Probabilistic Seismic Demand Models and Fragility Estimates for Reinforced Concrete Bridges with Two-Column Bents
Publication: Journal of Engineering Mechanics
Volume 134, Issue 6
Abstract
Probabilistic models are developed to predict the deformation and shear demands due to seismic excitation on reinforced concrete (RC) columns in bridges with two-column bents. A Bayesian methodology is used to develop the models. The models are unbiased and properly account for the predominant uncertainties, including model errors, arising from a potentially inaccurate model form or missing variables, measurement errors, and statistical uncertainty. The probabilistic models developed are akin to deterministic demand models and procedures commonly used in practice, but they have additional correction terms that explicitly describe the inherent systematic and random errors. Through the use of a set of “explanatory” functions, terms that correct the bias in the existing deterministic demand models are identified. These explanatory functions provide insight into the underlying behavioral phenomena and provide a means to select ground motion parameters that are most relevant to the seismic demands. The approach takes into account information gained from scientific/engineering laws, observational data from laboratory experiments, and simulated data from numerical dynamic responses. The demand models are combined with previously developed probabilistic capacity models for RC bridge columns to objectively estimate the seismic vulnerability of bridge components and systems. The vulnerability is expressed in terms of the conditional probability (or fragility) that a demand quantity (deformation or shear) will be greater than or equal to the corresponding capacity. Fragility estimates are developed for an example RC bridge with two-column bents, designed based on the current specifications for California. Fragility estimates are computed at the individual column, bent, and bridge system levels, as a function of the spectral acceleration and the ratio between the peak ground velocity and the peak ground acceleration.
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Acknowledgments
This work is partially supported by National Highway Institute under Award No. UNSPECIFIEDDDEGRD-06-X-00457 through a fellowship to the first writer. Opinions and findings presented are those of the writers and do not necessary reflect the views of the National Highway Institute.
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Information & Authors
Information
Published In
Journal of Engineering Mechanics
Volume 134 • Issue 6 • June 2008
Pages: 495 - 504
Copyright
© 2008 ASCE.
History
Received: Mar 6, 2007
Accepted: Aug 17, 2007
Published online: Jun 1, 2008
Published in print: Jun 2008
Notes
Note. Associate Editor: Arvid Naess
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