Effects Of New Underground Structure On The Seismic Response Of The Existing High-rise Building

Seismic design method of the high-rise building structure with the basement generally adopt assumption of the basement roof built-in, assuming that the foundation soil can completely constraints lateral displacement and rotation in the basement. The seismic design code used by many countries also adopt assumptions of the basement roof built-in and put forward the corresponding design method. But the foundation soil will make the constraint stiffness of the basement have change, after constructing the new underground garage around the existing high-rise buildings. Meanwhile the effect of the change of the foundation soil on structure seismic performance rarely considered in the design of engineering, but the seismic code in our country do not make the detailed rules for this. Therefore, it has theoretical and practical significance that the new basement around the existing high-rise buildings influence the seismic performance of the original structure.At first, the foundation soil- structure interaction is analyzed theoretically and this article first to the foundation soil and structure interaction are analyzed in theory, and in this foundation soil are introduced in the structure of limited constraint stiffness calculation diagram. This thesis has carried on the theoretical calculation by M method and modified D-value method for restraining stiffness of the the existing high-rise buildings that is constructing the new garages around and get the corresponding restraint stiffness values, then set up two models though changing the the boundary conditions of structure: one calculation model is embedded solid end built in roof slab of the basement, another is based on main roof, and considering the limited constrained stiffness that the basement affected by the foundation soil. At last, centered on the influence of adding new garages on the seismic behaviors of the remaining high-rise buildings, the main work is comparing the cycle, inter-story displacement, inter-story shear, shear-weight ration, the ration of rigidity to gravity, by adopting the response spectra analysis and time history analysis respectively, which are considered with program Midas Gen.The major conclusions are summarized as following: under the effect of frequently occurred earthquake action, the inter-story displacement of the structure will increase, and the top displacement has largely increased, and the displacement between layers of structure in the lower will be significantly increased. Under severe earthquake, the inter-layer displacement and inter-story shear of the structure in the lower greatly f increase. In this paper, by choosing different restraint stiffness value of structure has carried on the further analysis, concluding the inter-layer displacement and inter-story shear of low-level structure constantly increase as the constraint stiffness decrease gradually within a certain range of constraint stiffness.Therefore, we can draw a conclusion that the decrease of the restraint stiffness will be harmful to the lower structure of the high-rise building, which can make the structure of local failure. In this paper, theoretical analysis and calculation of the structure demonstrate convincingly the necessity of constructing the underground structure influence on the seismic performance of the existing structures.