power stations,

bypass channels, chlorination stations, and standby pumping

stations. The complex is designed so that normal water

supply to the City of Los Angeles can be maintained even if

one or more facilities are out of service. Other damages in

the Upper San Fernando Valley included damage to Maclay

Reservoir, 750 broken mains, 756 damaged service connections,

35 gate valves, 44 fire hydrants, 20 safety valves, and 2

storage tanks.

Damages to the Van Norman Reservoir complex and other

distribution systems are discussed below with reference to

the various items identified by numbers in figure 8.2.

365
366
1. Both Los Angeles Aqueducts, which deliver 80 percent

of the total supply to the city, were damaged in the

area immediately above the Cascades. The first

aqueduct, built in 1913, delivers some 495 cu ft

per second at a hydraulic gradient of 1449 feet.

It was damaged at an inverted siphon transition

segment (location 1) and was restored to full

service condition in two days. The second aqueduct

(Saugus Pipeline) delivers 250 cu ft per second at

a hydraulic gradient of 1805 feet. It was moderately

damaged with ruptures in the 77-inch welded steel

pipes (location 2). The Los Angeles Department of

Water and Power returned the line to service April 8,

1971 .

2. Two major trunk lines, the 54-inch Susana and the

48- inch Granada Trunk lines, (locations 3 and 4)

serving areas west of the Van Norman Reservoirs

sustained numerous breaks in all-welded steel

construction. The Maclay High Line (location 5),

serving areas east of the reservoirs, is an old

unreinforced concrete culvert. It sustained little

damage

.

3. The old penstock (location 6), which is made of

riveted steel construction, was not damaged. However, the power house (location 7) which is

located at the upstream side of the Upper Van

Norman Reservoir dropped about three feet, thereby

shearing off the end of the penstock. The penstock

has been sealed and a bypass pipe (location 8) has

been installed to carry water from the penstock

into the upper reservoir.

4. The Upper Van Norman Reservoir (location 9) with a capacity of 1800 acre-feet, was damaged. The Upper

San Fernando dam, which was built in 1919-1921, is

about 1200 ft in length along its axis and about 60

ft high. It settled about three feet and displaced

laterally about five feet at the crest. However,

the dam did not collapse and has been in use at

about one-third capacity. Of the two intakes, the

old one (Outlet No. 1) has cracked at the base;

whereas, the new one (Outlet No. 2) did not sustain

damage. Some water seepage appeared at the downstream

side of the upper reservoir dam (fig. 8.3) as a result

of damage in the drain system.

5. The 99-inch bypass pipeline (location 10) around

the Lower Van Norman Reservoir and the 240 acre-feet

bypass reservoir and dam (location 11), both completed in 1970, were undamaged.

367
368
Both the bypass line and reservoir are now

being used to convey water from the Upper Van Norman

Reservoir to the Chatsworth High Line and major

trunk lines at the outlet to the Lower Van Norman

Reservoi r

.

6. The Lower San Fernando Dam was severely damaged but

did not collapse. It was built by the hydraulic fill

method in 1913-1915 and raised and improved in 1930

and again in 1940. The reservoir can hold some 20,000

acre-feet of water at the water level of 1134 feet.

At the time of the quake, the water level was 1110

feet, containing about 11,000 acre-feet. With this

lower water level, although the crest of the dam

collapsed during the quake (see fig. 8.4), the dam

held back the water. With only a few feet of freeboard to relieve the water pressure on the damaged

dam, the water was immediately drained through the

collapsed intake at a rate of 800 cubic feet per

second (cfs) and discharged by 11 pumps at a rate

of 190 cfs. The Lower Van Norman Reservoir is now

out of service and is almost completely drained.

METROPOLITAN WATER DISTRICT FACILITIES

The Metropolitan Water District (MWD) distributes water

throughout Southern California. It channels water to the

Los Angeles Department of Water and Power through a 242-mile

Colorado River Aqueduct. The aqueduct together with its

distribution lines escaped major damage. However, MWD's

Joseph Jansen Filtration Plant, a $24.8 million facility

under construction (85 percent complete at the time of the

earthquake) in the Sylmar area, experienced damage to both

steel and concrete installations.

The intensity of ground movement at the Jensen Filtration Plant can be envisaged from the buckled 1.9-milliongallon water storage tank shown in figure 8.5. The tank,

which was made of 3/8-in thick steel plate, was 30-ft high

and 100-ft in diameter. This tank was located in the northwest area of the plant and was reported to be approximately

one-half full at the time of the earthquake. Some of the

anchor bolts, which held the tank to its foundation, were

pulled out of their anchorage. The amount of pullout was,

in general, greater on the north and south sides than the

east and west sides. This indicates that some rocking motion

of the tank occurred during the earthquake about an axis

oriented in the east-west direction. The amount of uplift of

the tank was greater on the south side than on the north side,

as indicated by the amount of pull-out of the anchor bolts.

The amount of pulled-out length was several inches on the

369
Figure 8.3 Downstream face of the Upper San Fernando Dam.

Note the seepage at the foot of the dam.

Figure 8.4 Collapsed crest of the Lower San Fernando Dam.

370
north side and as much as 19 inches on the south side (fig.

8.6). This difference in the amount of pull-out can possibly

be explained by heavy machinery which was attached to the

north side of the tank and apparently restrained the uplift.

In addition to damages to the structures above the ground,

the reinforced concrete wall, the 14-in thick concrete roof

slab, the 16-in thick concrete floor slab, and the spiral

columns of the plant's 50-mi 1 1 i on-gal 1 on underground reservoir

were severely damaged during the earthquake. It has been

reported that most damages at the plant were on filled ground

which was consolidated by the ground shaking.

Total damages to the MWD are estimated at about $7

million as of April 1971. This damage figure includes the

damages sustained by the Jensen Filtration Plant, the Balboa

inlet tunnel, the San Fernando tunnel, and other MWD's water

distribution facilities in Los Angeles and Ventura counties.

CITY OF SAN FERNANDO

Water consumed by more than 400,000 inhabitants in

the City of San Fernando was supplied by seven underground

wells located within and around the city. All seven wells

suffered damage during the earthquake. Shortly after the

earthquake, two wells were restored to service.

Within the city limits, the water supply system in the

extreme north corner, bounded by Harding Avenue, Glenoaks

Boulevard and Hubbard and 8th Streets, was completely

destroyed. The original s i x- to- ten- i nch diameter cast iron

riveted pipes were removed and replaced.

8.2 El ectrici ty

Electric power in the Los Angeles area is distributed

by the Los Angeles Department of Water and Power (DWP) and the

Southern California Edison Company (SCE). The DWP provides

the power to customers within the Los Angeles city limits and

the SCE to customers in the areas exclusive of the City of

Los Angeles. Facilities of both DWP and SCE sustained damages

from the earthquake.

DEPARTMENT OF WATER AND POWER (CITY OF LOS ANGELES)

The DWP suffered an estimated $45 million damage to its

power facilities with most of it occurring at four locations

These are the Sylmar Converter Station, the Sylmar Switching

371
Figure 8.5 Buckled steel (3/8 in. thick) backwash tank at

Joseph Jensen Filtration Plant.

372
station, the Olive Switching Station, and the San Fernando

Power Plant (see fig. 8.7),

As a result of power distribution facility damages,

services to 363,000 customers (representing a load of

418,000 kilowatts) was temporarily disrupted. Most service

was restored to customers within a period ranging from 15

minutes to 1 1/2 hours. Most power service was restored by

the evening of February 11, some 60 hours after the initial

shock, with the exception of the evacuated area" below the

Lower Van Norman Reservoir. Power was restored to this section

on February 12, when residents returned from evacuation.

SYLMAR CONVERTOR STATION

The most serious damage to the DWP's power facilities

was the loss of service of the Sylmar d.c. Convertor Station,

with an estimated $30 million ^'.amage. The station is the

southern terminus of the 846 mile, direct current, 800,000 - volt line bringing power from hydroelectric plants on the

Columbia River (fig. 8.8K The DWP shares ownership of the

station and the 581 mile southern section of the transmission

line with the Southern California Edison Company and the

cities of Burbank, Glendale, and Pasadena.

With the loss of the d.c. convertor station, which was

dedicated in September 1970, the DWP lost 525,000 kilowatts

of capacity which constitutes 12.7 percent of its total

system capacity of 4,144,000 kilowatts. Anticipated peak

load for August 1971 is 3,340,000 kilowatts. As of June 1971,

the station was scheduled to resume partial operation in

early December 1971, and should be capable of receiving full

capacity of 1,440,000 kilowatts by August 1972.

An aerial view of the Sylmar Convertor Station is shown

in figure 8.9. The station consists of the main steel

frame structure and two adjoining radio-shielded open steelframe structures. The three-story main structure has 6- to

8-in concrete floor slabs on steel floor beams and metal

deck roof. The steel frames have vertical "X" bracings to

resist lateral loads. The exposed steel frames which cover

the transformer yards have horizontal and vertical "X"

bracings and are covered with wire mesh.

The main building structure performed well and damage

to it was minimal, although many wide cracks in the parking

lot pavement indicate that the structure was subjected to a severe ground motion. Most damages in the main building

occurred in the basement where service and equipment sections

were joined. Steel columns of the two sections were supported

on common concrete columns at this juncture. The upper portion

373
374
Figure 8.8 The Pacific Intertie System.

375

of these columns was damaged due to what appears to be

independent movement that took place between the two sections

of the building. The floor slab and the basement wall in this

vicinity were also damaged. On the other hand, numerous

damages were sustained by the bare steel frame structures over

the transformer yards. Many braces were buckled, stretched,

and broken at gusset plates (fig. 8.10 and 8.11). Some

columns were bent and, in several places, cracks occurred

between the column pedestal and the concrete wall which

surrounded the yard (fig. 8.12).

The most severe damage, which resulted in more than $28

million loss, occurred in the valve bays and outdoor electrical equipment yards. The valve bays house 42 mercury arc

convertor valves. These valves, each costing $0.5 million,

are designed to change direct current to alternating current,

or vice versa. The upper half of the valve is suspended by

four insulated wires and the lower half is supported on four

insulated supports. Both the upper and lower supports were

fractured and cracked, apparently due to vertical and lateraltors ional motions of the valve during the earthquake.

Much outdoor electrical equipment was supported on

insulators, (fig. 8.13). Equipment collapsed due to failure

of these insulators during the earthquake as shown in figure

8.14.

Several large oscillators were toppled and dislodged

due to failure of their anchorage to the foundation pad

(fig. 8.15). Each oscillator was attached to four 12-in by

12-in by 3/4-in anchor plates. Each of these plates was

anchored to the concrete pad with four 1/2-in studs. A

close examination showed that all studs were fractured at

the base metal. Some fractured studs showed only partial

fusion to the base anchor plate. The base steel plates and a concrete pad to which the plates were embedded are shown in

figures 8.16 and 8.17, respectively. In figure 8.17 the

broken studs are indicated by arrows.

Numerous large transformers in the radio-shielded yards

were moved laterally on their foundation slabs as anchor bolts

were sheared off due to lateral forces. A typical example of

such a failure is shown in figure 8.18.

SYLMAR SWITCHING STATION

The Sylmar Switching station is located just north of

the Sylmar Convertor Station. Damage to this station caused

a disruption to the DWP interconnection to the Southern

California Edison system. A temporary interconnection has

been established since March 1971.

377
Figure 8.10 Buckled lateral bracing.

Figure 8.11 Fractured gusset plate.

378
111

II Figure 8.12 Concrete spalling

at one of the

joints between a column pedestal

and an enclosure

wall surrounding

the electrical

transformer yard.

379
Figure 8.14 Destroyed electrical capacitor banks (in

background) at Sylmar Converter Station.

380
Figure 8.16 View showing bottom of toppled oscillator with

its steel base plates and top of the foundation

slab.

381
Damage to equipment at this station included broken

circuit breakers and transformers which fell from their

supports

.

OLIVE SWITCHING STATION

Olive Switching Station is located on San Fernando Road

near Olden Street. This Station, which received power from

Owens Valley and the San Fernando Power Plant, sustained

damage to power receiving and distribution systems. Much of

the insulator-supported equipment in the yard collapsed and

transformer banks rolled over.

By the night of February 9, a temporary bypass was

constructed to connect the Owens Gorge Transmission line to

Receiving Station J, thus making the Owens Gorge Power

available to the DWP system.

SAN FERNANDO POWER PLANT

The power plant which is located just north of the

Upper Van Norman Reservoir was dropped about three feet,

thereby shearing off the end of the penstock and breaking

the bypass gate. This station had a generating capacity of

6000 kilowatts and is out of service indefinitely. Severe

ground failure around the plant is shown in figure 8.19.

OTHER DAMAGED FACILITIES

Two distribution stations in the Syl mar- Granada Hills

area suffered damages. One station in Sylmar, located at

the corner of Glenoaks Boulevard and Polk Street, had its

high voltage lines and voltage regulators damaged. The other

station which is located near Balboa Boulevard and Woodley

Avenue received mainly structural damages to the tilt-up walls

supporting steel columns. Many steel columns were bent and

some ruptured in the web.

Other damages to DWP included collapsed underground

vaults and many fractured ducts. In Tujunga canyon, several

power towers shifted up to 20 feet due to land slides.

Others had their lightning arresters cracked.

SOUTHERN CALIFORNIA EDISON COMPANY

SCE suffered an estimated damage of $720,000. Damage to

the SCE systems were minor compared with those of DWP. Except

for that portion of damage related to the Sylmar Converter

382
Figure 8.18 Electrical transformer which moved laterally

on its foundation slab.

Figure 8.19 Aerial view of the San Fernando Power Plant.

383
station, of which SCE is part owner, damages were confined to

transmission lines. A total of 47 towers were found to be

unstable due to loss or movement of footings. In addition,

while not in imminent danger, as a consequence of deep

fissures through and around the tower, a moderate rain could

result in excessive erosion and land slides.

Some 330,000 customers were affected by power interruption. Approximately 180,000 customers were interrupted

for less than one minute, and less than 1,000 customers

had interruptions up to a maximum of 32 hours.

8 . 3 Gas Suppl i es

The Southern California Gas Company distributes natural

gas throughout the Los Angeles area. Estimated damage to the

company's facilities was about $2.0 million, mostly in

distribution lines, which are typically two- to six-inch

diameter steel pipes which are buried three-feet deep. The

only area where the distribution piping system was seriously

damaged occurred within the 11- to 1 2-square-mi 1 e area in the

northeast section of the San Fernando Valley. The area was

bounded by Golden State Freeway, Foothill Boulevard, and

Pacoima Wash (fig. 8.20 - Area 1). Gas in this area was

supplied by major lines at a pressure of 170 psi. Shortly

after the quake the pressure was reduced to 35 psi in the

distribution systems. Gas supply in the damaged area was

shut off within two hours and the gas in the distribution

system dissipated into the atmosphere.

The following report was given by W. C. Mosteller,

Manager of Engineering of the Southern California Gas Company

before the Los Angeles County Earthquake Commission on March 17, 1971

.

"In general, the distribution piping system

withstood the stresses of the quake remarkably

well. This is borne out by the fact that in many

areas where buildings sustained appreciable

damage, the system remained intact."

"The major transmission lines from out-of-state,

30- in diameter and above, did not suffer any

apparent damage. Service to the great majority

of the company's 3.1 million customers was

little affected.

"The transmission system handling the deliveries

of California gas from the San Joaquin Valley

to the Los Angeles basin was damaged to the

extent that four lines had to be shut down in

384
Figure 8.20 Areas with interrupted gas service.

385
the San Fernando area. Damage to the four

lines, which range from 12 to 26 inches

in diameter, occurred between Newhall and San

Fernando and resulted in the loss of supply

to the distribution system in the Sylmar-San

Fernando area

.

"The distribution system in this hard-hit area

consists principally of a network of 2-, 3-,

and 4-in welded steel mains serving approximately 17,000 customers. The violent earth

movement there pulled, compressed, and twisted

the piping system, resulting in broken mains,

valves and service risers. Approximately 450

breaks have been discovered."

"Damage to the remainder of the Company's

distribution system was confined to isolated

fractures or pipe separations that did not

result in serious impairment of service to

cus tomers .

"Repairs to the damaged gas mains in the

San Fernando area were commenced almost

immediately after the quake. Gas service

to customers was restored commencing

Sunday, February 14, and completed for

the most part by Saturday, February 20th."

There were several gas fires within streets at broken

gas lines, one at the intersection of Glenoaks Boulevard and

Hubbard Street. A number of other fires damaged buildings

after the quake; however, none had been identified as associated with gas.

Many broken gas lines were flooded with water from

broken water mains. The greatest damage of this type occurred

in the northern corner of the City of San Fernando where, as shown in figure 8.21, ruptured gas, water, and sewer lines

were buried adjacent to each other. Some 10 days after the

quake, a problem of a similar nature occurred in the SunlandTujunga area, some 6 miles east of the City of San Fernando,

where earthq uake- 1 oos ened soil worked its way into the

broken gas lines and filters in a regulator station. This

disrupted gas service to about 10,000 customers for a period

of up to one day, in the area bounded by Sherman Grove Avenue,

Haynes Canyon Avenue, the San Gabriel Mountains and Verdugo

Mountains (fig. 8.20, Area 2).

386
8 . 4 Telephone Facilities

The General Telephone Company sustained severe damage

to its buildings and equipment. It is estimated that the

damage to the company was approximately $4.7 million. Of

this figure, about $0.2 million is attributed to building

damages and $4.5 million to equipment damages.

These figures suggest that the damage to building

structure was miminal. Of a total 27 buildings inspected,

one was vacated as unsafe, one was structurally damaged and

nine suffered non-structural damages.

The equipment damage was concentrated at the Sylmar

Central Office where all the switching equipment was rolled

over (fig. 8.22). Loss of this central office left 9,500

Sylmar customers without telephone service.

The buildings were designed in compliance with all

governing building and safety codes at their respective

locations. In addition, the equipment areas were designed

for 150 lbs per square foot of live load.

It appears from what happened at the Sylmar Central

Office that while the buildings are, in general, adequately

designed for lateral forces, the equipment supporting frames

did not have adequate lateral supports to prevent them from

toppling.

It was reported that, at present, there are two basic

systems for equipment structural support. These systems are

used in California and other states. One system which is

supplied by many of the telephone equipment manufacturers

consists of the following:

The placing of a steel angle ledger on the

perimeter walls of the equipment room. At

right angles to this ledger and perpendicular

to the equipment frame a steel channel is bolted

to the ledger and the equipment is framed to it

by means of mechanical connections.

The other system, primarily in use by the General

Telephone Company, consists of the following:

Continuous dovetail anchors are embedded in the

roof structure and/or 5 lb/ft channel section

is bolted via inserts to the structure with

threaded rods dropped down to support cable

racks and secondary steel superstructure run

perpendicular to the equipment frames. As an

387 «
Figure 8.21 Close-up view of ruptured sewer, water, and

gas lines.

Figure 8.22 Toppled and damaged telephone switching

equipment at Sylmar Central Office of General

Telephone Company.

« 388
integral part of this structure, diagonal

bracing is used to provide a Warren truss.

Equipment frames are erected under the

above described structure and fastened by

means of mechanical connections.

In both systems the equipment frames are anchored to the

floor by power-driven concrete inserts and/or steel anchors,

shields, etc

.

The equipment frames consist of vertical angle sections

supporting horizontal rows of equipment fastened to the two

supporting systems described above.

The post-earthquake survey revealed that improvement in

the mechanical connections that provide the lateral support

to the equipment frame is required.

The mechanical connections which are presently used

should be re-evaluated for strength and need to be improved

to insure that the equipment supporting structure has at least

equivalent structural integrity to that of the building.

8 . 5 Sewers and Storm Drains

The preliminary estimate (March 9, 1971) made by the

Department of Public Works, City of Los Angeles, for the

sewer and storm drain repair work required to place the

damaged facilities in a satisfactory condition is as

f ol 1 ows :

These estimates are based upon the results of physical

examinations made by the Department of Public Works up to

March 9, and further study may indicate that additional

construction may be needed.

The Department of Public Works of the City of Los

Angeles has conducted a survey to determine the changes in

elevation caused by the earthquake. Their results are

presented in figure 8.23. The numbers indicate changes of

evaluation, assuming that the reference point--the intersection of Van Nuys and Foothill Bou 1 evards--has remained at

the original elevation. The maximum change of 7.5 ft was

measured in Lopez Canyon, with a rise of about 5 ft near the

northern part of the City of San Fernando (intersection of

Harding Street and Foothill Boulevard). Figure 8.23 also

Sewe rs Storm Drains

$1 ,000 ,000

800 ,000

Total $1 ,800 ,000

389
• Ms

c; Qj o

0) 3 O

0) bl -rH tn -IJ

Sh O ^ rc O O 0) --H

390
shows the observed and estimated location of many surface

breaks and faults in the area. Much damage to sewers and

storm drains occurred in these areas which experienced

considerable ground movement.

Most of the damaged sewers were 10 to 12 inches in

diameter and were located 8-ft deep. Of the 120 miles of

sewers in the Sylmar and San Fernando area, about 10 percent

have been examined by television as of March 11. (The cost

of this television work ranges from $0.80 to $1.00 per lineal

foot.) Damage has been found in about eight percent of the

sewers examined which lie along the northeast-southwest

streets and about one to two percent along the northwestsoutheast streets

.

Damage has also been detected in some of the deeper

sewers. For example, the 18-in diameter, 25 ft deep sewer

on Telfair Avenue, east of the Lower Van Norman Reservoir,

is extensively damaged.

In the City of San Fernando complete rebuilding of the

sewer system will be needed in the area bounded by Hubbard

Street, Glenoaks Boulevard, Harding Street, and Eighth

Street (see fig. 8.23 for location).

Storm drain facilities to be repaired consist of mainline storm drains, sidewalk culverts, manholes, open channels,

and reinforced concrete box structures. Despite the damage,

the Department of Public Works reported that most of the

drains are intact and functioning well.

8 . 6 Fire Damage and Protection

Relatively little fire damage occurred as a result of

the February 9 earthquake. A si ngl e- f ami ly dwelling and

several commercial buildings destroyed by fire are shown in

figures 8.24 and 8.25. The number and types of incidents

that occurred during the three 24-hour period following the

earthquake are given in table 8.1. To serve as comparison,

the 1970 daily averages are also given in the table.

The resources of the Los Angeles Fire Department (LAFD)

were actively involved in the post-quake activities. With

the telephone system out in many areas, and no street boxes

in the San Fernando Valley, helicopter surveilance was used

and radio communications became vital. The LAFD was called

to help in the rescue operations at the San Fernando Veterans

Administration Hospital. They also had some 17 pumps operating (total 2492 pump-hours) to supplement the water supply.

Based on preliminary reports, only five Los Angeles

391
Figure 8.24 House in Knollwood area destroyed by fire.

Figure 8.25 Commercial buildings destroyed by fire

(Chatsworth Street and Zelzah Avenue,

Granda Hills)

.

392
Table 8.1 Earthquake Related Incidents

(Based on data compiled by Los Angeles

Fire Department February 23, 1971)

Feb. 9 Feb. 10 Feb. 11

(0600) (0600) (0600)

to to to 1970

Feb. 10 Feb. 11 Feb. 12 Daily

Type of Incident (0600) (0600) (0600) Total Average

Electrical Failure 23 12 9 44 6.5

Explosion-Flammabl

e

Gas 1 1 2/month

False Alarm—Accidental 26 8 11 45

False Alarm—Malicious 21 32 2 / 80 30

Fire Not in Structure 49 51 40 140 60

Fire in Structure 62 34 35 131 29

Fire Not in Structure - Out 8 14 16 38

Fire in Structure - Out 9 5 9 23

Food on Stove 8 7 3 18

Invest. Other Than

Accident 23 3 1 27 1

Leak, Natural Gas 28 13 5 46 2

Leak, Refrigerant 1 1

Power Lines Down 52 2 1 55 1.5

Rescue 9 3 4 16

Smoke Scare 21 12 10 43 8

Spill, Chemical 4 1 1 6 1/week

Spill, Flammable Liquid 1 3 1 5

Washdown, Gasoline 3 7 7 17

Water Flow 17 .4 1 22 1.5

Water Surge 1 1 1 3 3/week

393
Fire Department stations (out of a total of 104 stations)

suffered severe wall cracking or major structural damage.

The fire protection of many old buildings, particularly

in downtown Los Angeles was affected by the collapse of the

protecting material. In some of these buildings the fire

protection consisted of terracotta hollow tiles covered with

cement mortar and gypsum plaster.

8 . 7 Flood Control Facilities

Three separate agencies, the U. S. Army Corps of Engineers,

Los Angeles County Flood Control District, and the City of Los

Angeles Department of Public Works are responsijle for drainage

and flood control in Los Angeles. In general, the Corps of

Engineers is responsible for the improvement of the larger

streams which traverse the metropolitan area. Its projects

are to protect against more severe storms then those that

fall under the jurisdiction of the Flood Control District and

the City; storms of such intensity occur on an average of

about once every one hundred years. The Flood Control

District's channels are built to accommodate the waters of a fifty-year storm while the Los Angeles City and the Flood

Control District normally design their underground drainage

facilities to provide relief from the effects of a ten-year

storm [8.1].

Damage Estimates - Damage to the Los Angeles Flood

Control District facilities has been estimated at $2.5

million [8.2]. The only Corps of Engineers project which

suffered significant damage was the Lopez Debris Basin [8.2

and 8.3]. The cost to repair this project has not been

reported at this time.

Dams - Pacoima Dam, built in 1928 as a 370 ft high

concrete-arch structure, is the only major District dam in

the Sylmar area (see fig. 8.26). Significant damage occurred

to the gunite abutments (figs. 8.27 and 8.28), and massive

rockslides occurred in the vicinity of the dam (fig. 8.29)

[8.4]. Although damaged evaluation is not compl ete ,

' prel i m- inary reports indicate there was no structural damage

to this dam. Water level behind the dam was low at the time

of the earthquake.

Debris Basins - At the Wilson Canyon Debris Basin, damage

consisted of slides on the access road, cracked and destroyed

roadway, cracked upstream concrete facing, fallen right-ofway fencing, displaced headwall and cracked earth levee. At

the Schoolhouse Debris Basin, damage consisted of slides on

the access road, destroyed right-of-way fencing, cracked

spillway and spillway walls out of plumb. At the Stetson

394
395
Figure 8.27 Damage to gunite

left abutment,

Pacolma Dam.

396
397
Debris Basin, there were cracks in the dam fill on both sides

of the spillway (fig. 8.30) and in the facing slab parallel

to the spillway invert (fig. 8.31). Hog Debris Basin and

Sombrero Debris Basin also suffered similar damage.

Channel

s

- The Wilson Canyon Channel has a reinforced

concrete box which was badly damaged (figs. 8.32 and 8.33).

Concrete walls along the Lopez Canyon Channel were also badly

damaged (figs. 8.34 and 8.35). Other channels which were

damaged are the Mansfield Channel and the Pacoima Wash

Channel

.

8.8 References

8.1 Drainage Plan - City of Los Angeles; Publication prepared

by Department of City Planning and the Department of

Public Works Engineering Bureau, 1968.

8.2 C. Martin Duke, "Damage to Water Supply Systems, The

San Fernando, California Earthquake of February 9,

1971," Geological Survey Professional Paper 733,

U. S. Government Printing Office, 1971.

8.3 Los Angeles District, Corps of Engineers, Post Earthquake Inspect"! on and Evaluation Survey, February 18,

1971 .

8.4 Damage Report, Earthquake of February 9, 1971, Los

Angeles County Flood Control District, Operation

and Maintenance Division Preliminary Report.

398
Figure 8.30 Looking northwesterly toward basin showing

crack in the pavement and a 2-inch vertical

displacement of paved crest of dam (Stetson

Debris Basin)

.

Figure 8.31 Looking easterly showing damage to facing

slab; Stetson Debris Basin.

399
400
Figure 8.34 Lopez Canyon Channel. A 50-foot section of

the wall has failed on the right bank. The

50-foot section adjacent upstream also shows severe structural damage.

Figure 8.35 Lopez Canyon Channel. A 2-foot displacement

of the channel had caused complete failure of

the walls and invert, with the upstream portion

moving over the downstream portion.

401

CHAPTER 9 CONCLUSIONS AND RECOMMENDATIONS

The conclusions and recommendations given in this

chapter are based on the site investigations which were made

immediately following the San Fernando earthquake and the

subsequent study of a number of damaged structures as well

as seismic code requirements. The recommendations, however,

are not limited only to the San Fernando area but are also

applicable to other earthquake-prone areas in the United

States

.

1. REVIEW OF CURRENT DESIGN PRACTICE

An immediate review should be made of the

adequacy of present design requirements

for seismic design.

Most buildings near the epicenter, which were severely

damaged, such as the Olive View Medical Center, San Fernando

V.A. Hospital, Pacoima Memorial Lutheran Hospital, and Holy

Cross Hospital were not designed under the latest building

code requirements (1968 SEAOC or 1970 UBC). Nevertheless,

the performance of these structures should be reviewed in

detail, with proper consideration given to the code requirements used in their design, so that these data and information

can be used to assess the adequacy of present seismic design

requirements for buildings.

Many bridges designed under present specifications

collapsed. Thus, these design requirements are in need of

revi ew

.

Numerous recordings of horizontal accelerations which

greatly exceeded those envisioned in formulating the current

lateral force requirements are reason to review and possibly

increase seismic coefficients currently in use. It may be

necessary in the future to adopt a design procedure which

reflects the dynamic response characteristics of structures.

However, as an intermediate action, the existing values of

the coefficients used in design equations should be modified.

In view of records of vertical ground accelerations of

the same order of magnitude as horizontal accelerations, the

presence of vertical seismic forces can no longer be ignored.

403
2. UPDATING DESIGN REGULATIONS

Present procedures used to update design

regulations should be reviewed in order

to evaluate more expeditious ways to

incorporate new knowledge into design.

Building codes are continually-changing documents. As

codes are updated, design requirements may be made more

liberal or more conservative. It is important that unsafe

requirements be corrected as rapidly as possible.

The Olive View Medical Center provides an excellent

example of the delay in revising building codes to change

requirements which had been found to be unconservati ve . As

indicated in the discussion of Olive View (sec. 5.2), a possible cause of the collapse of the Psychiatric Unit was

insufficient first-story column shear strength. The concrete

unit shear stresses used in design were based on the 1956 ACI

Building Code. The 1956 ACI unit shear stresses were found

to be unconservati ve . Thus, the 1963 ACI Code adopted more

restrictive unit shear stresses than the 1956 Code. It was

not until November 1966 that the Los Angeles County Code was

updated to use the newest ACI Code unit shear stresses. The

use of the more restrictive unit shear stresses would have

required the use of additional lateral reinforcement in the

columns, which could possibly have prevented the collapse of

the Psychiatric Unit. This can not be stated conclusively,

since it must be noted that ground accelerations were much

larger than those anticipated in formulating code design

equations.

There does not appear to be a simple solution to the

problem of updating codes more rapidly. However, as pointed

out above, it may be legally possible to design an unsafe

structure. Thus, the problem is clearly in need of study.

3. CRITICAL FACILITIES

Critical facilities should be designed

so that they remain functional after a severe earthquake

.

Facilities, in this context, include hospitals, emergency

services (fire, police, etc.), utilities, communications,

404
transportation networks, schools, and high occupancy buildings. Design requirements should reflect the importance of

the facility and the degree of danger involved in its

f ai lure.

Four hospi tal s -San Fernando V.A. Hospital, Olive View

Medical Center, Holy Cross Hospital, and Pacoima Memorial

Lutheran were critical facilities which were severely damaged

and were unable to fulfill their functions.

Public facilities which have a high occupancy use should

be considered critical due to the potential loss of a large

number of lives involved in a collapse.

Water, sewerage, gas, and electricity were severely

damaged in the San Fernando Valley area. Many communities

were without these facilities for a considerable period of

time.

The collapse of bridges at the intersection of the

Golden State Freeway and Foothill Freeway blocked an extremely important potential evacuation route from the Los

Angeles area. Although crews worked remarkably well in

constructing detours, these routes would not have been

immediately available for evacuation as well as for rescue

operations had the damage been more widespread.

The damage at the Sylmar Convertor Station indicates

the potential for disruption of power. The damage of the

telephone switching equipment at the Sylmar Central Office

disrupted communications to the extent that full service

was not restored until 6 1/2 weeks after the earthquake.

Due to such disruptions of required services in a disaster it is recommended that a seismic occupancy multiplier should be applied to the lateral force design and

should be a function of the hazard potential of the facility.

Emergency facilities such as hospitals, police stations, fire

stations, utilities, and other installations that must remain

operational after a disaster should have a seismic multiplier

of possibly 2 or greater. Structures such as schools, places

of assembly, and other establishments subject to a high panic

potential should have a multiplier of perhaps 1 1/2.

4. REHABILITATION AND STRUCTURES UNDER CONSTRUCTION

Buildings in existence or under construction

should conform to up-to-date design regulati ons

.

405
Evaluation of the earthquake hazard of structures built

under older codes should begin immediately. This is

particularly important for critical public buildings. For

instance the San Fernando V,A. hospital buildings which

collapsed were built well before the existence of earthquake

requirements. Where required, critical public buildings

should be scheduled for rehabilitation or removal. Such a program is feasible as was demonstrated by the performance

of rehabilitated schools (chapter 6) which were constructed

prior to 1933 but were reinforced after 1933 to resist earthquake forces

.

A problem of equal importance is that of establishing

a mechanism by which a structure under construction can be

re-evaluated in light of important changes in design regulations. An example of this is the Olive View Medical Center.

During, or shortly before, the construction of the medical

center, the 1965 L.A. County Code was amended in November

1966 to include significant changes in design procedure.

5. CONSTRUCTION INSPECTION

• - Revised design regulations should include

provisions for cons true t ion inspection of

'Critical facilities by a qualified

structural engineer

.

In general schools constructed under the Field Act

performed well during the earthquake. Several schools constructed prior to the Field Act performed poorly and had to

be demolished. Possibly the most significant provision of

the Act is the requirement for strict construction supervision.

Although no apparent signs of faulty construction were

observed in the major structures surveyed, this requirement

seems to be particularly important for critical public

buildings.

6. DEFORMATION AND DEFLECTION

Earthquake design should cons i der

deformation and deflection as well as

strength

.

Deformation and deflection, as well as strength, should

be considered in earthquake-resistant design. This is

406
illustrated by the horizontal and vertical movements which

caused bridge girders to move off their supporting abutments

and piers. Ground displacements must be studied carefully

to determine appropriate magnitudes of movement which should

be accounted for in design. Details must be developed to

allow for such movement.

7. DUCTILITY

An accurate appraisal must be made of

the amount of ductility which can be

expected in a particular type of structural

design and material.

Design regulations should require material properties

and connection details which are consistent with the amount

of ductility allowed in dissipation of seismic energy. For

example, the specific recommendations listed below to

increase the ductility in reinforced concrete should be

studi ed i n deta i 1

.

(a) The tied column behavior at Olive View illustrates that

the maximum spacing of column ties should be limited to onehalf the effective depth of the cross section to insure

effectiveness as shear reinforcement.

(b) Columns and piers should be designed to resist a shear

at least equivalent to that imposed by a complete moment

reversal on the column equal to the flexural capacity of the

column. This is necessary to prevent a shear type failure

since such a failure is not ductile.

(c) Extra column ties or spiral wraps should be provided

in the end sections of all columns and into the beam-column

connections.

(d) The use of lap slices for lateral reinforcement such as column ties should be discouraged. All ties should be

anchored by hooks or embedment into the core in order to

remain effective after covering concrete has spalled off.

8. MOMENT-RESISTING CONCRETE FRAMES

Consideration should be given to modifying

the requirements for moment-res i s ti ng

concrete frames to include at least some

of the rein fore ing requirements for

407
ductile moment- res i s t ing frames.

The first-story column failure of the Psychiatric Unit

at Olive View illustrates the consequences of the failure of

a column in shear (as indicated in chapter 5 it is felt that

shear was the most likely cause of failure). Once a concrete

member has cracked in shear, its shear capacity becomes

essentially zero. This is in contrast to the case of a flexural type of failure where the member may continue to

deform but can still carry load.

The psychiatric unit was designed as a moment-resisting

frame using K=0.67. Under current practice such a frame

would have to be a ductile moment-resisting frame which has

special reinforcing requirements beyond those of the momentresisting frame. For example, ties should be spaced no

farther apart than one-half the least column dimension. The

moment- res i s ti ng frame with a K=l .0 does not have these

special requirements. For practical purposes, the Psychiatric

Unit was not a ductile frame. Under current practice a K=1.0 would be used (with the same reinforcement details).

However, it is entirely likely that the same type of failure

would have occurred, even if the design had been based on somewhat larger lateral forces.

Thus to provide some shear resistance, after shear

cracking of concrete, it is recommended that ties be spaced

no greater than one-half the effective depth of the column

cross section in moment-resisting frames as well as ductile

moment- res i s ti n g frames.

9. DESIGN OF APPENDAGE CONNECTIONS

Connect i ons of appendages should be

designed to resist the same seismic

forces as the structure which supports

them .

Appendages such as light fixtures, emergency lights,

suspended ceilings, and other overhead objects fell during

the earthquake. The connection of such appendages to

structural elements should be given engineering consideration

since its failure presents a hazard.

408
10. DWELLINGS AND MOBILE HOMES

Specific recommendations for dwellings

and mobile homes are listed below.

(a) Positive means of transferring lateral forces are

required where large openings exist in walls and where

changes occur in configuration. Numerous failures were

observed in apartments and single family homes where

large openings in walls were provided for garages or

entranceways . Numerous single-family dwellings collapsed

or were near collapse due to the inadequate tying together of adjacent units.

(b) Chimneys should be adequately reinforced and anchored to

the main structure. Numerous failures due to lack of

reinforcement and anchorage were observed.

(c) Improved methods for supporting mobile homes should be

developed and implemented.

n. DAMS

Seismic res istance and design of dams

whose failure would present hazards to

heavily populated areas should be

revi ewed

.

The near-failure of the Lower San Fernando Dam which is

located above a densely populated residential area required

the evacuation of about 79,000 people. This is sufficient

cause for the review of the seismic resistance of such

structures. All existing dams located close to a dense

population should be examined for strength and stability due

to ground faulting and acceleration.

The adequacy of present design requirements for the

seismic design of dams should be reviewed. A vertical

acceleration component should be considered, particularly

for gravity dams.

409
12. UNDERGROUND INSTALLATIONS

Underground installations such as water,

gas, and sewer pipes should be designed

to minimize service interruption

.

Gas, water, and sewer lines may fracture during severe

ground movements. Seepage of sewage into the water line is

a source of contamination. Seepage of water and sewage into

gas lines causes extensive system damage. A possible means

of minimizing damage is to install flexible joints and

automatic cut-off valves. Alternate service routes are also

desirable.

13. MACHINERY AND EQUIPMENT

Machinery and equipment should be anchored

to resist the same seismic forces as the

structure which supports them.

Heavy electrical equipment suffered damage at the

Sylmar Convertor Station due to inadequate support or anchorage. Boilers at Olive View and Juvenile Hall caused damage

to buildings which housed them due to their movement. Proper

anchorage of such equipment to structural elements is essential. Telephone switching banks were also destroyed in

Sylmar due to inadequate support.

14. ELEVATORS

The design of elevator systems should be

reviewed to insure their operation after

a disas ter

.

As indicated in this report, many elevators could not be

operated after the earthquake. This was due either to power

loss, bent guide rails, and/or cables tangled by loose

counterweights. Thus, elevators were not available for use

during or after a disaster. Furthermore it seems possible

that, had the earthquake occurred during hours of heavy use,

lives would have been endangered. This could have occurred

due to counterweights falling through the car. Had fires

occurred, the passengers of immobile elevators almost surely

410
would have died. It should be pointed out; however, that

such fires did not occur as a result of this earthquake.

15. GEOLOGIC HAZARDS AND FAULT ACTIVITY

Improved methods should be developed to

identify the potential activity of faults

and associated geologic hazards

.

The San Fernando Earthquake, as well as the Kern County

Earthquake, occurred along faults not generally recognized

as active before the earthquake. These earthquakes point

towards the need for developing improved methods for characterizing the potential activities of faults and applying

these methods in geologic field studies of faults in seismic

areas. Information gained from such studies can then be

taken into account in planning for the use of land.

16. SEISMIC RISK ZONING

More detailed and concise seismic risk

maps should be developed

.

Present seismic risk maps, such as the ones given in the

Uniform Building Code, are based on the Modified Mercalli

Intensity scale. As a result only short-period (less than

one second) effects are considered. Since more and more

highrise structures will be built in the future, a seismic

risk map incorporating long period effects will be needed.

Furthermore, the present risk map reflects potential

seismic risks on a large regional basis. Micro-regional

seismic risk maps are urgently needed to cover potential

seismic risks representing a small region, such as the San

Fernando Valley. Such a micro-seismic risk map should

consider (1) distribution and frequency of earthquake, (2)

local (site oriented) geology and (3) regional geologic

features, such as ground faulting, etc.

17. EXPANSION OF SEISMOGRAPH NETWORK

The present seismic monitoring program

should be expanded and improved

.

411
Information provided by the strong-motion seismograph is

single best source of scientific data that can be used in

post earthquake studies of structural performance. Even in

the Los Angeles area, with the largest number of strong-motion

seismographs installed in buildings in the United States, the

seismic monitoring network was not as complete as it could

have been. For example, while many buildings in downtown Los

Angeles had strong-motion seismographs, none of the severely

damaged buildings in the upper San Fernando Valley had the

seismographs. In view of this, to complete the seismic

monitoring network, strong-moti on seismographs should be installed in public structures in regions where large buildings

are not present.

It should also be emphasized that comprehensive seismic

monitoring programs are needed not only in the western states

of the U. S. but in all earthquake-prone regions of the

country

.

In general the system of accelographs in the Los Angeles

area performed well and obtained much useful data. However,

there were cases where data were not obtained due to dead

batteries, traces too faint to read, or lack of paper in the

instrument. Adequate funding should be made available for

maintenance of the system.

412

* U. S. GOVERNMENT PRINTING OFFICE : 1971 O - 451- 866
FORM NBS-114A (1-71) U S. DEPT. OF COMM. I. PUbUlCAilUN UK KhFUKl NU. ^. uov t Accession

BIBLIOGRAPHIC DATA

3. Recipient's Accession No.

4. TITLE AND SUBTITLE

Engineering Aspects of the 1971 San Fernando

Earthquake

5. Publication Date December 1971

6« Pcrfonning Or^sntzidCion Code

7, AUTHOR(S)

Hai Sanq Lew, Edqar V, Levendecker, and Robert D. Dikkers

8. Performing Organization

9. PERFORMING ORGANIZATION NAME AND ADDRESS

NATIONAL BUREAU OF STANDARDS

DEPARTMENT OF COMMERCE

WASHINGTON, D.C. 20234

10. Project/Task/ Work Unit No. 421 3116

11. Contract/Grant No.

12. Sponsoring Organization Name and Address Office of Emergency Preparedness, Washington, D. C. 20504

Office of Civil Defense, Washington, D. C. 20310

National Bureau of standards, Washington, D. C. ^:0234

13. Type of Report & Period Covered

Final

14. Sponsoring Agency Code

15. SUPPLEMENTARY NOTES

16. ABSTRACT (A 200-word or less factual summary of most significant information. If document includes a significant

bibliography or literature survey, mention it here.) Immediately following the San Fernando, California earthquake

(February 9, 1971), a four-man team from the Building Research

Division of the National Bureau of Standards' Institute for Applied

Technology, surveyed the damage to buildings and other structures.

This report is based primarily on the data gathered during the survey

but includes some data provided by other agencies and individuals.

Based on study of these data and observations made during the survey,

recommendations are made pertaining to the improvement of building and

other structural design and construction practices.

17. KEY WORDS (Alphabetical order, separated by semicolons) Bridge; building; COdCS; damS;

earthquakes; earthquake damage; foundation geology; highways; housing;

hospital; mobile home; seismic; standards; structural engineering.

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21. NO. OF PAGES

419

22. Price$ 3. 00

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