Multiple-span reinforced concrete highway overpass bridges constitute a large portion of the total inventory of bridges in California, particularly among bridges of new design. Probabilistic valua- tion of performance of these bridges under rare but strong ground motions is therefore essential for successful evaluation of the entire regional transportation network performance during and after an earthquake. Additionally, probabilistic quantification of bridge seismic performance and vulnerability provides insight into the shortcomings of current designs and into the potential advantages of proposed new technologies at varying levels of seismic hazard and for different site conditions.
Performance of bridges at the demand, damage, and loss levels can be evaluated using the
Pacific Earthquake Engineering Research (PEER) Center’s probabilistic performance-based seismic evaluation framework. Use of this framework to evaluate two classes of benchmark reinforced concrete bridge types typical of new construction in California is presented. Each bridge type has a variety of column designs for different seismic demands. Models of these structures are created that account for the nonlinear behavior of the columns, deck, abutments, and expansion joints at the abutments. Seismic demand models are then developed using nonlinear time history analysis, considering both near- and far-field excitation types. Damage in the bridge components is deter- mined using experimental and empirical databases. Structural components are then classified into performance groups according to the repair methods corresponding to their damage states. Finally, approximate repair cost ratios and repair durations are estimated from both discrete bridge-level damage states and the assembly of discrete damage states from all performance groups.
Three realistic damage scenarios are developed to calibrate the repair cost and the repair
working days estimate data. The results are presented in the forms of repair cost ratios and repair time loss models and fragilities. The performance of the benchmark bridges, particularly bridge Type 1A, is intended to serve as a baseline for other PEER researchers to measure the change of bridge seismic performance due to the use of new experimentally calibrated models of column, abutment, and foundation components; due to the use of new enhanced-performance structural elements and response modification devices; and due to explicit consideration of liquefaction and lateral spreading. The performance of the benchmark bridges is also intended to serve as a baseline for transportation network studies by other PEER researchers.
An implementation of the PEER Center’s probabilistic performance-based seismic evaluation framework is also presented in this report. This implementation, developed for the testbed bridges, is modular to allow plug-and-play incorporation of emerging structural components, response mod- ification technologies, analysis methods, and repair techniques. The implementation is founded on a general closed-form solution of the PEER framework total probability integral based on the demand, damage, and loss models developed in this report for the benchmark bridges. A method for developing such models for other structures is presented. A Matlab-based tool is developed to facilitate the integration of the PEER framework total probability integral. Finally, a data structure designed to efficiently organize and store the data and interim results is presented. Together, the implemented tools and data structures form a solid basis for conducting probabilistic performance-based seismic evaluations of any structure using the PEER Center framework.
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