The Research On Simplified Analysis Methodology Of Dynamic Pile-Soil-Structure Interaction

The foundation soil is considered to be rigid in general aseismatic analysis of structures. That is to say the movement of foundation is the same as near site in earthquake. In fact, the feedback from the inertia force of the upper structure will alter the movement of foundation and accordingly alter the dynamic behaviors of the upper structure. Thus it is necessary to consider the effect of soil-structure interaction for high buildings, especially those built on soft soil. Now pile foundation is the common form of foundation for tall buildings rested on soft soil. Therefore, there is a need to study the dynamic behaviors of soil-pile-structure interaction system. The main contents in this paper are summarized as follows:1 .In this paper, sub-structures technique was adopted to analyze the soil-pile-structures interaction system. In which, the dynamic impedance of soil-pile system was represented by lateral and rotational springs with complex stiffness. And the impedance was gained by using the dynamic impedance of single pile and dynamic interaction factors of piles.2.Because the damping of soil and upper structures varies in magnitude and type, general classical modal analysis is not strictly applicable to a interaction system. Therefore, based on the hypothesis that the upper structure in interaction system has classical modal, a modal analysis methodology was presented in this paper. Using this method the structural response of a interaction system was solved same as the conventional frequency domain analysis for a fixed-base structure.3.Soil-pile-structure interaction analysis is usually carried out in the frequency domain, because the impedance of soil-pile system is known only in the frequency domain. Since the non-linear analysis cannot be carried out in the frequency domain, a multi-parameter lumped spring-dashpot system with frequency independent parameters was used to simulate the frequency-dependent dynamic impedance of soil-pile system. Based on it the time history response analysis of soil-pile-structure interaction system can be carried out easily.4.Numerical examples of shearing-type structure with pile group foundation were given in this paper, and the effects of the earthquake wave, the stiffness of underlying soil medium, and the height and stiffness of upper structure were discussed.