3.9 Getty Seismic Strengthening of Adobe Project (GSAP)

Project Team:

Charles C.Thiel Jr.Consultants
E. Leroy Tolles
Edna Kimbro
Fred A. Webster
William S. Ginell
The Getty Conservation Institute
James R. Druzik
Neville Agnew

Advisory Committee

Edward E. Crocker
New Mexico Community Foundation
Anthony Crosby
National Parks Service
Wayne Donaldson
Architect, Milford Wayne Donaldson
Melvyn Green Melvyn
Green and Associates, Inc.
Jim Jackson
California Dept. of Parks and Recreation
Helmut Krawinkler
Stanford University
John C. Loomis
Thirtieth Street Architects, Inc.
Nicholas M. Magalousis
Museum Director, Mission San Juan Capistrano
Julio Vargas Neumann
Parque Antequera, Lima, Peru
Period of Activity: Current Research

Project Abstract
The goal of the Getty Conservation Institute's Seismic Strengthening of Adobe Project (GSAP ) is to develop guidelines and technical procedures to improve the seismic performance of existing adobe structures consistent with maintaining the architectural conservation values. GSAP focuses on the Spanish Colonial Missions and historic adobes in seismic areas of California and the American Southwest, with expected applications to adobes in other seismic regions, particularly in Latin America.

The intermediate term goals of GSAP are to develop and evaluate design tools and practices that can be used by the professions while the guidelines are under development, to foster development of the capacity and capability to implement the final guidelines, and to mobilize knowledgeable people, agencies, and organizations to address seismic safety issues of adobe structures.

Primary Publications
Tolles, E. L., C. C. Thiel Jr., and W. S. Ginell, "Seismic Retrofitting of Historic Adobes," Terra 93, October 1993, Portugal.

ABSTRACT-A stability-based approach for retrofitting historic adobe buildings is the most effective way to take advantage of their inherent structural characteristics and to minimize the impact on the historic fabric. Cracks exist in virtually all historic adobes and should not be characterized as significant damage. A stability-based methodology is the only valid approach once cracks have formed. The main goals of a stability-based retrofit are (a) to prevent walls from overturning (out-of-plane collapse) and (b) to restrict the relative displacements of adjacent blocks, thus enabling the structure to withstand repeated seismic events. Recent shaking table tests clearly demonstrate the effectiveness of stability-based techniques.

Tolles, E. L.., C. C. Thiel Jr., E. E. Kimbro, F. A. Webster, and W. S. Ginell, "Recent Developments in Understanding the Seismic Performance of Historic Adobe Buildings," Paper presented at Conference on Seismic Retrofit of Historic Buildings, San Francisco, California, November 18-19, 1991.

ABSTRACT-The purpose of this paper is to provide insights into understanding the seismic performance of adobe buildings. An acceptable approach to seismic retrofitting of historic adobe buildings must meet three distinct requirements: provide essential levels of occupant safety; preserve the historic fabric of the structure during the retrofitting process; and provide acceptable performance in earthquakes. The work described is part of the Getty Conservation Institute's Guidelines for Seismic Strengthening of Adobe Project (GSAP). The initial phase of GSAP focused on examining existing knowledge and retrofit practice for adobes and on developing a philosophy of design to guide their seismic retrofitting. Results of this initial phase are summarized in this paper. It is argued that the seismic evaluation and retrofit design of buildings made of adobe should be distinctly different in both philosophy and detail from those used for conventional building materials. Conservation principles specifically applicable to historic adobes are discussed to establish the important conservation issues that must be respected when designing and applying a retrofit. Two engineering analysis approaches are assessed-the first is the conventional strength-based analysis procedure and the second is a stability-based approach. The stability-based approach is preferred because it can directly utilize adobe construction's unique characteristics and explicitly addresses the collapse potential of these buildings. A summary of results of testing programs on adobe structures conducted at Stanford University and the University of California at Berkeley during the mid-1980s is presented and conclusions that are applicable to the seismic performance of historic adobes are given. Several retrofit designs that have been implemented during the last fifteen years are assessed. Finally, important design issues are discussed that need to be addressed in the seismic analysis and retrofit of adobe buildings. These provide a framework for understanding the seismic behavior and retrofitting of adobe buildings. Over the longer term, GSAP will undertake research and development efforts to supplement what is currently known and develop recommendations for seismic retrofitting of historic adobes.

Kimbro, E. E., "Conservation Principles Applied to Seismic Retrofitting of Culturally Significant Adobe Buildings," Paper presented at Conference on Seismic Retrofit of Historic Buildings, San Francisco, California, November 18-19, 1991.

ABSTRACT-Seismic retrofitting of culturally significant adobe buildings presents designers with tremendous challenges to ensure life safety while respecting inherent cultural values. The nature of those values and the architectural conservation principles followed to maximize the preservation of historic fabric and safeguard authenticity are discussed to further sound preservation planning of seismic retrofitting interventions. The necessity of a multidisciplinary approach and the value of historic reports are emphasized; relevant use issues are discussed.

Thiel Jr., C. C., E. L. Tolles, E. E. Kimbro, F. A. Webster, and W. S. Ginell, "GSAP-The Getty Conservation Institute Guidelines for Seismic Strengthening of Adobe Project," Final Report to the Getty Conservation Institute, October 1991.

Table of Contents

1. GSAP-The Getty Conservation Institute Guidelines for Seismic Strengthening of Adobe

2. A Framework for Understanding the Seismic Performance of Adobe

3. Survey of Selected Historic Adobe Buildings in California (twenty structures)

4. Conservation Principles and Seismic Retrofitting Technology for Culturally Significant Adobe Buildings

5. Engineering Decisions in Seismic Retrofitting of Historic Adobes

6. Enhancing Utilization of GSAP Results

7. Glossary of Spanish Colonial Architectural Terminology

8. Bibliography of Source Materials on the Seismic Performance of Adobe

9. Census of Historic Adobe Buildings in California