Nonlinear Seismic Analysis Of Reinforced Concrete Coupled Wall Systems Subjected To Strong Earthqauke

Reinforced concrete(RC)coupled wall systems have good seismic performance and sufficiently lateral-resistant stiffness,and thus are extensively applied to seismic design of high-rise buildings.Previous earthquake damage investigations have illustrated that this structural type is able to avoid the global collapse of building structures under extrem earthquake loads.However,the local brittle failures or even collapse occurred in the key components frequently happen in each of large earthquakes such as the shear failure of RC coupling beams,and the brittle failure occurs without any signs.As such,people who live in these buildings located at the places where earthquaks happened are probably subjected to serious life-loss risk,and people who live in older high-rise buildings designed by past codes will confront greater risk.Therefore,it is necessary for these older buildings to conduct seismic performance assessment(SPA).Development of simple,reasonable,reliable,and robust analysis model to accurately predict nonlinear response characteristics of RC coupled walls subjected to strong earthquakes is required before performing SPA.On the basis of this background,the major research work in this thesis is summarized as follows:1.Based on the theory of Timoshenko beam,the flexibility matrix of modified force-based fiber element(MFBFE)is improved to build the theory of analytical element used to simulate the seismic behavior of RC coupled walls,and to state the principle of nonlinear iterative algorithm of the analytical element.At the section level in addition to defining the constitutive models of steel bars and concrete,sectional shear law also allows to be defined.At the element level,the shear force and bending moment are coupled along the element because of the enforced equilibrium equation.It is worthy noting that this element not only keeps the advantage of fiber model,that is,interaction between axial and flexural deformations,but also can simulate the behavior characteristics induced by nonlinear shear deformations of RC members.2.Two hysteretic shear models for two types of RC coupling beams with small span-depth ratios commonly used in actual engineering(i.e.,conventionally and diagonally reinforced coupling beams)are developed.Both of these two models consider the nonlinear behavior characteristics probably occured in the coupling beams during loading history,including concrete cracking,longitudinal reinforcements yielded,maximum load-carried capacity,and ultimate shear faiure caused by longitudinal or diagonal bars buckling and concrete crushing.The skeleton curves for these two models both are multi-linear including cracking,yielding,maximum,and failure points.Each of control points can be calculated according to corresponding proposed equations.The hysteretic rules are determined in terms of exclusive behavior character of RC coupling beams with small aspect ratios(e.g.,stiffness and strength deterioration,and pinching effect).At last,these two models are combined with the improved MFBFE respectively to form analytical models of conventionally and diagonally reinforced coupling beams.Then,these two models are respectively applied to nonlinear simulation of 8 specimens(4 conventionally and 4 diagonally reinforced coupling beams)under reversed cyclic loading.The analytical results are compared with the corresponding experimental data,and are discussed in detail.3.Two RC shear wall specimens constructed at 1/2 scale were tested by our group under cyclic loading reversal with allowing for interaction between shear force and moment.The improved MFBFE then is adopted to simulate these two specimens respectively.In the process of modeling,different from previous loading modes(i.e.,only considering axial and shear forces),the moment acted on the top of two specimens are also taken into account to objectively validate the accuracy level and reliability of improved MFBFE under actual force situation in modeling nonlinear behavior of RC wall piers.4.The analytical model for RC coupled wall systems is developed through integrating the proposed models of RC coupling beams and shear wall.Then,two large-scale RC coupled wall specimens are simulated using the proposed model.Comparisons between predicted results and corresponding experimental findings are performed and discussed in detail.