Effect of spatially varying earthquake ground motions on seismic response of a railway viaduct considering multiple site configurations

Currently, it is admitted that extended structures are subjected to spatially varying earthquake ground motions. It has been recognized that the causes of this variability are time delay at each support of the structure, coherency loss effect caused by the propagation of seismic waves and local site effect. The spatial variation of local characteristics of the soil profile defines the site effect, which affects the amplitude and the frequency content of seismic ground motion. The main objective of this work is to provide comparative results and evaluate the variation of the dynamic response of a bridge adopting varying characteristics of soil foundation. Based on the density spectral method, an efficient simulation method of spatially varying earthquake ground motions is developed. The simulation of spatially variable seismic ground motions is performed for different locations on the ground surface with varying site conditions. According to of soil classification described in seismic codes, four different soil configurations were considered for generating sixty-four displacement time series. Several dynamics analyses of a bridge to three cases of spatially variable seismic ground motions, besides the uniform case, are made. The results of this study indicate that depending on soil configurations beneath each support, the seismic response may vary significantly.