Nonlinear modeling of Texas highway bridges for seismic response-history analysis
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A recent increase in the number of earthquakes across the state of Texas has raised concerns about seismic performance of highway bridges in the state inventory, the vast majority of which were not explicitly designed to withstand earthquake loading. Potential causes of seismic damage include column shear failure due to low transverse reinforcement rations and non-seismic detailing, girder unseating due to excessive bearing deformation or instability, deck pounding, and others. The objective of the study is to develop bridge numerical models for nonlinear response-history analysis taking into consideration Texas-specific design and detailing practices. Using the models developed, the fragility of Texas bridges can be analyzed and systematically quantified, allowing state highway officials to efficiently identify the bridges most likely to be damaged after an earthquake. Component models for all major bridge parts were developed for this study, including the superstructure, deck joint, bearing, bent, foundation, and abutment. The models were developed based on past experimental, analytical, and numerical work from the literature, accounting for the mass, stiffness, and damping properties of each bridge component. Damage was accounted for using nonlinear hinge models capable of simulating stiffness-degradation and hysteretic behavior based on specific properties and expected limit states of each bridge component. Finally, a MATLAB script was developed to assemble bridge component models into full bridge models depending on user input of geometric and material properties of an individual bridge sample.