Report - PEER - University of California, Berkeley

develop data on EDP limits associated with specific performance targets. Once suchEDP limits have been established, together with IMs that represent discrete hazardlevels for which the EDP limits apply, the challenge is to device structural systemsthat efficiently accommodate these EDP limits. This paper is concerned with thesetwo challenges.2. PERFORMANCE TARGETS AND HOW TO EXPRESS THEMIt is widely accepted that earthquake design decisions should be based on the threeDs, i.e., death, dollars, and downtime. Unfortunately, there are many variations tothis simple phrase. For one, we have not yet succeeded in quantifying death, or moreappropriately, casualties. Thus, in the following discussion we will stop short andreplace casualties (life safety) with collapse. Furthermore, we still have only vagueinsight into downtime and the quantification of associated losses, which may affectnot only the owner but may have more global consequences. Therefore, alsodowntime is not discussed explicitly here, although it can be incorporated into theloss-EDP relationships discussed in the next section.2.1 Loss or Function Controlled Performance TargetsThe following is an attempt to illustrate how performance targets can be quantified,based on the existence of three subsystems in a building, a structural system (SS), anonstructural drift sensitive system (NSDSS), and a nonstructural and content systemthat is sensitive to floor acceleration (NSASS). It is assumed that the NSDSS andNSASS subsystems are known and can be quantified before structural design decisionshave to be made. The SS system is design dependent, but it usually is a relativelysmall contributor to total investment [in a loss estimation study on a Californian hotelbuilding the SS contributed less than 20% to the total investment (Miranda 2004)].The objective is to establish a relationship between a loss parameter and a “mostrelevant” engineering demand parameter (EDP), so that the latter can be used by theengineer to guide design decisions. The EDP has to be well correlated with losses inall components of the subsystem, and it has to be well correlated with globalstructural response in order to permit deduction of global design decisions.One way of expressing desired performance is by specifying acceptable losses inearthquakes associated with specific hazard levels, such as 50/50 and 10/50 hazards.Implementing such a performance target implies the ability to compute componentlosses as a function of a relevant EDP and summing the losses over all components inthe building, resulting in loss-EDP relationships for selected subsystems. Story driftand floor acceleration are examples of relevant EDPs. The process of computingloss-EDP relationships requires the following ingredients and steps:1. The availability of a set of fragility curves for each component of the subsystem,which define, as a function of the EDP, the probability of being in, or exceeding,specific damage states requiring specific repair actions.508