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United States. Natlo/Deslgn, siting, and TA435 U58 V48;1974;C2 C.I NBS-PUB-C 197 COMMERCE

PUBLICATION

BUILDING SCIENCE SERIES 48

Design, Siting, and Construction

of Low-Cost Housing and

Community Buildings

to Better Witlistand Earthqualtes

and Windstorms


(

Effects of earthquake in Huaraz, Peru. Thousands ofpeople were

buried under collapsed houses. {Courtesy of United States Geological Survey.)
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74 . 4n

Design, Siting, and Construction of Low-Cost Housing

and Community Buildings to Better Withstand

Earthquakes and Windstorms

"Juildi/iQ Science St

cr A Report Prepared for

The U.S. Agency for International Development

Washington, D.C. 20523

by

Center for Building Technology

Institute for Applied Technology

National Bureau of Standards

Washington, D.C. 20234

Collaborating under a Participating Agency Service Agreement with

The Technical Assistance Bureau

U.S. Agency for International Development

Editors:

William F. Reps (Coordinator of the Project), 1971-1972

Emil Simiu, 1972-1973

U.S. DEPARTMENT OF COMMERCE, Frederick B. Dent, Secretory

NATIONAL BUREAU OF STANDARDS, Richard W. Roberts, Director

Issued January 1974
Library of Congress Catalog Number: 73-600310

National Bureau of Standards Building Science Series 48

Nat. Bur. Stand. (U.S.), Bldg. Sci. Ser. 48,152 pages (Jan. 1974) CODEN: BSSNBV

(

U.S. GOVERNMENT PRINTING OFFICE

WASHINGTON: 1974

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

(Order by SD Catalog No. C13.29/2:48.) Price $4.85 (cloth cover)

Stock Number 0303-01212
PREFACE

Earthquakes and windstorms are responsible for great loss of life

and property throughout the world. In the period 1926-1972, for example,

earthquakes alone caused almost one million deaths, as well as damages ^.

to buildings and public works totaling an estimated fifteen billion dollars— , Windstorms may be even more destructive than earthquakes. For example,

a typhoon-generated flood killed an estimated half million people in

East Pakistan in 1970.

Improved design, siting and construction procedures can contribute

significantly to the reduction of such losses. In developing countries,

however, cultural patterns, severe socio-economic constraints, and inadequate

technical expertise make the adoption and implementation of such procedures

particularly difficult and are thus an indirect cause of continued losses

on a massive scale.

In recognition of the need for achieving low cost housing and community

buildings with better resistance to earthquake and windstorms, the Agency

for International Development (AID) requested the National Bureau of

Standards (NBS) to conduct a study on the potentials of applying housing

technology to mitigate earthquake and windstorm disasters in developing

countries and on relevant socio-economic and cultural constraints.

The AID Office of Science and Technology of the Technical Assistance

Bureau monitored the project for AID. The Institute for Applied Technology,

Center for Building Technology, NBS, was responsible for conducting

the study. An interagency steering committee served as an advisory group

to the NBS in the execution of the project.

The specified goals of the project were as follows:

- Examine existing knowledge relevant to the design, siting

and construction of earthquake and windstorm resistant

buildings, including recent American technological innovations

applicable within the framework of socio-economic and cultural

requirements in developing countries.

- Suggest promising technological innovations applicable within

this context.

- Evaluate the potential of these innovations through consultations and on-site "case study" investigations in Peru, Turkey

and the Philippines.

- Identify technical and socio-economic constraints concerning

construction in earthquake and windstorm areas of developing

countries

- Describe alternative approaches to overcome technological

and socio-economic barriers against more effective building

practices in each of the selected countries.

In order to assess the current state of the art as it relates to

low-cost housing technology and to define typical socio-economic constraints

in developing countries, field trips were made to Peru, Turkey and the

Philippines, countries that suffer frequent devastation from natural

disasters such as earthquakes and typhoons.

"Report on Seismology and Earthquake Engineering," Department of Advancement

of Science, UNESCO (United Nations Education, Scientific and Cultural

Organization), Paris, 196S. . . Ill
CONTRIBUTORS

Ing. Dante E. Brambilla Picasso

Consultant § Geologist

Porta 370

Miraflores, Lima 18, Peru

Mrs. Tarja Cronberg

Research Worker

M.S.C. Lund Institute of

Technology

Lund, Sweden

Ing. Juan la Cruz L. Chief Geologist

Commission for Reconstruction and

Rehabilitation of the Zone Affected

by the Earthquake of May 31, 1970

c/o Dante E. Brambilla Picasso

Porta 370

Miraflores, Lima 18, Peru

Dr. George E. Ericksen

Chief, Branch of Latin American and

African Geology

United States Geological Survey

800 18th Street N.W.

Washington, D. C. 20244

Dr. S. George Fattal

Structural Research Engineer

Center for Building Technology, lAT

National Bureau of Standards

Washington, D. C. 20234

Dr. Arthur Grantz

Geologist

Branch of Alaskan Geology

United States Geological Survey

Menlo Park, California 94025

Dr. George Plafker

Geologist

Branch of Alaskan Geology

United States Geological Survey

Menlo Park, California 94025

Mr. Thomas W. Reichard

Physicist

Center for Building Technology, lAT

National Bureau of Standards

Washington, D. C. 20234

Mr. William Reps

Civil Engineer

Center for Building Technology, lAT

National Bureau of Standards

Washington, D. C. 20234

Dr. Emil Simiu

Postdoctoral Research Associate

Center for Building Technology, lAT

National Bureau of Standards

Washington, D. C. 20234

Sycip, Gorres, Velayo 5 Co.

Management Services Division

P. 0. Box 589

Manila, Philippines

Ing. Enrique Tola M.

Consultant § Civil Engineer

c/o Dante E. Brambilla Picasso

Porta 370

Miraflores, Lima 18, Peru

Turkish National Committee for

Earthquake Engineering

c/o Professor Rifat Yarar

Technical University

Istanbul, Turkey

iv
ACKNOWLEDGMENTS

Many contributors and reporters have graciously given of their time

and knowledge during these field investigations. A number of organizations

in Peru, Turkey and the Philippines provided timely and appropriate information

for the special requirements of the socio-economic study for each country.

A Project Steering Committee comprised of representatives from the

National Bureau of Standards, Department of Housing and Urban Development,

United States Geological Survey, and Agency for International Development

provided valuable assistance and guidance in the overall investigation.

The following individuals and organizations (listed alphabetically)

collaborated in various phases of the work that has led to the successful

completion of this project:

Project Steering Committee (1971-1972)

1. Mr. Thomas R. Callaway - Director , .division of Technology

and Documentation, Office of International Affairs, Department of Housing and Urban Development.

2. Dr. George E. Ericksen - Chief, Branch of Latin American

and African Geology, U.S. Geological Survey, Department of

the Interior.

3. Mr. William H. Littlewood - Associate Director, Office of

Science and Technology, Technical Assistance Bureau, Agency

for International Development, Department of State.

4. Dr. Richard D. Marshall - Structural Research Engineer,

Center for Building Technology, Institute of Applied

Technology, National Bureau of Standards.

5. Dr. E. 0. Pfrang - Manager, Office of Housing Technology,

Center for Building Technology, Institute of Applied

Technology, National Bureau of Standards,

6. Dr. Norman F. Somes - Chief, Structures Section,

Center for Building Technology, Institute for Applied

Technology, National Bureau of Standards.

7. Mr. John H. Street - Deputy Disaster Relief Co-ordinator

Agency for International Development, Department of State.

8. Mr. William N. Womelsdorf - Consulting Architect, Federal

Housing Administration, Department of Housing and Urban

Development

9. Dr. Richard N. Wright - Deputy Director (Technical), Center

for Building Technology, Institute for Applied Technology,

National Bureau of Standards.

V
Peru

1. Ing. Edilberto Alarcon - Civil Engineer, US Agency for

International Development Mission, Lima.

2. Arq. Francisco Hoyos Jiminez - Inter-American Development

Bank, Lima.

3. Mr. Peter Land - Director, Experimental Housing Project,

United Nations Development Program, Lima.

4. Mr. Guido Nadzo - Housing and Urban Development Advisor,

US Agency for International Development Mission, Lima.

5. Ing. Carlos Rodriquez Cavero - Inspector General, Ministry

of Housing, Lima.

6. Dr. Ricardo Yamishiro - Head, Structural Department,

National University of Engineering, Lima.

Turkey

1. Mr. Nedret Akbas - Architect, General Directorate of Natural

Disaster, Ministry of Reconstruction and Resettlement, Ankara.

2. Mr. Koeksal Anadol - The Building Center, Istanbul.

3. Mr. Ersin Arioglu - The Building Center, Istanbul.

4. Mr. Alkut Aytun - Director, Earthquake Research Institute,

Ministry of Reconstruction and Resettlement, Ankara.

5. Miss Marjorie S. Belcher, Assistant Director for Technical

Assistance, US Agency for International Development Mission,

Ankara

6. Dr. Harry Buchberg - Professor, School of Engineering and

Applied Science, University of California Los Angeles;

currently Fulbright Professor, Department of Mechanical

Engineering, Bebek, Istanbul.

7. Dr. Erhan Karaesman - Professor, Department of Civil

Engineering, Middle East Technical University, Ankara.

8. Dr. Muzaffer Ipek - Professor, Institute of Computer

Sciences, Istanbul Technical University, Istanbul.

9. Mr. Joseph B. Robinson, Economic Coordinator for CENTO,

Ankara

10. Professor Dr. Semih Tezcan - Department of Civil Engineering,

Bosphorous , University, Bebek, Istanbul.

11. Mr. Erol Tuncer - General Director of Natural Disaster

Affairs, Ministry of Reconstruction and Resettlement, Ankara.

12. Dr. Safak Uzsoy - Head, Computer Science Department, Middle

East Technical University, Ankara.

vi
13. Professor Dr. Rifat Yara - Chairman of the Civil Engineering

School, Istanbul Technical University, Istanbul.

14. Dr. Vedat Yerlici - Dean, School of Engineering, Bosphorous

University, Bebek, Istanbul.

The Philippines

1. Dean Cesar Concio - Architect, Makati, Rizal.

2. Dr. Roman L. Kintanar - Director, Philippine Weather

Bureau, Quezon City.

3. Mr. William Larson - Assistant Director for Industrial

Development, US Agency for International Development Mission,

Manila.

4. Mr. Rosalio A. Mallonga - Chief Structural Engineer, Bureau

of Public Works, Manila.

5. Mr. Roberto V. Ongpin - Managing Partner, Sycip , Gorres

Velayo § Company, Makati, Rizal.

6. Miss Josefina M. Ramos - Assistant, Senate Technical Staff

on Housing, Urban Development and Resettlement Congress,

Manila

7. Dr. Ernesto G. Tabujara - DCCD Engineering Corporation,

Makati, Rizal.

International

1. Dr. N. N. Ambraseys - Head of the Engineering Seismology

Section Department of Civil Engineering, Imperial College,

London, England.

2. Mr. R. G. Gokhale - Director, National Buildings Organization, Government of India, New Delhi.

3. Mr. A. A. Moinfar - Director, Technical Research Bureau,

The Plan Organization, Tehran, Iran.

4. Dr. Engineer Khosrow Pakdaman - Deputy Minister, Ministry

of Development and Housing, Tehran, Iran.

5. Professor Dr. Hubert N. Rusch - Chairman-Emeritus, Civil

Engineering Department, University of Munich, Munich,

Federal Republic of Germany.

Department of Housing and Urban Development

Mr. John G. Colby - Chief, Technical Assistance Branch, Division

of Technology and Documentation, Office of International Affairs.

vii
SUMMARY

The extensive loss of life and property caused by earthquakes and

windstorms in developing countries may be reduced to a considerable degree

by the use of improved design, siting and construction procedures. In

attempting to establish and implement such procedures, the technical

constraints which govern earthquake and windstorm resistant construction,

as well as the severe cultural and socio-economic constraints which prevail

in developing countries, must be taken into account. The purpose of

this report is to identify such constraints, to study the potentials

of housing and building technology for mitigating earthquake and windstorm

disasters in developing countries, and to propose practical solutions

toward achieving this end.

To provide the background required for assessing structural systems

and materials used in earthquake and windstorm resistant construction,

the structural characteristics of buildings and building materials are discussed. The structural performance of buildings under earthquake

and windstorm conditions is then described, and the factors responsible

for the occurrence of structural damage or collapse are identified and

explained in detail. Specific reference is made to actual structures

typical of developing countries. Suggestions for improvements to mitigate

earthquake and windstorm effects on buildings are classified according

to whether the cause of the destruction is related to the structural

configuration or aerodynamic features of the building, or to its foundations,

walls, frames, upper floors or roofs. It is shown by means of illustrative

examples that considerable improvement of the earthquake or winrlstorm

resistance of structures widely used in developing countries may be achieved by

relatively simple measures. These include, for example, horizontal

bracing of certain types of roofs over adobe masonry houses, rational

distribution of openings in shear walls, provision of adequate walls

or frames to withstand concentrated seismic load action, reinforcement

of critical areas susceptible to being over-stressed, and strengthening

of connections at critical joints. It is also pointed out that in order

to achieve safe and rational typhoon resistant construction in such

areas as the Philippines, special studies on the distribution of extreme

wind speeds and on the aerodynamics of full-scale buildings and of reduced

scale models are required.

A review of siting considerations to reduce the effects of earthquakes

and windstorms is presented, with specific application to Turkey and

Peru. Recommendations related to siting in earthquake and windstorm

zones include: development and improvement of seismic, tsunami and extreme

wind risk maps; preparation of geologic site plans and site evaluations

to be used in both short- and long-range community planning; preparation

from the former of microzoning maps to be used by engineers responsible

for construction; and siting of new structures at reasonably safe locations,

in accordance with indications furnished by geologic maps and studies.

For example, depending upon the risk category to which they belong, new

structures should not be located within 50-200 m* from main faults or branches

Traditional and industrialized methods of housing construction are described in an attempt to provide information on existing construction

technology capabilities in developing countries. The possibility of

upgrading these methods is discussed with reference to specific cases,

for which suggestions are made aiming at improved structural behavior

under earthquake and windstorm conditions.

The role of building codes and regulations in preventing the design

and construction of unsafe structures is also discussed. It is pointed

out that most of the countries affected by earthquakes do not have building

* See Conversion Table on Page 132.

viii
code provisions for aseismic design or construction. In the countries

in which building codes exist, the code provisions are in many cases inadequate. In Iran, for example, it appears that the disastrous consequences

of the Pars earthquake are attributable in a large measure to the use of an inadequate building code. In the Philippines, more stringent provisions

on items associated with typhoon- caused damage (such as anchorages of

roof trusses, purlins, roofing materials) are required. Deficiencies

are also noted in the Peruvian and Turkish codes. Among these is the

absence of provisions regarding local types of structures. The promulgation

of codes applicable to specific types of non-engineered structures would

significantly contribute to achieving better resistant structures built

in accordance with local needs and capabilities.

Code enforcement is in many cases unsatisfactory, mostly because

qualified personnel are not available. It is suggested that local creditgranting institutions be responsible for inspecting the building construction

they finance and make loans conditional upon compliance with building

codes. The enforcement of provisions applicable to local non-engineered

construction could be entrusted to properly trained inspectors with limited

formal education. Finally, it is stated that building codes should not

inhibit technological innovation.

Social and economic factors affecting housing construction in developing

countries include: shortage of funds, heavy migration of rural population

to urban centers, population growth, markets of insufficient size to

insure economies of scale in prefabricated construction, insufficiently

developed transportation and distribution systems, shortage of skilled

labor, generally low standards of workmanship. An additional negative

factor is users' resistance to certain construction materials and systems.

Such resistance can in many cases be overcome. For example, user acceptance

of adobe blocks (which are still considered in Peru and Turkey less

"noble" than bricks) will be considerably improved by the quite satisfactory

appearance of adobe upgraded through stabilization and improved manufacturing

techniques

Feasible technical improvements include the upgrading of materials

such as, for example, adobe or bamboo. Stabilized adobe can be produced

in vast quantities at low prices, and exhibits superior structural, architectural, thermal and acoustical properties. Deterioration of bamboo can

be prevented by chemical preservatives which can be manufactured in developing

countries. Building techniques that can be improved include masonry

construction which, if properly designed (particularly with reinforcement),

exhibits superior aseismic properties, and to which a considerable body

of knowledge, available particularly on the West Coast of the United

States, may be successfully adapted; building prefabrication to which

techniques used in various European countries or in the United States

may be applied; production of industrialized dwellings such as the CARE,

Inc. units developed in Bangladesh.

New construction materials such as jute fiber, reinforced concrete

with vegetable or plastic reinforcement, stabilized adobe, and lightweight structural sandwich systems which are now being utilized in the

United States, could be employed for low-cost housing in developing countries.

Improved production methods and equipment could result in lowered costs

and better quality of these new materials. National research institutions

can play a significant role in developing technical improvements.

To stimulate such improvements, institutional action at various

levels is required. Operations related to housing construction of various

institutions, governmental, international, and to a limited extent, private,

are described in this context. Effective communication and transfer

ix
o£ technology can be achieved within the process of interaction between

experts of both the assisting agencies and the developing countries involved

in specific cooperation programs. An important role is also played by

training, educational and fellowship programs and by seminars. Building

information centers serving professionals as well as laymen building

their own houses can provide information on material selection, and technical

guidance and advice on building know-how. Production units serving as models or pilot plants can contribute to the diffusion of advanced technological

methods. Prototype buildings can be built for the purpose of acquainting

the public with innovative systems designed to provide better resistance

to earthquakes and windstorms.

A considerable potential for technical improvements leading to structures

better resistant to earthquakes and windstorms exists. Decisions as to which areas should be accorded priority depend on the specific needs

of the developing countries involved.
CONTENTS

Page

Preface iii

Contributors iv

Acknowledgments v Summary viii

1. Introduction 1

2. General Structural Characteristics of Buildings and

Building Materials 3

2.1 Introduction 3

2 . 2 Structural Types 3 2.2.1 Bearing Wall Buildings 3

2.2.2 Frame Buildings 3 2.2.3 Shell and Membrane Buildings 5

2.3 Structural Elements 5 2.3.1 Foundations 5

2.3.2 Frame Elements 5 2.3.3 Walls 6

2.3.4 Roofs and Upper Floors 6

2 . 4 Materials and Their Mechanical Properties y 2.4.1 Concrete • • 7

2.4.2 Masonry 7

2.4.3 Soil 8

2.4.4 Wood 9 2.4.5 Metals 10

2.4.6 Plastics 10

References 12

3. Structural Performance of Low-Cost Housing and Community

Buildings Under Earthquake Conditions 13

3.1 Nature of Earthquakes 13

xi
3.2 Seismic Effects on Buildings

3.2.1 Influence of Structural Configuration, 13

3.2.2 Foundations 15

3.2.3 Walls, Frames and Shells 15

3.2.4 Roofs and Upper Floors 22

3.3 Building Improvements to Mitigate Earthquake Effects 22

3.3.1 Structural Configuration 22

3.3.2 Foundations 24

3.3.3 Walls, Frames and Sheila 25

3.3.4 Roofs and Upper Floors 25

3.4 Needed Research 26

References 26

4. Structural Performance of Low-Cost Housing and Community

Buildings Under Windstorm Conditions 28

4.1 Characteristics of Windstorms 28

4.2 Effects of Windstorms on Buildings 29

4.2.1 Influence of Building Shape on Magnitude of

Wind Loading 29

4.2.2 Foundations 29

4.2.3 Walls, Frames and Shells 29

4.2.4 Roofs and Upper Floors 31

4.3 Building Improvements to Mitigate Windstorm Effects 33

4.3.1 Aerodynamic and Structural Considerations 33

4.3.2 Foundations 33

4.3.3 Walls, Frames and Shells 33

4.3.4 Roofs and Upper Floors 36

4.4 Needed Research 36

References 36

5. Siting Considerations to Reduce the Effects of Earthquakes

and Windstorms 38

5.1 Introduction 38

5.2 Earthquake Hazards , 39

xii
5.3 Windstorm Hazards 40

5.4 Siting Considerations for Low-Cost Housing in Turkey 40

5.4.1 Geologic and Seismic Setting 40

5.4.2 Seismic Zones of Turkey 41

5.4.3 Seismic and Related Hazards to Low-Cost Housing

in Turkey 44

5.4.4 Ground Failures 46

5.4.4.1 Landslides 46

5.4.4.2 Unconsolidated Deposits 47

5.4.5 Floods 48

5.4.6 Recommended Site Investigations for EarthquakeResistant Low-Cost Housing in Turkey 48

5.4.7 Methods of Guiding and Controlling Site Selection

and Preparation 48

5.4.8 Proposed Site Investigations 49

5.4.8.1 Planning-Stage Investigations 50

5.4.8.2 Site-Intensive Investigations 50

5.4.8.3 Scope of Investigations 51

5.4.8.4 Single -Family and Small Multifamily Houses. . 51

5.4.8.5 Multifamily Houses 52

5.4.8.6 Improvement of Existing Houses 52

5.4.9 Technical Supervision 52

5.5 Case Study: Engineering Geology and Siting Problems

Related to the Peru Earthquake of 1970 52

5.5.1 Introduction S2

5.5.2 Geologic Environment 54

5.5.3 Regional Siting Problems 55

5.5.4 Behavior of Unconsolidated Sediments in Flat-Lying

Areas 57

5.5.5 Landslides, Rockfalls and Soil Slips 63

5.5.6 Debris Avalanches 67

xiii
5.5.7 Conclusions 71

5.5.8 Recommendations 72

5.6 Summary of Recommendations 73

References 73

6. Methods of Housing Construction. 75

6.1 Introduction 75

6.2 Traditional Construction Methods 75

6 . 3 Industrialized Construction Methods • • 7

6.3.1 Labor-intensive Industrialization 7fe

6.3.2 Prefabricated Housing in Turkey 79

6.3.3 Prefabricated Housing in Philippines 83

6.3.4 Prefabricated Housing in Peru 8 3

7. Building Codes and Regulations 89

7.1 Introduction , 89

7 . 2 Difficulties Encountered in the Promulgation and

Enforcement of Codes and Regulations

7 . 3 Building Codes. Local Conditions, and Innovative

Technology 90

7.4 Building Codes in Peru 90

7.5 Building Codes in the Philippines 91

7.6 Building Codes in Turkey 91

References 93

8. Social Factors Which Influence the Advancement of Housing . . .

TgchTlolOgy 94

8 . 2 Social Framework in Low-Cost Housing. 94

8.2.1 Population Growth and Family Planning 94

8.2.2 Urban Growth 95

8.2.3 Slums § Squatter Settlements 95

8.2.4 The Role of Social Workers 96

8.3 User Requirements on Basic Housing

.

96

8.3.1 Outline of Requirements 96

xiv
8.3.1.1 Sources of Information 96

8.3.1.2 Type of Information Needed 97

8.3.2 Case Study: User Requirements for Basic

Housing in Peru 98

8.3.2.1 User Characteristics in Peru 98

8.3.2.2 User Activities in Peru 100

8.3.3 Summary and Recommendations 105

8.4 Acceptance of Innovative Designs and of New Materials .... io7

References HO

9 . Economic Factors Which Influence the Advancement of

Housing Technology . 112

9.1 Introduction . . 112

9.2 Housing Programs in Developing Countries . . 112

9 . 3 Economic Factors Directly Affecting Housing

Construction 113

9.3.1 Land Use 113

9.3.2 Availability and Cost of Labor and Construction

Materials 114

9.3.3 Credit Mechanisms for Housing 115

References

^^"^

10. Feasible Technical Improvements 118

10.1 Introduction 118

10.2 Stabilized-Soil Building Blocks 118

10.2.1 Oil-Stabilized Adobe Blocks 118

10.2.2 Polymer-Stabilized Adobe Blocks . . . . , 119

10.2.3 Lateritic Stabilization 119

10.3 Bamboo-Reinforced Concrete 119

10.4 Composite Systems 120

10.4.1 Structural Sandwich Panels 120

10.4.1.1 Characteristics and Uses of

Structural Sandwich Panels 120

XV
-* 10.4.1.2 Performance o£ Structural

Sandwich Panels 120

10.4.1.3 Materials Used in Structural

Sandwich Panels 121

10.5 Prefabricated Housing 122

References 123

11. Mechanisms for Stimulating Technical Improvements 124

11.1 Introduction 124

11.2 The Inter-American Development Bank 124

11.3 The World Bank 124

11.4 United Nations 125

11.4.1 U.N. Center for Housing, Building and Planning . . . 125

11.4.2 U.N. Industrial Development Organization (UNIDO) . . 125

11.4.3 U.N. Development Program 127

11.5 CARE, Incorporated 128

11.6 National Institutions 129

11.6.1 Peru 129

11.6.2 Turkey 129

11.6.3 The Philippines 130

11.6.4 Iran 130

Re ference 131

Conversion Units 132

xvi
LIST OF FIGURES

FIGURE PAGE

2.1 Illustration o£ force transfer mechanism 4

2.2 Illustration of bending under the effect of horizontal

loads 4 2.3 Examples of shell structures 4 3.1 Effects of ground motion on structures 14

3.2 Damages sustained by residential units at Chimbote, Peru 16

3.3 Field stone masonry house set in mud mortar, Turkey 17

3.4 Stone dwelling with wood ties near Bingol, Turkey 18

3.5 Corner failure of a two-story adobe wall with wood

tie-beams (Peru) 19

3.6 Town of Qir (Iran) after the 1972 earthquake 20

3.7 Collapsed two-story adobe building, Burdur, Turkey 21

3.8 Collapse of a dwelling in Casma, Peru during 1970

earthquake 23

4.1 Wind pressure on buildings 30

4.2 Bending stresses 31

4.3 In-plane stresses 31

4.4 "Marcos" school destroyed by Typhoon Sening (Joan),

October, 1970, the Philippines 32

4.5 Wind damage to roof overhangs 32

4.6 A church at Catanduanes, the Philippines, stripped

of its roof by Typhoon Sening (Joan) , October 1970 34

4.7 Roofing blown off by typhoon winds, the Philippines,

October 1970 34

4.8 Destroyed homes and institutional building in the

Bicol Region, the Philippines, October 1970 35

4.9 The Catanduanes school levelled to ground by Typhoon

Sening (Joan) 35

5.1 Seismic zones of Turkey 42

5.2 Region of northern Peru affected by the May 31, 1970

earthquake 53

5.3 Residential street in Casma, Peru, where all adobe-block

houses collapsed during the earthquake of May 31, 1970 56

5.4 Destruction of new home of unreinforced brick construction

in the Buenos Aires suburb of Chimbote, Peru 58

xvii

527-373 O - 74 - 2
5.5 Compaction of foundation material and destruction of

adobe, brick, and concrete block houses in low- lying area near the coast in southern Chimbote 59

5.6 Street in downtown Chimbote with cracking of concrete

sidewalks 60

5.7 Subsidence of roadway fill at side of steel plant

dock in northwestern Chimbote 61

5.8 Concrete block house at the Corporacion Peruana del

Santa housing development 62

5.9 Typical street scene in a 100-block area of central

Huaraz 64

5.10 Map showing distribution of landslides triggered by the

earthquake of May 31, 1970 65

5.11 Surficial slips in thin grass -covered soil and slope

debris on east side of Cordillera Blanca 66

5.12 Rotational slide in glacial outwash and underlying

thin-bedded sedimentary rocks at Recuay 68

5.13 Oblique aerial view of Nevados Huascaran and the

Huascaran debris avalanche that destroyed Yungay 69

5.14 Sketch map and profile of the Huascaran debris avalanche 70

6.1 Earthquake damage to a two-story adobe-filled timberframed structure in Turkey 77

6.2 Earthquake damage to a traditional Turkish adobe building 78

6.3 Earthquake damage to a precast light-weight reinforced

concrete panel building in Turkey 80

6.4 Timber-panel prefabricated house in Turkey 81

6.5 Unicreto precast concrete buildings in Chimbote, Peru 85

6.6 Plastic prototype house of CARE, Inc., Bangladesh 87

6.7 Construction of the CARE, Inc., dwelling 88

8.1 Polyurethane "igloo" homes at Caraz, Peru 109

xviii
DESIGN, SITING AND CONSTRUCTION OF LOW-COST HOUSING AND COMMUNITY

BUILDINGS TO BETTER WITHSTAND EARTHQUAKES AND WINDSTORMS

Edited byWilliam F. Reps and Emil Simiu

The extensive loss of life and property caused in developing

countries by earthquakes and windstorms (hurricanes , typhoons

and tropical cyclones) may be reduced to a considerable

degree by the adoption and implementation of improved design,

siting and construction procedures practicable within the

context of the cultural and socio-economic constraints prevailing

in these countries.

The report provides technical information regarding

characteristics of materials and building systems, and discusses

the structural performance of buildings subjected to the

action of earthquakes and wind forces with specific reference

to structures typical of developing countries. Potential

ways are described in which structures can be made more resistant to such action. Siting considerations are discussed

from a geological, seismic and climatological viewpoint,

and recommendations relating to siting problems are made.

Techniques of housing construction, both traditional and

industrialized, are described and improvements resulting

in better earthquake or windstorm resistance are suggested.

Building codes, their improvement and their enforcement

are also discussed.

The report discusses cultural and socio-economic constraints

influencing the adoption of improved practices, describes

various feasible technical improvements of construction

materials, composite systems and building systems, identifies

mechanisms for stimulating technical improvements and discusses

the role of institutions in this regard. Throughout the

report, specific references are made to Peru, the Philippines

and Turkey, countries which suffer from frequent devastation

from natural disasters such as earthquakes and typhoons

and which were selected as case studies for the purpose

of this report.

Key words: Buildings; construction; design; developing countries;

earthquakes; low-cost housing; natural disasters; structures;

windstorms

Chapter 1. Introduction

William F. Reps

National Bureau of Standards

The extensive loss of life and property caused in developing countries;

by earthquakes and windstorms (hurricanes, typhoons and tropical cyclones)

may be reduced to a considerable degree by the adoption and implementation

1
of improved design, siting and construction procedures practicable within

the context of the cultural and socio-economic constraints prevailing

in these countries.

As a first step toward establishing and implementing such procedures,

it is necessary that the relevant technical, cultural and socio-economic

constraints be identified and that solutions compatible with these constraints

be proposed. This report examines the technical problems related to

the destruction of structures in developing countries under the action

of earthquakes and windstorms. It describes potential ways in which

structures can be made more resistant to such action, either by upgrading

local materials and procedures or by transferring and adapting, in a practical and effective manner, technology from developed countries.

Cultural and socio-economic constraints influencing the adoption and

implementation of improved practices are identified and discussed.

Technical information regarding general characteristics of buildings,

building materials and structural performance of buildings subjected

to earthquakes and wind forces is provided in Chapters 2, 3, and 4.

The importance of siting considerations from the geological, seismic

and climatological viewpoint is outlined in Chapter 5. Chapters 6 and

7 review methods of housing construction, building codes and regulations.

Chapters 8 and 9 summarize the major social and economic factors that

influence the advancement of housing technology in developing countries.

These chapters drew extensively from the consultants' reports. Chapter

10 presents feasible technical improvements in construction materials,

composite systems, and building systems. Chapter 11 describes mechanisms

for stimulating technical improvements and the role of institutions

in this regard.

2
Chapter 2. General Structural Characteristics

of Buildings and Building Materials

S. G. Fattal

National BureaXi of Standards*

2.1 Introduction

This chapter provides background information for the discussions

in Chapters 3 and 4 regarding structural performance of buildings subjected

to wind and earthquakes. In Section 2.2 buildings are described according

to structural type and the manner with which they transfer lateral and

gravity forces. Section 2.3 describes and classifies building elements

according to shape and composition whereas construction materials and

their mechanical properties are discussed in section 2.4. Special attention

is given to types of construction and materials identified with lowcost housing development.

2.2 Structural Types

2.2.1 Bearing Wall Buildings

In buildings of bearing wall construction, the walls are designed

to transmit gravity and lateral loads to the foundation by functioning

as structural elements in compression, shear, tension, and bending.

Gravity forces consist of the dead load of the structure and vertical

live loads from human occupancy, furnishings, snow, ice, or other transient

loads. Vertical forces are also induced by wind suction, uplift and

direct pressure on the roof (see Chapter 4) , and by vertical movements

of the ground in an earthquake (see Chapter 3) . Lateral forces are produced by winds, floods, tidal waves, debris loading and horizontal

earthquake movements of the ground.

Figure 2.1 offers a simple illustration of the force transfer mechanism.

Vertical loads from the roof assembly produce the compressive forces

shown acting on the walls below. Resistance to lateral forces is provided

primarily by walls of the same orientation. For instance, in the figure,

shearing resistance of walls A and C is mobilized against horizontal

forces indicated by solid arrows. Similarly, walls B and D are mobilized

against transverse forces indicated by the broken arrows. In addition,

walls provide direct tensile resistance against overturning or uplift

forces and bending resistance against out-of-plane normal loads induced

by lateral forces.

2.2.2 Frame Buildings

The main identifying feature of a framed building is the presence

of a substantially complete vertical load-carrying frame consisting

of beam and column elements. Where the frame is also called upon to

participate in resisting lateral forces, the design usually provides

for bracing or for rigid connections so that the rotations at any joint

are collectively resisted by the interconnected framing elements in

proportion to their bending stiffnesses. For example, in the singlecell space frame of Figure 2.2, beams A to D are rigidly attached to

columns E to H at the top four joints. The deformed shape of the frame

under the simultaneous action of vertical and lateral loads is shown

exaggerated by the broken lines for the sake of clarity. Resistance

n—

Complete addresses for all contributors to this report are given on page iv.

3
4
to lateral forces is primarily contributed by bending and shearing of

columns and bending of beams. In addition, beams provide bending and

shear resistance against vertical loads transmitted from the roof through

floor joists and other attachments, with columns offering resistance

against axial loads and any bending moments induced by continuity of

joints

Walls of frame buildings are generally constructed for the non- structural purpose of providing enclosure. However, when they are attached to, or built integrally with the rest of the structure, as in the case of infilled frames, most of the lateral forces are carried

by the walls in shear since their in-plane stiffness is significantly

larger than the combined lateral stiffness of the frame columns.

2.2.3 Shell and Membrane Buildings

Shell type buildings consist primarily of single or double curvature

elements as illustrated in Figure 2.3. The dome shape in (a) provides

continuity of roof and wall. The truncated dome in (d) consists of

a flat roof bearing on walls of double curvature (i.e., vertical and

horizontal). The structure in (b) uses a cylindrical roof with flat

vertical walls and (c) depicts a "silo" shaped structure with flat roof

bearing on cylindrical wall enclosure.

The shell is a highly efficient structural form deriving its ability

to withstand loads from curvature which, when properly exploited by

the designer, gives it the ability to transmit loads through membrane

action (i.e., in-plane compression, shear and tension) with a minimal

amount of bending.

2 . 3 Structural Elements

2.3.1 Foundations

Building foundations are designed to transmit superstructure loads

to the ground below. The type of design is dictated by the bearing

capacity of ground material, intensity of loads to be transmitted and

allowable levels of tolerance to settlements. These factors become

less critical for low-rise dwellings of one to two stories than in highrise buildings. Certain foundation types, such as piles, are seldom

utilized for small buildings except in frequently flooded areas where

houses may be built on bamboo stilts driven into the ground to a length

sufficient to develop the required load capacity by friction with the

surrounding soil. Where flooding is not a major factor, rectangular

footings of plain or reinforced concrete or gravel with soil-cement

mortar are quite commonly utilized. Wall footings are usually laid

under the entire length of the wall with widths varying from tiNrice the

wall thickness for load-bearing walls to slightly larger than the wall

thickness for nonload-bearing walls and partitions. Depths of footings

commonly vary between 30 to 60 cm. For small dwellings rectangular

spread footings, similar to wall footings in composition, are used to

support individual column loads of frame buildings on rocks or highquality compact soil. Combined footings or mat foundations are used

with less favorable soil conditions.

2.3.2 Frame Elements (Figure 2.2)

A frame is an assembly of beam, column, and bracing elements of

small sectional dimensions relative to length. The structural behavior

of each element identifies it from the other types.

5
A beam transmits vertical loads horizontally to coluinns and walls

through the combined mechanism of shear and bending. Shearing may

be visualized as the tendency of two surfaces, formed by the splitting

of a section, to slide across one another in opposite directions. The

mechanism is actuated by opposite internal forces developed in the plane

of a section. Bending produces curvature in an element causing compression

at the concave side and tension at the convex side. For this reason,

beams made of materials of low tensile strength, such as concrete, require

reinforcing bars near tensile regions for effective action against bending.

Beam cross sections of reinforced concrete or wood construction are usually rectangular whereas the I -shape is the more common shape of

steel beams.

Columns transmit vertical loads and beam reactions to the foundation.

Their structural effectiveness is in compression although in most instances

they are also designed to transmit bending induced by continuity of

joints or eccentricities of axial loads. Square, circular, rectangular

or I-shaped sectional profiles are quite common. Columns are made

chiefly of reinforced concrete, masonry, wood, or metal.

Bracing elements in frames inhibit lateral deflections and provide

resistance against horizontal forces. A common application is the diagonal

cross bracing in which the tensile resistance of bracing elements is mobilized

against the lateral forces. Bracing is also used to increase the resistance

of columns against lateral buckling. Materials strong in tension are well

suited for bracing. Steel, wire, wood, bamboo or even rope are typical examples.

2.3.3 Walls

Structurally, a bearing wall is the counterpart of a column in

that both are designed to support primarily vertical loads in compression.

In addition, bearing walls develop substantial shear forces from lateral

loads which also produce some bending in these elements.

The assembly of a filler wall with a confining frame around it,

is known as an infilled frame. Under lateral loads, such as seismic

or wind loads, filler walls alter the basic behavior of the frame by

inhibiting lateral deflections and absorbing most of the shear. Axial

loads in filler walls are nominal.

The main function of nonstructural walls such as parapets and interior

partitions is to provide enclosure in buildings. Therefore, the contribution

of these walls to the overall structural resistance should be minimal.

Structural walls of wood, concrete, burnt clay or soil-cement composition

are quite common in low-cost housing construction. The walls may be

monolithic or of masonry type construction where staggered courses of

basic units are laid in beds of mortar. Clay brick and tile, adobe

brick and concrete block are conventional masonry units. Masonry mortar

of a desired consistency and strength is prepared by using certain proportions

of cement-lime-sand or soil-cement mixtures.

2.3.4 Roofs and Upper Floors

Floors above the ground level are designed to develop sufficient

capacity in shear and bending to transmit direct gravity loads to floor

joists, frame elements or bearing walls below. They also function as diaphragms distributing lateral forces to supporting elements. Typical

examples of floor systems are reinforced concrete slabs supported by

joists or at the edges of the building, and joist-supported wood floors.

6
Diverse types of materials and shapes are utilized in roof construction.

Pitched roofs are often attached to a wood supporting frame or a truss.

Flat roofs are similar to floor slabs in structural behavior although

the nature of loads is somewhat different mainly due to the presence

of suction and uplift forces. A traditional type of roof construction

used in Peru consists of wood joists or logs spanning across opposite

walls, overlain first by bamboo, straw or asphalt-impregnated burlap,

and then adobe

2 . 4 Materials and Their Mechanical Properties

2.4.1 Concrete

At the construction site, concrete is placed in preassembled wood

forms which are removed after setting. Near full strength is usually

attained in about a month. Standard cylinder control specimens may

be taken from different batches during construction for testing to determine

the compressive strength of the concrete used. This practice is desirable

in view of the dependence of concrete compressive strength upon the

proportioning and quality of its ingredients, rate of curing and many _ other factors. Compressive strengths ranging from 1,400 to 3,500 N*/cm

are typical.

Concrete is weak in tension and therefore, seldom used without

reinforcement. The use of steel, fiberglass, bamboo and other materials

capable of withstanding tension for reinforcement, coupled with properties

such as durability, fire resistance and suitability for molding into

different shapes, makes concrete a most versatile construction material.

Ferrocement is a material consisting of concrete reinforced with

wire mesh. Ferrocement construction can be successfully achieved with

local labor under minimal supervision. The materials needed are cheap

and readily available in developing countries. Its earthquake- and

wind-resistant properties, if used for such elements as slabs or silos,

are very good [l].i'

2.4.2 Masonry

The compressive strength of masonry with a specified type of mortar

is equal to the test strength of a standard size prism of the same composition

modified by a factor. Alternately, the strength is sometimes expressed

as a fraction of the strength of its unit for a specified type of mortar.

The ranges of compressive strengths of brick and concrete block masonry

used in construction are as follows:

(N/cm^) (N/cm^)

Compressive Strength Compressive Strength

Type of Masonry Units of Masonry

Brick 1,400-10,000 400-3,200

Block (Concrete) 350-2,000 100-6,500

Because of its low tensile strength, in the order of 5% or less of its

compressive strength, masonry requires the use of reinforcement to develop

N = 1 Newton = 1/9.81 kg.

Figures in brackets indicate figure references at end of each chapter.

7
any structurally significant bending resistance in the absence of axial

compression

2.4.3 Soil

In many parts of the world, particularly in developing countries,

natural earth is probably the most common material used in building

construction. Sun-dried adobe bricks containing sand, silt and clay,

often untreated against water penetration, have been the basic masonry

units for traditional low-cost housing construction. The more recently

introduced asphalt-stabilized adobe brick of high durability and waterrepellent properties marks a significant breakthrough in improved lowcost construction. With good workmanship, stabilized adobe bricks with

compressive strengths of 350 to 500 N/cm^ may be obtained. Mortars

used with adobe units are mixtures of soil and cement, with asphalt

added to give it the desired stability.

Several attempts have been made in Turkey to provide stabilization

with asphalt. A study recently conducted by the General Directorate

of Building Materials of the Ministry of Reconstruction and Resettlement

(Ankara) concluded that laboratory analyses of the adobe were necessary

to determine the kind and optimum amount of asphalt to be used for stabilizing

it. The analyses should include a sieve test (gradation) and a determination

of silt and/or clay amount. Liquid limit and plastic limit should be

determined to know the plasticity index (PI) of the soil. In general,

soils with a clay and/or silt content of more than 45% are not suitable

for asphalt stabilization. The kind of asphalt to be used is determined

by the type of soil, as follows:

Cut-back asphalts of RC (Rapid Cure) type and emulsion asphalts, are very

suitable for sandy soils, with a small silt and/or clay content. Soils of

low plasticity index are of this kind. As nonplastic soils are cohesionless

the stability of the mixture is a function of the binding power of the

asphalt used.

Cut -back asphalts of MC (Medium Cure) type provide a more homogenous

mixture in case they are used with soils of medium plasticity index. As

the plasticity becomes higher, cohesion increases. Consequently, the

stability of the mixture is determined by both the binding power of asphalt

and the cohesion effect of clay. This kind of soil gives satisfactory

results with emulsion asphalts.

Asphalts of SC (Slow Cure) type are good for clayey soils as they are highly penetrative. They can be used with soils of high plasticity index,

and silt and/or clay content higher than 301. The stability of the mixture

does not depend much on the binding property of the asphalt, as the soil

itself is highly cohesive.

Soil should contain approximately half of the optimum water content

for cut-back asphalts. In other words, the asphalt will substitute the

remaining half. When emulsified asphalts are used, the water content should

be 101 or slightly more. This amount of water facilitates the mixing of

asphalt

The following table shows the average results for two sets of tests

(one with 4% and the other with 1\ asphalt ratio, with 85-100 penetration

rate, in form of an emulsion containing 601 water):

8
Unit Weight

Pressure Strength

(a) Normal in dry air

Average

Minimum

(b) Absorbed with water

Average

Minimum

(c) After frost

Capillary water rise

Ca) cm/hour (23 hours)

(b) gr/hour (27 hours)

Water absorption

Cost per adobe block

(29 X 14 X 9.5 cm)

With 4^ Asphalt

1.879 kg/m^

848 N/cm^,

69.5 N/cm'

7 cm

160 gr

Collapsed

With 1% Asphalt

1.902 kg/m^

1,100 N/cm^

1 ,020 N/cm"^

86.5 N/cm^

70.5 N/cm^

Collapsed after

15th repetition,

19 gr

3. 64

0.387 T. ($0,027)* 0.738 TL. (0.0515)

Availability of Asphalts Used for Adobe Stabilization in Turkey

(a) MC (Medium Cure) Cut -back Asphalt : A mixture of asphalt cement

(AC) and kerosene. Grades 0, 1, 2 of this kind can be produced by Batman

Refinery. The current (1972) price from Batman is about 750 TL. ($52.50)

per ton.

(b) RC (Rapid Cure) Cut-Back Asphalt : A mixture of asphalt cement

(AC) and gasoline. Grades 0-5 of this kind of asphalt can be produced

by Batman Refinery. Unit price is about the same as MC type. It is

highly flammable and the Turkish General Directorate of Highways prefers

to produce it locally.

(c) SC (Slow Cure) Cut -Back Asphalt : A mixture of asphalt cement (AC)

and light oils. Crude oil and fuel oil are of this kind. It is not

produced nor used in large amounts but can be produced by Batman Refinery.

Current price from Batman is about 600 TL. ($42.00) per ton.

2.4.4 Wood

The structural uses of lumber in building construction are diverse

and extensive. Wood joists and plywood panels are used for roof and

floor systems. Sandwich panels with wood studs and plywood skins are utilized for exterior walls and partitions. However, lumber is not

everywhere available or economically feasible for low-cost housing construction,

1 TL = $0.07 (November 1972)

9
In such cases, nondimensional lumber, raw timber, cane, bamboo, palm

or thatch are used as alternates depending on their local availaoility

Generally, wood exhibits good strength in both tension and compression

in the direction o£ its longitudinal fibers. This property makes it

adaptable to construction of bending resistant elements in a building.

Cane, bamboo or split wood may also be utilized to reinforce adobe masonry

walls and elements of poured stabilized soil. Exposed wood generally

requires special protection against moisture, fire and insect infestation.

2.4.5 Metals

Steel in the form of reinforcing bars for concrete and masonry

elements is used extensively in housing construction. Individual reinforcing

bars of different diameter sizes are generally fabricated with deformed

surfaces for better bond. Wire mesh reinforcement is fabricated by

welding together two layers of spaced thin bars (usually 1 mm. or less

in diameter) in a grid pattern. Poultry netting or similar steel mesh

of hexagonal or triangular pattern is a relatively-inexpensive manufactured

product which merits exploitation as a reinforcing material for lowcost houses, particularly in ferro-cement , as it may be more readily

available locally than other types of reinforcement.

Steel exhibits high strength, stiffness and ductile properties.

Stiffness is a measure of resistance against deformation, whereas ductility

is the ability to sustain substantial deformation without rupture. Both

strength and ductility provide a measure of the capacity of a material

to absorb energy without rupture. Tensile strength of steel reinforcement

usually falls within the range of 25,000 to 45,000 N/cm . Mechanical

properties of steel change rapidly at temperatures above 400°C, and

surfaces exposed to moisture are subject to corrosion. In construction,

steel is protected by painting and by coating with fire proofing materials.

Other applications of metals in low-cost housing construction includes

the use of corrugated sheet metal of galvanized steel or aluminum for

roofing and wall siding, use of steel connectors for bolting and anchoring

various elements, and use of rods and cables for bracing purposes.

2.4.6 Plastics

Knowledge about weathering characteristics of plastics in outdoor

use and durability in relation to the traditional materials is still

incomplete, particularly in regard to their use in tropical areas such

as the Philippine Islands. However, plastics are finding increasing

use in housing construction in many developing countries, including

the Philippine Islands, South Korea and Taiwan, which are among the

chief plastics-producing countries in the Far East. A range of plastic

products, using indigenous and imported raw materials and processing

machinery, are manufactured in these and some other developing countries,

with certain plastic products proving of interest to the building industry.

In contrast, the Peruvian and Turkish plastics industries are only in

the very early stages of development, and plastics are little used by

the building industry.

Some advantages of plastics which have been considered by the building

industry are their adaptability to mass -production techniques, their

lightness, corrosion-resistance, and ease of manipulation in manufacturing

any specified design of building components. These characteristics

of plastics are currently enhancing their acceptance in building applications .

10
Cellular plastics [2] exhibit excellent thermal insulation and

thus reduce temperature fluctuations in hot, arid regions with a wide

range of temperature cycling. On the other hand, in hot, humid regions

less thermal advantage is to be gained by the use of plastics, except

as part of a lightweight system of construction or as a substitute for

the thermally- inadequate corrugated steel.

Plastics have yet to find full acceptance in the building industry,

which generally tends to be conservative in its approach to innovative

building materials and techniques. As a tradition in Turkey for example,

solid and durable materials are generally preferred for building construction.

However, a variety of plastic materials are recently emerging in the

market and some of them are being used in the newly constructed modern

buildings in urban centers. Greater acceptance of plastics as a construction

material is likely to occur in the near future.

Replacement of the traditional materials used in the manufacture

of various goods and articles by plastics has resulted in rapid development

of the plastic industry in Turkey. Whereas certain polymers and plasticizers

began to be produced in recent years, industry depended mostly on imports

for raw and auxiliary materials until the end of 1969.

Of the plastics now produced in Turkey [3] (about 300,000 tons

in 1972), only the items listed below are used in buildings (all reflect

recent developments in Turkey)

(a) Vinyl -asbestos floor tiles have recently become popular in

cities and towns, and are substituted for cement and mosaic tiles.

Production is growing rapidly, and the rate of acceptance shows that

this material may well be adopted in villages in the near future.

(b) Clean and/or waste water plastic installation pipe : Plastic

pipes are already used widely for irrigation and other agricultural

purposes. It should be acceptable for plumbing in rural dwellings,

for it has advantages such as lightness, workability, and durability.

(c) Kitchen and bathroom fixtures, water reservoirs, washbasins , handrails, plinths : Use of plastic for such items is constantly increasing

in cities, and undoubtedly will increase in rural areas.

(d) Flat or corrugated plastic sheets : Although corrugated plastic

sheets are widely used as roofing material in temporary structures (partly

for decoration purposes), they have not yet been widely accepted as

a general material in permanent structures.

(e) Sheets or bags of polyethylene films : Recently, thin plastic

sheets (films) are widely used on roofs (especially on earth roofs,

which provide a good thermal insulation but are poorly resistant to

water penetration), for waterproofing, or in hollow gables of roofs

for windproofing . Plastic bags are used to hold glass wool in place

for heat insulation.

(f) Plastic foam for heat and acoustic insulation : Although several

kinds of plastic form insulation materials exist on the market, they

are not yet used in dwellings, but are popular for industrial use (refrigeration,

industrial insulation) and for thermal and acoustic insulation of large

modern buildings.

(g) Styrofoam beads and panels are used to provide light-weight

insulation in prefabricated houses.

11
References

1. Raisinghani, M. , Pama, R. , Lee, S.L., "Mechanical Properties

of Ferrocement Slabs," Research Report No. 27, Asian

Institute of Technology, Bangkok, Thailand, 1972.

2. "Structural Potential of Foam Plastics for Housing in

Underdeveloped Areas," Architectural Research Laboratory,

The University of Michigan, Ann Arbor, Michigan, November

1965.

3. "Socio-Economic Aspects of Earthquake Resistant Housing

in Turkey," Turkish National Committee for Earthquake

Engineering (Chairman: Professor Dr. Rifat Yarar, Istanbul

Technical University, Taksim, Istanbul, Turkey), Ankara,

1972.

12
Chapter 3. Structural Performance of Low-Cost Housing

and Community Buildings Under Earthquake

Conditions

S. G. Fattal

National Bureau of Standards

3. 1 Nature of Earthquakes

Major earthquakes are generally believed to be of tectonic origin

associated with large strains in the crust of the earth. Severe earthquakes

may affect large geographic areas, releasing large amounts of energy,

creating fissures, cracking and causing sudden relative changes in ground

elevation which results in damage and destruction to surface structures.

The point from which the first seismic waves propagate is known

as the focus or hypocenter of an earthquake. The epicenter is the point

on the earth's surface directly above the focus. The severity of an earthquake can be measured by the modified Mercalli scale and the Richter

scale. The Mercalli scale measures the intensity or degree of destruction

and is dependent on several factors including intensity of shaking,

condition of geologic foundation material, and distance from the hypocenter.

It is an arithmetic scale of 12 divisions, indicated by Roman Numerals,

wherein intensity I is barely felt by people and XII reflects total

destruction of well-built earthquake resistant structures. The Richter

scale measures the magnitude or energy released by an earthquake as estimated from seismograms. It is a logarithmic scale in which destructive

earthquakes generally have magnitudes greater than 6, and the great historical

earthquakes greater than 8. Post-earthquake experience is utilized

to develop seismic risk maps which are adopted by various codes and

building regulatory agencies in prescribing specifications for earthquake

resistant design of structures (see Chapter 7).

3. 2 Seismic Effects on Buildings

3.2.1 Influence of Structural Configuration

The distribution and relative intensities of seismic forces within

a structure are influenced, to a large extent, by the type of construction,

geometry, mass distribution and stiffness properties. In general, heavier

elements in a building develop greater "direct" forces while stiffer

elements receive a larger share of the forces transmitted between elements.

Peak lateral forces tend to concentrate at massive roof and floor levels

and propagate to other levels through vertical elements. For example,

in the structure of Figure 3.1a, the lateral force acting on the roof

is transmitted through connections to relatively lightweight columns

below, producing critical shear and bending forces in these elements.

Additional column bending occurs as a result of gravity load eccentricities

created by the lateral drifting of the roof. The introduction of lateral

stiffening elements such as cross bracing (shown dotted on the sketch)

or walls in faces parallel to the direction of ground excitation reduces

drift and its effects on columns, and alters drastically the force distribution

pattern (i.e., the bracing acting in tension, or the walls acting in

plane shear, assume most of the lateral forces transmitted from the

roof)

The geometry of a building may have a marked effect in distributing

seismic forces and influence the type and degree of failure. For example,

13
w

Figure 3.1 Effects of Ground Motion on Structures

14
twisting and warping are more likely to occur in buildings of irregular

shape (Figure 3.1b) or in buildings having nonuniform arrangement of

walls and openings. Failure commonly occurs at corners of openings

(Figures 3.1c and 3.2), at the top junctions of abutting walls, near attachments of projecting elements, or, as a result of "hammering" between

adjacent walls of detached buildings. In general, buildings marked

with sharp transitions in mass and/or geometry tend to develop structurally

unfavorable force distribution patterns.

3.2.2 Foundations

Frequently, structures designed to withstand earthquakes fail due

to inadequate foundation design. Cracking and failure of superstructures

may result from differential settlement of footings. Such settlement

may be due to differential compaction of ground, to liquefaction of

water-saturated soil, or to incipient slumping and sliding on slopes.

Certain types of foundations are more susceptible to earthquake

damage than others. For example, foundations of shallow, individual

spread footings are likely to be subjected to high differential settlements

and "rocking," particularly where the supporting ground consists of

different types of soils. Unfavorable conditions may also develop

when mixed types of foundations are used for the same structure.

Many houses in coastal areas are built on poles or foundations

of treated piles (see Chapter 4). In such cases the house must be properly

fastened to the poles to give it sufficient stability against lateral

earthquake forces

Shallow foundations deteriorate with age as a result of exposure

to freezing and thawing of the surface ground in regions of cold climate,

and to frequent flooding in tropical regions. In seismic areas, some degradation of foundation material occurs as a result of the cumulative

effect of past earthquakes even though they may not create any visible

damage to the above-ground structure.

3.2.3 Walls, Frames and Shells

Unreinforced bearing walls of masonry, or concrete construction,

commonly used throughout the world, are highly susceptible to earthquake

damage as a result of their relatively low in-plane shearing capacity.

Further reduction in strength of such walls results from window and

door openings (Figure 3.1 c)

Walls commonly fail in racking shear, out-of -plane bending or a combination of both. Racking shear failures are recognized by the cross- diagonal cracking pattern commonly observed in building walls damaged

by earthquakes. This type of failure is initiated by cracks at points

of high stress concentration (corners of openings, centers of wall segments,

or piers flanking adjacent openings) which then may quickly propagate

outward causing complete rupture (Figure 3.2).

Out-of -plane bending failure is due chiefly to direct seismic forces

acting in a direction transverse to the wall. In general, bending

and shearing effects occur simultaneously in an earthquake since the

direction of seismic excitation is often inclined with respect to the

orientation of the walls.

Bearing wall failures are characterized by sudden, partial or complete

collapse of wall segments accompanied by collapse of roofs and upper

floors (Figures 3.6, 3.7). Such collapse may be widespread and is a 15

527-373 0 - 74 -3
/

Figure 3.2 Damages sustained by residential units at Chimbote,

Peru. Causes of damage: excessive size o£ openings

in relation to area of walls (note the absence of

cracks at the comers of the small openings); inadequate reinforcement at opening comers. Damage could

have been prevented by reducing size of openigns,

providing adequate tie-beams and lintels sufficiently longer

than the opening; strengthening the connections between roof

to walls and floor to walls.

16
Figure 3.3 Field stone masonry house set in mud mortar, Turkey. Such

construction is highly undesirable in earthquake -prone

regions. Note, however, that wood ties have preserved the

integrity of the wall at the comer. Field stone may be

used in earthquake resistant construction provided that

adequate tie-beams are used and that the mortar is o£

acceptable quality (see Figure 3.4).

ll

17
Figure 3.4 Stone dwelling with wood ties near Bingol, Turkey. The

ability to withstand earthquakes is markedly improved in

the case o£ this dwelling by the good quality o£ the

workmanship and materials used (see Figure 3.6).

18
Figure 3.5 Comer failure o£ a two-story adobe wall with wood tiebeams (Peru) . In this type of building, the roof does

not act as a unit and thus does not transfer loads to the

lateral walls (which would act in shear and thus easily

sustain the loads). Instead, during the earthquake the roof

exerts a thrust upon the frontal wall (the wall with openings

in this picture) and detaches it from the lateral walls.

19
Figure 3.6 The town o£ Qir (Iran) after the 1972 earthquake. Most houses

in Qir were built wdth sun-dried adobe blocks or rock rubble and

adobe mortar, and had heavy roofs of logs first overlain by straw

or burlap and then covered by adobe. Two -thirds of the people in

Qir perished in the debris of their homes. Contributing factors

to the magnitude of the disaster were the poor quality of the

building bibcks and of the mortar, the heavy roofs and the absence

of adequate horizontal and vertical reinforcement and ties

(courtesy of U . S . G . S . )

20
Figure 3.7 Collapsed two-story adobe building, Burdur, Turkey. The

poor quality of the adobe blocks and mortar was a contributing factor in the collapse of this dwelling.

Note the careful brickwork of the building standing in

the background. Improved adobe block and mortar quality as well ad the provision of adequate ties and connections

substantially decreases the risk of failure under earthquake

loads.

21
major cause of injury and death in developing countries as shown bydestruction of adobe wall dwellings during the 1970 Peru earthquake

and the 1972 Pars earthquake in Iran.

Bearing wall collapse also may be due to failure of connections

between roofs and walls (Figure 3.2) and between walls and foundations.

As a result the building lacks the necessary structural integrity to

act as a unit against earthquake shock (Figure 3.8). Tension cracks

between abutting walls propagating from the roof downward (Figures

3.1c and 3.5) are indicative of inadequate wall-to-wall connections.

The structural weakness of bearing walls is also inherent in filler

walls confined within load-bearing frames. Due to the effect of frame

enclosure, however, filler walls tend to develop increased shear and

bending capacity although this is partially offset by the absence of

compressive loads, which up to a certain level, increase the capacity

of a wall to resist in-plane shear forces.

Rectangular frames of the type shown in Figures 2.2 and 3.1a resist

lateral forces through the combined bending and shear action of their

elements. Collapse of frames under lateral forces may be caused by

excessive column bending or by failure of rigid joints of frame elements.

Certain types of shell enclosures such as cylindrical or spherical

shapes (Figure 2.3), have found their use in low-cost housing construction

in the past. These dwellings are commonly built with traditional materials

such as adobe block, without any reinforcement. Under seismic loading,

failure is likely to be initiated by cracking at corners of openings

or near ground or roof attachments where localized bending stresses

are greatest.

3.2.4 Roofs and Upper Floors

One of the major concerns in the mitigation of earthquake disasters

is to prevent collapse of roofs and floors which cause great loss of

human lives. The use of heavy nonstructural roofing materials account

for the high incidence of roof failures in low-cost houses in past earthquakes.

Generally, roof failures may be attributed to insufficient strength

or to lack of adequate connections. Roof collapse may also occur as

a result of the rupture of supporting walls, columns and other loadbearing elements. The different modes of roof failures are dependent

on the structural configuration of the system. For example, the rupture

of the bottom chord of a roof truss (Figure 3. Id) may trigger a complete

structural collapse by forcing the supporting walls outward as indicated

by the broken lines. On the other hand, under a horizontal seismic

movement, the roof transmits transverse forces to the supporting walls

causing the formation of tension cracks and separation of abutting walls.

This mode of failure is also characteristic of massive flat roofs (or

floors) supported by beam joists that in turn are supported only by

opposite bearing walls (Figure 3.5).

3. 3 Building Improvementg to Mitigate Earthquake Effects

3.3.1 Structural Configuration

The following is a list of recommendations regarding structural

configurations that result in improved behavior under seismic loads:

22
Figure 3.8 Collapse of a dwelling in Casma, Peru during 1970 earthquake.

The collapse was due to inadequate arrangement of walls,

leading to unbalanced stress distribution in building, poor

connections between vertical and horizontal elements, and

the absence of sound horizontal tie-beams

23
1. Low-cost housing construction should be limited to one- or

at most two-story units. This practice permits maximum

exploitation o£ locally available construction materials

and increases the feasibility of producing better seismicresistant structures.

2. The weight of roofs and floors should be kept to a minimum.

3. The shape of the building, the arrangement of walls, partitions

and openings should be made in a balanced manner to obtain

as uniform a stress distribution in the building as possible.

4. Heavy elements should not be attached to non-structural

walls

5. The size and spacing of openings should be governed by

requirements of minimum width of piers flanking adjacent

openings, maximum permissible length of lintels spanning

across the top of openings, and uniformity of overall layout.

(Figures 3.2 and 3.4).

6. Exterior walls forming a rectangular enclosure may be

prevented from separating at the top corners by providing

a continuous collar or ring beam having sufficient

tensile strength to resist forces acting on the upper

peripheral junctions of the walls.

7. Structural damage resulting from hammering of unattached

adjacent walls may be avoided by providing connections

between these walls for integral action against earthquakes,

or by providing sufficient space between adjacent buildings

to avoid impact.

3.3.2 Foundations

For low-cost single-story housing construction the only type of

foundation of reasonable cost in relation to the cost of the structure

is the superficial foundation. Where soil conditions require the use

of deep or piled foundation, or where the possibility of soil liquefaction

exists, an alternate construction site should be selected if possible.

The following requirements should be met in order to achieve more earthquake -resistant construction:

1. The base of the foundation should be below superficial or

"top soil" level, and below the major vegetal root level.

In locations subject to freezing, as in Turkey

and Iran, the bottom of the foundation should be below

the freezing level of the ground.

2. Continuous wall footings should extend under the entire

length of the wall and sufficient vertical dowel reinforcement should be provided between wall and footing to develop

continuity and capacity for integral action. This practice

should minimize differential settlements and local damage to

the walls and should permit a more uniform distribution of

bearing pressures in the soil.

3. For single story construction the width of the continuous

footing should preferably be more than one and one-half

times the thickness of the wall or '35 cm., whichever is

larger. Depth should not be less than 45 cm.

24
4. Foundation materials of gravel mixed with soil stabilized

with asphalt or road oil may be used unless better materials are available at comparable cost. Stabilization of the

foundation material provides protection against moisture

and other deteriorating agents.

5. Split cane, bamboo or wire mesh may be used for vertical

reinforcement to provide continuity between walls and

footings

3.3.3 Walls, Frames and Shells

The seismic resistance of walls constructed out of stabilized adobe

block may be improved considerably by utilizing locally available reinforcing

materials. Results of preliminary tests (Improved Adobe Construction

Program at the National University of Engineering in Lima, Peru) of

several wall sections constructed by traditional methods but utilizing

split cane for reinforcement and oil-stabilized adobe block show an increase of over 100% in resistance to static lateral force.

Asphalt and soap emulsification provides a means of increasing

the compressive strength of adobe blocks. Adobe walls may be further

strengthened by the use of cane or wire-mesh reinforcement to inhibit

brittle shattering and rupture of walls and to control cracking. The

extension of reinforcement into neighboring walls and foundations provides

an effective means of achieving continuity and improved seismic-resistant

construction

An effective method of improving the strength of walls is to provide

a ring beam at their top. The purpose of a ring beam is to tie the

top of this walls together and to prevent tensile cracking from developing

at the upper corners. In order to function in this capacity a ring

beam should be reinforced with materials of high tensile strength such

as bamboo, wire or steel rods.

The structural resistance of walls is significantly impaired by

the location and size of openings. To a certain extent, it is possible

to strengthen walls by using smaller openings and by providing equalized

space between openings or between an opening and the vertical edge

of the wall. Nevertheless, the danger of brittle collapse initiated

by the failure of piers adjacent to openings can be reduced by providing

effective reinforcement around these openings.

Tests on frames with properly tied-in infilled walls have indicated

a considerable increase in strength of the frame -wall assembly as compared

to the individual strengths of frame or wall [1]. The observation was made on reinforced concrete frames with brick masonry filler walls.

Whether this increased capacity can be realized if the infilled frame were made of rammed earth, adobe, or other materials of low tensile

strength, with cane or other reinforcement, should be determined by

future research. Filler walls may also be designed in such a way as to permit most of the energy released in a severe seismic disturbance

to be dissipated through the process of cracking of the walls leaving

the main load-bearing frame relatively undamaged.

3.3.4 Roofs and Upper Floors

An effective way to improve the seismic performance of a building

is to reduce the weight of its roof. To a certain "extent , this may

be achieved without loss of strength by substituting lighter-weight

materials for roof covering in lieu of heavy materials such as mud or

25
tile which have had widespread use in traditional low-cost dwellings

in the past. Reduction of weight can also be achieved by using shorter

spans which require the use of load-bearing interior partitions. This

practice may be justified because (a) the addition of load-bearing partitions

will increase the lateral resistance of the system, and (b) the reduction

of weight is greater than the reduction of the span, often by significant

amounts. Lightweight panel systems, which are highly efficient in bending

may also be a substitute for traditional heavy roofs as discussed in

Chapter 10.

3.4 Needed Research

As noted in Section 3.3.3, tests made on assemblies consisting

of reinforced concrete frames with brick masonry filler walls have indicated

a considerable increase in strength compared to the individual strengths

of frame walls. Whether this increased capacity can be achieved if

the infilled frame were made of rammed earth, adobe or other materials

of low tensile strength, with cane or other reinforcement, should be

determined by future research.

References

1. Blume , J., Newmark, N. , Corning, R. , "Design of Multistory

Reinforced Concrete Buildings for Earthquake Motion,"

Portland Cement Association, Chicago, 1962.

2. "Design Essentials in Earthquake Resistant Buildings" by

Architectural Institute of Japan, Elsevier Publishing

Company, New York, 19 70.

3. Wiegel , R.L., "Earthquake Engineering", Prentice-Hall,

Englewood Cliffs, N.J. , 1970.

4. "The Agadir, Morocco Earthquake," Committee of Structural

Steel Producers, American Iron and Steel Institute, New York,

1962.

5. Berg, G.V. , "The Venezuela Earthquake," American Iron

and Steel Institute, New York, 1964.

6. Hanson, R.D. § Degenkolb, H.J., "The Venezuela Earthquake,"

American Iron and Steel Institute, New York, 1969.

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

Aspects of the 1971 San Fernando Earthquake," Building

Science Series 40, National Bureau of Standards, Washington

D.C. 1971.

8. "Manual of Asphalt Emulsion Stabilized Soil Bricks,"

International Institute of Housing Technology, California

State University, Fresno, California, 1972.

9. "Earth for Homes," Department of Housing and Urban Development, Washington, D.C, June 1970.

10. "Properties of Earth Wall Construction" Building Materials

and Structures Report BMS 78, National Bureau of Standards,

Washington, D.C, 1941.

26
11. "Report on Seismology and Earthquake Engineering,"

Department of Advancement of Science, UNESCO, Paris,

January 20, 1965.

12. Ambraseys , U.N. , Moinfar, A., Tehalenko, J.S., "The

Karnaveh Earthquake of 30 July 1970," U.N.E.S.C.O.

Paris, April 1971.

13. Ayarza, H. , "Aseismicity in Low-Cost Housing," Santiago,

Chile, 1971.

14. "Earth for Homes", Ideas and Methods of Exchange No. 22,

Department of Housing and Urban Development, Washington D.C.,

1970.

27
Chapter 4. Structural Performance of Low-Cost Housing and

Community Buildings Under Windstorm Conditions

Emil Simiu

National Bureau of Standards

4 . 1 Characteristics of Windstorms

Windstorms of sufficient intensity to cause damage to buildings

include tropical cyclones, extratropical cyclones, orographic winds,

and severe local storms.

Tropical cyclones , of which the most destructive are called hurricanes

in the North American area and typhoons in Asia, are most frequent during

the summer and autumn of the hemisphere in which they occur. Upon moving

to higher latitudes, they tend to assume the characteristics of extratropical

storms, i.e., become less symmetrical and are accompanied by lighter

rainfall. The damage caused by tropical cyclones is due to the direct

action of winds, which may reach surface velocities of 150 mph or more,

to rainfall, and to storm surges, i.e. violent piling up of water by

the wind. The damage caused by storm surges is restricted to coastal

areas and depends upon the distance from the shore and upon the elevation

above mean tide level. The intensity of storm surge is measured in

terms of the surge height which depends upon wind speed and direction,

atmospheric pressure, coastline geometry, and bottom topography offshore.

The approximate average number of tropical cyclones and hurricanes

per year for various geographical areas is given in table 4.1 [1].

TABLE 4.1. AVERAGE NUMBER

AND HURRICANES

OF TROPICAL

PER YEAR

CYCLONES

Tropical

Cyclones

Hurricanes

(typhoons)

Eastern North Pacific Ocean 8 3 North Atlantic Ocean 8 5 Indian Ocean 15

South Pacific Ocean 5 Central § Western North Pacific 28 20

Ocean

Extratropical cyclones occur in the middle latitudes and are usually

more intense in winter and spring.

Orographic winds are winds intensified by the mechanical action

of hills or mountains. Damage from such winds has been reported frequently

on the eastern slope of the Rocky Mountains, and has occurred on a considerable

scale in Sheffield, England [2].

Severe local storms include thunderstorms and tornadoes.

28
Thunderstorms are characterized by violent winds of relatively

short duration Csometimes on the order of minutes). In certain areas

of the world as much as 501 of maximum winds occur in thunderstorms

[3].

Tornadoes ( tatsumakis in Japan) are funnel-shaped windstorms attaining

speeds estimated at 200 mph or more. The damage they cause is due

to the direct action of their high wind speeds as well as to the very

rapid drop in ambient pressure as the vortex of the tornado moves over

an area. Buildings literally explode because of the intense pressure

differentials imposed on them.

4.2 Effects of Windstorms on Buildings

4.2.1 Influence of Building Shape on Magnitude of Wind Loading

The magnitude of the critical wind pressure is dependent, to a large

extent, upon the geometric characteristics of a building. A few examples

of this dependence are shown in Figure 4.1, in which coefficients proportional

to the pressure intensities for given wind speeds are shown for various

height to width ratios and for various roof slopes. Pressures may also

depend upon the relative position of buildings in a group. It follows

that the wind resistance of buildings may be improved, sometimes considerably,

by avoiding shapes or configurations which cause undesirable aerodynamic

effects

The aerodynamic behavior of a given building or its parts may be

determined on the basis of available theoretical and experimental data,

or by performing a wind tunnel model study.

4.2.2 Foundations

The mechanical action of wind forces may cause sliding or overturning

of a building, and storm surges and heavy rainfall characteristic of

hurricanes and typhoons may result in floods that damage the foundation

soil or the foundation itself. Other potential ground effects are scouring,

landslides, and loss of bearing capacity of the foundation material.

4.2.3 Walls, Frames and Shells

Wind-induced stresses in walls may be classified as either outof-plane bending or in -plane stresses. Out-of-plane bending is produced

by the direct action of wind pressures or suctions on a wall and become

more critical as the wall thickness decreases. Damage caused by tornadoes

is largely due to the high bending produced by the explosive action

of suctions due to pressure drop in the tornado. In-plane stresses

develop in walls as a result of their action as shear resisting elements

within the building (see Chapter 2).

For wind acting in the direction indicated by the arrows in Figure

4.2, the frontal wall (ABCD) will be subjected to bending stresses.

The lateral walls (CDEF and ABGH) , which prevent the building from racking

under the wind action, will be subjected to in-plane stresses. The

effect of wind on wall ABCD is illustrated in Figure 4.3.

29
WIND

DlRECTIOff

( Length = Width = 2 x Height) (Length = Height = Width)

WIND

DIRECTION

Figure 4.1 Wind pressures on buildings. (Shaded areas are areas o£ maximum wind pressure; numbers shown are a measure of

the wind pressure intensity. For example, the pressures

on the side areas of horizontal roofs (a, b) are twice

as high as in the case of the 30° pitched roof (d) )

30
G

C

Figure 4.2 Bending stresses Figure 4.3 In-plane stresses

Openings in walls create stress concentrations which may be critical,

particularly at the opening corners (Figure 3.2). Connections at

the intersection of two walls, or between walls and foundations, floors,

and roofs, are subject to exceptionally high stress, and if not properly

designed or built may fail under the action of wind.

The structural function of lateral walls may be performed by frames,

either prefabricated or built on the site. Frame joints are particularly

vulnerable to effects of wind. The attachment of cladding or sheathing

to walls or frames also requires special care (Figure 4.4), especially

in areas of high suctions near the corners of the building and near

the eaves. Relatively rigid shells have been used in cylindrical -type con- struction and may present considerable advantages over boxlike construction,

both structurally and aerodynamically

4.2.4 Roofs and Upper Floors

The magnitude of wind pressures or suctions on roof surfaces is a function of the roof pitch, as illustrated in Figure 4.1.

The effects of wind on roofs may be direct or indirect. Direct

effects may be local or extend over the entire roof. Direct local

effects consist of high pressures or suctions over localized areas of

the roof and may result in damage to roofing (shingles, tiles, sheets)

or to parts of the roof structure. Overhangs are particularly susceptible

to wind damage, as they are subjected to a positive pressure from below

and suction from above (Figure 4.5). Indirect effects are associated

with the transfer to lateral walls of wind loads acting on the frontal

walls (Figure 4.2).

527-373 0-74-4

31
Figure 4.4 "Marcos" school destroyed by Typhoon Sening (Joan), October 1970,

the Philippines. The inability o£ this structure to withstand

wind loads was due to inadequate strength o£ the frame joints

(particularly at the foundation level), of the roof connections,

of cladding to building framing, of the end walls.

Measures to improve behavior under wind loads would include

provision of interior vertical bracing parallel to the short

direction of the building (or a substantial increase of the

bending capactiy of the frames) , improvement of roof and

cladding connections, reinforcement of the end wall (or

provision of in-plane bracing in end wall)

Figure 4.5 Wind damage to roof overhangs

32
I£ the positive pressures on the overhangs and the suctions on the roof become strong enough, the capacity of the connections will

be exceeded and the roof lifted (Figures 4.4, 4.6, 4.7, 4.8). Since

the roof performs a structural function in the building, in that it

acts as a horizontal diaphragm for the transmission of wind loads from

the frontal to the lateral shear walls, serious damage to roofs may- result in loss of support at the upper part and consequent collapse

of frontal or lateral walls (Figure 4.9).

4 . 3 Building Improvements to Mitigate Windstorm Effects

4.3.1 Aerodynamic and Structural Considerations

Critical pressures resulting from the action of wind may be reduced

considerably by proper aerodynamic design. Sharp edges, low roof pitches,

large overhangs, and aerodynamically unfavorable shapes or grouping

of buildings (see Section 4.2.1) should be avoided wherever possible.

Improvements in the aerodynamic behavior of buildings or of parts of

buildings may be achieved in certain situations by providing rough surfaces

or ribs at the exterior side of walls [4]. Grass roofs have been noted

to have pressure relieving characteristics. Aerodynamically smooth

transitions between planes may also be effective in decreasing pressures

or suctions induced by wind.

The shape of the building affects its behavior not only from an aerodynamic, but also from a structural standpoint. Therefore, the

selection of a shape which permits as direct a stress path as possible

is recommended when the expected wind loads are high. Experience has

shown, for example, that cylindrically shaped buildings are particularly

well suited for resisting direct tornado action.

4.3.2 Foundations

The structural integrity of a building subjected to wind forces

depends largely upon the strength of the connections and anchorages

to the foundations. Such strength should be consistent with that of

the building structural elements. Undesirable stress concentrations,

or stresses, should be avoided. For example, anchorage lengths should

not be less than determined by tests performed on the materials used.

The damaging effects of storm surges or floods on the foundation

itself may be avoided by providing adequate foundation materials whose

properties do not deteriorate under the prolonged action of water. If

the foundation is constructed of soil, mortar and stone, a stabilizing

ingredient can be added which will improve its resistance to water damage.

Inexpensive protective banks or pole-type foundations [5] may serve

to protect the building from severe storm surges.

4.3.3 Walls, Frames and Shells

Adequate connections must be provided between walls and between

walls and foundations, floors, and roofs. Horizontal or vertical reinforcement

may be required for the strengthening of certain types of walls, including

adobe walls. Such reinforcement may be provided by inexpensive, locally

available materials (for example, split cane, bamboo). Where vertical

reinforcement is used, adequate grouting should be provided, using

methods and mortars appropriate to the type of material available for

wall construction. Buttressing of walls, bond beams for lateral support,

and vertical or horizontal bracing may be required for the purpose of

improving the structural capacity of walls, including walls built with

33
Figure 4.6 A church at Catanduanes, the Philippines, stripped of its

roof by Typhoon Sening (Joan), October 1970.

Figure 4.7 Roofing blown off by typhoon winds, the Philippines, October

1970. Sound attachment of roofing to roof members would have

prevented damage to roof of buildings in the foreground and

background of the picture.

34
Figure 4.8 Destroyed homes and institutional building in the Bicol

Region, the Philippines, October 1970. Cause of roof collapse:

inadequate connections between roof members, inadequate

anchorage of roof to walls.

35
such materials as adobe and/or bamboo. Adequate design of corners and

openings should result in decreased stress concentrations through elimination

of sharp transitions between planes. Wind resistant types of sheathing

and appropriate fasteners should be used. Protruding elements (such

as parapets) are particularly vulnerable to the action of wind (see

masonry building in the background of Figure 4.4) and should be provided

with adequate anchorage.

4.3.4 Roofs and Upper Floors

In the areas of high suction of roofs of various types, connections

consistent with the magnitude of the expected loads should be designed.

Roofs known to be vulnerable and which for various reasons cannot otherwise

be improved should be anchored against a predicted storm, for example,

by using wind-storm anchorage kits [6] consisting of coconut fiber nets

in 0.6 m. squares thrown over the building and anchored to the ground,

or using anchorage ropes or cables. Large overhangs and parapets should

be designed so that localized damage due to overstress is kept from

extending to the entire roof. This could be accomplished, for example,

by the provision of specially designed pinned connections. It is also

possible to design overhangs which allow easy removal and storage of

the overhanging roofing sheets. The removal would follow a storm warning

and considerably reduce the vulnerability of the roof if the storm actually

occurs [6]

Appropriate thicknesses of roofing and sizes of washers should

be used in metal sheet roofs to avoid tearing of the roof sheeting.

4 . 4 Needed Research .

1. Data on tropical and cyclone wind structures and speeds, applicable

for structural engineering purposes, are scarce. Full scale field studies

of tropical cyclones, designed to provide the data required for such

purposes, are therefore needed in the future.

2. Most theoretical and wind tunnel studies performed so far are applicable to high-rise buildings only. Aerodynamic studies of lowrise buildings, especially those in tropical regions, are needed as

a basis for better design and construction of wind-resistant structures.

These studies should be carried out on both full-scale buildings and

wind-tunnel models.

References

1. "Hurricane" ESSA/PI 670009, U. S. Department of Commerce,

Washington, D.C. 1969.

2. Page, J. K. , "Field Investigations of Wind Failures in

the Sheffield Gales of 1962," Proceedings of a Symposium

on Wind Effects on Buildings and Structures, Loughborough

University of Technology, Loughborough, England, 1968.

3. Davenport, A. G. , "The Dependence of Wind Loads on Meteorological Parameters," Proceedings International

Research Seminar on Wind Effects on Buildings and

Structures, Ottawa, 1967.

4. Aynsley, R. M. , "Wind Effects on High and Low Rise

Housing," A.N.Z.A.S.C.A. Conference, Melbourne, 1971.

36
5. "Houses Can Resist Hurricanes," U.W. Forest Service Research

Paper FPL35, U. S. Department of Agriculture, August 1965.

6. Finney, C. A., "Materials and Construction Techniques

Considering Wind Effects on Buildings and Structures,"

UNESCO Regional Seminar on Wind Effects on Buildings and

Structures, Manila, 19 71.

7. Mackey, S. , Finney, C. , Okubo, T., "The Typhoons of

October and November 1970," Philippines, U. N . E . S . C . 0.

Paris, May 1971.

8. Kintanar, R. L., "Nature of Typhoons," UNESCO Regional

Seminar on Wind Effects on Buildings and Structures

Manila, 1971.

9. Thorn, H.C.S. , "Tropical Cyclone Crossing Frequencies for

the World and Their Application," Seventh Conference on Hurricanes and Tropical Meteorology, Barbados, December

6-9, 1971.

10. "American National Standard Building Code Requirements for

Minimum Design Loads in Buildings and Other Structures

A58-1," American National Standards Institute, New York,

1972 .

37
Chapter 5. Siting Considerations to Reduce the Effects

of Earthquakes and Windstorms

George E. Ericksen, Arthur Grantz, George Plafker

United States Geological Survey

and

L. Juan La Cruz

Commission for Reconstruction and Rehabilitation of

the Zone Affected by the Earthquake of May 31, 1970, Lima, Peru

5. 1 Introduction

This chapter consists chiefly of two studies, one by Arthur Grantz

(section 5.4), which discusses seismic and related hazards to low-cost

housing in Turkey, and the other by George Ericksen, George Plafker,

and Juan La Cruz, which is a case study of engineering geology and siting

problems related to the Peru Earthquake of May 31, 1970. These reports

are preceded by a brief summary of earthquake and windstorm hazards

and their identification.

Seismological data collected during the past 70 years have shown

that earthquakes generally take place within two principal seismic belts:

the Circum-Pacific belt, extending from New Zealand north to Japan and

Alaska, then south along western North and South America to Chile; and

the Mediterranean-Alpine belt, extending from Morocco, through the Mediterranean

and Middle East into central and southeastern Asia. Other belts of

activity are associated with large rift systems, such as the Mid-Atlantic

Ridge and the East African Rift Valley.

An earthquake as a geophysical event is measured in magnitude of

energy release and in duration and intensity of ground shaking. An

earthquake as a human event is measured in loss of life and property.

The scale of the human event is not always proportional to that of the

seismic event, for casualties and property damage depend on population

density, type of structures, stability of geologic foundations, and

time of occurrence, as well as on the magnitude, duration and focal

distance of the earthquake.

Destructive windstorms include tropical storms, hurricanes of the

Caribbean region and typhoons of the western Pacific, and cyclones,

which occur most frequently in rather well-defined belts in the temperate

climatic zone. On the whole, windstorms cause far greater destruction

and loss of life than do earthquakes. Damage may be directly due to

galeforce winds, to wave action or wind-generated tides at the sea coast,

or to inland floods caused by heavy rainfall.

Considerations of siting to lessen the hazard of destruction are different for earthquakes than for windstorms. In the case of earthquakes,

the total geologic environment must be taken into account--the danger

from failure of geologic foundations and from landslides is of paramount

importance. Damage during windstorms is generally restricted to that

caused directly by force of wind or indirectly by flooding. As a consequence,

site evaluations for earthquake -resistant construction are complex,

time consuming, and costly, whereas those concerned with construction

to resist windstorms are relatively simple and deal largely with the

topographic configuration of the site and surrounding region.

38
5 . 2 Earthquake Hazards

Estimates of seismic risk may be presented in the form of seismicrisk maps, which show the maximum intensity of earthquakes likely to occur within the area covered by the map. Such maps are based mainly

on a statistical analysis of the number and intensity of earthquakes

actually recorded in the area since observations began. Map reliability

is a function of the length of the period of observation and of the

volume and quality of data collected, and therefore is greatest for areas of high seismicity for which much data exist.

A seismic-risk map does not indicate the probable future frequency

of earthquakes of a given intensity but permits one to extrapolate the

maximum intensity to be expected, knowledge that is essential in determining

structural design. As such an extrapolation is based on the observed

relation between magnitude and frequency of previous earthquakes in

the area, the probability of occurrence of a large earthquake may be

predicted from the observed frequency of smaller ones. Unfortunately, instrumental records, which are available only for

about 70 years, are still an inadequate base for a statistical analysis

of probable earthquake frequence. In many areas, however, instrumental

data can be supplemented by information obtained from historical records.

Geologic and tectonic data furnish additional information for preparation

of seismic-risk maps of some areas, as has been done in Turkey and Iran.

A good seismic-risk map will contain reliable information on the

relative level of risk from damaging earthquakes in an area, but it

will not tell when such earthquakes will occur. The problem of predicting

the time and location of earthquakes, which is of considerable importance,

has only recently become the subject of intensive study, chiefly in

Japan, the Soviet Union, and the United States. The need for extending

such studies to other regions is critical. Success in this research

would be a major scientific achievement.

At any specific site, earthquake hazard is governed by seismic

probability, foundation conditions, topography, local and regional geology,

proximity to surface-water bodies (lakes, bays, and streams), occupancy,

and structural design. All these variables can be shown on maps from

which one may interpret level of risk at each point on the ground surface.

Such maps may be of great aid in determining appropriate land use. They

also may be used to identify specific or potential hazards and thus serve as a guide to engineering design as well as site planning. These

types of maps, however, are still in the development stage, and it may

be many years before standards are established, and still longer before

such maps become generally available.

When an earthquake occurs at sea, a segment of the ocean floor

may be elevated or depressed, owing to faulting or warping of the floor,

causing a complex high-velocity sea wave, or tsunami. When such a wave

approaches land, it loses velocity but gains amplitude, and depending

upon the local bathymetry, it may produce a high wave that devastates

low-lying coastal regions in its path. To evaluate potential disaster

from such waves, special tsunami -hazard maps should be prepared for

coastal areas, such as those of the Pacific Basin, which are subject

to seismic sea waves. Although the intrinsic value of geologic site plans and their use

in community development are widely recognized, such plans have not

been widely used, even in the so-called developed nations. Meaningful

site plans could greatly reduce future earthquake destruction of new

communities. Detailed site evaluations by qualified earth scientists

are particularly important as a preliminary phase in construction of

39
large buildings such as schools, hospitals, high-rise apartments and

offices, and other public buildings.

A good site plan will accommodate both short- and long-range expansion

needs and take account of potential hazards, such as low-lying ground

liable to flooding, landslides, tsunamis, and active faults, and watersaturated ground subject to compaction and lateral spreading. As a part

of site planning, it is desirable to determine soil behavior in response

to seismic shaking, especially under load, and at various degrees of

saturation. Laboratory study of behavior of both dry and wet soil under

vibrational loading is essential to site planning and for predicting

the potential of different soil types for compaction or liquefaction

during an earthquake. The behavior of soils under conditions of load

and vibration also may be determined by measuring micro-seismal characteristics

and by in. situ soil study.

A microzoning map prepared from such data may greatly aid site

planning. Microzoning maps should give the natural period of the foundation

material and portray potential hazards in a manner that is readily understandable to engineers and others who are responsible for construction. A

report on seismic microzoning of the Chimbote area in Peru [1] provides

an excellent example of site evaluation. The report provides information

about the geologic foundation conditions that will permit reconstruction

of Chimbote as an "antiseismic" city.

In seismic areas, the public needs to be better informed on the

nature of earthquakes as well as on potential local hazards and means

of dealing with them. Such information might be introduced into school

curricula. In such areas, officials dealing with environmental hazards

and the professional community of earthquake engineers and scientists

would share the responsibility of keeping community decision makers

informed of new knowledge of earthquake hazards and of assessing these

hazards as a basis for action to minimize destruction and loss of life

during an earthquake.

5 . 3 Windstorm Hazards

Good site location or orientation in terms of local topography

and natural cover can be determined to some degree from historical wind

data that give the frequency, velocity, and direction of the prevailing

or predominant wind. This information can be utilized to locate building

sites and position individual dwelling units to minimize the hazard

from wind. Windstorm damage may be minimized by placing buildings so that they are protected by hills or by stands of trees. How effective

wind planning and aerodynamic positioning will be in improving the resistance

of structures to tropical windstorms remains to be determined. In the

future, effective designs that consider shape, size, and type of building

as well as position and orientation, may be developed that minimize

wind damage from tropical storms.

5 . 4 Siting Considerations for Low-Cost Housing in Turkey*

5.4.1 Geologic and Seismic Setting

The geologic, seismic, and hydrologic hazards that pose a threat

to low-cost housing in Turkey have their roots in the unusual degree

Publication authorized by the Director, U.S. Geological Survey,

40
of mobility of the earth's crust in the Mediterranean region, and particularly

in Turkey. This mobility has persisted, with pauses, for perhaps the

last 200 million years of earth history. Although geologic hazards

in Turkey are serious and widespread, they can to a considerable degree

be anticipated and either avoided or provided for in site preparation.

This chapter first reviews the origin and nature of these hazards and

then proposes ways of coping with them at sites of low-cost housing.

The work in Turkey, on which this report is based, was undertaken by

the author during parts of February and March 19 72.

Turkey is astride the Alpine earthquake belt, one of Earth's two

major zones of strong and frequent earthquakes. This belt is thought

to owe its seismicity to continued differential motion between the Eurasian

and Afro-Arabian crustal plates.

Turkey is almost wholly within a belt of strongly deformed sedimentary

rocks that were deposited in a seaway separating Eurasia and Afro-Arabia

in pre-early Tertiary time. Intense compression of the rocks laid down

in this seaway was caused by the progressive drift of Eurasia and AfroArabia toward each other during the last 200 million years. This compression

produced a generally east-trending belt of strongly folded, faulted,

and locally intensely sheared and broken rocks, to which the name Alpine

Orogenic Belt has been applied. In many places, large volumes of submarine

volcanic and intrusive igneous rocks were added to (and churned into)

the sedimentary rocks of the Alpine belt. The collision of Eurasia

and Afro-Arabia in early Tertiary (50-60 million years ago) closed the

intervening seaway and what is now Turkey became an area of mountains

separated by narrow seaways and lowlands. The seaways and lowlands

received locally thick accumulations of marine, lagoonal , and continental

sediments (some of which are still poorly consolidated) and volcanic

rocks

Subsequent uplift and local deformation during Tertiary time contributed

further to the folding, dismemberment, and crushing of the pre-Tertiary

rocks and locally produced complex structures in the Tertiary rocks

themselves. Such movement has continued into modern times, producing

the mountainous terrain that dominates much of the present Turkish landscape.

Other manifestations of this young crustal mobility are repeated fault

displacements, earthquakes, and volcanic activity.

5.4.2 Seismic Zones of Turkey

Some 40 percent of Turkey is subject to severe earthquakes. Since

the advent of modern instrumental seismology some 70 years ago, Turkey

has suffered the largest shocks, in terms of Richter scale magnitude,

of any country in the Mediterranean region. Records dating from late

Roman times indicate that, on the average, catastrophic earthquakes

have occurred in Turkey every 60 to 80 years. The distribution and

character of these shocks , and the location and activity of the four

main seismic zones of Turkey (Figure 5.1), are directly related to the

location and type of the geosuture zones that traverse the country.

These seismic zones are: 1) Aegean-Marmara zone, 2) Northern Anatolian

zone, 3) Central Anatolian zone, and 4) Southeastern Anatolian zone

[2].

Aegean-Marmara Zone - -The Aegean-Marmara zone is the most complex

seismic zone in Turkey and the only one having a significant number

of deep earthquakes. Deep earthquakes in Turkey are those having focal

depths greater than 60 km [3]. Many earthquakes of both shallow and

deep origin in the Aegean-Marmara zone have exceeded magnitude 7 on

the Richter scale. Thirty-five major earthquakes per hundred years,

as judged by reports of heavy damage to cities, have shaken this roughly

41
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42
200,000 km seismic zone since the 11th century A.D. [2].

The earthquakes of the Aegean-Marmara zone are of two types: 1)

deeper shocks, which become progressively deeper from west to east,

are due to westward movement of the Anatolian crustal plate over the

Aegean plate, and 2) shallower shocks, commonly accompanied by fault

displacements that extend to the earth's surface, which seem to be related

to subsiding linear fault-bounded troughs, called grabens , that extend

east-west across the Aegean-Marmara zone. Surface faulting and shallow

earthquakes in the Anatolian plate in the Aegean-Marmara zone are especially

damaging because settlements of the area tend to be localized in the

long, narrow east-trending valleys that have been formed in part by

these same seismically active faults and grabens.

When vertical displacements occur beneath large bodies of water,

as they commonly do in the Aegean-Marmara zone, tsunamis may accompany

earthquakes of moderate to large magnitude.

Northern Anatolian zone - -Destructive shallow earthquakes are caused

by horizontal fault displacement, or slip, between the Eruasian and

Afro-Arabian crustal plates along the steeply to vertically dipping

Northern Anatolian fault zone. Along this fault zone, which is a major

geosuture, Eurasia is moving eastward relative to Afro -Arabia. In Turkey,

the zone can be traced for about 1,100 km; seismic evidence indicates

it to be an additional 400 km long. Although the Northern Anatolian

zone is relatively narrow, reflecting the linearity and relative simplicity

of the fault zone and its branches, it accounts for fully half the major

destructive earthquakes in Turkey. The western part of the Northern

Anatolian fault zone trends into the northern part of the Aegean -Marmara

seismic zone, where it appears to split into several branch faults.

In this area, the seismicity associated with the North Anatolian fault

zone cannot be distinguished in all cases from that associated with

faults of the Aegean-Marmara zone. Earthquakes in the Northern Anatolian fault zone are typically

related to large fault displacements that reach and rupture the earth's

surface. These features thus pose a direct hazard to structures. Individual

episodes of rupture along faults of this zone have, in historic times,

displaced the earth's surface as much as 4.3m horizontally and 1.5 m vertically. The surface displacement, which accompanied the earthquake

of December 26, 1939, was traced for a distance of 340 km along the

fault zone. Long, linear valleys have been eroded by streams along the crushed

rocks of the Northern Anatolian fault zone, creating some of the larger

areas of arable ground in the mountainous region traversed by the fault.

These valleys have served to concentrate settlement along the fault

zone, thereby making a larger proportion of the population of the area vulnerable to damage from both earthquake vibration and sudden fault

displacements than might otherwise be the case. Reports of heavy damage to cities indicate 10 or 11 major earthquakes

per 100 years since the second century A.D. From 1939 to 1967, eight

or nine earthquakes along the zone were accompanied by fault displacement

of the earth's surface. One of these, the earthquake that struck the

Erzincan region on December 26, 1939, killed 40,000 persons.

Central Anatolian zone . --The earthquakes of the Central Anatolian

zone, which is less active seismically than the Aegean-Marmara zone, are related to block faulting. Some of the block faults extend into

this zone from the Aegean-Marmara zone, but are included in the Central

Anatolian zone because: 1) associated earthquakes occur less frequently

43
than in the Aegean-Marmara zone, and 2) earthquakes o£ deep focus such

as characterize the Aegean -Marmara zone are rare or absent.

With the exception o£ two strong earthquakes at the border with

the Aegean-Marmara zone, recorded earthquakes in the Central Anatolian

zone have had Richter magnitudes o£ less than 7. Since the year 1205

A.D., about six major earthquakes per hundred years have occurred in

the zone. Southeastern Anatolian zone .- -A relatively narrow zone of earthquakes,

called the Southeastern Anatolian zone, trends northeast from the Gulf

of Iskenderun to the Northern Anatolian zone near Lake Van, a distance

of about 600 km. These earthquakes are related to horizontal movement

on a fault zone along which the Arabian Peninsula is being displaced

relatively northwestward with respect to the eastern Mediterranean

sea and Central Anatolia. The nature of the intersection of this fault

zone and the Northern Anatolian fault is presently unknown. They may

merge, or one may cut the other.

Since A.D. 110, there have been seven or eight major earthquakes

per hundred years along the Southeastern Anatolian zone. Although recent

earthquakes in this zone have been of small or moderate magnitude,

the historically important city of Antioch, at the southwest end of

the zone in Turkey, never recovered its classical splendor after it was demolished by a great earthquake in 527 or 528 A.D.

5.4.3 Seismic and Related Hazards to Low-Cost Housing in Turkey

Building sites in the seismic zones of Turkey are subject to four

types of seismic and related hazards as shown in table 5.1. The seismicrisk categories used in the table are analogous to those adopted by

Algermissen [4] for the Seismic Risk Map of the United States. They

are based, however, on judgments derived from a comparison of recent

faulting and seismicity of Turkey and the United States, rather than

on a detailed analysis of Turkish seismicity. These relative ratings

are presented only as a guide to the application of the lateral- force

requirements of the 1970 Uniform Building Code [5] to the design of

low-cost housing in Turkey, and not as a substitute for a carefully

considered seismic-risk map of that country. The UBC uses the Seismic

Risk Map of the United States as the basis for its lateral -force requirements.

The risk categories for tsunamis (table 5.1) cannot, of course,

be applied to building design in terms of lateral -force requirements,

nor is it feasible to design buildings to resist tsunamis. The categories

of foundation failures include numerous or widespread failures such

as compaction and liquefaction of soil and slumping or sliding of rock

and soil. Efforts to alleviate the danger of such foundation failures

are costly, and may be unsuccessful. Fortunately, such risks are local

and it is generally possible to select a safer nearby site.

Future multistory-multifamily low-cost housing plans, if designed

for Turkey, should strive for lateral-force requirements at least as stringent as those specified by the U.B.C. These requirements should

be supported by a modern seismic risk map of Turkey. Such a map does

not now exist, although one is being prepared by the Earthquake Research

Institute of the Ministry of Reconstruction and Resettlement of Turkey.

To be realistic, this map should be based on geologic and tectonic criteria

of recent and anticipated future seismicity, on the long historic record

of Turkish earthquakes, and on modern seismographic records and field

investigations of earthquake intensity.

44
TABLE 5.1. SEISMIC-RISK CATEGORIES

—^Risk categories for direct effects

of seismic shaking and tsunamis:

2/—Risk categories for foundation

failures during earthquakes:

0 - Negligible risk of damage

1 - Significant risk of minor damage;

small risk of moderate or major damage

2 - Significant risk of moderate damage;

small risk of major damage

3 - Significant risk of major damage

0 - Negligible risk

A - Small risk

B - Moderate risk

C - High risk

It may not be economically and culturally feasible to design traditional

single-family housing for Turkey that will meet the lateral force requirements

of the U.B.C. Nevertheless, efforts should be made to improve such

housing and perhaps approach U.B.C. requirements.

With respect to siting of low-cost housing near active faults,

it is recommended that: (1) New single-family low-cost housing in Turkey

be sited at least 50 and preferably 100 meters from main faults, fault

strands, and branches that can be observed or inferred to have displaced

geologic formations or deposits of Holocene age (the last 10,000 years),

(2) all high-population-density (multistory-multifamily) low-cost housing

be sited at least 100 meters, and preferably 150 meters from faults,

fault strands, and branches that can be observed or inferred to have

displaced geologic formations or deposits of Holocene age, and at least

50 meters from faults that can be observed or inferred to have displaced

deposits of pre-Holocene Quaternary age (the last 2 or 2 1/2 million

years); (3) all critical structures (those with many people per unit

area, such as schools, auditoriums, and hospitals, and those that provide

essential services, such as power plants or water- treatment plants)

should, in addition to the requirements in category 2, be sited at least

50 meters from any fault not proven to have been inactive (i.e., has

not undergone displacement) since the beginning of Quaternary time.

The difference between categories 2 and 3 is in the character of the

evidence required for judgment. In category 3, definite evidence of

lack of Quaternary activity is required; in category 2, lack of evidence

for Quaternary activity is accepted in lieu of definite evidence of

lack of such activity. The distinction is necessary because bedrock

in Turkey is broken by so many faults that application of Category 3 to all multistory buildings would be unrealistically restrictive.

The width of the proposed setback zones along faults of Holocene

or Quaternary displacement is adequate for most, although not all, faults

or fault zones. It is rather conservative, however, for faults that

show repeated surface rupture in the same location. Consequently,

setbacks could be reduced where detailed site studies, which should

include the excavation of trenches across the fault zones, showed that

smaller setbacks would be safe. In no case, however, should the setbacks

be less than 20 meters. Detailed investigations undoubtedly will also

show that in some places setbacks should be even larger than those specified

above

The relative hazard from tsunamis given in the tabulation applies

only to the most susceptible parts of the coastal areas categorized.

45
Tsunami hazard is not uniform along a given coast because the severity

of impinging tsunami wave trains varies markedly with the local configuration

of the shoreline and nearshore bathymetry. Bold headlands and coasts

having deep water near shore are generally little affected by tsunamis,

whereas low-lying coastal areas bordering a shallow moving platform

or narrowing or shoaling inlets are subject to large and destructive

wave trains. Thus, some sites on low ground at the head of narrow,

shoaling inlets in the Aegean-Marmara zone are in danger of destruction

by tsunamis

During some earthquakes around the world, large rockfalls or landslides

falling into deep water have created surge waves that have devastated

adjacent shorelines to recorded heights of at least 565 m. Subaqueous

slides in deep water have also set in motion local surges that have

destroyed entire communities on adjacent shores. In Turkey, such surge waves are a potential hazard in a few areas where bold topography underlain

by poorly consolidated or intensely sheared rocks abuts deep tidal inlets,

reservoirs, or lakes.

5.4.4 Ground Failures

Landslides (slumps, mudflows , and rockfalls), landspreading , and

differential compaction of weakly or irregularly consolidated alluvium

and other surficial deposits locally pose serious siting problems for

structures of all sizes in Turkey, even in the absence of earthquakes.

Such ground failures are especially common, however, under the dynamic

stresses induced by strong earthquakes. The physiography and climate

of Turkey and the character of many of its geologic formations make

large areas of the country susceptible to landslides, and it is not

surprising that field reports of the effects of strong earthquakes in

Turkey commonly mention landslides, soil slumps, and lurching (cracking

of soft ground induced by lateral movement) as important, and often

damaging, secondary geologic effects. The hazard from landslides, mudflows

and rockfalls is not, of course, limited to site disruption, but includes

both slow and extremely rapid modes of site inundation.

5.4.4.1 Landslides

The distribution and relative abundance of landslides is controlled

chiefly by slope, precipitation, character of underlying soils and rocks,

and cuts and fills or other perturbations created by the activities

of man. Studies in California and elsewhere [6] show that most landslides

form on slopes of 15° to 35°; a lesser, but appreciable percentage form

on slopes of 5° to 15° and greater than 35°. Very few landslides form

on slopes of less than 5°, and these are commonly caused by liquefaction

or landspreading during earthquakes. In California, landslides are also rare in areas receiving less than 250 mm of mean annual precipitation.

The absolute amount of precipitation above 250 mm per year does not,

however, seem to be as important as the character of the underlying

soil and rock which is the dominant control on the distribution and

abundance of landslides in areas having slopes greater than 5° and more

than 250 mm of mean annual precipitation. Soft, water-saturated, poorly

consolidated formations and intensely sheared or fractured rocks, especially

when water-saturated, and rocks containing minerals that swell or decay

readily in the presence of ground water, are especially susceptible

to sliding and slumping. The activities of man in undermining slopes

by cuts and excavations, or in overloading slopes by excessive or inappropriately placed fills, commonly induce sliding and slumping on otherwise

stable slopes. The addition of water to certain slopes by irrigation

and by seepage from pipes, septic systems, springs, or other sources

is a common cause of sliding, because the water increases the weight

of the ground while simultaneously decreasing its resistance to shearing

stresses.
Landsliding is a significant problem in Turkey because large areas of the country have slopes that exceed 5°, and slopes of 15° to 35° are common; mean annual precipitation in almost all of Turkey exceeds

250 mm per year; many of the rocks that underlie Turkey are poorly consolidated

or intensely sheared; and swelling clays are probably widespread and

abundant in the rocks and soils. The extensive steep tracts that are underlain by 1) soft sedimentary rocks of Tertiary, and especially late

Tertiary age; 2) crushed and sheared rocks along many of the fault zones;

and 3) ophiolite melanges (chaotic mixtures of diverse rock types that

are characterized by widespread intensely sheared rocks 'and by serpentine),

are all especially susceptible to sliding. The stability of potential

building sites on these lands lide -prone terrains, particularly where

slopes exceed 15°, should be examined with special care. The relatively

small proportion of lowlands in Turkey will inevitably lead to more construction of houses , roads , and a variety of other engineered works

on hills and mountainsides where the risk of damage from landsliding

is especially high, particularly during strong earthquakes.

5.4.4.2 Unconsolidated Deposits

The distribution and intensity of damage due to shaking during

a given earthquake has been observed by many workers to be strongly

influenced by the local character, geometry, and thickness of the underlying

soils and unconsolidated deposits, and by the position of the water

table. The relationship between these properties of the substrata at

a site, and the nature and intensity of damage is complex, however,

and one that is strongly influenced by the amplitude, frequency, content,

and duration of the seismic wave train at the site. Thus, the predominantly

short -period shaking from nearby shocks may produce very different amplitudes

and periods of shaking and adversely affect very different kinds of

structures from the long-period shaking that dominates the wave trains

from more distant earthquakes. Study of the relation of the local distribution

of earthquake damage to local soil and rock conditions should be made

as a basis for selecting sites for low-cost housing developments.

Patterns of damage from strong earthquakes, particularly to multistory

buildings sited on unconsolidated deposits, are closely related to lateral

variations in the thickness, composition, and water saturation of the

underlying soils and shallow geologic formations. Variations in these

factors can, for example, cause the horizontal velocity of ground motion

from a moderate earthquake to vary by a factor of 2 to 10 with respect

to nearby sites on bedrock [7] , and the response of given types of structures

to vary by factors ranging from 3 to 6 [8]. Liquefaction, differential

settlement and landspreading of unconsolidated deposits, and block glides

and slumps on gentle to steep slopes are also common geologic foundation

failures that have created extensive damage during moderate and large

earthquakes

Methods of predicting the dominant period and relative amplitude

of earthquake -induced shaking at a particular building site are currently

under study by many workers, and steady progress is being made toward

widely applicable analytical procedures [8,9]. Such predictions, however,

require fairly detailed knowledge of the thickness and physical properties

of the soils and poorly consolidated rocks of the site, and a realistic

assessment of the seismicity of the area [10]. Some of the analytical

procedures are moderately sophisticated, but estimates can be made from

relatively simple formulas. Modern practice requires that, in areas

of significant seismic risk, large buildings should be designed to

have a different fundamental period of vibration from that of the natural

ground at the site.

527-373 O - 74 - 5 47
Unconsolidated deposits containing liquefiable (noncohesive) materials

and having abrupt lateral variations in density and compact ibility are susceptible to flowage , differential compaction, lurching, and landspreading

during earthquakes; these deposits can be recognized by sufficiently

detailed surface and subsurface site examination. Examples of geologic

foundation materials in Turkey that are especially susceptible to failure,

particularly where the water table is shallow, are fine-grained, noncohesive,

or very soft cohesive alluvial, pluvial, estuarine, bog, and delta

deposits. Failures in such materials have caused damage in past earthquakes

in Turkey, and will be subject to failure during future earthquakes.

Although deep piles will sometimes protect a structure resting on such

material, such site preparation is costly. Consequently, it is generally

best to select an alternate site with more stable foundation material.

5.4.5 Floods

The high mountains and narrow alluvial valleys that characterize

much of Turkey have created a significant hazard from local, but sometimes

large floods. In some years, heavy snow accumulations on the higher

mountains may melt at rates that exceed the capacity of the river channels,

resulting in overflow and flood damage to settlements. The magnitude

of the problem is difficult to gauge from the literature available to

the writer, but the Menderes and Seyhan River systems, for example,

which drain high mountains in southern Turkey have periodically been

the scene of destructive floods. Accordingly, dikes and other floorcontrol structures have been built on some rivers in Turkey, and have

reduced flood hazards. Additional flood-control structures on these

and other rivers in Turkey would further reduce the danger of floods.

However, to completely eliminate the danger of floods, particularly

flash floods in mountainous areas, would not be feasible. The danger

can best be eliminated by selection of sites away from potential floods.

5.4.6 Recommended Site Investigations for Earthquake-Resistant Low-Cost

Housing in Turkey

In Turkey, the significant risk to low-cost housing from the seismic

and other geologic hazards outlined above can be substantially reduced

by using geologic, hydrologic, and soils engineering principles in selecting

and preparing building sites. Furthermore, it is certain that rapid

advances now being made in these disciplines will increase their effectiveness

for guiding the selection of building sites. Accordingly, it is recommended

that any large-scale program to construct low-cost housing in Turkey

include such investigations in the selection and preparation of building

sites. The program of such investigations proposed below envisions

more than a pilot study, because the usefulness and practicability of

such investigations have been demonstrated in comparable studies elsewhere.

On the other hand, it is not offered as a national program of land- use analysis, although it contains elements that would be included

in a national program.

5.4.7 Methods of Guiding and Controlling Site Selection and Preparation

Two methods exist for applying scientific and engineering knowledge

to the selection and preparation of building sites to reduce seismic

and other hazards. One uses regional geologic, soils engineering, hydrologic,

and other studies to guide the initial selection of sites. The second

consists of inspection and approval of site preparation and building

plans by a building official or inspector after a builder (private or governmental) has selected a site and prepared plans for its development.

The two methods are quite compatible, and can be used in sequence.

48
The first method, which emphasizes regional studies, serves to

help find the best building sites in an area in advance of costly site

and building plan preparation. It requires fewer well-trained professionals

than the second method, which is based on individual inspection of all

sites or projects. The principal disadvantages of siting control at

the planning stage are that it is too expensive for isolated single

houses or small developments and insufficiently detailed to control

site selection and preparation for large buildings.

The second method typically relies upon a building code administered

by local offices of national or regional agencies, and generally requires

intensive site investigations of problem areas. If based upon a wellprepared building code, this method has the advantages of uniformity

and clarity in its requirements. It has the drawbacks, however, of

being costly and time-consuming, of exercising review and control only

after a considerable effort has been expended on site selection, planning,

and design, and of requiring greater numbers of technical people to

review site selection and planning than will likely be available in

Turkey for many years

The building-code approach to assuring the safety of foundations

is exemplified by Chapters 29 and 70 of the 1970 edition of the Uniform

Building Code [5] . Chapter 70 deals with grading practices and makes

specific recommendations on the dimensions, slope, drainage, and erosion

control of cuts and fills. Chapter 29 relates building foundation requirements

to the character of the soils and geologic formations beneath a building

site. These chapters serve as general guides to site preparation.

Adherence to at least these minimum recommended grading practices is

especially desirable for earthquakeresistant construction because geologic

foundation failures are a common cause of building damage and loss during

earthquakes. However, the U.B.C. does not provide specific guidelines

for treating such seismic and related hazards as active faults , offsite

landslides, mudf lows , and liquefaction. Nor can a general code provide

adequate guidance to the influences that local geology, soils, ground

and surface water, macro- and micro -climate , and topography may have

on the safety or suitability of a site. As is true of all generalpurpose codes, the grading requirements specified by the U.B.C. are

too restrictive for some sites and insufficiently restrictive for others.

Recognizing this, the U.B.C. specifies that soils engineering and engineering

geologic investigations for cuts and fills be made at the option of

the responsible building official. Of necessity, the code neglects

local customs and local technical and administrative capacity for adequate

inspection and control of building sites. Indeed, such inspection and

control are rarely available for single-family and small multifamily

dwellings in smaller cities, villages, and the countryside anywhere

in the world.

S.4.8 Proposed Site Investigations

It is recommended that planning -s tage studies be the basis for

selecting and preparing sites for all earthquake -resistant housing for

which more than one or two alternative sites are available. Site-intensive

investigations (detailed studies of foundation conditions at a building

site and its environs) should be made of all sites proposed for large

engineered buildings, whether or not the sites were selected on the

basis of planning-stage studies.

A practical program to guide site selection and preparation for

low-cost housing in Turkey must deal realistically with the following

conditions

49
1) Recognition of many siting problems is difficult,

and the assessment of the risk presented by these

problems, even after they are recognized, requires a high level of technical competence.

2) Level of risk varies widely, even between adjacent sites.

3) Several disciplines (principally geology, soil

engineering, and hydrology) are required to recognize

and evaluate even the most common siting problems

and hazards.

4) The number of competent professionals in these disciplines is in short supply in Turkey and in most

developing countries.

Accordingly, a program of site investigations in Turkey should:

1) rely more on active site investigations by multidisciplinary teams

of professionals than on the enforcement of detailed codes by local

or regional building officials; 2) concentrate on housing units or projects

that are large enough or extensive enough to warrant the application

of necessarily expensive site investigations; 3) utilize regional reconnaissance studies as an alternative to site-intensive studies for some types

of low-cost housing projects; and 4) incorporate a review board to provide

for continuing review and updating of site evaluation and selection

procedures and criteria, and to guide continuing training of the siteevaluation and selection teams.

5.4.8.1 Planning-Stage Investigations

Effective planning-stage studies require that the entire region

under consideration for low-cost earthquake-resistant housing be evaluated

for suitable building sites. Experience in California and elsewhere

has shown that specialists who are able to extend or detail existing

soil, geologic, and hydrologic data by use of aerial photographs in

conjunction with field investigation can evaluate areas of a few square

kilometers or more at much less cost than by standard field methods

alone. Mapping scales for planning-stage investigations ordinarily

range from 1:10,000 to 1:250,000.

5.4.8.2 Site-Intensive Investigations

Site-intensive investigations consist of field and laboratory study

of geology and soils of selected sites and their relevant environs.

"Relevant environs" refers to the minimum area surrounding a site that

must be studied to evaluate its seismic and related hazards. This area most commonly ranges from one or two hectares to a few tens of hectares

in extent, but in special cases it may be much larger. Study of an area much larger than the building site may be necessary because the

critical evidence for many siting hazards, such as landslides, is commonly

difficult to find within a small site. Subsurface investigation by

drilling, trenching, and geophysical surveys would ordinarily be conducted

at and near the site, particularly for large structures. Mapping scales

will ordinarily range from 1:100 to 1:1,000. Evaluation of the engineering

data about geologic features and soils must take into account the nature

of the seismic risk zone in which the site occurs. For sites on flood

plains, or those having shallow ground water, poor drainage, or other

water-related problems, hydrologic studies may be required.

50
5.4.8.3 Scope of Investigations

Both planning-stage and s ite -intensive investigations should include

consideration of the following possible foundation problems and siting

hazards, but a complete list for any site will require study of the

site itself by qualified experts.

Geologic: 1) Active faults at and near the site; 2) landslides or other slope failures beneath or upslope

from the site; 3) liquefiable or easily compactable

materials beneath the site; 4) lateral inhomogenities

in compactable materials beneath the site; and

5) expansive and/or creeping soils.

Hydrologic: 1) Anomalous drainage or foundation conditions

due to permanent or seasonally shallow ground water,

springs, or seeps; 2) eroding shorelines of seas,

lakes, reservoirs, and rivers; 3) floods and mudf lows

4) tsunamis and surge waves.

Seismic: 1) Estimation of magnitude, epicentral distance,

duration, and frequency of damaging earthquakes; and

2) estimation of the base motion at the building site

due to the most damaging earthquake that might be

expected

Soil engineering: 1) Natural period of vibration of

building sites; 2) bearing strengths of the surface

and substrata; 3) estimate of the effect that soils

and poorly consolidated geologic materials beneath

a site will have on the character of shaking caused

by an earthquake; 4) slope stability; and 5) liquefaction potential.

Economic and cultural factors: Rural and village populations apply a variety of economic and cultural factors

in siting their houses, factors that will commonly be

equivalent or greater in importance than the seismic,

geologic, and hydrologic considerations. Serious

conflicts and economic hardship may befall the

occupants of low-cost housing that is sited without

regard to such economic and cultural factors.

Accordingly, the planning-stage site-selection teams

should include a person or persons knowledgeable about

the life style and economic pursuits of the relevant

populations. Interviews with the people to determine

their needs and wishes are important in order that

the technical studies can concentrate on finding safe

sites that are also economically and culturally acceptable and satisfying to the people.

5.4.8.4 Single-Family and Small Multifamily Houses

Site control for single-family and small multifamily housing is

practical only by planning-stage investigations; the cost of site-intensive

studies generally is too great for such buildings. Even planningstage investigations, however, are practical only for large projects

of such housing. Siting control for isolated individual units (or small

groups of units) of low-cost earthquake -resistant housing will have

to be limited to existing procedures, if any, until suitable regional

studies are made on behalf of larger housing projects, or for other

purposes

51
5.4.8.5 Multifamily Houses

Site investigations for large, engineered multifamily-multistory

low-cost housing should follow two patterns. Where the choice of sites

is limited or predetermined, site-intensive investigations of the geologic,

soil engineering, and hydrologic conditions at the site and the relevant

contiguous terrain should be made. Where there are alternative sites,

selection should be based on a regional environmental (planning-stage)

study followed by site -intensive investigations of the most suitable

site or sites. The cost of many of the site-intensive investigations

will be significantly reduced if the site is selected through a regional

study

5.4.8.6 Improvement of Existing Houses

Site studies can be of assistance in preparing proposals to improve

the earthquake resistance of existing housing by structural or foundation

modifications. Where extensive housing tracts or large buildings are involved, regional planning-stage and site-intensive studies can be

used to guide expenditures for modification of those houses that are

at suitable sites. Unsuitable sites might then be designated for eventual

conversion to parks or other low-risk uses.

5.4.9 Technical Supervision

The site-selection program should strive for technical excellence

through the establishment of an independent review board composed of

scientists and engineers from university faculties, private consulting

firms, and governments at home and perhaps abroad. International financial

assistance for obtaining foreign technical participation might be obtained.

The most important task of the review board would be the establishment

and continual improvement of a set of recommended investigations and

site standards that are realistic to the specific area or region of

the country at each stage in its development, and commensurate with

available budgets and professional staff. The board should also provide

guidance for the site-selection teams in difficult or special problems,

assist in the recruitment and selection of personnel for study teams,

and administer a program of continuing training of team members in the

newest technical developments in their various disciplines.

5 . 5 Case Study: Engineering Geology and Siting Problems Related to the

Peru Earthquake of May ^1, 1970 *7

5.5.1 Introduction

The Peru earthquake of May 31, 1970, offers a model for examining

the effects of the geologic environment on destruction, because it caused

a wide variety of geologic foundation and slope failures that were major

contributors to the extensive destruction and death toll. In the affected

region (Figure 5.2), the rugged topography, extreme variation in relief,

proximity to the sea, and great range of climatic conditions have given

rise to most of the geologic hazards that might be found in any earthquakeprone region, all within a relatively small area. This earthquake was probably the most catastrophic natural disaster in the history of the

Western Hemisphere and ranks high among the world's greatest natural

n Publication authorized by the Director, U.S. Geological Survey,

52
Figure 5.2 Region of northern Peru affected by the May 31, 1970,

earthquake showing the epicenter of the main shock and

the region of principal aftershocks (diagonal line

pattern) . Heavey dashed line shows the approximate limit

of compaction and fissuring of unconsolidated sediments,

of landslides, and of widespread damage of buildings

(from Ref [11]).

53
disasters. The extent of destruction- -roughly 49,000 people killed

and 184,000 buildings dsstroyed- -was largely due to unstable terrain

and to failure of classical adobe construction that had little resistance

to seismic shaking. Destruction was far out of proportion to the magnitude

of the earthquake C'^ichter Scale 7.7), which in terms of seismic energy

release does not place it among the truly great earthquakes of historical

times

The initial shock occurred on May 31, 1970, at 3:23 p.m., Peruvian

time, according to the U.S. Coast and Geodetic Survey (P.D.E. card,

June 1, 1970). The epicenter was at lat 9.2° S., long 78.8" W. , at sea 25 km west of the port city of Chimbote in the northwestern part

of the Department of Ancash. The hypocenter, or focus, was determined

by the Coast and Geodetic Survey to be at a depth of 56 km. Most of

the after-shocks having magnitudes between 4 and 6.25 and hypocentral

depths of 44-66 km, occurred in a well-defined zone 25-50 km wide that

extends about 140 km southward from the main shock epicenter (Figure

5.2).

The area of moderate to severe structural damage and pronounced

ground effects extends along the coast from near Trujillo to Pativilca,

and inland for a maximum distance of about 135 km (Figure 5.2). A maximum

intensity of shaking of VIII on the Modified Mercalli scale is indicated

in the coastal region between Casma and Chimbote, and at Huaraz in the

Andean region.

This report is based on information in earlier reports on fieldwork

carried out by Juan La Cruz and other geologists of CRYRZA, and on fieldwork

by Ericksen and Plafker during June and July 1971 [11] , [12] .

5.5.2 Geologic Environment

The Andean region of Ancash has extremely rugged topography and

great relief; oversteepened slopes tend to be extremely unstable and

subject to destructive landslides and rockfalls during earthquakes.

In the high glacier-covered Cordillera Blanca (Figure 5.2), rock and

ice avalanches are an extreme hazard, as are the more than 200 glacial

lakes, which may burst during an earthquake to cause devastating floods

and debris flows. Volcanic and granitic rocks on steep slopes of the

Cordillera Negra (Figure 5.2) are locally deeply weathered or strongly

fractured and consequently are subject to sliding during the rainy season,

or during a seismic event. Many thousands of landslides in both these

ranges during the 1970 earthquake caused extensive damage to farm lands

and rural communities. Fortunately, none of the glacial lakes ruptured

during the earthquake.

The valley of the Rio Santa is partly filled with unconsolidated

deposits of streams, debris avalanches, debris flows, and moraines.

The behavior of these sediments, which are the principal foundation

materials of the communities in the valley, varied greatly in response

to seismic shaking. The oldest sediments, constituting the earliest

valley fill, are well -cemented and relatively stable, whereas younger

terrace gravels, glacial moraines, and alluvium are poorly-cemented

and subject to landslide failure. Fine-grained water-saturated sediments

and soil tended to fail by differential compaction, liquefaction, and

lateral spreading during the earthquake.

Most of the coastal communities are built on the alluvial deposits

of flood plains of the major streams draining westward from the Cordillera

Negra. Stream valleys for distances of 5-10 km inland from the coast

are generally flat bottomed and have valuable agricultural land and

many rural settlements. Towns and cities along the coast, Chimbote,

54
for example, have extensive areas underlain by lagoonal and beach deposits,

commonly with a shallow water table. These fine-grained water-saturated

deposits, which tend to be very unstable under seismic shaking, underlie

most areas where geologic foundation failure contributed to extensive

structural damage.

No detectable vertical coastal uplift was associated with the earthquake,

nor does there appear to have been a significant seismic sea wave (tsunami

or maremoto) of the type that has accompanied some great coastal earthquakes

in Peru and elsewhere around the Pacific margin. This suggests a probable

absence of shallow dip-slip faulting on the sea floor during the earthquake

and is compatible with the seismologic data, indicating that the earthquake

was of subcrustal origin.

Surface faulting was not observed anywhere in the earthquake-affected

region, and, to judge from the location of the epicenter and major aftershocks

offshore from the coast, major faulting would not be expected onshore.

Nevertheless, recent faults are widespread in the region; the most prominent

constitute a system of en echelon normal faults along the west flank

of the Cordillera Blanca. The faults are marked by well-defined scarps

as much as 20 m high that displace Holocene glacial moraines and beds

of streams cutting these moraines. Undoubtedly, movement has taken

place on some of these faults during the past few hundred years, but

evidently not during the 19 70 earthquake.

5.5.3 Regional Siting Problems

Throughout the area affected by the Peru earthquake of May 31,

1970, the degree of destruction in any one community was determined

largely by the type and age of buildings, by the type of geologic foundation

material, and by relative stability of slopes of nearby hills. In general,

old two- and three-story adobe buildings, such as those of Huaraz (many

having supporting timbers weakened by age and termites) , or buildings

constructed of very poor quality adobe, such as those of Casma (Figure

5.3), were more heavily damaged than well -constructed adobe buildings.

Other types of buildings showed various degrees of damage, but most

of the modern reinforced-concrete buildings, or buildings with reinforcedconcrete frames and brick filler walls, sustained little or no damage.

Extensive damage due to failure of geologic foundations resulted

from differential compaction, slumping, and lateral spreading of watersaturated fine-grained sediments such as lagoonal and beach deposits

and manmade fill. The most notable example of foundation failure in

deposits of these types was in Chimbote. To a far lesser degree, similar

foundation failures took place in several other communities on the coast

and in the Andes. Furthermore, buildings constructed on dry dune sand

and on mudflow material associated with piedmont aprons and slope-debris

accumulations in the extremely arid coastal region, showed greater damage

than buildings of similar construction on compact stream gravels and

bedrock

There seems to be no obvious correlation between the intensity

of structural damage and foundation materials in many areas where foundation

failure did not occur. Adobe structures failed on foundations as diverse

as granodiorite and saturated alluvium or thick soils. Some villages

were almost totally destroyed, whereas nearby villages of apparently

similar construction and geologic foundation were only moderately damaged.

Similarly, in the towns, one could find adobe houses that had collapsed

next to houses of similar age and construction that were either moderately

damaged or undamaged. The reasons for these striking variations in

degree of damage are uncertain: subtle differences in composition and

55
Figure 5.3 Residential street in Casma, Peru, where all adobe -block

houses collapsed during the earthquake o£ May 31, 1970.

Adobe used in construction here was of extremely poor

quality, containing a high-percentage o£ silt and sand, with

little or no straw binder. It crumbles easily in the hand.

Casma, a torn, of about 15,000 inhabitantas before the earthquake

was almost totally destroyed during the earthquake.

56
(or) water content of the foundation material could be an important

factor, but slight differences in construction and the pattern of seismic- wave propagation may be equally important.

The most widespread damage due to earthquake shaking was to residences

made of adobe blocks, which constitute the overwhelming majority of

smaller buildings. Significantly, good adobe construction, such as the 3-story Hotel Chimu in Chimbote , survived the earthquake with little

or no structural damage. Unreinforced brick or concrete-block buildings

generally withstood shaking better than adobe, but in some areas, buildings

of this type were extensively damaged (Figure 5.4). Well -constructed

houses and most small buildings of reinforced concrete generally showed

little or no damage in most towns , even where they were entirely surrounded

by demolished adobe-block structures. Damage to large reinforced concrete

and brick structures ranged from negligible to total collapse, depending

upon design, quality of construction, and stability of the geologic

foundation

5.5.4 Behavior of Unconsolidated Sediments in Fiat-Lying Areas

Failure of unconsolidated sediments in flat-lying areas caused

extensive damage to structures during the May 31, 1970, earthquake.

The most serious damage was due to compaction and spreading of finegrained water-saturated sediments. Coarse unconsolidated sediments,

such as stream gravel and glacial moraine, were subjected to little

or no compaction during the earthquake and consequently caused little

damage. Dry unconsolidated sediments were comparatively stable, but

some dry sediments, such as coastal desert soils containing highly porous

mudflow material or manmade fill, failed by differential compaction

and slumping. Such failure, which was commonly accompanied by fissuring

at the surface, caused damage to roads and buildings. Differential

compaction of dry slope debris containing mudflow material and manmade

fill caused widespread damage to the steel plant in Chimbote, chiefly

by breaking of heavy concrete floors and misalignment of heavy equipment.

The observed settlement at the steel plant ranged from a few centimeters

to about 30 cm. Although compaction of unconsolidated sediments probably occurred

to some degree throughout the earthquake-affected region, its effects were most noticeable in the Chimbote and Casma areas and along those

segments of the coastal transportation routes that cross alluvium- filled

valleys. Compaction of water-saturated materials was locally accompanied

by ejection of water or water-sediment mixtures and the formation of

sand boils. Near-horizontal movement or landspreading of v\fater -saturated

sandy, silty, and clayey deposits toward free faces occurred at several

coastal localities. This process has been termed "landspreading" [13]

to differentiate it from landsliding, which connotes downslope movement.

The most spectacular examples of compaction and landspreading of

water-saturated sediments in Chimbote include: 1) settling and flooding

of a residential area in the southern part of the city (Figure 5.5),

where there was almost total destruction of unreinforced buildings;

2) differential compaction in the downtown business district (Figure

5.6); 3) compaction and landspreading near the steel plant dock, which

caused subsidence of about a meter (Figure 5.7) and damaged roads and

buildings; and 4) spreading of liquefied sand on a beach berm that resulted

in opening of a fracture more than a block long, along which masonry

houses were ripped apart (Figure 5.8).

57
Figure 5.4 Destruction o£ new home of unreinforced brick construction

in the Buenos Aires suburb of Chimbote, Peru; all buildings

in this suburb were damaged beyond repair. None of the

homes collapsed, probably because of the reinforced concrete

stairway that connected concrete floor slabs.

58
'[ Figure 5.5 Compaction o£ foundation material and destruction of adobe,

brick, and concrete block houses in low-lying area near the

coast in southern Chimbote. Before the earthquake, the

I ground surface was dry, and the water table was reportedly

'] at a depth of about 50 cm.

59
Figure 5.6 Street in downtown Chimbote where differential compaction of

water -saturated beach deposits and manmade fill caused

settling of buildings and cracking of concrete sidewalks.

Here, 2-, 3-, and 4-story buildings settled 20-30 cm into the

foundation material.

60
Figure 5.7 Subsidence o£ roadway fill at side of steel plant dock in

northwestern Chimbote, resulting from compaction and seaward

spreading of underlying water -saturated sediments. Roadway

settled about 1.2 m here. The dock, which is on deep concrete

piles, did not subside.

61
1

i

Figure 5.8 Concrete block house at the Corporacion Peruana del Santa

housing development, northwestern Chimbote, torn apart by

seaward spreading of the underlying beach sands that became

liquefied during the earthquake.

62
The near-total destruction of central Huaraz (Figure 5.9) was the

result of collapse of old relatively-unstable adobe buildings owing

to a combination of shaking and probable incipient compaction and landspreading

of water-saturated foundation material. This geologic foundation consists

of a layer of silty and clayey sediment, at least 2 m thick, resting

on gravelly material of an alluvial fan.

Compaction of water-saturated sediments, fissuring, and landspreading

at many other localities in the Santa Valley, particularly in fields

along old terraces or flood plains of the Rio Santa, caused local damage

to roads and buildings. Notable slumping and landspreading occurred

in a gently sloping field just south of Caraz. Here, slump material

in an area 50-75 meters in diameter spread downslope, with formation

of fissures and tilted blocks in the soil at the head of the slump area and a surficial flow of liquified soil at the toe.

Many earth flows were formed by liquefaction of water-saturated

silt and sand associated with extensive glacial outwash and morainal

deposits in the southern part of the Santa Valley. This is a grassy

area of subdued topography, and the flows took place on gentle to moderately

steep slopes. Because these flows formed in a sparsely populated area,

the only damage they caused was to roads and trails.

5.5.5 Landslides, Rockfalls, and Soil Slips

The earthquake triggered thousands of landslides and avalanches

throughout the area of about 65,000 km outlined on Figure 5.2. The

landslides included a wide variety of falls, slides, and flows involving

bedrock, unconsolidated sediments, and snow and ice, in varying proportions.

The overwhelming majority of the slides occurred on the steeper slopes

of the Cordillera Blanca and Cordillera Negra, within the area outlined

in Figure 5.10, and in the region of deeply incised drainage along the

western flank of the Cordillera Negra, just west of the outlined area. The largest and most destructive slide was the Huascaran debris avalanche.

At least six of the slides blocked stream drainage, forming landslidedammed lakes. Many small rockfalls occurred along the steeper natural

slopes and in roadcuts in the relatively low-lying arid coastal region,

but none is known to have resulted in noteworthy damage. The total

volume of material moved downslope during the earthquake is conservatively

estimated to be between 100 million and 200 million m -- perhaps a quarter

to half of which was in the great Huascaran debris avalanche.

Most landslides involved falls or slides of rock and slides of

poorly consolidated debris and soil along steep valley walls, streambanks,

and roadcuts. The largest slides, which could be discerned on vertical

airphotos , are plotted on Figure 5.10. Some of these are so closely

spaced that a single symbol on the figure may represent many slides.

In general, the large slides were mainly in the Cordillera Blanca,

whereas most of the smaller ones occurred in the Cordillera Negra, particularly

near the north end of the range and in deeply incised canyons elsewhere.

Most of the individual landslides are rockfalls and rockslides that

involve at least a few thousand cubic meters of material. Rockfalls

and slides are so numerous in and near the Canon del Pato downstream

from Caraz that it is virtually impossible to delineate individual

slides.

Shallow soil slips of unconsolidated materials were observed throughout

the area but were especially common on slopes mantled with water-saturated

glacial till, volcanic ash, and colluvium. Soil slips are characterized

by a series of irregular transverse open fissures, as shown in Figure

5.11, and by areas where thin slablike soil masses have broken away

63

527-373 0-74-6
Figure 5.9 Typical street scene in a 100-block area of central Huaraz

where nearly all adobe block buildings were destroyed, ^tost buildings were 2 or 3 stories high and had heavy tile roofs.

Thousands of people were buried here in the narrow streets

as well as in collapsed houses.

64
Figure 5.10 Map showing distribution of landslides triggered by the

earthquake of May 31, 1970. Dots --rockfalls , rockslides, and

debris slides; crosses- -block slumps and rotational slides;

letters- -landslides -dammed lakes.

65
Figure 5.11 Surficial slips in thin grass -covered soil and slope debris

along trail on east side of Cordillera Blanca, from CatacSan Marcos road about 2 km north of pass across range.

66
and slid or tumbled downslope. Although they are subtle features, soil

slips caused extensive damage because they commonly formed on cultivated

hillsides where they disrupted irrigation canals, trails, and fences,

and destroyed fields and buildings. In some very steep areas on the

west side of the Cordillera Negra, the thin soil of steeply- inclined

fields (many having slope angles of 30° or more) slipped away, leaving

bare rock. In this same area, soil slips destroyed trails that were

the only access to many fields. Many of these fields still were not

accessible a year or more after the earthquake because of the difficulty

and expense of blasting trails across newly exposed steep rocky slopes.

Eleven landslides involving slumps and rotational slumps of large masses of coherent materials were identified within the area outlined

in Figure 5.10, the area for which post -earthquake aerial photographs

were available. Each of these slides is estimated to contain more

than a million cubic meters of material, chiefly poorly-consolidated

fluvial -glacial deposits, pyroclastic volcanic rocks, and thin-bedded

shaly sedimentary rocks. The largest rotational slide block, at Recuay

(Figure 5.12), involved at least 8 million cubic meters of material,

and perhaps as much as 20 million cubic meters, depending upon curvature

and depth of the failure surface . The upthrust toe formed a dam across

the Rio Santa. At least five of the other rotational slides temporarily

blocked streams.

5.5.6 Debris Avalanches

By far the most destructive and geologically- fascinating aspect

of the earthquake was the cataclysmic avalanche of rock and ice from

the glacier-covered north peak of Nevados Huascaran (Figure 5.13). This

avalanche appears to be an event that, in terms of destructiveness

height of fall, velocity, and probably volume, far exceeds any avalanche

known to have occurred during historic time.

The debris avalanche originated as a rock and icefall from the

sheer west face of the north peak of Huascaran, between the altitudes

of 5,500 and 6,400 meters. The original slide mass, in which the amount

of rock apparently far exceeded the amount of ice, probably involved

a volume of at least 50 million cubic meters. This mass gained velocity

as it slid over Glacier 511 (Figure 5.14) for a slope distance of 2.4

km and vertical drop of nearly 1 km. Below this glacier, part of the

debris was funnelled along the valley of Quebrada Armapampa; the remainder

broke out of the valley and sped across major topographic irregularities

on a more direct course toward Quebrada Incayoc. Below the confluence

of Quebradas Armapampa and Incayoc, the main tongue of the avalanche

was channelled down the Rio Shacsha valley to the Rio Santa. Within

a few minutes after the first tremors of the earthquake were felt, the

avalanche had sped 16 kilometers from Huascaran to the Rio Santa. The

debris blocked the Rio Santa, temporarily causing it to back upstream

for a distance of about 1 kilometer; it also lapped up onto the west

bank of the river, reaching and destroying part of the town of Matacoto,

and flowed downstream. Yungay was buried by a relatively small tongue

of debris that swept over the ridge between the city and the valley

of Rio Shacsha. In overtopping this ridge, the avalanche climbed as much as 230 m above the adjacent valley floor.

According to eyewitnesses, the Huascaran debris avalanche was triggered

within a few seconds after strong earthquake tremors were first felt.

It moved downslope at high velocity with a deafening noise, and was accompanied by a strong turbulent blast of air. An eyewitness account

indicates that the debris avalanche travelled the 14.5 km distance from

its source to the vicinity of the cemetery at Yungay in less than 3

67

i
o

iH >^ <Dm

aa o

•H 13 +-> t3 u o S

rt (D 0) c3

i-H Pi

d) ,^ i-< u <D H O +-> rH i-( 0

!/) S

i=! ti tl O p!QJ o _ -s

•i-> 'd O 0) I/)

CO

<D •

+-> Ph

(L) W)O U !-> O O

XI P.

•H

tin

68
Nvdo. Huandoy

Figure 5.13 Oblique aerial view of Nevados Huascaran and the Huascaran debris

avalanche that destroyed Yungay, part o£ Ranrahirca, and other nearby

comiiiunities . Vertical relief between the avalanche source and the

Rio Santa averages 3,500 m (11,500 ft.). (Courtesy of the Servido

Aerofotografico Nacional de Peru)

69
70
minutes and possibly as little as 2-1/2 minutes--an average velocity

of between 280 and 335 km/hr (Mateo Casaverde, oral communication, July

3, 1970). Extremely high instantaneous velocities are indicated by

the distances that boulders were hurled across the Rio Shacsha valley.

For a vacuum ballistic range of 1,600 m, the estimated maximum horizontal

distance that boulders were thrown, the initial projectile velocity

had to be at least 450 km/hr. The effects of air drag would increase

this initial velocity by some 25-50 percent, suggesting an initial velocity

of as much as 600 km/hr.

5.5.7 Conclusions

The extensive destruction and loss of life in the Peru earthquake

of May 31, 1970, was due largely to 1) poor construction of buildings,

chiefly adobe, which had little resistance to lateral forces imposed

by earthquake shock, and 2) the Huascaran debris avalanche that buried

Yungay and parts or all of several smaller communities, and destroyed

extensive areas of farm lands. To a lesser, but significant degree,

destruction was caused by the widespread landslides and by differential

compaction, landspreading , and fissuring in unconsolidated geologic

foundation materials. Geologic conditions influenced the distribution

of the landslides and foundation failures during this earthquake, and

will undoubtedly do so in future earthquakes in Peru. Although neither

lake breakouts, surface faults, nor a destructive tsunami accompanied

the earthquake, they remain potential earthquake hazards in this part

of Peru.

Large landslides and debris avalanches and flows constitute the

major geologic hazard in the mountainous regions of Peru. Steep slopes

are extremely unstable and are periodically subject to sliding, particularly

when the ground becomes water saturated during the annual rainy season. Earthquakes often cause widespread downslope movement of unconsolidated

material and may trigger some larger slides than those that would normally

be expected to occur sporadically in mountainous regions. Failure

of unstable dams of moraine, alluvium, and landslide debris that impound

lakes in steep-walled glacial valleys may result in disastrous floods

and debris flows during earthquakes. Such a debris flow, triggered by

the January 6, 1725, earthquake, buried the colonial town of Ancash,

which is in the Santa valley about 3 km downstream from Yungay (Figure

5.2) . Differential compaction, landspreading, and fissuring may cause extensive destruction during large earthquakes, particularly to structures

that are built on water-saturated fine-grained unconsolidated deposits

or on poorly compacted natural or artificial dry materials. In Peru,

these materials are generally most widespread in valleys of coastal

regions, which commonly are also areas of highest population density.

Surface faulting was associated only with the 1946 Ancash and 1969

Pariahuanca earthquakes in Peru (Ernesto M. Deza and Daniel Huaco , oral

communication, June 1970 [14]). Because most known active faults in

Peru are in remote, sparsely populated areas, damage by direct fault

displacement does not appear to be a major hazard. However, active

faults are serious hazards in most other earthquake -prone regions, and

movement of them can cause extensive destruction to works of man.

A major earthquake-related hazard in coastal regions of Peru is

from destructive sea waves or tsunamis that could be generated by sudden

large-scale vertical displacement of the sea floor at the continental

shelf or slope. No such waves were generated during the 1970 Peru earthquake,

presumably because the causative fault displacement was relatively deep

71
seated. Nevertheless, many large destructive tsunamis have accompanied

previous major earthquakes along the Peruvian coast (Berninghausen

unpub . data, 1962 [14]) and will undoubtedly occur in the future. Both

distant and near-source tsunamis could cause widespread inundation of

low-lying parts of Peru, as well as of other coastal settlements of

the Pacific basin.

5.5.8 Recommendations

The investigation of the Peru earthquake of May 31, 1970, has

shown the need for systematic geologic and seismologic studies in Peru

in order to better select sites for construction that will avoid potential

geological hazards. The following systematic seismologic and geologic

studies should be carried out in Peru to identify hazards and to undertake

corrective measures to minimize destruction and loss of life in future

earthquakes: a) Preparation of a seismic-risk map of Peru; b) preparation

of a tsunami -hazard map of the Peruvian coast; c) preparation of geologic

foundation maps of the principal cities of Peru (investigations should

include borehole and trenching tests and study of microtremor characteristics);

d) monitoring of glacial lakes of Peru in order to evaluate the potential

for breaking of morainal dams that could result in disastrous floods

and debris flows; and e) identification of areas or regions that are particularly susceptible to major landslides and rockfalls.

A single agency of the Peruvian Clovernment should be designated

to undertake the above-mentioned investigations as well as continuing

studies of seismicity in Peru, and engineering geology and seismology

of individual earthquakes. In addition to carrying out investigations,

this agency could act as coordinator for earthquake studies carried

out by other institutions in Peru, particularly the intensive studies

that immediately follow each major earthquake and involve international

as well as national institutions. Among the agencies in Peru that have

been most active in seismological and/or geological studies related

to earthquakes are: the Instituto Geofisico del Peru (IGP) , the Comision

de Reconstruccion y Rehabilitacion de la Zona Afectada por el Terramoto

del 31 Mayo de 1970 (CRYRZA) ; the Escuela de Ingeneria del Peru, the

Servicio de Geologia y Mineria, and the Centro Regional de Sismologia

para America del Sur (CERRSIS) . Of these institutions, the IGP, which

has been most deeply involved in seismological studies on a long-term

basis, would probably best qualify as the prime agency responsible

for earthquake studies.

The staff for earthquake -related investigations, as outlined above,

need not be large, perhaps not more than ten scientists, and should

include soils scientists and hydrologists as well as engineering geologists

and seismologists. Equipment will be needed in addition to that now

in Peru. Of particular importance are portable seismographs, strongmotion seismographs , and portable seismometers of high sensitivity for

microtremor observations.

CRYRZA, which was formed specifically as the agency to undertake

diverse studies and reconstruction of the area affected by the 1970

earthquake, represents an innovative type of institutional development,

It has a wide variety of specialists, from geologists to structural

engineers and economists, that allows a multidiscipline approach to

the problems of reconstruction of an earthquake-devastated area. Such

an institution is potentially the most effective means of organizing

relief after an earthquake and bringing about the efficient reconstruction

of the affected area and revitalizing local industry and the overall

economy

72
. 6 Summary of Recommendations

1. Minimize wind damage by placing buildings so that they are protected by hills or by stands of trees.

2. Design future housing for adequate lateral - force requirements.

In Turkey, these requirements should be at least as stringent

as those specified by the Uniform Building Code [5] and

be supported by a modern seismic-risk map of Turkey.

3. New housing be sited at adequate distances from faults or fault strands. In Turkey, siting with respect to faults

or fault strands and branches should meet the requirements

set forth in Section 5.4.3.

4. Planning-stage studies should be the basis for selecting

sites for all earthquake -resistant housing for which more

than one or two alternative sites are available. Siteintensive investigations should be made of all sites

proposed for large engineered buildings (see Section 5.4.8).

5. Prepare seismic-risk maps in Peru.

6. Prepare a tsunami -hazard map of the Peruvian Coast.

7. Prepare geologic foundation maps of the principal cities

of Peru.

8. Monitor glacial lakes of Peru in order to evaluate potential

for disastrous floods and debris flows.

9. Identify areas or regions in Peru that are particularly

susceptible to major landslides and rockfalls.

10. Designate a single agency of the Peruvian Government to

undertake investigations and studies of seismicity in Peru.

References

1. "Report on Seismic Microzonic of Chimbote Area, Peru,"

Overseas Technical Cooperation Agency, Government of

Japan, Tokyo, 1971.

2. Ilhan, Emin, "Earthquakes in Turkey," Geology and History of

Turkey, Campbell, A.S., ed.. Petroleum Explor. Soc. Libya,

Am. Field Conf . , No. 13, 1971.

3. Ergin, Kazim, Ugur , Guglu, and Uz , Zeki , "A Catalog of

Earthquakes for Turkey and Surrounding Area," Istanbul

Tech. Univ., Fac . Mining Eng., pub. 24, 1967.

4. Algermissen, S. T. , "Seismic Risk Studies in the United

States," Fourth World Conference on Earthquake Engineering,

Santiago, Chile, Proceedings, Chilean Assoc. Seismology

and Earthquake Eng., Santiago, v. 1, pt. Al , 1969.

5. "Uniform Building Code," International Conference of

Building Officials, Pasadena, California, 1970.

6. Radbruch, D.H., and Crowther, K.C., "Map Showing Areas

of Estimated Susceptibility to Relative Landsliding in

California," U.S. Geol. Survey open-file rept., 1970.

73
7. Borcherdt , R. D. , "Effects of Local Geology on Ground

Motion Near San Francisco Bay," Seismol. Soc. America

Bull . , V. 60 , no. 1 , 1970.

8. Seed, H. B. , and Idriss, I. M. , "Influence of Local Soil

Conditions on Building Damage Potential During Earthquakes,"

California Univ. Earthquake Eng. Research Center Rept.

no. EERC 69-15, 1969.

9. Seed, H. B._, Idriss, I. M. , and Dezfolian, H. , "Relationship Between Soil Conditions and Building

Damage in the Caracas Earthquake of July 29, 1967,"

California Univ. Earthquake Eng. Research Center Rept,

no. EERC 70-2, 1970.

10. Seed, H. B. , Idriss, I. M. , and Kiefer, F. W.

"Characteristics of Rock Motions During Earthquakes,"

California Univ. Earthquake Eng. Research Center Rept.

no. EERC 68-5, 1968.

11. Plafker, George, Ericksen, G.E., and Fernandez

Concha, Jaime, "Geologic Aspects of the May 31, 1970,

Peru Earthquake," Seismol Soc. America Bull., v. 61,

No. 3, 1971.

12. Ericksen, G.E., Plafker, George, and Fernandez Concha,

Jaime, "Preliminary Report on the Geologic Events

Associated with the May 31, 1970, Peru, Earthquake,"

U. S. Geol. Survey Circ. 639, 1970.

13. McCulloch, D.S., and Bonilla, M.G., "Effects of

the Earthquake of March 27, 1964, on the Alaska

Railroad," U.S. Geol, Survey Prof. Paper 545-D, 1970.

14. Silgado F., Enrique, "Historia de Los Sismos mas Notables Occurridos en el Peru," (1515-1960), Inst.

Panamericano de Geografia e Historia, Comite Panamericano de Ciencias Geofisicas, Bol, 1968,

Bibliog. Geofis. Oceanogr. Am., v. 4, p. 191-241.

15. Kinzl, Hans, "Nevado Huascaran, Cordillera Blanca, Peru,"

Sociadad Alpina Austriaca, Inst. Cartagrafico FreyburgBerndt y Artaria, 1 sheet, scale 1:15,000, Vienna, 1970.

16. Russell, R.J. , "Alluvial Morphology of Anatolian Rivers,"

Assoc. Am. Geographers Annals, v. 44, 1954.

74
Chapter 6. Methods of Housing Construction

William F. Reps

National Bureau of Standards

6. 1 Introduction

Viable technologies capable of responding to the urgent need for

large numbers of inexpensive earthquake and storm resistant dwellings

in developing countries can only be achieved if the resources available

in the area of housing construction are properly utilized. One such

resource, often overlooked, comprises traditional methods and skills,

which may be changed and improved by the application of innovative technologies

requiring only limited investments and training programs. The resulting

improved methods could achieve considerably higher standards of quality

and productivity while being compatible with local conditions and needs.

In recent years, industrialized methods of construction have been

introduced and used in various developing countries, often with encouraging

results. Such methods represent an extremely promising technical solution

to the problem of providing safe, inexpensive construction on a large

scale. Progressive technologies compatible with local capabilities

and needs should therefore be used in an effort to develop and improve

industrialized methods of construction.

This chapter contains a brief review and discussion of traditional

and industrialized methods of construction in three developing countries

selected as case studies: Peru, Turkey and the Philippines.

6 . 2 Traditional Construction Methods

Peru . Stone masonry was used in Peru by the Incas for fortifications

which are still standing today.

On the north coast rural houses are commonly built on stilts with

walls made of woven mats and with roofs made of reeds and banana leaves.

Pegs or thongs of leather are used as binding elements.

Various types of cane are used for housing throughout the Coast.

A common type of dwelling consists of a framework of thick cane or wood

uprights imbedded in the earth to a depth of 15 cm. Walls are made

of cane mats fastened to bamboo or wooden stringers with rails or thin

rope and lined with earth mortar or with wrapping paper. Roof mats

have a light covering of earth.

In urban areas of the Coast, quincha construction is widely used

because it is earthquake resistant, inexpensive and easy to build. This

system consists of a framework of wood uprights placed at 80 cm to 100 cm intervals between a floor and a roof beam and braced with diagonals

and an intermediate stringer. Cane is placed vertically and tied to

the framework with cord or leather strips. The wall is then plastered

with mud and finished with a coat of whitewash. In spite of its advantage,

quincha construction is now less favored by potential users mainly due

to shifts in social and cultural acceptance.

Adobon is the most common construction type in the Sierra and consists

of mud mixed with straw, manure and pebbles molded in place between

wood planks. The width of the wall is 60-80 cm. Adobon houses generally

have two stories of about 2.80 meters height each and are built with

75
no windows. Tiny openings are left in the walls for ventilation. Roofs

are made with eucalyptus poles covered with wild straw.

Adobe construction is prevalent throughout the Coast. Adobe is

generally considered by potential users to be inferior and undesirable.

This attitude can probably be changed by upgrading the quality of adobe

bricks. Modern techniques applied to adobe construction have great

potential in so far as achieving inexpensive, socially acceptable, good

quality earthquake resistant structures Csee Chapters 2 and 10). An

example of a typical adobe construction is shown in Figure 3.5.

Turkey . Wood is widely used in Northern Anatolia where log houses

are built in the forest regions.

Stone masonry construction is used in almost 50 percent of the

rural dwellings in Turkey and are especially frequent in eastern, southeastern,

south and southeastern Anatolia (see Figure 3.4). Walls are generally

40-60 cm thick and stones are usually bound with mortar. Horizontal

wood, metal or reinforced concrete ties are placed at about one meter

intervals.

Almost 30 percent of existing rural dwellings are built with adobe

which is the most common material around Marmara and in western, central

and eastern Anatolia. Adobe is used in blocks, or poured in place with

or without tree branches as reinforcement. Its social acceptability

is at present low. As in Peru, upgraded adobe construction is a promising

technological development.

Brick construction is mainly used near Marmara and in northern

and northeastern Anatolia.

Timber is used for framing and is filled with mud, tree branches,

adobe, stone or bricks. Adobe, stone or brick filled construction is

dangerous in earthquake zones if the timber members and their connections

are not sufficiently strong (Figure 6.1).

Thick earth roofs are frequently used, especially in adobe construction

(Figure 6.2). Unless the roofs are adequately braced horizontally while

diagonal bracing is provided in the walls, they may constitute a hazard

in earthquake regions. Their use should therefore be limited by building

codes (see Chapter 7)

6 . 3 Industrialized Construction Methods

6.3.1 Labor-intensive Industrialization

In order to promote more efficient use of scarce resources of capital

and skills in a community having an abundant labor supply, it is natural

to develop labor-intensive industrialization, as the first phase of

a transitional technology that will evolve with and stimulate the economy.

Labor-intensive methods are not incompatible with the use of new techniques.

For example, foam plastics appear to offer significant promise for lightweight roof insulation and wall in-fill. Honeycomb and corrugated cardboards

show potential in sandwich panel configurations using gypsum, jute fabrics

and foam insulation. The production of adobe blocks or bricks also

lends itself to labor-intensive industrialization.

Before the actual initiation of a local production setup, a determination

of economic feasibility is necessary. While quality and quantity are important, costs of production and revenue possibilities are clearly

the most critical factors in evaluating the feasibility of such a program.

76
Figure 6.1 Two-story adobe-filled timber -framed structure in Turkey.

Damage is due to poor quality of framing and connections.

77
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78
In marketing the product, in addition to considerations of design, construction

and site planning, the individual user's demand for such attributes

as choice and control of dwelling environment must be taken into account.

6.3.2 Prefabricated Housing in Turkey

Prefabricated housing in Turkey was first introduced in 1957 when

a Turkish construction firm built a housing complex consisting of one,

two and three-story units in the Eregli region, using the Danish LarsenNielsen procedure. However, until a few years ago when the Turkish Government

became involved in this field, only a few prefabricated houses had been built.

Prefabricated housing efforts have increased considerably since 1967,

mainly due to successive natural disasters (earthquakes, floods, other)

occurring in Turkey since this date which produced an urgent need for housing.

The government awarded initial contracts to private firms for the construction

of partially-precast dwellings. Later the fabrication of construction

components was started in the workhouses of the MKE (State Mechanical and

Chemical Industry Institution) and in the plants of the Land Resettlement

Directorate

The following prefabricated frame and wall units are now being manufactured

in Turkey for housing construction:

(i) Steel skeleton and timber partition walls

(ii) Reinforced concrete panels

(iii) Lightweight, reinforced concrete panels (Figure 6.3)

(iv) Plastered panels

(v) Steel frames and walls filled with lightweight concrete

(vi) Timber panels (Figure 6.4)

(vii) Prestressed concrete units

(viii) Plastic dome elements

These prefabricated units now are produced mainly by three plants , the

Lodumnu and Etlih plants, which belong to the Ministry of Reconstruction

in Ankara, and a plant owned by the Swedish "Ytong" firm in Istanbul.

The "Lodumnu plant" in Ankara was founded in 1968 and prepares

timber components which are used primarily for housing but are also

used in the construction of mosques. Initially, the plant produced

six dwellings a day for the regions of Kigi, Igdir, Amasra and Bartin.

After the Gediz earthquake in 1970, the production capacity was increased

to sixteen dwellings a day. At present, seven dwellings are produced

in a normal shift and sixteen a day in emergencies.

The plant manufactures several types of timber panels including

both outside panels and inside panels on a modular size of 1.20 m. Outside

panels are 10 cm thick. Half of this thickness is insulating glasswool. They are covered by 19 mm thick hard board on the inner face

and by 8 mm thick asbestos on the outer face. Inside panels are 6.0

cm thick and are doubly faced with thin hardboard. Some panels have

window and door openings. The panels are mostly used in construction

of one-story, single-,family dwelling units of 48 m clear surface for

urban units and 43 m for rural units, in accordance with prototype

79

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81
architectural plans. In addition, the plant also manufactures and delivers

the timber roof system which consists of 37 panels, 7 roof trusses,

and additional miscellaneous items.

The thermal insulation provided by the glass-wool is satisfactory.

Laboratory tests show that the heat transfer from 10-cm-thick external

panels is equivalent to a 60-cm-thick brick wall. The earthquake resistance

of the panels has not been tested in the laboratory, but the earthquake

hazard risk of house of this type of construction is far less than for

brick masonry dwellings of the same size.

The prices of these panel units vary between 140 and 167 TL.* (1972

prices) for inside panels and between 194 TL. and 233 TL. for outside

panels. The components and miscellaneous items required for the construction

of a dwelling are sold by the plant at a price of 13,000 TL. With foundation,

erection, and installation of sanitary and electrical equipment, the

price rises to 21,000 TL . For a total construction area of 51.8 m

(a clear surface of 48m^) this corresponds to a unit price of approximately

400 TL./m2, or 2.5 times less than for similar dwellings made by private

firms.

The Etlik plant, near Ankara, was founded in 1970 and produces

prefabricated light-weight concrete panels. The aggregate used in the

lightweight concrete is imported Styro^or , a product of the German BASF

firm. Styropor will soon be produced in Turkey in the PETKIM (State

Petrochemical Industry) plants. Concrete with this light-weight aggregate

has a compressive rupture cube strength of not less than 40 kg/cm^.

The panel components also are based on a 1.20 m modular size, with

a typical panel size of 1.20 m x 2.40 m. Panel thickness is 6 cm for

inside walls and 8 cm for outside walls. The panels are covered by

1.5 cm-thick concrete on outer faces and by 0.2 cm- thick concrete on inner faces. Typical dwellings built with these panels in earthquake

regions have a prototype plan of 6.08 m x 7.28 m. Prices in 1972 of

these panels range from 136 TL. to 179 TL.

A typical dwelling is constructed using 39 panels and 47 additional

elements, including timber roofing elements. The price of all the items was 11,500 TL. Including erection costs, the total price of one dwelling

is 17,200 TL. or 400 TL./m2.

The heat insulation capacity of these panels is equivalent to that

of a 50 cm- thick brick wall. The earthquake resistance is estimated

to be good, although no tests have been conducted.

The two plants of the Ministry of Reconstruction are now producing

components for the construction of school buildings and for dormitory

buildings used by the Turkish Army, in addition to use in dwellings

and other structures.

The "Ytong" firm of Turkey, founded in 1966, utilizes a Swedish

process which utilizes a mixture of ground limestone, alumina powder,

and Portland cement. Hydrogen is released in the chemical reaction

which takes place after the contact of the dry mixture with water.

Within two hours after the chemical reaction, the material reaches a sufficient degree of strength to be cut into blocks which are then placed

in autoclaves with steam circulating under pressure. This forced curing

and drying process takes about 10 hours. The resultant material can

be cut into desired shapes and sizes, such as bricks, panel wall units,

panel slab units, etc.

1 U.S. $ = 14.30 TL (Turkish Lira) in 1972.

82
The "Ytong" standard products used in the partial prefabricating

are

(i) Panel Slab Units are the rectangular prismatic blocks

with standard width of 50 cm. Their length ranges

from 1.0 m to 6.0 m, in increments of 0.2S m. Their

thicknesses range from 7.5 cm to 25 cm, in increments

of 2.5 cm. The slab panels are also used as precast concrete

joists. Empty spaces left between the panels are filled with reinforced concrete joist beams.

(ii) Panel Wall Units have a width of 50 cm and lengths

ranging from 0.50 m to 3.00 m, in increments of

25 cm, thicknesses range from 15 to 25 cm.

6.3.3 Prefabricated Housing in the Philippines

Only two companies are presently involved in the manufacture of

prefabricated components in the Philippines, a private firm producing

wall panels and roof trusses and a government firm producing lightweight concrete panels. The government firm, as the result of reported

technical difficulties, has not yet produced the porous concrete wall

panels for which it was designed.

Filipino builders are aware of the savings intrinsic in prefabrication

and are confident of their capacity to undertake prefabricated construction

work. However, the volume of such work is small at present, most likely

because of lack of adequate financing to develop a viable industry.

6.3.4 Prefabricated Housing in Peru

Wood Construction

According to the official registers of the Ministry of Industry

and Commerce, there are two plants for the production of prefabricated

wood houses, one located in Lima and the other in Pucallpa in the jungle

region. In 1955 these companies produced 123 units at a total value

of S/6 ,912 ,000 ,* i.e. an average value of S/56 ,195 per unit, whereas

in 1968 they produced 190 units at a total value of S/25,075,785 and

an average unit value of S/131,978. The available statistics include

as units not only houses but also temporary sheds erected at the beginning

of civil construction projects. An estimate of the construction capacity

for prefabricated wood houses shows that between 1965 and 1968 only

30% of the installed capacity was used.

In the city of Lima about fifty carpentry shops produce wood houses,

of which less than ten account for about 70% of the production. It

is estimated that the present installed capacity, working two shifts,

can deliver between 500,000 and 600,000 units a year, provided there

is a sufficient supply of the appropriate wood.

It is noted that the consumption of lumber and plywood was only

8.5 bd ft per capita in 1970, lower than in most Latin American countries.

It was estimated that resources available in the natural forests of

the eastern slopes of the Andes and of the upper Amazon basin amount

to approximately 500 bd ft per capita yearly. The present under-uti li zation

is due to rudimentary exploitation techniques , to transportation

1 U.S. $ = 43.4 Soles (S/) in 1972.

83
difficulties, and to the difficulty of harvesting selected trees in

a mixed forest, where more than 1,500 species are estimated to exist

(only 300 species exist in Europe) of which only 25 are exploited commercially

in Peru.

Concrete Construction

At Chimbote, where cement is readily available from the plant at

Pacasmayo, large concrete panel and modular systems are competing with

conventional permanent construction (Figure 6.5).

The Unicreto plant, located south of the city, produces a variety

of "U" shaped modules , or units, averaging 3 m wide, 2-1/2 m high and

1-3/4 m deep. The units are placed on 7-1/2-cm-thick concrete slabs

in an inverted position forming walls and roof. In this fashion three

inverted "U's" shipped to the site with trimmed window and floor openings

form a space of approximately ISm^. The present output of this plant

is approximately sixty modules per day. An average house consists of

nine basic units. The concrete used has a strength of 210 kg./cm.^

Presently the Unicreto plant is producing 328 complete houses and

872 basic units under a contract which will probably be extended to

include an additional 2,000 units. In addition, the national plan

of Peru calls for an additional 6,000 units by the end of 1973. The

cost of units currently being built average S/70,000 for a 46 m^ complete

home. Land and utilities are an additional S/50,000. Total cost thus

averages S/2600 per m^ of floor space ($6.10 per ft^.). For a basic

unit of 29 m^ the cost is S/31,000 and S/32,000 for the site and utilities,

an average of S/2,200 per m^ of floor space. Lot sizes average 150 m2.

The plant as it now exists is an efficient operation occupying

40,000 square meters and employing 150 persons, of whom four are skilled.

Delivery problems cause difficulties because the number of special vehicles

available to deliver modules to the site presently is inadequate. Inasmuch

as production is on schedule, a large number of units are accumulating

at the plant awaiting delivery. Additional delivery vehicles are being

adapted from conventional dump trucks.

At the Listos plant, also located south of Chimbote, columns and

panels are manufactured under a process patented in Peru. Four basic

units are produced: a hollow wall panel of 3 m x 3 m x 20 cm, a solid

wall panel of 3 m x 30 cm x 12 cm, a 15 cm^ column notched to receive

the solid wall panels, and a narrow hollow roof panel similar to the

hollow wall panels. It is estimated that at least two crews of seven men each and three to four days' time is needed to produce the components

for a single housing unit.

The Listos plant has its own large clientele in the private sector,

and also has won the public bidding for the construction of 200 dwellings

in Chimbote (in an area devastated by the 1970 earthquake). Plant owners

also are negotiating to build a similar plant in Mexico, where they

have apparently won a public bidding. The plant is being enlarged in

order to reach a production of between 50 and 100 dwellings per month.

The cost of construction of houses of this type is as much as S/1,600

per square meter for low-cost types of housing. Although relatively

expensive, this system has the advantage of a short construction time,

with resistance to earthquake approximately equal to Unicreto.

84
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85
Miscellaneous Systems

Other systems use wood or steel frames, and panels made of asbestoscement, fiber-cement, plywood, "maderita," "mapresa," reinforced expanded

polyurethane , etc. Extensive studies of special roof panels, first

developed in India, using thick cloth as both forms and reinforcement

for light air-entrained concrete with pumice stone aggregate, were carried

out at the National University of Engineering between 1957 and 1972.

Such panels, if successfully developed, may be used to advantage in

earthquake resistant construction.

A prototype house made from jute core laminated with fiberglass

was designed, developed and constructed by CARE, Inc. in Bangladesh

(Figures 6.6, 6.7). The reaction to the full size model in Dacca was highly favorable as the construction uses a high proportion of locallyavailable materials and appears to be of superior resistance and durability.

The house is still in the experimental stage, both from the structural

and the social acceptance standpoints.

86
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87

Chapter 1. Building Codes and Regulations

William F. Reps

National Bureau o£ Standards

7.1 Introduction

Building Codes and Regulations contain mandatory requirements,

one o£ the main purposes of which is to prevent the design and construction

of structures deemed to be unsafe. In a seismic region, for example,

building codes should specify the magnitude of the minimum seismic loads

that structures must sustain, the quality of materials and workmanship

consistent with an adequate aseismic behavior of structures, and positioning

of structures in relation to potential site hazards.

In order that effective building programs be undertaken, it is

necessary that building codes be developed which take into account local

conditions and needs. The compilation of national seismic codes published

in 1960 by the Organizing Committee of the Second World Congress on Earthquake Engineering reveals that more than half of the 70 countries

which lie within the main seismic zones of the world, do not have building

code provisions for aseismic design or construction. The absence of

adequate building codes may have serious, and sometimes disastrous technical, economic, and social consequences. Improvement of existing building

codes is therefore a required phase of any effort to provide safe, lowcost housing on a major scale.

In this chapter a brief discussion will be presented of problems

related to building codes that are typical of developing countries.

The questions of whether codes exist, of the scope of existing codes,

of whether they would be effective if enforced and of whether they are enforced will be examined with reference to the case studies of Peru,

the Philippines and Turkey.

7 . 2 Difficulties Encountered in the Promulgation and Enforcement of Codes

and Regulations"

The promulgation and enforcement of building codes and seismicresistant structures presents problems of particular difficulty in developing

countries. For example:

(a) Many local materials or construction systems have

not yet been studied scientifically. Their technical

design parameters are therefore not known.

(b) In many regions, local geology and soil conditions

have not been investigated.

(c) In many regions , seismic or extreme wind records are not available.

(d) In many areas, a reliable system of inspection and

enforcement does not exist and is difficult to

establish

The promulgation of conservative, i.e., safe, building codes may

meet with resistance motivated by short-term economic factors. For

example, in Nicaragua the promulgation of a code similar to that used

in California was advocated by various experts long before the Managua

89
earthquake o£ December 1972. It is only after this disaster that the

decision to adopt such a code appears to have been made.

For housing built with funds borrowed by the owner from a local

savings institution, improved enforcement of codes may be achieved by

making the granting of credits contingent upon satisfactory compliance

with building code requirements. The inspection of the building site

to insure enforcement of the codes could in this case be performed by

qualified agents of the savings institution.

7 . 3 Building Codes, Local Conditions, and Innovative Technology

In order to effectively perform their function, building codes

must be compatible with local conditions. Codes in developing countries

cannot be based on conditions prevailing in countries with a highlydeveloped technical base. It is, in addition, necessary that, within

the same country, local conditions that may vary from region to region

or even within the same region, be properly taken into account. For

example, modern buildings located in the Fars region of Iran were designed

by Tehran engineers using criteria which did not take into account the

geologic characteristics of that region. In the recent earthquake which

devastated southern Fars, over 60 percent of the victims perished as

a result of the collapse of such buildings.

Building codes also must be compatible with local capabilities.

If this is not the case, systematic evasion of unrealistic requirements

occurs, and the protection offered by the codes becomes illusory.

The relationship between codes and the development of new technologies

must also be considered. Innovative technical solutions, compatible

with local conditions, must be sought in order that the protection to

the public provided by properly-enforced building codes not be achieved

at the expense of prohibitively-high construction costs. Rigid formulation

of the codes may have the effect of hindering the development and use

of progressive technologies. Properly-formulated codes should therefore

exhibit sufficient flexibility to allow the adoption of new techniques.

7 . 4 Building Codes in Peru

Since the creation in 1962 of the College of Engineers of Peru,

only engineers and architects graduated from or associated with the

College can present construction plans. Until recently, the regulations

utilized were, depending upon the type of construction or the judgement

of the engineer, selected from German, North American, French, or Japanese

sources

In 1967, the government named a commission to formulate a unified

construction code. After the 1970 earthquake the commission accelerated

its work and in that same year approved the National Construction Regulations

which are now in force in all parts of the country. The National Construction

Regulations of Peru is a detailed document that represents a significant technical advance. It is believed, however, that further progress

is possible in the area of aseismic design. Indeed, while the present

aseismic regulations prepared by the National Technical University contain

provisions applicable to construction, they do not include provisions

for design. With regard to adobe construction, the Regulations do not

include limitations on the height of adobe buildings [1]. In addition,

progress can be made in standardizing manufacture and construction of

adobe blocks and of other materials and construction elements. i

90
With respect to the application of the codes, it should be kept

in mind that few municipalities have the staffs of professional experts

required to monitor construction to assure compliance with the established

regulations and to interpret the code requirements in the light of local

conditions

Requirements specifically applicable to local conditions may substantially

increase the effectiveness of building codes. For example, in addition

to the general code requirements that adequate bracing be provided to

insure structural integrity, specific requirements for structures of

the type shown in Figure 3.5 may be added to local codes of regions

where such structures are frequently built. These requirements would

refer in sufficient detail to the horizontal bracing of the roofs needed

to achieve satisfactory aseismic behavior. Detailed requirements applicable

to structural types widely used locally would greatly enhance the ability

of properly-trained local officials with modest formal education to

enforce the codes

7. 5 Building Codes in the Philippines

Regulations governing building construction exist in the Greater

Manila area and in a few other urban centers such as Baguio, Cagayan

de Oro , Cebu, Bacolod, Iloilo and Davao City. Enforcement of these

codes is reported to be generally satisfactory. Most areas and particularly

rural areas do not have such regulations at this time. A bill is pending

in Congress ("An Act to Ordain and Institute a National Building Code

of the Philippines") , the purpose of which is to meet the need for a nationally applicable set of building regulations [2]. The proposed

code, prepared by a committee of technical experts and assisted by United

Nations consultants, would provide for normal structural safety and,

within the limits of the state of the art, for safety under fire, earthquake

or typhoon action. A Joint Building and Environmental Planning Research

and Standards Commission would be entrusted with enforcing the code,

but the City or District Engineer would be charged with implementing

the code at the local level.

Code improvements which would contribute to solving some of the

problems of providing safe and inexpensive typhoon-resistant housing

on a massive scale include:

(a) more strict provisions governing structural

elements most frequently associated with typhooncaused damage. Such elements include anchorages

of roof trusses, purlins and roofing materials,

and are described in Chapter 4.

(b) greater flexibility in the introduction and

use of appropriate innovative designs, especially

those related to prefabricated structures.

(c) wind-loading provisions based on climatological

studies using modern methods of wind speed

records analysis and on full-scale aerodynamic

studies.

7.6 Building Codes in Turkey

The Turkish Association for Bridge and Structural Engineering is an unofficial professional organization established to supply technical

91
assistance for Turkish engineers working in the fields of bridge and

structural engineering. One of the main tasks of the association has

been to publish recommendations for construction and design. Such recommendations have proven of great assistance to Turkish engineers until the

early 1960 's, when they were superseded by the comprehensive specifications published by the Ministry of Public Works, and construction

and materials standards were prepared by the Turkish Standards Institution.

A building code now specifies requirements for construction and

design in various seismic zones in Turkey. The code is limited to structures

other than dams , bridges , minarets, mosques, stacks, transmission towers,

etc, for which special design criteria are determined by the government

ministry concerned with the structure in question. The code contains

provisions regarding earthquake-resistant construction, and gives specifications for five different types of construction: reinforced concrete,

masonry, semi -masonry , wood-frame, and adobe [3].

(a) Reinforced Concrete Building Structures . Specific requirements

are given for the aseismic design of structural elements of reinforced

concrete buildings, such as foundations, foundation connections, columns,

beams, slabs, and walls. Recommendations on the design of a structure

considered as a whole are also made. The code also indicates the dependence

of earthquake loads upon the building stiffness.

(b) Masonry . The maximum number of stories Cexcluding basement)

that masonry buildings can have is three in seismic Zone I, and four

in Zones II and III (zones are shown in Figure 5.1). Regulations for

foundations and footings are given according to the seismic zones. Minimum

wall thicknesses are also given according to seismic zones, number

of stories and type of material. Three types of material are specified

for walls; these are stone or concrete, brick and solid concrete brick.

(c) Semi-masonry . These structures can have a maximum of two stories,

excluding the basement. Foundation design is the same as for masonry.

Minimum thicknesses are specified as a function of the number of stories

and of the material used.

(d) Wood Frames . The code requires that wooden frame structures

have a maximum of two stories excluding the basement and that each story

have a maximum height of three meters. Foundations are to be designed

using the regulations for masonry structures.

(e) Adobe . For foundation and basement, uncut stones f moloz tasi ) may be used. It is required that bearing walls be made of clay soil.

Organic soil cannot be used for walls. In seismic Zone I, the building

may not have a flat earth roof.

The control of construction of buildings in the cities and towns

is governed by the Municipal Construction Offices. The architectural

design and construction project of each private building are examined

in accordance with the master city plan and also with the current building

codes. If the projects are found to be adequate, a construction license

is issued by the Municipal Construction Office. During the construction

period and after the completion of the building, municipal engineers

check the building for compliance with the approved projects. If the

building is found to be adequate, a license for occupancy is issued.

The above mentioned system for controlling construction does not

appear to always work efficiently in practice because of shortcomings

existing in the current Municipal Regulation. For this reason, a more

strict Municipal Regulation for controlling private construction is

being prepared by the Government.

92
References

1. Brambilla, Dante P., "Socio-Economic Study Submitted to

the National Bureau of Standards," Lima, Peru, 1972.

2. Sycip, Gorres, Velayo 5 Co., "Research Study on the Socio-Economic Aspects of Low-Cost Housing in

the Philippines," Manila, May 1972.

3. "Socio-Economic Aspects of Earthquake Resistant Housing

in Turkey," Turkish National Committee for Earthquake

Engineering (Chairman: Professor Dr. Rifat Yarar, Istanbul

Technical University, Taksim, Istanbul, Turkey), Ankara,

1972.
Chapter 8, Social Factors Which Influence the Advancement

of Housing Technology

Tarja Cronberg*

M.S.C. Lund Institute of Technology, Lund Sweden

8. 1 Introduction

Socio-Economic Studies . Innovative technologies capable of responding

to the need for low-cost earthquake and storm-resistant housing can be

successful only if compatible with local social and economic conditions.

So that existing and future constraints or barriers to the successful

implementation of this project could be determined, socio-economic studies were undertaken by consulting organizations in Peru, the Philippines,

and Turkey [2 , 3 , 4] . The objective of this chapter is to discuss the social factors

which affect decision making on housing projects. The following items

will be discussed: social framework for low-cost housing, user requirements,

and acceptance of innovative designs and of new materials. The analysis

of user requirements for basic housing in Peru is based on References

[2] , [12] , [14] and on observations made on a field trip by the writer.

8 . 2 Social Framework in Low-Cost Housing

8.2.1 Population Growth and Family Planning

It has become increasingly difficult to raise housing standards

and to maintain even the present quality of life in the face of the

world's population growth, especially in the developing countries.

The high rates of population growth being experienced by most developing

countries result from their traditional high birth rates and declining

mortality rates. Improved health services and medical technology will

cause mortality to decline further, which will require fertility rates

to be reduced from present levels simply to avoid further increases

in population growth rates.

The three countries included in this study: the Philippines, Turkey

and Peru have experienced a process of rapid demographic growth during

the last two decades. In the Philippines, growth of the national population

is expected to average at around 3.01 annually, with the urban population

increasing at a higher rate of 3.71 compared to the rural populace's

2.6% rate of increase. Despite the present efforts of the Philippine

government to promote family planning, household size has increased

from 5.7 in 1969 to 6.0 in 1970 and is expected to further increase

to around 6.2 by 1980 [4].

In Turkey the death rate decreased since 1940 from 27.2% to 12.6%.

At the same time the birth rate increased from 37.1% to 44.0%. To slow

down the rate of increase, a population policy based on family planning

was put into effect in 1965 [3]. In Peru the yearly demographic growth

until 1970 was 3.12%, the birth rate being 4.2% and the death rate 1.1%

[2].

Tt This study was made while Mrs. Cronberg was a Guest Worker in the

Center for Building Technology, National Bureau of Standards , (1972-1973)

94
8.2.2 Urban Growth

From 1920 to 1960 the urban population of the developing world

grew by 255 million, i.e., from 73 to 328 million. The projected increase

in the urban population of the developing countries in the 40 years

from 1960 to 2000 is over one billion, more than four times the increase

in the previous 40 years and about three times the total urban population

of the developed countries in 1960 [1],

In the Philippines the annual population increase is 3.7% in urban

areas and 2.6% in rural areas. The primary contributory factor to the

high growth-rate of the urban population is the net in-migration flows

to those regions with large metropolitan centers such as the Southern

Tagalog region, specifically the Greater Manila area, and the two Mindanao

regions [4].

In Peru the growth in urban areas

in rural areas. Migration is directed

the Sierra towards the coastal region,

Lima [2]

has been 4.31 compared to 1.93%

mainly from the rural areas in

especially towards Metropolitan

Of all the problems of urbanization, that of providing shelter

for the expanding city populations and of improving housing conditions

of a majority of existing inhabitants appears in many respects the most

difficult. In the developed countries, the basic issues concern primarily

social and institutional rigidities rather than a basic lack of national

resources. In the developing countries, national resources including

skills are generally grossly inadequate for investment of the magnitudes

required while maintaining economically-productive investment. Progress

in solving the housing problem in the cities of the developing world

has been, with few exceptions, conspicuously slow. The housing situation

is deteriorating progressively each year.

8.2.3 Slums and Squatter Settlements

Squatter settlements and slums are typically the fastest-growing

areas of cities and already frequently cover one-quarter, sometimes

over a half of the city area. They can be constructed quickly and in

a variety of forms to meet rapid population growth, providing accommodation

at rents, if any, that can be afforded. The squatters are themselves

providing a housing solution and community development, rudimentary

but effective. In their expansion, they are shaping the fundamental

structure and character of the urban areas. Rather than attempt their demolition, attention should therefore

be directed to improving squatter settlements and slums. Self-help

and community action are typical of squatter settlements. More permanent

structures and facilities are constructed as the settlement becomes

more established. High morale of the inhabitants is evident in most

squatter settlements. This provides hope for dealing more effectively

with the housing problem than has been possible so far.

Also provision should be made for such settlements on a more organized

basis. It is suggested that new development areas with minimum services

be provided for self-help housing. In the site and services concept,

for example, in the World Bank's pilot scheme in Dakar, Africa, attention

is centered on provision of the barest housing infrastructure and the

stimulation of self-help measures in actual construction work.

95

527-373 O - 74 - 8
8.2.4 The Role of Social Workers

The role of social workers is central in preventing any program

from being too mechanical and losing sight of the human dimension.

The social worker should enter into the community long before any

program or project is undertaken. Many future projects can be successful

if there is someone who really feels the pulse of the community.

The social worker should be trained and prepared in the best professional

manner, with an in-depth knowledge of the project envisioned for the

community

The social worker must, at the same time, have access to those

doing technical planning, conveying to them the real sentiments and

aspirations of the community. Subsequent collaboration depends greatly

upon this communication.

In the Philippines , the Department of Social Welfare has decentralized

and expanded in social services by setting up eight regional offices.

These offices are authorized to make all necessary decisions to suit

national programs to local needs . Evicted squatters are given special

attention with financial and material aid, counselling services, training

in vocational skills, self-help projects and relocation to designated

sites for rehabilitation.

8 . 3 User Requirements on Basic Housing

8.3.1 Outline of Requirements

Access to decent housing and community services is defined in the

U.N. Declaration of Human Rights as a basic right for all. However,

in spite of the recognition of the role played by housing in man's development,

the world housing situation is claimed to be worsening during the Second

U.N. Development Decade. Words like "crisis" and "critical state" have

been used on occasion to describe the situation.

User needs and their relations to elements in the physical environment

are complex and not well understood even in the most developed countries.

The methodological problems encountered when identifying individual

user needs and relating these to user requirements on the physical environment

are often considered to account for this situation. However, a systematic

analysis of the user and his requirements on the basis of information

and methods available today will increase our knowledge of the user's

preferences and contribute to the elimination of some of the main causes

for the deterioration of human settlements.

8.3.1.1 Sources of Information

To study the user requirements

areas where the need for earthquake

urgent, several problems arise:

in developing countries , in geographic

and storm resistant housing is most

- When housing, built by traditional methods and using

conventional building materials, does not exhibit the

necessary characteristics of earthquake and storm resistant

housing, new designs and non- traditional building materials

will most likely be recommended. No past experience

data on the user acceptance and reaction to these designs

and materials will thus be available.

96
- Earthquake- and storm-resistant housing is sometimes

provided in an emergency situation. No time will be

available for extensive studies on local user requirements.

- The techniques usually employed for gathering data on user requirements , surveys of users or observations in

the existing building environment will have to be modified

due to the occupant's limited experience of various

built environments, his illiteracy and unfamiliarity with

strangers and the interviewer/observer's lack of understanding of the user's way of life.

Because of these anomalies three main sources of information are recommended

when gathering data on user requirements in these areas:

1. Statistical sources of information. Information is

usually provided in each country concerning: birth

rate, age of marriage, size of families, average

income, type of employment, average family income,

expenditure on housing, etc.

2. Interviews with local builders, architects or con- struction workers. These persons are probably the

best source of information concerning the user's way

of life, and preferences in relation to the built

environment

3. Observations of existing built environment.

8.3.1.2 Type of Information Needed

Independently of the sources used, certain types of data should

be provided in order to enable conclusions on user requirements and

their consequences for design and choice of technical solutions. The

information needed is divided into two categories and discussed below

[8].

- user characteristics

- user activities

User Characteristics

Physiological characteristics of the user, of interest for design,

are

- Physical development: size and proportions

- Motor development: the ability to move and manipulate

features in the environment.

- Sensory development: sight, hearing, smell, taste

and tactile sensitivity.

Psychological characteristics such as the occupant's attitude,

values, his intellectual and emotional development determine his identification

with the community and the dwelling, his desire to maintain or modify

his physical environment and his acceptance of available technical solutions

and materials

97
Socio-economic characteristics of the user include family size

and structure, mobility, group identification Cethnic, religious, geographic),

as well as educational background and past and present employment and

income level.

User Activities

The design of a house may stimulate certain activities or make

them easier whereas others will be excluded. Knowledge of activities

is not only important when studying the spatial attributes of the physical

environment but also for the requirements of safety and comfort as well

as the need for privacy and social interaction.

8.3.2 Case Study; User Requirements for Basic Housing in Peru

User requirements, outlined in general terms in the above section,

will in here be related to the specific information available on Peru,

one of the earthquake -prone areas to be dealt with in this report. Since

the information available is not related to any specific housing project

and/or any specific occupants, no detailed list of user requirements

can be provided. The considerations presented will thus only provide

a broader framework for the formulation of the individual user requirements

within a specific design process.

3.2.1 User Characteristics in Peru

The following general user characteristics for the whole population

are abstracted [2]

- ethnic origin:

- language:

- religion:

- age distribution:

- education:

rural/urban

communities

size of family:

- economic situation;

461 Indians, 43% mestizos, 111

Caucasians

Spanish, for the mountain Indians

Quenchua or Aymara

Roman Catholic

45% under 15 years, 32% over 64

years, life expectancy 59 years

55% of adult population

illiterate

53% of population lives in com- munities of less than 1000 (68%

of the above in communities of

less than 50) , migration from

rural to urban areas, from mountains to coastal area (especially

to metropolitan Lima)

average about 5 persons (mostly

4-7)

yearly GNP growth 4.7%. 53% of

all families are estimated to

have a minimum monthly income

of S/4000* of which 16-22% is

spent on housing.

1 U.S. $ ^ 43.4 Soles (S/) in 1972,

98
- occupation/ mainly agriculture, cattle breedemployment: ing in the Sierra (only 73% of

total agricultural labor force

is estimated to be employed)

According to an estimate, about 300,000 persons or about to 25%

of the population in Lima in 1969 were living in the "pueblos jovenes"

or young towns - urban communities, where the great majority have built

their dwellings without having title to the land or access to community

services [14] . In 1968 the Junta Nacional de la Vivienda published

a survey on the occupations of the family heads in such communities

with the following results: 49% workers and artesans, 15% merchants,

12% office and service employees, 18% other occupations [14]. Thirty

percent of the potential labor force was estimated to be unemployed.

No statistics are provided on the income level, which is likely to be

considerably lower than the national average.

- physiological characteristics : No detailed data provided. Only 4.2%

of the dwellings in the young towns have potable water connections in

the dwelling and only 6.7% have sewage [12],

- psychological characteristics : One of the main factors which creates

a successful low income housing project is the user's acceptance of

the project and the technical solutions provided. A positive reaction

will lead to pride and identification with the community and to participation

in local activities aimed at the improvement of the physical environment.

Through the participation of residents of several young towns, roads

and schools have been built and the original straw houses there have

been replaced by brick constructions.

Several factors contribute to identification:

- Satisfaction with location: availability and proximity of employment

being one of the main determinants. This question must be dealt with

individually in each housing project.

- Ownership and control: Title to land and the dwelling.* Autonomous

housing projects built and later improved by the occupant/owner are more advantageous than identical projects where the occupant has no influence on the location, design, financing and construction and where

the control of the settlement is maintained by investment interests

even after occupancy.

- Acceptance of technical solutions and materials. The residents of

the young towns have a strong interest in building a house of "noble

material" - in Lima of brick and cement ("adobe is shunned as a weak

material, perhaps because it is less prestigious than brick") [14],

This factor will be dealt with in more detail in another section of

this chapter.

A psychological factor of importance when considering the earthquake

and storm resistance of housing is the attitude which the people exhibit

towards these catastrophies . When they are viewed with concern, the

occupants will be more motivated to spend more on housing of this type

and to take precautions, than when the attitude is one of indifference.

- Socio-economic characteristics : The overall growth of GNP gives only

a very inadequate measure of these changes in the low- income group.

(Information on land ownership not provided)

99
Even within the latter group the pace of social change will vary greatly

and should therefore be individually studied within each housing project,

Factors determining the socio-economic characteristics of the occupants

in a housing project are: employment opportunities, participation in

community activities, social interaction and the psychological factors

mentioned above. Social interaction is supposed to be very limited

for newly-arrived immigrant families without relatives in the city.

Neighborhood kinship is developed only after several years. In the

squatter settlements the relationships are also impeded by cultural

differences between the "criollo" - usually a coastal mestizo speaking

Spanish and the "serrano" - an indian from the Sierra speaking Quenchua

or Aymaro . Class lines between these groups are maintained in the

settlement until the "serrano" becomes a "criollo", for which he usually

needs 3-4 years. Differences between these groups have been discussed

by Patch [13]

In order to study the economic requirements of the users, more detailed information on the income distribution and trends should be

provided.

8.3.2.2 User Activities in Peru

Information of user characteristics should be supplemented with

information on user activities in order to get a comprehensive picture

of the user requirements to be satisfied by housing.

In the information sources used, very little data is provided on user activities. Some conclusions may, however, be drawn on the basis

of the information provided on existing housing conditions in Peru.

The available data is summarized below:

- 68^ of the units have one or two rooms; 851 of the households living

in these units have more than four members

- 161 of the households in the country are estimated to have both potable

water and sewage service in the units, 701 are estimated to lack potable

water and 501 are estimated to lack sewage facilities;

- 38% of the households have electricity, 451 use kerosene for lighting

(remaining 17% use various other means for lighting;)

- 75% of the houses have floors of stamped earth, 541 have adobe walls

and S3% have flammable roofs.

Corresponding figures for the residents of the young towns are [14]

42% have potable water service in the home;

- only 6.71 of these households have sewage facilities, 11.8% use irrigati

ditches and 81.5% have no service at all;

- 7.6% have electrical lighting, 23% partial electrical service and

68.7% lack all forms of electrical service.

No data is available on the size of the houses or the number of

family members but the percentage of households living in overcrowded

conditions in these communities is no doubt higher than the overall

percentage for the whole country. Because of this, most of the basic

activities of the household must be either staggered in time or performed

partly outside the house. Because of this, the question of semiprivate

open space - where, depending on the climate, laundry, drying, receiving

visitors, recreational activities and in some cases even cooking can

100
take place - should be considered together with the space inside the

house (possibility of tradeoffs).

When listing activities which the design should support and which

are to be performed in the dwelling, attention should be paid to the

family size and structure, the activities of a one-person household

being essentially different from those of a family of five. In Peru

special attention should be given to the fact that over A7% of the population

is under 15 years of age, indicating that activities such as recreation

and play, learning and education, child care and supervision should

be provided for accordingly.

Below, some basic activities are discussed in relation to the following

attributes: health § safety, comfort, functional characteristics and

acceptability. The solutions to these problems in existing housing

are presented where relevant information is available. The list is

by no means exhaustive, its objective being to clarify the proposed

way of identifying user requirements. The discussion is confined to

the low income group of users, whose characteristics have been considered

above

Activity

Attribute

Design

Parameters

Present

Solutions

Sleeping

Health and Safety;

Comfort

intrusion

(people/

animals)

ventilation

urban: iron gratings

in windows

rural/coast: provided

through holes in the

structure

rural/sierra: minimum

ventilation to avoid

heat loss ; windows

and other openings

often blocked by

adobe blocks

heating

Functional

Characteristics

space and

spatial arrange'

ments

urban: windows

coast: not needed

sierra: small space

(1 room) , insulation

by use of adobe, blocking

of openings , additional

heat provided by all

family members sleeping

in the same room, and

cooking inside in the

evening

average space provided

5-7m2/person, majority

of homes have 1-2 rooms

101

coast: usually two

rooms, one of which is

used for sleeping
Acceptability

Food Preparation

Health and Safety

Comfort

Functional

Characteristics

Storage

Health and Safety:

privacy

fire

storage of

food

disposal of

wastes

ventilation

lighting

space

- equipment

fire safety;

storage of

fuel (kerosene, wood)

sierra: usually only

one room, providing

space for all inside

activities including

s leeping

family members sleep

in one room, no privacy

provided

open fire or kerosene

stove used. Since roofs

are of flammable materials, fire protection

is probably provided

through caution and

experience (learning)

see storage

see personal sanitation

when cooking inside

see above

coast: windows, holes

sierra: only limited

daylight, windows

blocked to avoid heat

losses, kerosene lamps

coast: cooking often

done on a patio or semiprivate courtyard

sierra: indoors, in the

only room provided,

(heating)

kerosene stove or open

fire

security: storage of personal

belongings

102
Functional

Characteristics

contamination

storage of

garbage

storage space

and location:

food (human/

animal)

when no garbage collection is provided (rural/ some urban areas) this

is either burned or dumped outside (road

nearby field)

depends on size of family, the access to

stores/markets and

whether the family produces its own food

(agriculture/cattle) , in the latter case storage space is necessary

for the whole season. water when no connection in

the home, water is provided by public storage

tanks or trucks , and

stored in 50 gallon

tanks outside the house

fuel

personal belongings

sleeping equipment (during

daytime to

allow for space

for other ac- tivities)

utilities for

work (artisans,

farmers

see health and safety

Personal Sanitation

Health and Safety access to

water

access to sew- age/disposal

of body waste

washing of body/clothes

usually takes place

rural : on a river or irrigation ditch, drying

of clothes on the ground

urban: semiprivate

courtyard

since majority of the

low income housing lacks

any kind of sewage facilities, open air latrines in backyards,

nearby vacant lots

(urban) or fields (rural) are used to excrete.

103

527-373 O - 74 - 9
Acceptability: - need for privacy

- Most activities performed without provision for privacy

Work

Functional

Characteristics

Acceptability:

need for space

when work done

at home or in

close vicinity

(artisans, shop

keepers, etc.)

storage of

utilities (farm

ers , etc.)

location of

house in relation to employment opportunities for the

family members

possibility

for childcare

and supervision while

away at work

Recreation/Play

Functional

Characteristics

access to space

Acceptability: - possibility to

creative and

joint activities for parents and children

Receiving of Guests,

Social Interaction

Functional - access to space

Characteristics

- access to TV,

radio, etc.

urban: only 21% of the

employed work in the

vicinity of their

residences [12]

small children are known

to be locked inside the

home when parents are working

most activities performed in the streets,

football fields provided in few areas

urban: robberies,

thefts because of lack

of organized activities

and amount of time

spent away from home

by the parents

rural: participation

together with parents

in work (guarding cattle)

because of the lack of

private space, streets,

shops and markets function as places of so- cial contact

the homes of families

with TV are meeting

points of the neighborhood

104
Acceptability

Identification/

Participation

Learning

Acceptability

Orientation

Functional

Char acteris tics

access of social

interaction re- lated to ethnic

groups, religion,

etc

design parameters affected

should be

es tab lished

location in

relation to

schools

- criollo/serrano

location/

orientation

of home

urban: most "young towns"

have elem.entary scliools, no childcare centers are provided by community

urban: exposure to

different physical and

social environments is

limited, children

exposed to delinquency

in several of the "young

towns"

roads, alleys

- special characteristics : monuments

squares etc.

- inside of

home: view of

the outside

world

- in the sierra

openings blocked

by adobe for

better insulation

8.3.3 Summary and Recommendations

Summary

It is generally recognized that the provision of a physical shelter

is not a sufficient goal for housing. Its acceptability from the point

of view of the user; to allow for his personal development and fulfillment

of social needs, is considered to be at least equally important. To

achieve this latter goal two main constraints are set on the designer:

- inadequate knowledge of user requirements

- costs

105
Analysis of user requirements is discussed from two aspects:

- how to find the necessary information

- which type of information one should look for

The methods used to generate this information based on surveys

and observations have been developed in the industrialized countries

and may not be feasible in the geographic areas to be studied. Therefore,

other sources of information are suggested, including statistical data

in the country in question, interviews and discussions with local people

involved in the building trade, and observations of existing built environments,

It is evident that no single solution exists to fulfill the social

needs of various low-income groups in different geographic areas. At

all times, therefore, housing should be looked upon as a process corresponding

to the user's social and economic situation. The process will be defined

both by the level of social development as well as by the trends of

development, thus enabling us to better understand why similar physical

environments in certain conditions decay and others upgrade. By studying

the user's characteristics - physiological, psychological and socioeconomic - and his activities, which housing is to support, the parameters

of this process can be established. The combined information on user characteristics and user activities will implicitly state the user requirements

to be considered in each design process.

To demonstrate the approach proposed for the identification of user requirements, examples are discussed both for basic housing in

general and for basic housing in Peru.

Recommendations

1. In order to avoid future deterioration or abandonment of the

physical environment to be provided, identification of user requirements

for individual housing projects is essential.

2. This should be done in cooperation with local experts familiar

with the existing conditions and the user's way of life, combined with

actual observations of existing built environments.

3. The information provided should include data both on the user's

physiological, psychological and socio-economic characteristics and

on the user's activities (all family members) for which the home is

to provide a framework.

4. In order to establish priorities for the satisfaction of user requirements, more information is generally needed on

- health standards in existing physical environments

(urgency for community services)

- need for personal space and privacy (in the generally

overcrowded housing conditions)

- contact patterns for social interaction within the

neighborhood and community

- activities of specific user groups such as children

and the effect of the provided physical environment

on them.

5. Because of its vital importance for the development trends

for the physical environment more basic knowledge should be provided

106

1
on the factors affecting the user's identification with his community and dwelling and his interest in participating in community activities.

8.4 Acceptance of Innovative Designs and of New Materials

The Philippines C4") The economic advantages of standardized designs have resulted in

their relatively-widespread acceptance by most low- and middle-income

homeowners, especially when, as is often the case, small individual

modifications in the housing units are possible during occupancy.

Most practicing architects and engineers readily accept new construction

materials which exhibit desirable technical properties and are economically

advantageous

Peru C2)

The introduction of new construction materials in Peru has always

resulted in an initial period of strong rejection, and there are very

few products which have survived this reaction and maintained a place

in the market.

In 1957 an attempt was made to introduce the product "Durisol,"

manufactured under a Swiss patent, which consists of mineralized vegetable

fibers encased in cement and used for the manufacture of hollow blocks

for walls, thick panels for partitions, and thin panels for facings.

These products had been widely accepted in Switzerland and Germany.

A "Durisol" operation was set up in 1959 with a capital of S/20 million

(about $1.25 million) but had to close down at the end of 1960 after

losing its capital.

In 1965 a factory was built for the production of products of expanded

(or cellular) gypsum, under the "Belroc" patent. The principal product

consisted of 2.40 x 1.20 x 0.10 meter panels for building partitions.

The product had good structural characteristics and was easy to handle

and install; however, the manufacturer was never able to expand the

initial market, and the demand lessened gradually until production was stopped recently.

Innovative construction materials produced in Peru include reconstituted

wood, asbestos-cement products, glass-fiber plastics and fiber-cement

sheets

"Mapresa" or reconstituted wood, is made of shavings or fragments

of soft wood mixed with synthetic resins and then pressed. It is offered

on the market as sheets of various thicknesses (0-6 cm to 5 cm) and

in sections of 1.2m x 2.4m and 1.2m x 3m. This product enjoys broad

use in furniture manufacture, generally in veneered or duco-painted

pieces, but its application to the construction of houses has been limited

to temporary camps. As a construction material it possesses the disadvantage

of absorbing moisture.

"Maderita" is a product similar to the above, based on sawdust.

Its use in construction of housing is even more limited than that of

Mapresa, as it is very fragile and brittle.

Corrugated sheets of plastic (PVC) and glass fiber for roofs, which

had considerable initial acceptance, are losing their market because

of high price and poor mechanical properties

107
Sanitary fixtures of glass fiber, such as bathtubs and basins, were relatively expensive and have not had any better acceptance. Their

production recently ceased. However, the manufacture of plastic tubing

for water supply and sewerage (rigid PVC) has had success and its market

continues to grow.

Fiber-cement is a product extensively used in industrial construction.

It consists of wood (shavings) or cane fiber held together by cement.

It is made in sheets 1.2 cm to 5 cm in thickness, 0.50 m wide and 1.00

to 2.00 m long. Its mechanical and physical properties are poor, however.

The introduction of "sandwich" panels based on wood has not had

much success in Peru, even in building construction, because masonry

walls and partitions are preferred despite their dead weight. Because

brick and concrete are more economical to use and adobe and quincha

dwellings are cheaper to construct, the above mentioned products have

had little success in the field of housing construction.

The only construction materials which have had broad acceptance

are "calamina" (corrugated sheets of galvanized steel) and corrugated

sheeting of asbestos-cement. Although calamina is widely used both

on the coast and in the sierra, its physical properties, especially

those of thermal and acoustic insulation, are very poor. Nevertheless,

due to its relative light weight per sheet and resistance to fracture,

it can be easily and inexpensively transported, even on the backs of

beasts of burden, and this makes it much prized in the Sierra region.

Corrugated sheets of asbestos-cement have better thermal and acoustic

properties than calamina. Due to their fragility, they are mainly used

on the coast as there is a high percentage of breakage during transport

on second-class or inferior roads and in handling. The high number

of sheets lost by breakage during transport and delivery in the sierra

(which can reach 301 of the cargo) makes it an expensive product. Asbestoscement is also used in the manufacture of flat sheets , tubing for water

and sewerage, posts for electric wires, and other preformed products,

such as water tanks

After the May 31, 1971 earthquake, emergency shelters consisting

of sprayed polyurethane domes, or igloos, developed by Farbenfabriken

Bayer, Leverkusen, Federal Republic of Germany, have been provided in

Caraz (see Figure 8.1). The igloos were soon abandoned by their occupants,

for the following reasons:

1. The lack of corner areas became a source of family

strife as, in the opinion of the inhabitants, one could never put anything "out of the way."

2. The interior acoustics were such that the sound

of two or more people speaking simultaneously

proved unnerving.

3. The lack of conventionally defined property lines made it

impossible to fence in animals raised for consumption.

It is noted that igloos provided by the German Red Cross near Gediz.

Turkey, after the March 28, 1970 earthquake were also abandoned.

In a Peruvian survey done in 1962 by students of the Architecture

Department of the National University of Engineering with the purpose

of finding out the attitude of the public toward prefabricated housing,

the following conclusions were reached:

108
Figure 8.1 Polyurethane "igloo" homes at Caraz, Peru, built by the

German firm Bayer, A. G. These homes failed to gain

acceptance on the part of their users, who abandoned them

after being adversely affected by

1) the lack of comer areas in the homes

2) the poor interior acoustics

3) the lack of private plots.

109
1. The lack of consumer interest in this type of

housing is due to the following reasons:

a. Prefabricated houses represent only a small

margin of economy compared to brick and concrete

houses

b. Prefabricated houses are more expensive than

adobe and quincha dwellings.

c. Prefabricated houses built enmasse have the

disadvantage of being 'of uniform architecture.

d. The public did not truly appreciate the savings

caused by the shorter construction time required

for this type of housing.

2. The lack of interest of builders in this type of housing

is due to the following reasons:

a. The market was very restricted, and this resulted

in high sales costs.

b. Because of limited acceptance of prefabricated housing,

there was no system of financing prefabricated housing

projects in Lima.

c. Prefabricated housing projects in the provinces outside

the area of Lima turned out to have very high con- struction costs because of the difficulty and high

cost of freight transportation.

Housing constructed by so-called conventional procedures has greater

acceptance than any new procedures that have been proposed, and at present

most approved projects involve conventional construction types.

References

1. "Urbanization," Sector Working Paper, World Bank, Washington

D.C. 1972.

2. Brambilla, Dante, P., "Socio-Economic Study Submitted to the

National Bureau of Standards," Lima, Peru, 1972.

3. "Socio-Economic Aspects of Earthquake Resistant Housing

in Turkey," Turkish National Committee for Earthquake

Engineering, (Chairman: Professor Dr. Rifat Yarir, Istanbul

Technical University, Taksam, Istanbul, Turkey), Ankara,

1972.

4. Sycip, Gorres , Velayo and Co., "Research Study on SocioEconomic Aspects of Low-Cost Housing in the Philippines,"

Manila, May 19 72.

5. Blachere, G., "Human Requirements," paper to the 5th CIB

Congress, Versailles, 1971.

6. Hole, v., "User Needs," Building Research Station, London.

110
7. Cronberg, T. , "Defining Functional Requirements in Building

Materials," UNIDO expert group meeting on the Use of Plastics

in the Building Industry, Vienna, 1971.

8. Cronberg, T., Saeterdal, A., et al , "Human Requirements

for Buildings, RILEM-ASTM-CIB Symposium, Philadelphia,

1972.

9. "Physiological Obiectives in Hot Weather Flousing," Housing

and Home Finance Agency, Washington, 1963.

10. "Human Settlements," Vol. 1, No. 1, United Nations, January

1971.

11. Mohan, D. , et al , "Socio -Psychological Considerations in

Housing in the Low Income Croup," Central Building Research

Institute, Roorkee U.P., India, 1972.

12. "Housing in Peru," Union Panamericana , Secreteria Ceneral

Organization de los Estados Americanos, Washington, B.C.,

1963.

13. Patch, R. , "La Parada, Lima's Market," I-III, American

Universities Field Staff, Reports Service, N. Y., 1967.

14. Conger, L., "Public Services and the Pueblos Jovenes of

Lima, a Brief Survey," Lima, November 1969.

15. "Planning Sites and Services Programs," IME No. 68,

Office of International Affairs, HUD, Washington, D.C.,

20410.

Ill
Chapter 9. Economic Factors Which Influence the

Advancement of Housing Technology

William F, Reps

National Bureau of Standards

9 . 1 Introduction

The economic conditions and policies in developing countries have

direct bearing upon theri capactiy for undertaking large-scale safe

10t</-cost earthquake and windstorm resistant housing construction. In

developing countries, relatively small amounts of capital combined with

properly-utilized large supplies of unskilled low-cost labor may result

in significant increases of both output and employment. Given the considerable

weight of the construction sector in the national economy, particularly

in the case of developing countries , such increases in turn produce

important beneficial effects on the development of the economy as a whole.

The housing construction sector is directly affected by such economic

factors as labor rates and productivity, availability and cost of construction

materials, land prices and credit mechanisms. Additional information

and details on the economic aspects of housing construction in Peru,

the Philippines and Turkey may be found in References [1] , [2] and [3]

of Chapter 7. The reader is also referred to Section 7.2 of this report

for a brief discussion of the possible contribution of credit-granting

institutions to improved building code enforcement.

9 . 2 Housing Programs in Developing Countries

The Inter-American Development Bank (IDB) [1] distinguishes two

basic approaches to the housing problem in Latin American countries.

The first approach envisages the problem as one of insufficient

quantities of standard modern housing units , coupled with inadequate

financial resources to remedy the situation. In the second approach,

housing is not evaluated on an arbitrary standard which may be unrelated

to the social, cultural and economic levels of the residents, but on

the basis of how well it facilitates access to areas where family activities

occur daily, how adequately it provides protection from a hostile environment,

and to what degree it assures security of tenure. In other words,

"traditionalists" are more aware of the appearance of the housing, whereas

"environmentalists" are concerned with the way in which the housing

accommodates the residents in relation to their life situations.

The traditional approach which is frequently used for planning

housing programs has been criticized for the following reasons. First,

housing deficits are calculated arbitrarily without taking into consideration

the values or preferences of the persons to be housed. Secondly, some calculations of housing deficits show the traditional solution to be

well beyond current capital investment rates. In the case of Latin America,

for example, the traditionally conceived housing deficit in 1967 was estimated to be about 22 million units, projected to be at least 100

million by the year 2000. It was estimated that it would be necessary

to build more than 3 million units per annum in order to eliminate the

deficit over the period to that time. If each unit of land cost only

$US 1,800, the annual investment in housing would be $US 5.4 billion,

or 6.6 percent of the regional gross domestic product of Latin America

at 1967 levels.

112
Even in developing countries in which the expected rates of growth

are relatively high, the competing demands of development programs in

agriculture and industry leave funds available for housing construction

in amounts far inferior to actual needs. It is therefore necessary

that self-help be encouraged for the partial fulfillment of these needs.

For example, in Peru the Organismo Nacional de Desarrollo de los Pueblos

Jovenes has the responsibility of studying, planning, proposing, and

co-ordinating programs to intensify efforts at incorporating slum-dwellers

into the development process. More than 20 percent of the urban population

(over 1.3 million) live in squatter settlements; some 78 percent are entirely without services, 10 percent have only electricity, and just

12 percent enjoy water and sewage facilities. Under such conditions,

"site-and-services" type schemes warrant emphasis. Several laws were passed in 1968-69 for the purpose of facilitating improvement of these

conditions; the progress achieved has been so far relatively slow. In

Turkey, where the urban and rural housing requirements for the period

1968-1972 have been estimated at 900,000 and 300,000 respectively, the

second five-year national development plan aims specifically at encouraging

self-help for squatter house dwellers, by providing roads, basic and

other services, and allocating plots and making long-term loans in order

that houses be built by their future dwellers themselves.

For the period 1960-1980, it is estimated that 5,790,000 additional

new houses will be needed in the Philippines, plus another 3,640,000

owing to replacement, obsolescence, disuse, disrepair, and natural

disasters. This would call for twelve new dwellings per 1,000 population,

requiring about 5.7 percent of the gross national product. Whereas

in 1965 only 1.5 percent of the gross national product was invested

in housing, 2.8 percent was invested in 1967. In either case, the small

investment did not create conditions benefiting the low-income groups.

As a result, slum and squatter conditions accelerated; and 10 percent

of the total population of Manila and 30 percent of the population of

Jolo City, Luzan, Visayas and Mindanao currently live in slums.

In the Philippines, self-help (known as "Bayanikan") is used extensively

for the construction of dwellings and buildings.

The magnitude of the task of providing low-cost housing has led

to government involvement in the housing construction sector in a large

number of developing nations, including Peru, Turkey, the Philippines,

and Iran.

9 . 3 Economic Factors Affecting Housing Construction

9.3.1 Land Use

Land use is regulated by building codes, by legislation on zoning,

pollution, and public purchase of land, and by taxation of land and

property. Proper planning for land use should include zoning for industry

and housing, consolidation and acquisition of land for specific other

purposes such as parks and recreation, and regulatory laws to prevent

land speculation. Ineffective land use regulation and inadequate policies

of public acquisition of land present a serious obstacle to rational

urban development.

To the extent that provision of subsidized housing is not feasible,

"site-and-services" type schemes (wherein land and utilities are provided

for self-help housing) may offer an interim solution.

113
9.3.2 Availability and Cost o£ Labor and Construction Materials.

Peru . Salaries paid in civil construction in Peru are fixed by

the government. Generally, salary changes are a consequence of longstanding demands by labor unions and are retroactive, at times up to

6 months, so they may cause difficulties in the construction industry.

Average salaries in 1970 were approximately S/90-S/125* daily, depending

on skill. Foremen and specialized operators generally are not available

outside the Lima area so that it is necessary to import managers and

skilled labor from Lima for major projects in the provinces. On projects

in isolated areas, which have their own construction camps, personnel

are given food and lodging at an estimated cost of S/50.00 daily per

person. In cases involving minor projects, without such camps, an additional

amount of approximately S/180.00 is paid per person per day for food

and lodging.

By official decree the Ministry of Labor has fixed minimum output

standards for labor in civil construction for the area of Metropolitan

Lima. These standards, which are a measure of the productivity of labor

at the present time, are summarized in Table 2, Section 13 of the Peruvian

socio-economic study. In practice, to obtain a higher output it is

necessary to offer some program of economic incentives. Even if these

do not decrease construction costs, they often reduce the time needed

for the completion of the project. Minimum output standards have not

been established for areas outside Metropolitan Lima, but as a general

rule productivity is about 10 percent less.

Construction materials are generally available. In particular,

adobe is abundant and inexpensive. Adobe construction upgraded using

stabilization techniques and adequate aseismic designs (see Chapters

2 and 10) should therefore be extensively used.

Turkey . The salaries of craftsmen vary considerably according

to specialities (from 40 TL* to nearly 100 TL daily). Plasterers have

the lowest salaries, masons earn slightly more, but less than carpenters,

and those in mechanical trades get the highest salaries. No statistical

data regarding the differences in salaries between rural areas and cities

and between regions are available.

For unskilled workers who constitute 70 percent of the manpower

employed in the construction sector, the labor law of 1969 had fixed

the minimum gross salaries between 15.50 TL. and 19.50 TL daily. Unskilled

workers in the construction sector are paid at most 20 TL. per day,

based on minimum rates in Eastern Anatolia (East of the Samsun-Gaziantep

line) , whereas salaries in the Western region are slightly higher and

may reach 30 TL. per day in July and August.

Construction materials are generally available with adobe being

the most abundant and least expensive.

The Philippines . Average daily wage rates in the Greater Manila

area in 1971 ranged from 9.34 Pesos* for common laborers to 17.50 Pesos

for foremen.

Construction materials in the Philippines as well as skilled labor

needed for conventional methods of construction are readily available.

Delivered prices of materials are reasonable because production is dispersed

throughout the country. The potential for cost reduction exists notably

1 U.S. $ = 43.4 Soles (S/) in 1972.

*

1 U.S. $ = 14.30 Turkish Lira (T.L.) in 1972.

1 U.S. $ ~ 6.80 Pesos in 1972.

114
in the area o£ bulk handling and of delivery. Prefabricated construction

components are relatively expensive because the current size of Philippine

markets is not large enough to achieve economies of scale, and because

transportation and distribution costs are high.

The chemical process industry for plastic products is small, protected

by high tariffs and generally produces simple types of household construction

materials

Under the recent Investment Incentives Programs, the 1970 's will

witness the development of larger and more complex chemical process

plants and of an integrated petro -chemical complex base. Judging from

experiences of countries which do possess such a base now, it is doubtful

that the capability to produce plastic materials will have a strong

impact on the construction industry until the 1990 's.

9.3.3 Credit Mechanisms for Housing

In order to illustrate conditions and procedures for granting dwelling

credits, a description of credit mechanisms for housing in Turkey, where

most dwelling credits are provided by the Social Insurance Institution

and by the Real Estate and Credit Bank, is presented below.

The Social Insurance Institution . The Social Insurance Institution

is a large governmental organization that provides medical and social

care for workers and helps them to finance cost of construction of homes.

The conditions and the procedures of dwelling credits may be summarized

as follows

(a) The insured individuals who want dwelling credits

must form a cooperative.

(b) To be entitled to a dwelling credit, the insured,

his wife or husband or children should possess no dwelling and have received no credit from the

Institution

Cc) The insured or his relatives should not be members

of any cooperatives formed for similar purposes.

(d) The insured should have paid a certain minimum

amount in premiums to the Institution.

(e) The dwellings to be built should meet minimum

social dwelling standards.

(f) No credit is provided for dwellings outside the

municipal areas of cities or towns, or in settlements with a population less than 10,000. However,

the Institution may approve exceptions after

conducting a survey.

(g) No credit is given for dwellings with a gross area larger than 100 square meters.

(h) The maximum amount of dwelling credit is TL. 60,000,

regardless of the income of the insured.

(i) The term of credit is 20 years and the rate of interest

is 41. The term starts from the date that a housing

permit is given.

115
Cj) The payment is done according to a payment plan,

based on equal monthly payments.

(k) The dwellings may not be sold to another person for

a 10-year period.

The credits provided by the Institution in the years 1969 and 1970 were as follows:

Year No. of Dwelling Units Value (TL.)

1969 1,449 45,527,129.00

1970 1,649 55,000,495.00

The Real Estate and Credit Bank . The Real Estate and Credit Bank,

which is connected to the Ministry of Reconstruction and Resettlement,

is the main bank that provides credit for dwellings. The requirements

and procedures are as follows:

(a) The bank opens a "Dwelling Saving Blocked Account"

upon the request of the individual.

(b) This money is not subject to interest or to any kind

of lottery for encouraging savings

(c) The quality of the dwelling should conform to the

specified regulations.

(d) The person, his wife or husband or children should

not possess a dwelling and should have received no loans from the bank.

(e) The nominal value of the saving account, called the

contract amount, may be between 10,000 TL. and

50,000 TL. Included is 251 of the total amount that was deposited by the individual.

(f) The contract amount can be increased or decreased,

provided that it remains between the upper and

lower limits, and the approval of the bank is

obtained.

(g) No money can be drawn from this account. Only under

obligatory conditions the bank may approve a partial

payment. In this case, the priority points of the

person are reduced accordingly.

(h) The individual may cancel the contract at any time

with a written application.

(i) The individuals who can preserve the account in the

bank for at least two years, who deposit 251 of the

contract amount in cash, are deemed as qualified to

receive dwelling credit.

(j) These rights can be transferred to children, father,

mother, wife or husband, provided that the bank

approves. A second transfer is not accepted.

116
(k) The term is 15 years and the annual interest is 6%.

The interest rate may be, however, subject to change

if new rates are stipulated by the State.

Cl) The money can only be used within the boundaries of

the municipalities and the urban reconstruction

areas

The impact of the Real Estate and Credit Bank program is relatively

small to date. The numbers of credits provided under this scheme in

the years 1969, 1970, 1971 are respectively 632, 492, 757.

References

1. Financing Housing in Latin America's Urban Settlements,

United Nations Interregional Seminar on Improvement of

Slums and Uncontrolled Settlements, 15-February - 1-March

1970, Medillin, Colombia.

2. "Socio-Economic Aspects of Earthquake Resistant Housing

in Turkey," Turkish National Committee for Earthquake

Engineering (Chairman: Professor Dr. Rifat Yarar, Istanbul

Technical University, Taksim, Istanbul, Turkey), Ankara,

1972.

117
Chapter 10. Feasible Technical Improvements

William F. Reps

National Bureau of Standards

10.1 Introduction

The preceding chapters have defined, in broad terms, the various

factors to be considered in determining the feasibility of improving

the dwelling environment. In this chapter, a discussion will be presented

of some technical improvements that are feasible in the context of the

social, economic and technical constraints typical of developing countries.

The improvements discussed offer substantial advantages in so far as the achievement of inexpensive construction better resistant to earthquakes

and windstorms is concerned.

The potential of oil stabilization for the manufacture of the basic

building block component is discussed in the next section. Polymer

and other chemical stabilization procedures appear worthy of further

investigation, particularly in those countries where there is an abundance

of lateritic soil.

Bamboo-reinforced concrete is presently in the development stage

and appears to offer promise as a material to be used in secondary members

of which the bamboo would appreciably increase the resistance in tension

and flexure.

The structural sandwich panel as an innovative building system

merits serious consideration for application in developing countries

where labor-intensive production and local materials are used to create new methods of building technology appropriate to the region.

A technical development which can greatly contribute to the production

of inexpensive earthquake and windstorm resistant dwellings is the development

of building systems utilizing modular components in various schemes.

The provision in the future of complete prefabricated mechanical cores would further contribute to reducing costs and construction time. Mechanical

cores have in certain schemes the additional advantage of eliminating

the need for various non-architectural openings in the structure, thereby

improving its ability to withstand earthquakes and windstorms.

10.2 Stabilized-Soil Building Blocks

Among the numerous and varied methods of soil stabilization currently

in use, the following methods appear to offer the highest potential

for innovation and improved performance in low cost housing.

10.2.1 Oil-Stabilized Adobe Blocks

As a result of mixing certain types of asphalts - -which contain

a curing agent --with water and a clayey soil, the surface of the clay

particles is covered by an oil film which remains after the water and

curing agent evaporate. The oil film repels moisture thus eliminating

the expansive characteristic of the clayey soil.

Adobe blocks or bricks stabilized with rapid-curing road-oil, or emulsified asphalt, exhibit desirable characteristics of good insulation,

impermeability, erosion resistance, vermin and termite resistance and

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durability. The blocks or bricks are relatively maintenance - free and

need not be plastered or painted which significantly reduces construction

time and labor costs.

The manufacture of modular stabilized adobe block or brick would

lend itself to the design and construction of low-cost, earthquakeresistant buildings or building systems, utilizing labor-intensive techniques

Generally speaking, sun-dried adobe block or bricks are less expensive

than common fired-clay bricks or concrete blocks. The cost of manufacturing

the adobe block or brick varies with the method of manufacture, the

characteristics of the soil, and the cost of delivery if the block or bricks are not made in the immediate vicinity of the construction site.

The price of adobe block manufactured by hand in Cuzco, Peru was about

.05(f per block in 1971 at the plant site.

10.2.2 Polymer-Stabilized Adobe Blocks

Chemical soil stabilization techniques for unstable excavations

or lining of deep cavities are also well known and frequently utilized.

Polymer stabilization techniques were suggested as a result of preliminary

experiments and research into the potential uses of plastic resins in

low-cost housing schemes. An applied research project should determine

the feasibility of using polymer chemicals and soil mixed with various

organic fillers such as bagasse, rice hulls, and jute, or mineral fillers

such as vermiculite and expanded shale for the production of inexpensive

building materials.

10.2.3 Lateritic Stabilization

An example of a recent breakthrough in technology is the production

of blocks or bricks from lateritic soils. Laterite is the common reddish

soil that can be found in large land areas of the earth's surface, particular

in tropical and subtropical areas of South America, Africa, South-East

Asia and India. Laterite is the residual product of rock decay with

a high content of iron oxides. Lateritic soil is usually considered

unsuitable for production of building blocks such as burnt brick or tile because it generally lacks sufficient silicates and also has an excess of aluminates . However, the use of a chemical additive can alter

the characteristic reaction of a mixture of lateritic soil and water

to produce a sun-cured brick or block that should compare favorably

with a baked product [3] . The lateritic soil block is handmade in the same manner as the classic adobe block, using a wooden mold and rudimentary

mixing techniques. The manufacturing process can be adapted for labor

intensive production.

10.3 Bamboo-Reinforced Concrete

Results of recent studies of the feasibility of using bamboo as reinforcement for temporary reinforced concrete structures indicate

that bamboo reinforcement can develop from two to four times the ultimate

flexural load-carrying capacity of unreinforced members of equal dimensions.

The study is based on results obtained from small cane and is believed

to be conservative when other species of bamboo are used. The principal

problems associated with bamboo reinforcement are swelling and 'shrinking

due to moisture changes and low bond strength. Pre-soaking split bamboo

for 72 hours and applications of surface coatings are effective in mitigating

these problems [4]

119

527-373 O - 74 - 10
10.4 Composite Systems

10.4.1 Structural Sandwich Panels

10.4.1.1 Characteristics and Uses of Structural Sandwich Panels

One of the most efficient structural systems is the structural

sandwich. Basically a structural sandwich has a relatively thick, low

strength core bonded to thin, relatively high strength facings. The

structural sandwich system when used as a flexural member in a roof

system would consist of three components; the upper, exterior facing,

a core material, and the lower, interior facing.

The exterior facing material must have reliable compressive properties

and must either be water resistant or be waterproofed by an applied

coating

The interior facing material must have reliable tensile properties

and be fire resistant. An alternative to the fire resistance requirement

for the facing would be application of an auxilary fire resistant layer

to protect the interior facing.

The core material must have reliable shear properties and should

be of relatively low unit weight, and should provide the required thermal

insulation

The bonding medium used in sandwiches must have sufficient strength

and durability against moisture and under temperature extremes of the

exterior environment, and resistance against insect attack.

The strength required in this bond depends on the sandwich design,

on the materials used and on the loads expected in service. For example,

the tensile strength of the bond between the core and the interior facing

must be sufficient to support the dead weight of the facing. In addition,

the shear strength of the bond must be sufficient to transfer all shear

stresses to the facings without excessive creep. The magnitude of the

shear stresses is a function of the thickness and span length of the

panels as well as the intensity of applied loads.

Roof systems for structures utilizing low flexural strength wall

constructions should be of relatively 1o\-j mass in earthquake zones.

To achieve low mass in the roof there are but two alternatives: 1) either

use small amounts of high-strength materials, or 2) use lower-strength

materials in a highly efficient manner. High strength materials are usually relatively expensive and their use is often not possible in

many areas. As a result the only method available in many developing

areas for construction of a suitable roof system is to use locally available

^aterials as efficiently as possible. Structural sandwich panels, which

are both light and structurally effective, are therefore suitable for use in roof systems.

Structural sandwich panels may also be successfully used for interior

and exterior walls.

10.4.1.2 Performance of Structural Sandwich Panels

Tests recently conducted on an experimental unit constructed in

1947 by the U.S. Department of Agriculture -Forest Service, Forest Products

Laboratory, Madison, Wisconsin, using structural sandwich panels showed

that their performance was quite satisfactory.

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The sandwich panels in the experimental unit were constructed of

paper honeycomb cores with plywood or other wood-base facings, and other

materials. The paper honeycomb cores were produced by assembling sheets

of Kraft paper weighing about 22 kilograms (45 pounds) per ream, impregnated

with phenolic resin. The plywood facings were treated with phenolic

resin. The walls, floor and roof of the experimental unit was constructed

of sandwich panels. The Forest Products Laboratory of the U.S. Forest

Service issued the following summary of observations in publishing the

results of the tests carried out in Wisconsin, U.S.A.:

"Performance of sandwich panels in the experimental

unit over 21 years indicates that panels of nominal

thickness and construction can be satisfactorily

used for housing construction. Minimum stiffness

and strength requirements are easily achieved, and

most constructions retain their stiffness and

strength properties even after long-time service.

Adhesive bonding techniques proved to be adequate

with good bonds even after as much as 21 years of

service. No moisture problems at the bond were

observed. Synthetic resins in the honeycomb

material also afford a degree of moisture resistance

that insures adequate strength and stability even

if the material is immersed. Plywood- faced panels

have demonstrated excellent performance during 21

years of service. They had a minimum of movement

due to temperature and moisture changes , and retained

stiffness and strength. Mechanical fasteners used

in assembling a house might govern the thickness of

facings. In some cases, thinner prefinished plywood

with a non-marring plastic surface might be used

for the interior facing.

Although plywood was relatively stable, the other

wood-base facings were more affected by moisture

and temperature changes. In normal construction,

much of the bowing would be eliminated by fastenings

however, restricting the panel edges might result

in cross bowing or cupping. Therefore, facings

that are highly sensitive to temperature and moisture

changes are undesirable. . . Minimum insulation requirements for many areas of

the United States are satisfied by the corrugated

core. . . The panels with styrofoam core or urethane

foamed into expanded core both have insulating

properties comparable to conventional wood-frame

house construction with two inches (5 cm) of blanket

insulation. The long-term durability test with

panels exposed for periods as long as 21 years has

shown the feasibility of using this type of con- struction in housing. The requirements for satisfactory

sandwich panels are selection of proper combinations

of facings, core, and adhesives; careful fabrication

techniques; and good quality control."

10.4.1.3 Materials Used in Structural Sandwich Panels

One commonly used core material is paper honeycomb which is made

from a phenolic-resin-impregnated kraft paper. The phenolic-resin impregnation

stiffens the paper, increases the wet strength, and provides fungus

121
resistance. Paper honeycomb is manufactured in both a hexagonal configuration

and a corrugated configuration similar to that in cardboard used in

making paper cartons

Sheet metals are often used as facing material, but other materials

that are available in large flat shapes such as plywood, hardboard,

gypsum board, plastic laminates, cement-asbestos board are also used.

In evaluating the possible materials for use in the roof system,

paper honeycomb as the core material is considered feasible in most

countries, particularly in systems designed to utilize modular prefabricated

building components. Alternative core materials would be a low-density

pressed- fiber board or even bundled reeds, although the density would

not be as low as paper honeycomb. Most countries have corrugated paper

plants in which corrugated honeycomb could be made. These products

would have to be impregnated with either phenolic resin, an inexpensive

polymer product that may be produced locally, or some other material

which would provide the required properties.

A possible facing material is gypsum plaster which would have to

be reinforced for the interior facing because of its poor tensile strength.

The use of emulsified asphalt and other additives in the exterior facing

should be studied in connection with the effect of weathering on the

mechanical properties of the facing material. Also needed are tests

on the durability of the panel materials in highly humid climates.

The use of locally available core material such as bundled reeds

and split bamboo has also been considered. Polyurethane - foam sandwich

panels using bamboo cane reinforcement have been experimentally tested

at Washington University in St. Louis, Missouri. Also being evaluated

is an application of polyurethane foam on a woven- thatch wall panel.

The results of the experiments indicate that one may anticipate difficulties

in the production and control of the polymer and thus the finished panel.

The high comparative cost of the basic resin appears prohibitive at

this time.

10.5 Prefabricated Housing

Technical improvements which may contribute substantially to the

capability of producing inexpensive dwellings better resistant to natural

disasters include the use of prefabricated systems compatible with local

conditions and lending themselves to large scale industrial production

[5].

Among innovations that may be introduced is the pre -assembled utility

core package, housing appropriate mechanical, electrical and sanitary

systems. These units may contain the kitchen, the toilet or bathroom

area and the utility complex. All wiring, plumbing, heating and cooling

lines and ducts are pre -assemb led , and may include a heating unit, plumbing

fixtures, lights, storage units, and sinks. They eliminate from the

building site the most difficult and costly portion of the entire construction

process. Typically, one may erect the utility core on the building

site, usually over a foundation or sub-core with the remaining units

or components of the house then built around it. The core may be stacked

like a sectional box, with all connections between sections of the core made in the field. Solar energy may be used in mechanical cores for

the heating of water and possibly for other purposes (water treatment,

heating and cooling) [6].

122
Re ferences

1. Earth for Homes," Department of Housing and Urban

Development, Office of International Affairs, Washington

B.C. , June 1970

2. "The Manufacture of Asphalt Emulsion Stabilized Soil

Bricks," International Institute of Housing Technology,

California State University, Fresno, California, 1972.

3. Thomas Ringsholt and Torben C. Hansen, "Building with

Laterite locks," Building Materials Laboratory, Technical

University of Denmark, April 1972.

4. H. G. Geymayer and F. B. Cox, "Bamboo Reinforced Concrete,"

ACI Journal, October 1970.

5. "Industrialized Housing: The Opportunity and the Problem

in Developing Areas," Office of International Affairs,

Department of Housing and Urban Development, Washington

D.C. , 1972.

6. "Solar Energy in Developing Countries: Perspectives and

Prospects," National Academy of Sciences, March 1972.

123
Chapter 11, Mechanisms for Stimulating Technical Improvements

William F. Reps

National Bureau of Standards

11.1 Introduction

The development, adoption and implementation of improved earthquakeand windstorm-resistant housing technologies in developing countries

can be effectively stimulated by appropriate action in the areas of

financing, design, construction and education. Financing institutions

can contribute to improving such technologies by requiring that the

projects they finance be designed and built in accordance with building

code requirements (see Chapter 7). Cooperative programs involving specialized

agencies provide the opportunity for interaction between workers and

experts at all levels, during which communication and transfer of technology

can be effectively achieved. In addition to developing new or improved

building materials and systems, research institutes such as exist in

Indonesia [1] can be active in transferring existing technology through

building information centers serving professionals as well as laymen

who build their own houses. The centers can provide information on proper selection of materials, and technical guidance and advice on building know-how. Production units serving as models or pilot plants

can contribute to the diffusion of advanced technological methods. Prototype

buildings can be built for the purpose of acquainting the public with

innovative systems designed to provide better resistance to earthquakes

and windstorms.

In order to illustrate various ways in which such interaction can

occur, the programs and goals of several agencies involved in housing

development programs are briefly described in the following.

11.2 The Inter-American Bank

The Inter-American Development Bank (IDB) has played a significant

role in the last ten years with regard to urban development activities

by financing two types of projects: 1) basic infrastructure and 2) construction

of housing (not including land) . The bank is now interested in integrated

or total community development wherein all appropriate infrastructure

is provided, including surface access and potential transportation networks.

As of December 30, 1970, the IDB had twelve on-going projects in

Latin America. These projects range from infrastructure to integrated

community development.

The IDB offers technical services along with financing of projects.

Transfer of technology is achieved mainly in the process of providing

these services.

11.3 The World Bank

The World Bank does not contemplate direct lending for house construction

at this time. It considers, however, lending for seed capital to develop

housing finance institutions. The emphasis here is on the leverage

effect in prompting savings and developing capital markets in a form

which will lead to amelioration of the overall housing and employment

situation. Particular attention will be paid to the income groups for

which housing is proposed, the mobilization of small savings and the

possibilities for supporting improvements to substandard housing.

124
In line with these considerations, the urban project program in

this field is concentrated on "site and services" and similar projects

to provide urbanized land on which the occupants can build their own dwellings using self-help methods. One project is already being appraised

in Senegal and several others are envisaged. The first project is

illustrative. The land provided by the Government will be equipped

with roads, water, sewage and power facilities. Most water and sewage

facilities will be provided on a community basis. Education and health

facilities are included in the project as well as sites for industrial,

commercial, recreational and other developments. Exclusive of the social

facilities and power grid, charges to occupants are expected to cover

costs which will be only a small fraction of those of minimal housing

schemes in the city. A new institutional organization will be built

up with technical assistance to form the basis of a national program

on similar lines. The emphasis on use of local labor and employment

will result in a somewhat higher proportion of local costs than has

been customary in bank lending.

11.4 United Nations

11.4.1 U.N. Center for Housing, Building and Planning

The United Nations Center for Housing, Building and Planning (UNCFiBP)

is performing most valuable work in devising housing programs compatible

with technical and financial resources, and on the social organization

of sites and services schemes. The World Bank is assisting the UNCHBP

in instituting regular inter-agency exchanges of information on activities

with a view to sharing information and completing necessary studies

by the most appropriate agency, avoiding duplication of effort, and

reducing the burden on developing country administrations resulting

from numerous uncoordinated missions . An area of Latin America has

been selected for trial exchange of information. In the field of water

supply and sewage, a joint program has been established with the World

Health Organization, and in education with UNESCO.

11.4.2 U.N. Industrial Development Organization (UNIDO)

A UNIDO sponsored Expert Working Group Meeting on the "Use of Plastics

in the Building Industry" was held at UNIDO headquarters, Vienna, Austria,

September 20-24, 1971. The meeting covered the following areas of interest:

building systems using plastics, plastics deterioration in building

in tropical areas, prefabrication trends with plastics in buildings,

user requirements and performance specifications, and research and development

needs. The basic thrust of the meeting was focused on developing mass produced low-cost housing schemes for the developing countries in Africa

and the Middle East.

The information and practical experiences exchanged during the

conference indicated a significant potential for plastics in low-cost

housing schemes. As a result of this meeting, experts are currently

participating in a practical development program of a plastic dwelling

for emergency use in Bangladesh. Also under way is an applied research

effort to investigate the potential of urea-formaldehyde (U-F) foam

for insulation in a lightweight roof sandwich panel composed of a cardboard

honeycomb core, U-F foam, and an outer skin of gypsum reinforced with

a jute fabric. Ultraviolet ray protection is provided by a surface

coating of a special water soluble plastic paint.

As a result of the discussions, the technical experts group formulated

certain recommendations for action that might be initiated by developing

125
countries and by UNIDO in cooperation with developed countries with

a view to encourage development, introduction and promotion of the use

o£ plastics in the building industry. Significant recommendations are summarized below:

1) Keeping in view the varied climatic and socio-economic

conditions in the developing countries, the development

and introduction of plastics building products should be

gradually and systematically organized.

2) It would be essential to educate architects, engineers

and building contractors in the proper selection and use of plastics building components. This would necessitate

organizing appropriate education/training programs.

3) Relevant performance specifications in respect of

plastics building components should be formulated to

facilitate their ready acceptance by the local building

industry

4) Assist the developing countries to encourage mass- production techniques for housing.

5) Take part in specific projects to encourage dissemination

of information about plastics for building applications.

This could include the provision of non-commercially

oriented literature and specialist advisers and the

provision of models and full-size samples of buildings

put up with systems suitable for use in developing

countries , to be displayed at seminars and building

exhibitions

6) Participate, as far as possible, in setting up industrialized housing systems to use present and potential

local resources.

The following recommendations pertain to action by United Nations

and other international organizations and agencies:

1) Provide inter-disciplinary teams of experts to developing countries to examine user requirements and relate

this information to the possibility of local industrial

production of housing using plastics with emphasis on present and potential local resources.

2) Initiate fellowship programs for experts from developing

countries and organize, as early as possible, interregional seminars in developing countries on the use of

plastics as building materials

3) In order to expedite the organization of necessary

meetings, consider the joint participation with outside

professional organizations in provision of facilities

and funds for such meetings.

4) Establish criteria for evaluating housing systems, which

incorporate the use of plastics, make available this

information at the request of developing countries and

assist them in evaluating the cost, performance and

adaptability of any proposed system to local climatic

and socio-economic conditions.

126
In view of the capacity of properly designed building systems using

plastics to withstand earthquakes or windstorms, the recommendations

of the UNIDO meeting are of particular interest in the context of the

present study and report.

11.4.3 U.N. Development Program

The U.N. Development Program CUNDP) is the world's largest program

of multilateral technical assistance. Typical of the type of project

that the UNDP has initiated in the past is the Experimental Housing

Project in Peru which was to assist the Government of Peru in establishing

a long-term housing policy through the planning, construction and initial

management of an experimental housing project with particular emphasis

on the needs of low-income sectors of the population. It consists of

four pilot projects the first three of which are located in Lima. The

fourth was added after the earthquake of May 31, 1970, to assist the

Government in reconstruction and is located in the affected region in

northern Peru. The Experimental Housing Project espoused methods and

techniques which might be applied on a larger scale as part of Peru's

housing policy.

The following is a brief outline of the project:

Pilot Project I (New Community)

The first pilot project is for the design and construction of a new community of approximately 1,500 low-cost houses complete with all

community buildings. The design of the community is based upon the

concept of high-density, low-rise houses with internal patios which

can expand and adjust to accommodate the changing requirements of lowincome families. Special emphasis is placed upon improved design, rationalized building methods and materials, dimensional standardization, and use of suitable building plant and equipment. In the first stage approximately

500 houses will be built. These consist of prototypes of thirteen Peruvian

and thirteen foreign- designs and also include community sub-center with

kindergarten and school. The first stage has been carefully planned

to compare and evaluate the various building methods, house types and

groupings. The favorably evaluated house types will be repeated in

larger numbers in the second stage which will complete the neighborhood

with all facilities and appropriate infrastructure.

Pilot Project II (Housing Rehabilitation)

The second pilot project is to develop procedures and techniques

to extend the functional life of existing sub-standard housing stock

by rehabilitating older dwellings and urban areas to meet contemporary

environmental standards. By applying these techniques on a larger scale

in urban areas a substantial contribution to the reduction of housing

deficits could be made at considerably less cost than through the alternative of new houses. In the selected location a comprehensive social

and economic survey on all families and condition-of -structure survey

on all houses has been carried out and this data forms the basis for

the rehabilitation planning. The rehabilitation program provides for

structural improvements and additions to sub-standard dwellings, new sanitary and electrical installations and general upgrading of groups

of houses and their urban environment. In the rehabilitation of the

individual dwelling, self-help methods will be widely employed for occupant

families. A community-action program will aim at maintaining social

homogeneity and obtaining maximum participation from the 300 families

in the area of the project.

127
Pilot Project III (Sites and Services)

The third pilot project is for families whose low incomes are not

sufficient to amortize a loan to purchase a contractor-built dwelling

unit. Self-help building methods, which can reduce the cost of a house

by 40%, will be fully employed. Families will be organized and trained

for building their own houses with new construction methods using small

building elements and improved traditional methods. Technical supervision will be provided to the families. A social plan runs parallel

with the training, construction and management aspects of the project.

The main work phases of the project are: a) defining socio-economic

characteristics of the families, b) development of community plan,

houses designs and building methods, c) community development and housing

management.

Pilot Project IV (Earthquake Resistant Housing)

The fourth pilot project is for low-cost, earthquake-resistant

and fast-to-erect permanent housing and includes the development of

basic building materials industries. Two groups of dwellings are planned.

One group of approximately 60 houses is to be located at Casma on the

coast and one group of approximately 60 units at Catac in the Sierra.

Small workshops are located on each building site for the production

of building components and the training of families in self-help building

methods by technical experts. Manuals of practical building methods

have been prepared as instruction aids and for widespread circulation

in the region for use by self-help builders. Social workers are collaborating

in the training of families and the organization of the groups of families

for participation in the project. The project also includes technical

assistance to small local industries to improve and expand the productivity

of building materials and components.

A workshop has been constructed on the site of Pilot Project I,

fully equipped with tools , machinery and plant provided by the United

Nations, for the development and testing of building materials and methods

to be employed in all four pilot projects.

The Project is directed by a project manager in cooperation with

a national director appointed by the Government. A Coordinating Commission

of representatives of national housing and planning agencies coordinates

the Project with related development agencies of the Government, The

planning and implementation of each pilot project is carried out by

a separate development group consisting of Peruvian and United Nations

personnel. An inter-development group and specialized personnel assist

each pilot project as required in technical areas including engineering,

productivity, costing and finance, training and housing management.

11.5 CARE, Incorporated

The Cooperative for American Relief Everywhere, Inc. is currently

employed in a major relief operation in Bangladesh where, in addition

to the many and diverse needs, housing has become critically essential.

The CARE, Inc. organization contacted the National Bureau of Standards

as a result of preliminary conversations with members of the Building

Research Advisory Board of the National Academy of Sciences in Washington,

D.C. CARE, Inc. requested an informal evaluation of a new composite

building material made of pulp from the core of the jute plant, jute

cloth and a plastic resin for binder and facing material. From this

combination, other variations of plastic resin and jute materials have

been formulated for laboratory testing, prototype construction and wind

128
testing o£ a full scale unit. With properly designed details, dwelling

units o£ the type developed by CARE, Inc. can successfully withstand

extreme environmental loads.

11.6 National Institutions

The initial phase or information gathering stage on this project

included the establishment of appropriate communication and exchange

of information with a number of national institutions. The opportunity

to develop potential areas of collaboration in the transfer and utilization

of innovative technology was evident in each country visited during

this phase of the project.

11.6.1 Peru

A program to develop improved methods for adobe construction was recently set up. The program will help fulfill one of the principal

objectives of a current technical assistance project initiated by the

U. S. Agency for International Development mission in Lima, Peru, in

collaboration with the following national institutions: Ministerio

de la Vivienda (Ministry of Housing) ; Banco de la Vivienda (Housing

Bank); Universided Nactional De Ingenieria (National University of Engineering);

the International Institute of Housing Technology of Presno State College,

California, and the National Bureau of Standards, Center for Building

Technology. The specific objectives of the program are:

1. Production of a low-cost, high quality stabilized adobe

block

2. Development of adequate structural designs and building

techniques for anti-seismic adobe construction.

3. Construction of a number of prototype houses and training

and technical assistance to families on the new construction methods and promotion of these new methods.

4. After the technical and economic feasibility of

constructing houses with stabilized adobe have

been determined, large-scale projects would be developed

and implemented throughout Peru, with different sources

of finance.

11.6.2 Turkey

Meetings were held in 1971 between N.B.S. personnel visiting Istanbul

and Ankara and representatives of the Istanbul Technical University,

the Bosphorus University (Roberts College), the Middle East Technical

University and the Ministry of Reconstruction and Resettlement (Earthquake

Research Institute and General Directorate of Natural Disaster Affairs).

In the course of these meetings the approach to the Turkish socio-economic

study was discussed. The study provided an opportune mechanism to join

together, for the first time, many of the leading engineers, architects,

and scientists in Turkey for a common goal. The National Committee

of Earthquake Engineering in Turkey was thus formed, headed by the Dean

of Turkish Engineers, Professor Dr. Rifat Yarar. Also, a Board of Research

Associates and Consultants were formed as contributory experts for the

socio-economic study, under the guidance of the National Committee.

129
The Minister of Reconstruction and Resettlement, the Director of

the Earthquake Research Institute and the General Director of Natural

Disaster Affairs supported and contributed to the socio-economic study.

The National Committee of Earthquake Engineering in Turkey is planning

future projects related to seismology, geology and innovative technology

transfer. An Earthquake Engineering and Training Center is envisaged

in conjunction with symposiums, seminars and other academic gatherings

for purposes of teaching and information exchange.

The Ministry of Reconstruction, Department of Building Materials,

Research and Testing Laboratories in Anakra has expressed interest in

construction and testing of prototype dwelling units in their facilities.

Interest was noted in applied research of low-cost housing constructed

of honeycomb cardboard cores, gypsum and stabilized adobe.

The General Directorate of Natural Disaster Affairs expressed interest

in a field mission to develop and teach improved methods and materials

for adobe construction and other innovative techniques that might be

appropriate

11,6.3 The Philippines

The Philippine Weather Bureau has proposed a five-year integrated

research project entitled "Typhoon Research" to the National Science

Development Board. The objectives of the project are to: 1. Assess

the prospects of artificial modification of typhoons; 2. Achieve a better

understanding of the structure of typhoons, their development and motion,

and improve their prediction; 3. Obtain adequate climatological and

hydrological data for the Philippines to support economic development

planning. The Typhoon Research Project may he managed by representatives

of a number of National Institutions including but not limited to: The

Department of Foreign Affairs, Office of the Executive Secretary, Department

of Agriculture and Natural Resources, National Science Development Board,

Weather Bureau and the Philippine Air Force.

Considerable interest was also expressed in an applied research

program to develop the design criteria and methodology for wind-resistant,

low-cost houses, and to construct one or more prototype units at selected

weather observation stations, and to instrument and measure the prototype

units under actual typhoon conditions. The National Science Development

Board is considering allocating some funds for such a project if additional

funding from other sources was made available. The Weather Bureau has

stated its readiness to provide the sites for the prototypes. The University

of the Philippines, Department of Engineering, is interested in technical

collaboration to develop and test a prototype in the University's Building

Research Institute -Civi 1 Engineering Laboratory. The National Bureau

of Standards has subsequently proposed to the Agency for International

Development a research project along these lines, and the proposal has

been accepted and funded.

11.6.4 Iran

Adobe brick was developed in Iran almost 5,000 years B.C. and as today, it was formed by hand using a primitive mold and a clay soil

mixture. It is estimated that almost 801 of all houses in Iran are constructed with adobe brick, wood, straw and stone.

Under Iran's Third Development Plan (1963-1968) approximately 17,000

government-assisted housing units were built. About 200,000 units were

130
built by the private sector, and private sector investment in urban

construction projects is increasing at a rate of about 121 per year.

The Fourth Development Plan (1968-1973) calls for a total of 275,000 new housing units, 25,000 of these governmentally assisted, not including

industrially oriented housing development or rural housing.

Most of the government-assisted units will be replacements for

slum housing, and efforts are being made to provide more living space

per unit. Most of the new housing is built of brick walls approximately

40 centimeters thick. The average size of the brick is about 5 x 11

X 22 centimeters.

Earthquake damage is virtually continual in several areas of Iran.

Many dwellings are destroyed by earthquakes and many people are killed

by collapsing of roofs and walls.

The Ministry of Housing and Development in Tehran has completed

a program of construction of prototype houses in an experimental village

located in Narmak , a suburb of Tehran. The houses are each of a different

design, with the majority constructed of adobe brick and adobe plaster.

Several prototypes are scheduled for static testing.

The Ministry of Housing and Development expressed a strong interest

in several areas of technical assistance, including an exchange of technical

information, a training program for qualified engineers and an extensive

field mission to develop and teach improved methods and materials for

adobe construction.

Reference

1. Abbas, Z.A., "The Role of the Indonesian Building Research

Institute in the Building Materials Industry," International

Seminar on Dissemination of Technology, November 20-22, 1972,

Korean Institute of Science and Technology, Seoul, Korea.

131
CONVERSION UNITS

Length

1 in = 0.0254* meter

1 £t = 0.3048* meter

Area

1 inl = 6.4516* x 10'^ meter^

1 ft = 0.09290 meter^

Force

1 lb (Ibf) = 4.448 newton

1 kip = 4448 newton

Pressure, Stress

2 1 psi = 6895 newtog/meter

2 1 ksi = 6.895 x 10 newton/meter

Mass/Volume

1 Ib/ft-^ (lbm/£t^) = 16.02 kilogram/meter^

Moment

1 kip-in = 113.0 newton-meter

* Exactly

132
FORM NBS-114A (1-71) U.S. DEPT. OF COMM. 1. PUBLICATION OR REPORT NO. 2. Gov't Accession

BIBLIOGRAPHIC DATA NBSBSS-48

3. Recipient's Accession No.

4. TITLE AND SUBTITLE

Design, Siting and Construction o£ Low-Cost Housing and

Coramunity Buildings to Better Withstand Earthquakes and

Windstorms

5. Publication Date January L974

6. Performing Organization Code

7. AUTHOR(S)

William F. Reps and Emil Simiu, Editors

8, Performing Organization

9. PERFORMING ORGANIZATION NAME AND ADDRESS

NATIONAL BUREAU OF STANDARDS

DEPARTMENT OF COMMERCE

WASHINGTON, D.C. 20234

10. Projcct/Task/Work Unit No. 4Dib4Ub

11. Contract/Grant No.

12. Sponsoring Organization Name and Address

Agency for International Development

Washington, D. C. 20523

13. Type of Report & Period Covered Final - 1973

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.) The extensive loss o£ life and property caused in developing countries by earthquakes and windstorms (hurricanes, typhoons and tropical cyclones) may be reduced to a considerable degree by the adoption and inplementation of improved design, siting and

construction procedures practicable within the context o± the cultural and socioeconomic constraints prevailing in these countries.

The report provides technical information regarding characteristics of materials

and building systems, and discusses the structural performance of buildings subjected

to the action of earthquakes and wind forces with specific reference to structures

typical of developing countries. Potential ways are described in which structures can

be made more resistant to such action. Siting considerations are discussed from a geological, seismic and climatological viewpoint, and recommendations relating to

siting problems are made. Techniques of housing construction, both traditional and

industrialized, are described and improvements resulting in better earthquake or windstorm resistance are suggested. Building codes, their improvement and their enforcement

are also discussed.

The report discusses cultural and socio-economic constraints influencing the

adoption of inproved practices, describes various feasible technical improvements of

construction materials, composite systems and building systems, identifies mechanisms

for stimulating technical improvements and discusses the role of institutions in this

regard. Throughout the report, specific references are made to Peru, the Philippines

and Turkey, countries which suffer from frequent devastation from natural disasters

such as earthquakes and typhoons and which were selected as case studies for the purpose

17. KEY WORDS (Alphabetical order, separated by semicolons) Of thlS rOpOrt

mildings; construction; design; developing countries; earthquakes; low-cost housing;

natural disasters; structures; windstorms.

18. AVAILABILITY STATEMENT 19. SECURITY CLASS

(THIS REPORT)

21. NO. OF PAGES

fxl UNLIMITED. UNCL ASSIFIED 152

1 1 FOR OFFICIAL DISTRIBUTION. DO NOT RELEASE

TO NTIS.

20. SECURITY CLASS

(THIS PAGE)

UNCLASSIFIED

22. Price

$4. 85

U.S. GOVERNMENT PRINTING OFFICE ; 1974 0 - 527-373