Nonlinear Planar Seismic Response Analysis For High-Rise Frame Structure Considering Soil-Structure Interaction

Nonlinear seismic response analysis for high-rise building structures considering soil-structure interaction is a complicated problem. In past twenty years, many researchers have worked at it and several analysis methods have been presented, such as time domain sub-structure method, time domain integrated finite element method etc. But these methods have not been widely used in practical engineering. Push over analysis method is a practical nonlinear seismic response analysis method. This procedure involves applying a predefined lateral load pattern which is distributed along the building height, the lateral force is then monotonically increased in constant proportion, with a displacement control at the top of building until a certain level of deformation is reached, then to evaluate the seismic performance of structures. In this thesis, push over analysis method was adopted to perform nonlinear planar seismic response analysis considering soil-structure interaction for high-rise frame structures with box foundation or raft foundation resting on natural foundation soils. In order to check the validity and applicability of the push over analysis method, the time-history analysis of nonlinear planar seismic response considering soil-structure interaction for high-rise frame structures with box foundation or raft foundation resting on natural foundation soils was also performed.In the time-history analysis of nonlinear planar seismic response, the sub-structure technique is adopted to establish the dynamic interaction analysis model and nonlinear motion equations of soil-foundation-upper-structure system. The upper-structures is modeled with the inter-story bar-system model. The foundation is simplified as a rigid rectangle mass. The dynamic impedance of foundation is modeled with springs and dampers, which are connected to the foundation. The coefficients of springs and dampers are determined by a set of approximate formulas which take the frequency dependence, the foundation shape and the embedment depth into account. The frequency dependence only considers the fundamental frequency of system in this thesis. A relevant time-history analysis program of nonlinear planar seismic response for high-rise reinforce concrete frame structures with box foundation or raft foundation resting on natural foundation soils is developed. Two case study is presented. The results of two examples show that after considering soil-structure interaction, the inter-story drifts and inter-story shear forces are not always reduced comparing to the condition of rigid soil, sometimes they are increased. Therefore the nonlinear seismic checking based on assumption of rigid soil is not always favorable.In the push over analysis of nonlinear planar seismic response, based on the principle of sub-structure, the push over analysis model and the nonlinear static incremental equations of soil-foundation-upper-structure system are set up. The way to model the foundation and upper-structure of system is the same as that of the nonlinear planar seismic response time history analysis. The impedance of foundation only take the still stiffness into account. Then, the specific procedure, the lateral load pattern and the target displacement in push over analysis for soil-foundation-upper-structure system are studied in detail. A relevant planar push over analysis program of soil-foundation-upper-structure system is developed. Applying this analysis program, The nonlinear planar seismic response for two high-rise reinforce concrete frame structure subjected to three lateral load patterns(they are uniform load pattern, curve load pattern, triangular load pattern ) are calculated, then compare the results of the push over analysis with that of time history analysis . The results of two cases show that the nonlinear seismic analysis for soil-foundation-upper-structure system using push over analysis method is valid, the results of curve load pattern are well consistent with that of time history analysis.