Preliminary Study Of The Soil-structure Interaction Subject To The Velocity Pulse

In recent years, the observation data of several strong earthquakes and the simulation of near-field strong ground motion have shown that a large velocity pulse usually exists in near field especially in near fault region during to the impact of rupture directivity effect. Generally, velocity pulse have a large peak and its period is between the 1 ~ 3 seconds. When the period of velocity pulse is close to the natural period of the structure, as a result of the effects of resonance, the structure would cause serious damage. That is the main reason for damages of long period structures. Most of current studies did not consider the soil-structure interaction; however, soil-structure interaction of soft foundation has a significant influence to seismic response of structures. The real seismic response of structure built on soft soil ground is very different with the result of the calculation model based on the rigid foundation hypothesis. In this paper, the differences of the structural response between that of the rigid foundation model and that of the soil-structure interaction subject to velocity pulse is discussed by numerical simulation method. The main works are as follows.(1) Some questions about the numerical simulation of soil-structure interaction, such as the dynamic soil constitutive model, the simulation of material non-linear, the grid division, the material damping mechanism of the foundation soil, the artificial boundary, the determination of system fundamental frequency, the damping ratio and the implementation of seismic excitation are introduced in this paper and the specific methods to achieve in ANSYS software are given.(2) The seismic response of a frame shear wall structure on the rigid foundation and that considering the soil-structure interaction are calculated by the ANSYS software, and differences of them are analyzed. The soil amplification effect is also studied. By changing the system parameters, such as the stiffness of the upper structure, the stiffness and the depth of the foundation, the effect of soil-structure interaction to different systems are analyzed.(3) By selecting 14 rock site records which include large velocity pulse from historical earthquakes as the input, the seismic response of 3 sets of models are analyzed. The difference between the results of models based on rigid foundation and that considering the soil-structure interaction are compared using the relative error factor. Some results are also compared with the standard, which shows that the standard is generally simply safe.Through the analysis of several types of structure come to the conclusion that whether the structure design need to consider soil-structure interaction depends on the structure form.(4) The seismic response of frame shear wall structure and frame structure is analyzed by using the record which generates the largest relative error in the above models as the input and considering the soil non-linear with D-P model.The seismic response of structure becomes small whether of soil-structure system or of the rigid foundation after considering the soil non-linear.