Study On Several Problems Of Complicated Soil-Structure Interaction

Soil-structure nonlinear dynamic interaction is a hot issue in civil engineering and earthquake engineering and usually the calculation is of great amount. In this paper, the substructure analysis of structure-base interaction is discussed using ANSYS program. Numerical analysis on pile-soil nonlinear dynamic interaction is performed under harmonic load by means of substructure method, with Goodman contact element simulating pile-soil interface, and with Drucker-Prager model simulating the nonlinear behavior of soil material. Finally, the three-dimensional nonlinear seismic analysis was carried out on soil-pile-structure interaction system under different earthquake intensity. By comparison with the linear model, the differences between two models are analyzed. Through the calculation and the analysis, the conclusions are obtained as below: (1) The substructure method was reliable in pile-soil nonlinear interaction analysis, the computational efficiency was enhanced by 5 times approximately than that of integral finite element method in this paper. (2)The displacement amplitude and the acceleration amplitude of cushion cap midpoint is much greater than that of linear model under the same load condition, when the nonlinear effect of pile-soil interaction system was taken into account. In addition, the relative slippage occurred apparently between the pile and the soil interface. (3) The model in this paper is not nonlinear under the frequent earthquake of magnitude of 7 and 8, however, the system represented obviously nonlinear behavior under the rare earthquake of magnitude of 7 and 8. (4) Compared with linear system, the displacement response of nonlinear interaction system was increased, with 23% and 36.1% separately at top of structure. The acceleration response of superstructure is reduced, with 22.8% and 40% separately under magnitude of 7 and 8. (5) Under the rare earthquake of magnitude of 7 and 8, the distribution of shearing force and overturning moment is that the maximum value is at mid-column, the less value is at border column, and the minimum value is at corner column. Nevertheless, the distribution of shear force and moment of pile is opposite. The shearing force and overturning moment of column is reduced, and the shear force and moment at the top of pile is decreased compared with linear interaction system.