Report - PEER - University of California, Berkeley

calculated using a 2 dimensional multi-normal CDF. Only 2 damage limit states werechosen to allow closed form integration of this CDF; however, it may be of furtherbenefit to describe collapse in terms of both the loss of lateral and vertical loadcarrying capacity and the residual displacement of the bridge piers.Table 1. Bridge performance level table: proposed values for limit statesObjective nameTraffic capacityremaining(volume)Loss of lateralload carryingcapacityLoss of verticalload carryingcapacityImmediate access 100% < 2% < 5%Weight restriction 75% < 2% < 10%One lane open only 50% < 5% < 25%Emergency access only 25% < 20% < 50%Closed 0% > 20% > 50%Figure 7. Collapse-prevention limit state fragility curves.7. CONCLUSIONSAn engineering basis for quantitatively evaluating the ability of a typical highwaybridge to function after an earthquake was presented in this paper for three limitstates: repair cost, traffic function, and collapse-prevention. The PEER frameworkwas utilized to cast these limit states in terms of damage and decision fragility curves.For the repair cost limit state, component-level (column) damage and loss data wasused in a direct application of the PEER integral. However, for the bridge-level trafficfunction limit state, several methods of obtaining the decision fragilities wereintroduced, the best method using EDP conditioning. Finally, an example ofcombining damage limit states to define the collapse-prevention limit state waspresented. The resulting fragility curves for all limit states can be used by engineers63