Spatial Variability Effects on the Seismic Response of RC Highway Bridges

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This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5)The earthquake induced ground motions are not the same at any two points on the earth?s surface. This occurs because the seismic waves travel from the earthquake source through different paths with different velocities, and reach the ground surface through different local site conditions. Often this spatial variability is ignored in the design of structures. However, for large spatially distributed structures, this ground motion variability can increase or decrease the dynamic response, depending on the structural system characteristics. This study will conduct a comprehensive investigation to determine what system parameters affect the seismic response of reinforced concrete bridge structures. The investigation will consist of the following steps: a careful selection of recorded seismic ground motions pertinent for the Eastern, Central and Western United States; the generation of spatially variable accelerations, velocities and displacements at uniform and variable site conditions based on the recorded data and rigorous models for the spatial variation of the motions; and the use of the generated input excitations for the evaluation of the nonlinear response of several representative reinforced concrete highway bridges. Typical bridge configurations of various lengths from across the country will be utilized and analyzed using multiple computer/numerical models and tools so as to reduce the uncertainty in the numerical modeling of the structures. The project will provide the methodology and framework for the evaluation of the effect of spatially variable ground motions on the response of bridges. Based on the research results, recommendations for incorporating the effect of spatial variability of seismic motion in the design and retrofit of the bridge structures will be made.The research will lead to a better understanding of the effects of the spatial variability of seismic ground motions on the structural response. It will identify important structural and ground motion parameters for which the spatial variability in the motion will have strong influence on the structural response. The bridge design professionals will be better equipped to evaluate the spatial variability effects and to incorporate them in bridge designs. This will eventually enhance the safety of the nation?s vital infrastructure. For wider dissemination of the research results to enhance the broader impacts, the generated spatially variable seismic ground motions and the numerical models of the structures developed in this project will be posted on a web site for use by both other researchers and practicing engineers. The outcomes of the effort will be directly disseminated to the profession through technical publications and presentations. The research will also provide advanced training to graduate and undergraduate students and incorporate active participation by K-12 science teachers. Underrepresented groups will be recruited in the project using well established institutional partnerships.