Decisions about seismic performance are the underpinnings of a rigorous approach to performance-based earthquake engineering and should specifically consider the decision variables within the PEER framing equation. This report considers the decision-making process for seismic safety from the perspective of organizations—building owners, investors, and others concerned with single facilities or a collection of facilities—and from the perspective of society.
The dominant mode of seismic performance decision making, “risk and safety as by- products of design,” falls short in not allowing trade-offs or choices in decisions concerning seismic risks. The opposite mode, “performance-optimized decisions,” focuses on desired performance levels but masks relevant choices and trade-offs. Only an “investment based” approach provides a framework consistent with the variables of the PEER framing equation for making explicit trade-offs in seismic performance and their costs. Decisions about desired levels of seismic performance should allow for explicit consideration of trade-offs associated with investment in seismic safety and in other forms of risk management. Particular attention should be given to public safety, to reparability of a structure, and to usability of a structure; each as separate dimensions of performance objectives.
Seismic safety is a matter of public welfare for which governmental regulation is necessary for establishing minimum standards for seismic performance. Such standards at least implicitly involve the controversial notion of “acceptable risks” to society. Determining acceptable levels of risk is a value judgment that requires collective choices about minimum standards. Knowledge of relevant risk considerations, technical details, and costs and benefits is crucial to establishing these standards. Finding the appropriate compromise between public processes and technical expertise in determining safety goals is a serious challenge. Recasting acceptable risk into a discussion of desired safety goals , the costs involved in achieving these, and the trade-offs imposed could address some of the limitations of the concept of acceptable risk.
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