Three dimensional elasto-dynamic infinite elements for soil-structure interaction analysis

Abstract

This dissertation studied a soil-structure interaction analysis(SSI) method for a three dimensional body subject to dynamic loadings using a direct approach incorporating 3D infinite element formulations. Two kinds of 3D dynamic infinite elements(IEs) were developed to model the far fielding the SSI problems. They are cuboidal & radial infinite elements. For the cases of the cuboidal IEs, the interface shapes between the near and far field zone must be rectangular parallelepiped. Five kinds of cuboidal IEs were developed as horizontal(HIE), horizontal corner(HCIE), vertical(VIE), vertical corner(VCIE) and vertical-horizontal corner(VHCIE) infinite elements. They contain wave functions considering multi-wave components in layered soil media. The wave numbers were modified in conformity of the Cartesian coordinates. For the cases of radial IEs, arbitrary shaped interface may be taken the near field zone and far field zones. More practical model technique can be applied, using the three kinds of radial IEs, named as HIE, VIE and CIE. The wave functions also include the multiple wave components. The wave functions of the proposed infinite elements were derived from the approximate expressions for analytical solutions. An efficient integration scheme was also applied to construct mass and stiffness matrices of the infinite elements involving multi-wave components. To verify the proposed IEs, non-dimensional compliances and impedances function of various rigid surface footings were calculated for cases on a homogeneous half space and on a layered half space. Numerical results compared with those using other methods indicated that the method based on the proposed infinite elements offers good solutions. The SSI analyses were also carried out for a disk on a flexible caisson embedded in a homogeneous half space. The CPU time for numerical analysis can be reduced significantly compare with SASSI analysis. The present earthquake analysis method was verified utilizi...