Study On Dynamic Computational Model Of Pile-Soil Interaction And Applications In Seismic Response Analysis Of Pile-Supported Structures

Because of its high strength, great bearing capacity and fine durability, pile foundations have been widely used in civil construction engineering such as high buildings, large workshops, hydraulic power stations, railways, highway roads, bridges, offshore platforms and nuclear power plants. However the dynamic interaction of pile-soil-structure system is very complex and there are some issues that have not been well solved in engineering practice. An intensive study is required for consideration on dynamic pile-soil-structure interaction effect in the analysis and design of pile-supported structures. Therefore the simplified and yet rational computational method and mechanical model for representation of lateral and vertical dynamic impedance function of piles, numerical method for evaluating dynamic response behavior of the interaction system of single pile or pile group and superstructure are mainly concerned in this dissertation. The main research and results involved in the dissertation includes the following parts.1. As one of the key issues in the study of dynamic behavior of pile-supported structures by the substructure method, the dynamic impedance of pile foundation should be rationally evaluated for considering the effect of soil-pile dynamic interaction. In this dissertation, based on a certain assumptions and the improved dynamic model of beam-on-Winkler's foundation, a simplified mechanical model for computing the lateral and vertical dynamic impedance of single pile embedded in layered soils is established by using the principle of soil dynamics and structural dynamics. The softening effect of soils around pile during vibration and non-homogeneity of soil strata as well as the discontinuous behavior such as the de-bonding and relative slippage along pile-soil interface are simultaneously taken into account. It is shown through comparative study for a given example that the dynamic impedance of single pile numerically computed by the proposed method are relatively rational and can well agree with the computational and experimental results currently available. Finally the parametric studies are made for a wide ranges of main varied parameters involved to examine the effect of the softening area and softening degree of soils around pile, the contact conditions of pile-soil interface, the slenderness ratio of pile and the pile-soil stiffness ratio on dynamic impedances of single pile embedded in layered non-homogeneous soils.2. The dynamic response characteristics of single pile is one of the most important aspects in the study of dynamic pile-soil-structure interaction. In this dissertation, considering the softening effect of soils around pile and the non- homogeneity of soil strata simultaneously, a simplified analytical method for computing the lateral and vertical dynamic response characteristics of single pile to harmonic excitation is established. It is shown through the illustrative studies on a given example that the dynamic response of single pile numerically computed by the proposed method are rather reasonable and can well agree with the numerical solutions gained from finite element analysis by using well-known software. Finally the parametric studies are made for a wide range of main varied parameters to examine the effects of the softening area and softening degree of soils around pile, the mechanical conditions of soil strata, the slenderness ratio of pile and the pile-soil stiffness ratio on dynamic response characteristics of single pile embedded in non-homogeneous layered soils to harmonic loading with different excitation frequencies.3. In engineering practice, pile group is a widely applied form of pile foundation. Since the pile-soil-pile interaction effect should be taken into account for pile group, the dynamic response characteristics of pile group are much more complex than that ofsingle pile. Based on the definition and solving procedures of dynamic interaction coefficient and a certain assumptions, lateral and vertical dynamic interaction coefficients of two piles are compute...