ng: Reports on Leading Edge Engineering from the 1996 NAE Symposium on Frontiers of Enginee http://www.nap.edu/catalog/5576.html 10 DESIGN RESEARCH force levels used to design most buildings are consistent with an expectation of structural damage, and buildings in the epicentral area are expected to sustain damage, even during moderate events. Clearly, the differences in th performance expectations of the general public and the structural engineering profession are significant. Experience from recent earthquakes in California demonstrates that U.S building codes have been successful in meeting the primary objective of lim- iting the loss of life(Table 1). However, many of the buildings that structural engineers consider to have performed successfully during an earthquake rep resent a substantial economic loss for the owner. Although it is usually possible to repair a structure damaged by an earthquake, often it is not practi al to do st of structural equipment, finishes, and contents. Consequently, the economic im- pact of building damage in terms of interruption of business, loss of housing and disruption to the community can be staggering. It is obvious that successful structural performance during an earthquake can no longer be defined merely in terms of preventing collapse. Funds available for disaster relief are not limitless, and the 1994 Northridge earth- quake provided convincing evidence that an economic crisis could develop if a major earthquake occurred near a densely populated area of the United States The concept of performance-based design was developed in an attempt to narrow the gap between the expectations that society places on building per- formance during an earthquake and the philosophy that structural engineers use to develop the building codes. In 1995 the Structural Engineers Associa- tion of California issued an overview of the objectives of performance-based seismic design. Although actual design procedures have not been developed, target levels of structural response are defined relative to the anticipated con dition of the building after earthquakes of varying intensity TABLE 1 Direct Losses from Recent Earthquakes in California Date Location Magnitude (million S 1994) Coalinga Whittier Narrows Loma prieta 6870 Landers Source: OTA(1995). Copyright National Academy of Sciences. All rights reserved10 DESIGN RESEARCH force levels used to design most buildings are consistent with an expectation of structural damage, and buildings in the epicentral area are expected to sustain damage, even during moderate events. Clearly, the differences in the performance expectations of the general public and the structural engineering profession are significant. Experience from recent earthquakes in California demonstrates that U.S. building codes have been successful in meeting the primary objective of lim￾iting the loss of life (Table 1). However, many of the buildings that structural engineers consider to have performed successfully during an earthquake rep￾resent a substantial economic loss for the owner. Although it is usually possible to repair a structure damaged by an earthquake, often it is not practi￾cal to do so, especially considering the often high replacement cost of non￾structural equipment, finishes, and contents. Consequently, the economic im￾pact of building damage in terms of interruption of business, loss of housing, and disruption to the community can be staggering. It is obvious that successful structural performance during an earthquake can no longer be defined merely in terms of preventing collapse. Funds available for disaster relief are not limitless, and the 1994 Northridge earth￾quake provided convincing evidence that an economic crisis could develop if a major earthquake occurred near a densely populated area of the United States. The concept of performance-based design was developed in an attempt to narrow the gap between the expectations that society places on building per￾formance during an earthquake and the philosophy that structural engineers use to develop the building codes. In 1995 the Structural Engineers Associa￾tion of California issued an overview of the objectives of performance-based seismic design. Although actual design procedures have not been developed, target levels of structural response are defined relative to the anticipated con￾dition of the building after earthquakes of varying intensity. TABLE 1 Direct Losses from Recent Earthquakes in California Damage Date Location Magnitude Deaths (million $ 1994) 1983 Coalinga 6.5 0 50 1987 Whittier Narrows 5.9 8 450 1989 Loma Prieta 7.0 63 6,870 1992 Petrolia 6.9 0 70 1992 Landers 7.3 1 100 1994 Northridge 6.7 57 20,000 Source: OTA (1995). Copyright © National Academy of Sciences. All rights reserved. Frontiers of Engineering: Reports on Leading Edge Engineering from the 1996 NAE Symposium on Frontiers of Engineering http://www.nap.edu/catalog/5576.html