This report summarizes the efforts of several in vestigators involved in reviewing, assessing, and applying the PEER performance-based methodology (PBM) to an existing viaduct in California. The expected seismic performance of the 5th and 6 th Street viaduct, denoted in this report as the I-880 viaduct, is investigated
probabilistically within the context of the PEER framework. The PEER approach consists of four essential components: development of a site-specific hazard curve; estimation of seismic demands given a set of ground motions consistent with the site hazard; prediction of damage measures as a function of the computed demands; and evaluation of the influence of the damage measures on selected decision variables. The damage measures considered in this study are the spalling of the column cover concrete and buckling of the longitudinal reinforcement in the columns, and the decision variable of primary focus is the probability of closure of the viaduct.
The evaluation presented in this report examines the performance of a three-frame section of the I-880 viaduct subjected to a series of ground motions representing three hazard levels. Fragility functions for demand, damage, and economic loss are derived, and the total probability theorem implied in the PEER framework equation is applied to estimate the closure probability of the bridge using the specified hazard at the site. Also included in the study is a reliability analysis of the simulation model to gain an understanding of mode l sensitivity to the demand estimates. A practitioner perspective of the PEER methodology in the context of seismic bridge design provides insight into the current stat e of practice and an outlook on the future of probabilistic PBM in engineering practice.
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