Theoretical And Experimental Study On Simplified Nonlinear Analysis Model Of Wall-frame Structure Based On The Continuum Technique

Performance-based seismic design is the hot research area in seismic engineering. The nonlinear structural history analysis is the important technique in the performance-based seismic engineering. There are a variety of mechanical models for engineers to develop nonlinear finite element model of wall-frame structures. Among these mechanical models, the detailed nonlinear model composed of beam-column elements is relatively accurate. But such method is time-consuming, inefficient and difficult to be applied to the seismic analysis of high rise wall-frame structures. It is necessary to simplify the detailed model reasonably to quickly analyze the weak position and evaluate effectively the overall seismic performance of the wall-frame structure under severe earthquakes. The purpose of this dissertation is to develop a simplified nonlinear analysis model which is applicable for wall-frame structure, and meets the engineering requirements. The main work of this paper includes the following aspects:(1) The theoretical study for the simplified nonlinear analysis model of wall-frame structures is carried out. The wall-frame structure with uniform distribution of mass and stiffness along the height can be simplified into two dimensional models. Based on the traditional continuous continuum technique, this paper proposes a simplified nonlinear analysis model for wall-frame structure:By employing rigid diaphragm assumption, the wall-frame structure is simplified into a model which is the combination of a flexural deformation and a shear deformation cantilever, and the flexural cantilever and the shear cantilever in every story is modeled by one flexural deformation element and shear deformation element respectively. The story mass is lumped in the floor lever. A series of rigid rods are used for connecting two cantilevers. At the same time, the theoretical derivation for the deformation and internal force under the inverted triangle lateral load is also carried out and the process for building up the simplified analytical model is obtained.(2) To discuss about the accuracy of the simplified analysis model, a 4-story reinforced concrete wall-frame structure is constructed and reversed cyclic loading test is conducted. The failure process, hysteresis property, stiffness and strength degradation, ductility and energy dissipation capacity of wall-frame structure are studied. After that, the spacemen is simulated by detailed structure model and simplified model respectively. The analysis results show that the three truss model can well simulate the development of plastic zone in the bottom of shear wall, and it can be used in both detailed structure model and simplified model. The compute results from detail model and simplified model agree well with test resulst, which indicated that the proposed simplified model has good accuracy;(3) To further discuss the applicability of the simplified analysis model for high rise buildings, the numerical study of a 20-story wall-frame structure are conducted. The detailed structural model and proposed simplified analysis model are developed respectively, and the Pushover analysis is conducted. Through the comparison of analysis results, it can be seen that the results from both numerical models are agree well with each other. Hence, it can be thought that the proposed simplified model is applicable in the nonlinear analysis of the wall-frame structures;(4) The results show that the proposed simplified nonlinear analysis model has the advantages of simplicity, efficiency, and accuracy. It can provide some references for the design and evaluation of seismic performance of real tall wall-frame structures.