Evaluating the Response of Cable-Stayed Bridges Subjected to Delayed Seismic Time-Histories Using Multi-Support Excitation

Seismic Spatially varying loads for cable-stayed bridges are either neglected or poorly addressed in the most of the current bridge design codes around the world.According to Canadian Highway Bridge Design Code (CHBDC) it is the responsibility of the designer to check the effect of the spatially varying loads while no details are provided.Given this, the objective of this study is to evaluate the effects of multi-support excitation on the response of a cable-stayed bridge.For the purpose of the study, a well-known Quincy Bayview bridge located in Illinois, USA is under examination.The results from the study show that the seismic excitation in the longitudinal direction has caused resonance in the bridge vertical direction, which is due to the delay of the finite shear-wave velocity of the propagation soil at the pier supports.Furthermore, it is observed that the resonance takes place not only in soft soil but also in stiff soil depending on the frequency content of the ground motion, and the modal properties of the bridge.A formula for dominant shearwave velocity for resonance is proposed along with a method to develop the velocity vs response curve.