Fragility Basis for California Highway Overpass Bridge Seismic Decision Making, PEER Report 2005-02


The seismic loss modeling of transportation networks is a multifaceted procedure for calculating monetary losses due to damage to the transportation links in an earthquake. This report focuses on providing a rational method to evaluate da mage potential and to assess probable highway bridge losses for critical decision making regarding the post-earthquake safety and repair of a highway network. Loss fragilities were defined for each individual bridge using PEER’s performance-based earthquake engineering framework. Decision variables were related to earthquake intensity through a series of disaggregated models (demand, damage, and loss). The fragilities provided in this report are intended for application in two ways. First, bridge designers may use them to investigate how variation of bridge desi gn parameters is reflected in the amount of expected losses after an earthquake. Second, highway network planners may use bridge fragilities to more reliably evaluate the losses in a highway transportation network.

In the process of developing bridge fragilities, intensity measures were first coupled with engineering demand parameters to formulate probabilistic demand models. Two damage models were then formulated. Component damage models utilized experimental data to predict response levels at which observable damage states were reached. System damage models utilized finite element reliability analysis to predict the loss of lateral and vertical load-carrying capacity. Improved methods for computing system damage were introduced. Last, two loss models were formulated. Component damage states were described in terms of repair costs of returning bridges to full functionality. System load-loss states were described in terms of bridge traffic capacity and collapse prevention. System loss fragilities were enhanced using the same improved methods developed for damage models.

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Kevin R. Mackie
Bozidar Stojadinovic
Publication date: 
June 2, 2005
Publication type: 
Technical Report
Mackie, K. R., & Stojadinovic, B. (2005). Fragility Basis for California Highway Overpass Bridge Seismic Decision Making, PEER Report 2005-02. Pacific Earthquake Engineering Research Center, University of California, Berkeley, CA.