Analysis Of Seismic Response Considering Soil - Structure Interaction

Currently, the design of most engineering structures tends to be assumed on the rigid foundation and seismic analysis only considers the upper structure. Only when the rigidity of foundation is large and the stiffness of upper structure is small, this assumption is reasonable within the accuracy of engineering. But when the stiffness ratio of upper structure to foundation increases, this assumption will produce large errors for the upper structure of seismic reaction. There are two main reasons to cause the errors. One is that the existence of foundation has changed the dynamic characteristics of the superstructure; the other is the difference between ground motion input and free-field input. Therefore, it is very important to consider soil-structure interaction analysis of seismic response.In this paper, the development of soil-structure interaction was outlined. During the work of thesis, overall finite element method was chosen to conduct analytical method and finite element software SAP2000 was used to establish rigid foundation assumptation and finite element model of interaction. Besides, following works were done as below:Firstly, soil-structure interaction of the dynamic equilibrium equation, dynamic analysis method, damping settings, ground motion input, artificial boundaries were summarized and an analysis method suitable for this thesis was chosen. Secondly, Viscous-spring boundary is simplified to elastic boundary, and four kinds of soil-structure interaction three dimension finite element models are seted up, according to the results of modal analysis, abtain the law of natural vibration period of four modes. The current common method, response spectrum method, is adopted to calculate the earthquake force and the maximal displacement of every layer under considering or not soil-struture interaction condition, and three kinds of column section and upper structure layers models were established to discuss the impact on earthquake by the column section and the layer number of upper structural. With the seismic analysis of free field ground, the acceleration time history of seismic waves to the surface of different fields is abtained. Put surface waves and the original bedrock waves into a rigid foundation assumptation and interaction model respectively abtained from the free-field analysis, acceleration time curve, each layer displacement curve, interlayer displacement curves and interlayer shear force considering upper structures and without considering upper structures.