Analysis On Dynamic Interaction Of Soil-Pile Group Foundation-High-Rise Buildings Under Seismic Effect

For a long time, the rigid ground assumption has been used for earthquake response analysis in the seismic design in which only superstructure is considered in the model and the free field surface input of ground motion is adopted. When the foundation has a huge rigidity and the superstructure has a small rigidity, the assumption is advisable in the engineering range. But when the building's rigidity is close to the foundation, this assumption will produces significant errors in determining the superstructure's response. For the tall-building structure has the character of complex system, enormous volume and huge weight, if it is built on the soft soil or deep soil foundation and depended on the hypothesis of rigid foundation without regard to the interaction of superstructure and base, the result will be unreasonable and cause a big discrepancy between calculation and reality. Superstructure, base and foundation are an organic whole which connect and influence each other. In recent years, with design and construction for many, such as nuclear power station, high-rise building, water and electricity dam with 200-300 height, ocean flat roof. The dynamic interaction is becoming a key science problem in many important projects.This paper has summed up the research background, analytic method, history actuality and also existent problems of soil-structure dynamic interaction. It's regarding one real project-the Building of Information Tower in Shaanxi Province as the research example, and building two models in rigid ground and interaction situation. Also based on the character of tube structure, the simply model equivalent to tube structure can be induced. At the same time, it has been analyzed separately of mode and time-history on the elaborate and macroscopic simplified model for the information building, based on ANSYS under the rigid foundation and interaction situation, through the comparison of the structure difference for internal force, displacement on seismic response, discussed the influence after interaction consideration. The primary content and conclusion of this article are as follows:(1) It has been selected the appropriate the material that suited this article to carry on the research on the soil - structure dynamic interaction. The superstructure has used the model of elastical constitutive relation; the pile-group foundation has quoted the soil-pile equivalent compound model. It has been analyzed the constitutive relation for soil-pile equivalent compound which regarded as the transversely isotropic body this construction relations, and determined the corresponding elastic constant.(2) In view of the radiation damping existence in the research of soil-structure dynamic interaction, when carried on the simulation of finite ground, introduced the artificial boundary. Based on ANSYS to the APDL language re-development, has realized the three dimensional viscoelasticity artificial boundary in finite element procedure application.(3) It has been put forward and established the macroscopical simplified model. The tube structure of information tower can be regarded as a vertical cantilever beam embbed in the foundation as a whole, and considered a Timoshenko beam. This paper has identified three system parameters of tube structure by special FEM program edited by individual. Using three parameters, it can be build the macroscopical simplified model, which equivalent to tube structure on mass and rigidity.(4) In view of the elaborate and macroscopic simplified finite element model for the information building, it has been done the mode analysis under rigid ground hypothesis and interaction of the two kinds of situations. Through the contrast of natural frequency and relevant mode pictures in two level principal axis direction for the first three step of X and Y, it has been validated the establishment rationality of the macroscopic simplified model from tallied nature, at the same time, and discussed the change of structure dynamic characteristic under interaction situation—the natural period was prolonged and the modes of viberation was changed.(5) Aiming at elaborate and simplified finite element model for the information building, through the analysis of time-history in rigid ground hypothesis situation, it has been compared with the seismic response on displacement and time-history, and explained that both had certainly tallies between the two models, proved that the macroscopic simplified model which established by this paper is feasible.(6) Carries on the free field to the information building soil layer for the analysis of the earthquake respond, the input different type also the different acceleration peak value of earthquake wave, through the acceleration time-history curve and the Fourier spectrogram comparison, has manifested the soil layer to the earthquake wave filter and the amplification.(7) In view of the finite element macroscopic simplified model for information building, it has been selected seismic motion parameter of finite element model boundary for the input, which inversed by the free field, carried on the elastic time-history analysis under the interactionsituation, and compared with the one under the rigid ground situation. It can be discovered that after considering interaction, the maximum displacement in storey has increased; the maximum of relative displacement have reduced; the maximum acceleration reduced obviously, also the appearance time of peak value lagged universally; the maximum shear force and bending moment reduced with varied degree. Through the contrast analysis on difference of structure earthquake reaction, it has been made the summary and the induction to the result regularity, and thought that under the seismic effect, the influence of interaction does not allow to neglect, and has provided certain reference for the engineering design.