Modeling of Seismic Wave Scattering on Pile Groups and Caissons; Tech. rept

摘要

This report documents practical modeling procedures adopted in the bridge engineering community that involve seismic design and retrofits of long span bridges relative to the treatment of wave propagation problems. It also discusses wave scattering issues that arise from irregular foundation boundaries and affect the seismic loading of bridges, which is not explicitly considered in current design practice. The research developed a systematic procedure that allows geotechnical engineers to perform wave scattering problems in the time domain considering all elements of boundary issues to minimize wave reflection and refraction. The solutions obtained from the time domain approach were rigorously compared against a traditional frequency domain approach. The established time domain procedure was shown to address not only free field conditions but also foundation systems subjected to earthquake loadings. Once the time domain procedure was established, the work was extended to address pile group foundations and gravity caissons under dynamic loading conditions, to gain an understanding of how the scattering of seismic waves from the foundation system alters the near field ground motion transmitted to the superstructure. The effects of wave scattering can now be more easily included in future design procedures.