An analytical technique of integrating a bridge structure and its soil-foundation system into thecomplete global model is proposed for seismic soil-structure interaction analysis of pile -supportedbridges. A simple yet realistic model for single piles and grouped piles is developed based ondynamic beam-on-nonlinear-Winkler-foundation methods. Performance of the proposed single -pile and pile -foundation model in predicting static and dynamic response to vertical and lateralloads is validated through comparisons with both experimental results and analytical results fromseveral other investigators. Performance of the integrated soil-foundation-structure model of theentire bridge is justified through comparisons with recorded responses of a road bridge in Japan.Parametric studies are also conducted to evaluate the sensitivity of the results to uncertainties indetermining system parameters.The presented modeling technique is applied for seismic analysis of an existing truss-archbridge spanning across the Mississippi River in southern Illinois (the Cairo Bridge). The nonlineartime-history analysis is performed using input motions obtained from ground response analysis ofbedrock motions artificially generated for the Cairo area. Comparison studies of dynamiccharacteristics and seismic response of the bridge obtained from the integrated model and thoseobtained from other foundation models (the fixed-base model, and the equivalent linear andnonlinear foundation spring models) are conducted. The results promote the use of the integratedmodel and emphasize the importance of the soil-structure interaction in seismic analysis of pile -supported bridges. The proposed model is applied to perform seismic performance evaluation ofthe Cairo Bridge for different excitation intensities and to identify an appropriate retrofit strategyfor the bridge. Applications of the pile group model to investigate the behavior of retrofittedfoundations and to develop a simple method of evaluating foundation characteristics are presented.
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