Influence of SSI and frequency content of non-uniform ground motions on bridge girder poundings

Abstract

Ph.D., Professor, School of Civil and Resource Engineering, the University of Western Australia, Crawley WA6009, Australia The study addresses the effect of the characteristics of Japanese design spectra on the pounding potential of two bridge girders. The spatially varying ground motions for soft; medium and hard soil condition are simulated stochastically. The effect of non-uniform ground displacements and accelerations, as well as soil-structure interaction is studied. The common design criterion for pounding mitigation is evaluated. The study reveals that a consideration of uniform ground excitation can strongly underestimate the pounding potential, especially when the ground motions have low dominant frequencies, and the soil is soft. The closer are the vibration frequencies of the adjacent girders, the more prominent is the non-uniform ground motion effect. The design recommendation for adjusting the structural frequencies should not be applied, if the ground is soft and a uniform ground excitation cannot be ensured.