Performance Based Seismic Resistant Design

Most structural engineers are convinced that methods of analysis, knowledge of material properties, and accuracy of earthquake intensity prediction have reached a point of sufficient development such that buildings and other structures can be designed with predictable confidence to resist specific earthquake shaking within certain performance limits. As the need for enhanced performance levels has become more obvious for certain uses (hospitals, emergency operations facilities, schools, essential facilities and other commercial and governmental buildings), and the need for maintaining operations in the transportation and utility fields has become more important to economic health, the application of performance-based design techniques are becoming more commonplace. Additionally, the recognition that many buildings and structures in the existing inventory are potentially collapse hazards in the event of strong earthquake shaking has stimulated a voluntary and mandatory movement toward seismic retrofit of the most vulnerable of these buildings and structures.

Performance-based design allows owners and facility managers to study the cost-benefits of specific predictable damage states of their facilities after strong earthquake shaking. It empowers engineering designers to work within the parameters chosen. A system of performance levels ranging from Operational to Collapse Prevention has been defined. United States Geological Survey and the California Division of Mines and Geology have published an array of predicted earthquake hazard levels for various return periods. By pairing a specific performance level with a specific earthquake hazard level, an engineer can establish a performance objective for a new building or retrofit.

Because performance is directly related to damage states and damage states are generally related to deformations, it has been necessary to modify traditional design and analysis procedures to be related to deformations together with stresses rather than to stresses alone, and to adopt new procedures that explicitly account for post-elastic behavior of components of structures.

To a large extent, these new design and analysis procedures have been developed and promoted under the auspices of the Federal Emergency Management Agency, working with the Building Seismic Safety Council, the Applied Technology Council, and the American Society of Civil Engineers, to further their efforts toward the protection of lives and property, diminish the cost, and hasten recovery from the effects of natural hazards. Daniel Shapiro was project engineer for FEMA’s seminal effort to introduce national guidelines for seismic rehabilitation of buildings, which included the first code-like descriptions of performance-based seismic design. SOHA’s engineers have been and continue to be active in the leadership of this effort.

Daniel Shapiro (danshap@soha.com), Principal/Founder of SOHA and current member of California’s Seismic Safety Commission, was the primary author of a paper entitled “NEHRP Guidelines and Commentary for the Seismic Rehabilitation of Buildings,” which appeared in the February 2000 issue of Earthquake Engineering Research Institute’s (EERI) Earthquake Spectra Journal. The paper has a discussion on performance-based design.

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