ABSTRACT
Most of previous studies of ground motion spatial variation effects on structures assumed a flat ground surface and uniform soil properties. Ground motion spatial variation is modeled with a coherency loss function and a phase delay, and the ground motion intensity at all the structural supports is assumed the same. In practice, many large dimension structures such as bridges have supports on a site of uneven surface and varying soil properties, e.g., a bridge crossing a canyon site. In this paper, theoretical derivation of ground motion spatial variations on a canyon site with varying soil properties are presented. Spectral analysis of structural responses is carried out. Numerical results of power spectral densities of various response quantities obtained with uniform ground motion, spatially varying ground motion modeled on a flat surface, and spatially varying ground motion on a canyon site are calculated and presented. Comparisons and discussions of the numerical results are made. The importance of properly modeling the ground motion spatial variation in structural response analysis is demonstrated.
