University of Vermont Transportation Research Center

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This report describes recommendations for seismic vulnerability screening for Vermont bridges. These recommendations are based on findings from a study by the authors from the University of Vermont Department of Civil and Environmental Engineering. The study involved evaluating seismic vulnerability evaluation methodology used by state transportation agencies, and those recommended by the Federal Highway Administration. The project work included detailed seismic analysis of two multiple span and multiple girder bridges for comparison with screening methodology findings, to validate the screening tool algorithms. This bridge type and dimensions represent and bound approximately eighty percent of the Vermont multiple span bridge inventory, including most interstate highway bridges. This validation analysis simulated two bridge condition configurations, for both pristine and fully-spalled concrete substructures, for the highest and lowest seismic hazard regions in Vermont, at bedrock and soft ground sites, for a total of eight combinations of structure, structure condition, seismic hazard, and site conditions. The analysis used 70 actual unscaled earthquake time-history records applied to non-linear finite element bridge models for a total of 380 individual analyses. The report provides the results for a Vermont Rapid Seismic Screening Algorithm (VeRSSA) for Vermont bridges using the recommended methodology developed in this study. This methodology was developed specifically to require only the data contained in Vermont’s National Bridge Inventory (NBI) database. The report includes recommendations for using supplemental site and bridge data beyond the database information to refine the screening. The recommended methodology addresses highway bridges, although the principles are applicable to railroad bridges, with appropriate engineering judgment.