Dynamic impedances of CPRF using coupled BEM-FEM approach: A parametric study and application

In this study, dynamic impedances of the Combined Piled Raft Foundation (CPRF) are calculated based on the coupled BEM-FEM approach. The piles, raft, and internal soil domain (near filed) are modelled with the finite element method (FEM). In contrast, truncated soil (far field) is modelled with the boundary element method (BEM). The piles and raft are perfectly bonded with the soil where rigorous pile-soil and raft-soil interaction conditions are imposed. The dynamic impedances are calculated under the horizontal, vertical, and rocking modes of vibration for the CPRF with 2 x 2 pile group. The parametric study is carried out for the CPRF to portray the influence of pile-soil stiffness, pile length, pile spacing, and raft thickness. In addition to the parametric study, the dynamic response of a Nuclear Power Plant (NPP) structure is carried out using the proposed spring-dashpot model. Results are compared with those obtained using FEM model. It can be concluded that the present model can simulate the seismic behavior of NPP under varying earthquake frequency and PGA with good accuracy.