Study On The Dynamic Interaction Analysis Method For The Structure-Pile-Horizontal Layered Soil Foundation

With the expansion of the scale of modern engineering construction, pile foundation is widely used in high rise buildings, ports, nuclear power structure. The dynamic stiffness of pile foundation has great effects on the dynamic responses of these structures. So the soil-pile-structure interaction should be taken into consideration for the earthquake analysis. In this thesis, the following contents related to the free field response of layered soil and the impedance function of pile foundation are discussed:(1) For the case of vertical incidence of plane body wave, based on the theory of one-dimensional wave equation solution, using relationship of wave in different layers between the propagation in time domain, the upward and downward waves at the interface are solved by using the recursive method step by step, and then he motion of any point in the soil can be got. For vertical incident seismic wave of viscoelastic foundation model, seismic wave is decomposed into a series of simple harmonic wave firstly by expansion in trigonometric series. Then the time-increment method is used to solve the free field motion for under the excitation by harmonic wave. Finally, the motion in the viscoelastic foundation under seismic wave action is made up of a superposition of all harmonic motions. Making use of the free field response obtained by the method mentioned above, the direction method, in which the finite element analysis with the viscoelastic boundary conditions applied on the boundaries of finite domain is performed, is employed for free field motions in the numerical way. Numerical examples demonstrated the effectiveness and applicability of the proposed methods.(2) The impedance function of pile foundation in layered soil can be decomposed into the superposition of the impedance function of half space, pile and dug soil by substructure method. The parts of impedance function can be solved by hybrid numerical method and finite element. Numerical results validate the accuracy of the method.(3) According to the system of large scale pile group, with viscoelastic artificial boundary conditions applied on the boundaries, based on the definition of impedance function, the solution to the impedance function of the pile foundation are completed by using the harmonic analysis in ANSYS. The method can comprehensively consider the kinds of inhomogeneous characteristics, such as holes, interlayer, non-horizontal layer.(4) Parametric studies have been carried out to clarify the effects of pile length diameter ratio, constraint conditions of pile cap, soil modulus on the dynamic behavior of pile-soil interaction by using the method in this paper. And the calculation and analysis of the dynamic stiffness of a nuclear power plant with pile foundation treatment are carried out.