Report - PEER - University of California, Berkeley

3.2 Loss AssessmentThe assessment of direct losses (e.g.,dollar losses associated with repair andreplacement costs) is essentially anextension of (3) to first determine themean annual frequency of DMs for allthe damage states (Figure 6) and thenintegrate these with their associated lossfunctions (e.g., Figure 4). However,since this requires integration of damageand losses over many components, thereis an added complication of accountingfor correlations in the maximum EDPs,which multiple components in the building are subjected to, and correlations amongthe EDP-DM and DM-DV (damage and loss) distributions for common families ofcomponents. These correlations were not an issue for collapse prediction, sincecollapse is assumed to be either simulated directly through the IDA (Figure 2) ortriggered by a single component.Aslani and Miranda (2004) and Miranda et al. (2004) outline an efficientapproach to resolve these issues and determine the MAF of loss, λ(IM). Briefly, theirapproach begins with calculated of an expected annual loss, which is the sum ofexpected annual component losses for the non-collapse case and the expected annualloss from collapse. Both of these are straightforward to calculate given the MAFs ofdamage, λ(DM), and collapse, λ(Collapse). Next, they calculate the dispersion on theexpected loss by combining the dispersion for those components that contributesignificantly to the loss, taking into account correlations among the components.Their preliminary findings show this to be a viable and effective method; and theirdata confirm that the MAF of the loss can be quite sensitive to the assumedcorrelations between component losses.4. RELATIONSHIP OF PBEE TO DECISION MAKING AND DESIGNWhile there are a multitude of opinions on seismic risk decision making, a commonlyagreed upon view is that PBEE should provide stakeholders with information to makebetter informed decisions. Further, in addition to providing data, PBEE approacheswill need to foster a change in mindset from the status quo where seismic riskdecisions are generally avoided due to reliance on minimum building coderequirements. In a report on organizational and societal considerations regarding riskdecision making, May (2003) dispels the notion of defining performance in terms ofan “acceptable risk” and, instead, promotes an approach that supports decisionmaking based on tradeoffs. How these tradeoffs are decided, and what the prioritiesare, can differ dramatically depending on the circumstances, as seen, for example, intwo recently completed testbed exercises (Krawinkler 2004, Comerio 2004).24Figure 6. Integration of EDPexceedence with component damage.