Seismic Hydrodynamic Effects on Group-pile Foundations with Caps Merged in Water

Abstract:

To meet the seismic design demands of bridges in deep water in China,an investigation was made into the hydrodynamic effects on seismic response of bridges.The cap of group-pile foundation was idealized as a truncated cylinder at first,and theoretical solutions of the added mass matrix and the added damping matrix for the truncated cylinder were developed.Approximate methods were proposed to obtain the added mass matrix and the added damping matrix for the truncated prism with arbitrary section by modifying the ones for truncated cylinder.The seismic motion equation was developed for bridges with group-pile foundation in deep water in frequency domain,and a software was coded for the computation of seismic response of bridges in deep water.The seismic responses of a bridge were obtained by the proposed methods and the software.The results show that the hydrodynamic effects may increase or decrease the seismic response by a percentage of ±20%.