Building Performance in the 1972 Managua Earthquake
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NITED STATES ARTMENT OF MMERCE NBS TECHNICAL NOTE 807 BLICATION Building Performance in the 1972 Managua Earthquake 575?> .SCI 1*113 tZ U.S. ARTMENT OF OMMERCE National Bureau of Standards NATIONAL BUREAU OF STANDARDS 1 The National Bureau of Standards was established by an act of Congress March 3, 1901. The Bureau's overall goal is to strengthen and advance the Nation's science and technology and facilitate their effective application for public benefit. To this end, the Bureau conducts research and provides: (1) a basis for the Nation's physical measurement system, (2) scientific and technological services for industry and government, (3) a technical basis for equity in trade, and (4) technical services to promote public safety. The Bureau consists of the Institute for Basic Standards, the Institute for Materials Research, the Institute for Applied Technology, the Institute for Computer Sciences and Technology, and the Office for Information Programs. THE INSTITUTE FOR BASIC STANDARDS provides the central basis within the United States of a complete and consistent system of physical measurement; coordinates that system with measurement systems of other nations; and furnishes essential services leading to accurate and uniform physical measurements throughout the Nation's scientific community, industry, and commerce. The Institute consists of a Center for Radiation Research, an Office of Meas- urement Services and the following divisions: Applied Mathematics — Electricity — Mechanics — Heat — Optical Physics — Nuclear Sciences 2 — Applied Radiation " — Quantum Electronics 3 — Electromagnetics 3 — Time and Frequency 3 — Laboratory Astrophysics 3 — Cryogenics \ THE INSTITUTE FOR MATERIALS RESEARCH conducts materials research leading to improved methods of measurement, standards, and data on the properties of well-characterized materials needed by industry, commerce, educational institutions, and Government; provides advisory and research services to other Government agencies; and develops, produces, and distributes standard reference materials. The Institute consists of the Office of Standard Reference Materials and the following divisions: Analytical Chemistry — Polymers — Metallurgy — Inorganic Materials — Reactor Radiation — Physical Chemistry. THE INSTITUTE FOR APPLIED TECHNOLOGY provides technical services to promote the use of available technology and to facilitate technological innovation in industry and Government; cooperates with public and private organizations leading to the development of technological standards (including mandatory safety standards), codes and methods of test; and provides technical advice and services to Government agencies upon request. The Institute consists of a Center for Building Technology and the following divisions and offices: Engineering and Product Standards — Weights and Measures — Invention and Innova- tion — Product Evaluation Technology — Electronic Technology — Technical Analysis — Measurement Engineering — Structures, Materials, and Life Safety * — Building Environment * — Technical Evaluation and Application * — Fire Technology. THE INSTITUTE FOR COMPUTER SCIENCES AND TECHNOLOGY conducts research and provides technical services designed to aid Government agencies in improving cost effec- tiveness in the conduct of their programs through the selection, acquisition, and effective utilization of automatic data processing equipment; and serves as the principal focus within the executive branch for the development of Federal standards for automatic data processing equipment, techniques, and computer languages. The Center consists of the following offices and divisions: Information Processing Standards — Computer Information — Computer Services — Systems Development — Information Processing Technology. THE OFFICE FOR INFORMATION PROGRAMS promotes optimum dissemination and accessibility of scientific information generated within NBS and other agencies of the Federal Government; promotes the development of the National Standard Reference Data System and a system of information analysis centers dealing with the broader aspects of the National Measurement System; provides appropriate services to ensure that the NBS staff has optimum accessibility to the scientific info.mation of the world. The Office consists of the following organizational units: Office of Standard Reference Data — Office of Technical Information and Publications — Library — Office of International Relations. 1 Headquarters and Laboratories at Gaithersburg, Maryland, unless otherwise noted; mailing address Washington, D.C. 20234. 3 Part of the Center for Radiation Research. 1 Located at Boulder, Colorado 80302. * Part of the Center for Building Technology. Building Performance in the 1972 Managua Earthquake National Bureau c' APR 2 9 1974 Richard N. Wright and Samuel Kramer Center for Building Technology Institute for Applied Technology National Bureau of Standards Washington, D.C. 20234 TOPc ^ <v / V % c U.S. DEPARTMENT OF COMMERCE, Frederick B. Dent, Secretary NATIONAL BUREAU OF STANDARDS, Richard W. Roberts, Direcfor Issued November 1973 National Bureau of Standards Technical Note 807 Nat. Bur. Stand. (U.S.), Tech. Note 807, 155 pages (Nov. 1973) CODEN: NBTNAE U.S. GOVERNMENT PRINTING OFFICE WASHINGTON: 1973 For sale by the Superintendent of Documents, U.S. Government Printing Office, Washington, D.C. 20402 (Order by SD Catalog No. 013.46:807). Price $1.60 ABSTRACT Following the Managua, Nicaragua, earthquake of December 23, 1972, a team of engineers representing the U.S. Department of Commerce's National Bureau of Standards (NBS) and the National Academy of Engineering (NAE) performed field investigations in Managua, Nicaragua, from December 26, 1972, to January 4, 1973. The objectives were to assist the Nicaraguan government in surveying major buildings to deter- mine whether each was suitable for emergency use, repairable, or appropriate for clearance. The team also viewed the patterns of successful performance and damage to identify needs for improvements in building practices for mitigation of earthquake hazards and opportunities for more detailed investigations which could provide information for future improvements in practices. The Managua earthquake, estimated at Richter magnitude 6.25, was not a great earthquake, but the loss of life approached 10,000, approximately 75 per cent of Managua's 450,000 occupants were rendered homeless, and property damages are estimated to approach $1 billion. In general, these damages cannot be attributed to unusual intensities of ground shaking or severity of surface faulting. Most damages appeared to result from deficiencies in building practices; deficiencies which had been exhibited many times before in previous earthquakes, deficiencies which would be avoided by implementation of up-to-date provisions for earthquake resistant design and construction. However, Managua did not employ a building code with seismic design requirements appropriate to its earthquake risk, and furthermore, did not have a building. regulatory system capable of effective imple- mentation of its building code provisions. This report documents the observations of damages by the NBS/NAE team and points out relationships to inadequacies in the building practices employed. Most of these inadequacies have been well known; however, the Managuan experience may serve as an incentive to improvement of building practices in many other areas which are subject to substantial earthquake risks and have not consistently accounted for these risks in their building codes and building regulatory system. Key words: Building codes; buildings; earthquakes; hazards; natural disasters; structures. m TABLE OF CONTENTS Page ABSTRACT iii 1. INTRODUCTION 1 1.1 General Situation 1 1.2 Earthquake Characteristics 6 1.3 Disaster Investigation 7 2. GENERAL OBSERVATION 19 2.1 Taquezal Construction 19 2.2 Critical Facilities 19 2.3 Comparison of Shear Wall and Unbraced Frames 25 2.4 Performance of Housing 28 3. CAUSES OF DAMAGES 31 3.1 Inadequate Strength in Vertical Planes 31 3.2 Inadequate Strength in Horizontal Planes 31 3.3 Detailing for Energy Absorption 31 3.4 Adequate Clearances or Connections 32 3.5 Direct Hazards from Nonstructural Elements 32 3.6 Anchorage of Equipment and Industrial Facilities 33 3.7 Structural Effects of Nonstructural Elements 33 3.8 Additions and Modifications 34 3.9 Building Codes and the Building Regulatory System 34 4. REPORTS OF INSPECTIONS OF BUILDINGS 36 5. SUMMARY 37 REFERENCES 38 APPENDIX A 39 APPENDIX B 41 IV BUILDING PERFORMANCE IN THE 1972 MANAGUA EARTHQUAKE by 1/ Richard N. Wright- and Samuel Kramer 1 . INTRODUCTION This report summarizes the field investigation conducted by a National Bureau of Standards' team following the Managua, Nicaragua, earthquake of December 23, 1972. The major emphases in the investigaiton were to assist Nicaraguan authorities in evaluating the conditions of public buildings immediately following the disaster, and to observe causes of building failures for guidance toward improvements of practices for design, construc- tion and occupancy of earthquake resistant buildings. 1.1 General Situation Nicaragua, shown in figure 1, is the largest of the Central American republics. Its area is approximately 57,000 sq. miles and its population 2/ was 2 million in a 1972 estimate [11- . Managua is located in the western central portion of the country at the south edge of Lake Managua. A chain of volcanoes traverses Nicaragua from the northwest to the southeast. As noted