Report - PEER - University of California, Berkeley

assessed for damage and corresponding repair costs or repair times are estimated. Forexample, damage could be considered in piles, pile caps, columns, expansion joints,abutment wing walls, approach slab and embankment, and numerous other locations.The system level addresses the overall performance of the bridge as a whole in a postearthquakescenario. For a highway bridge, functionality is primarily measured interms of the traffic load carrying capacity, lane closures, allowed axle loads and speedlimits. The total cost in a post-earthquake scenario is the summation of thecomponent, or direct losses, and the loss of functionality, or indirect losses.3.1 Repair CostThe repair cost limit state presented in this paper addresses only damage to the bridgecolumn because of current limitations in available reconnaissance and research datafor other bridge components. The data used in our study was collated into the PEERStructural Performance Database (http://nisee.berkeley.edu/spd/). Consequently,bridge longitudinal drift ratio was selected as the EDP describing the column demand,while discrete damage observations (DMs) selected from the database includeconcrete cover spalling, longitudinal rebar buckling, and column failure. Columnfailure was defined as the first observation of reinforcing bar fracture. Therefore, theDM can be thought of as component damage with specific values ranging fromspalling to failure. Finally, reconnaissance data (Basöz 1997) was used to generate aloss model relating the damage to repair costs.3.2 Traffic FunctionThe traffic function limit state presented in this paper addresses the bridge system as awhole in order to generate information about loss of its functionality. Functionality isdefined in terms of the lateral and vertical load carrying capacity of the bridge. Thiscapacity was assessed analytically using pushover and pushunder analyses pre- andpost-earthquake because hardly any experimental data exists on the systemperformance of bridges. PSDMs for functionality use the residual load carryingcapacity (units of force) as the EDP. Reliability analyses were performed to appraisecapacity levels pre-earthquake. These are then compared to post-earthquake residualcapacities to generate a bridge level DM that describes the percentage loss of loadcarrying capacity. It then remains up to engineers to determine the form of the lossmodel that relates the losses in capacity to changes in traffic loading and speed. Asample loss model is presented in this paper to facilitate application of themethodology and further discussion as to a more practical mathematical form.3.3 CollapseCollapse of a modern bridge is an unacceptable performance goal in California.Therefore, it was necessary to define the collapse or collapse prevention limit state in56