Study And Application On Damping Model Of Reinforced Concrete Frame-shear Wall Structures

The frame-shear wall structure is a widely used system of high-rise building structure. In this structure, shear wall and frame works together, in which frame mainly bears the vertical load of itself while t he horizontal load is mainly borne by the shear wall. When this structure is under horizontal load, the deformation of shear wall is in flexural mode and the deformation of frame is in shear mode. In the earthquake-resistant and wind-resistant design of frame-shear wall structure, damping ratio is an important parameter and difficult to estimate. In the current national specification, damping ratio of the RC frame-shear wall structure is assigned constant value(usually it is chosen as 5%), and is no different from frame, shear wall and any other RC structures. Obviously, the present constant damping ratio cannot fully consider characteristics of the stress and deformation of frame, shear wall and frame-shear wall structure. Therefore, it is not consistent w ith the damping mechanism and experimental result of damping ratio of buildings.On the basis of the damping data estimated from various experiments of frame, shear wall and RC frame-shear wall structures, the linear damping ratio and nonlinear damping ratio models of frame, shear wall and RC frame-shear wall structures have been systematically studied. Meanwhile, influences of different damping models on the seismic response of RC frame-shear wall structures are discussed. The main contents and results are presented as follows:(1) Based on the damping data estimated from full-scale measurements under ambient vibration condition, the damping data evaluated from shake table tests, the damping data identified from strong motion records and the damping da ta obtained by the dynamic tests on reinforced concrete cantilever specimens, the influence of the compressive strength, vibration measuring method, vibration direction, natural frequency and vibration amplitude on damping properties of reinforced concrete frame structures are examined, and predictors of linear damping ratios or nonlinear damping ratios with frequency or amplitude dependencies are obtained by the regression analysis method.(2) Based on the damping data evaluated from several shake table tests and quasi-static cyclic tests, some damping properties of reinforced concrete shear wall are discussed, predictors of damping ratios with amplitude dependencies are obtained by the regression analysis method. at last, the validity and feasibility of the proposed predictors of nonlinear damping ratios are verified by comparing with the related formula.(3) This thesis collected the natural vibration period data of some high-rise and super high-rise buildings computing by the finite element method, the natural vibration period data of some high-rise buildings evaluated from shaking table tests, and the natural vibration period data of some high-rise buildings estimated from ambient vibration tests and wind induced vibration tests. A new estimation fo rmula for fundamental natural vibration period has been established by fitting the collected data and comparing with other estimation formulas. Meanwhile, the influence of the building height, earthquake action, and different structures on the ratios of th e periods in the second and the third mode to the fundamental natural vibration period was discussed, and the statistical values of the ratios of the periods in the second and the third mode to the fundamental natural vibration period has been presented.(4) Since the frame and the shear wall has different damping mechanism, their damping ratio models is different. In this thesis, the RC frame-shear wall structure is regarded as a special composite structure. According to the characteristics of the parallel composite structure, the formulation of compute the equivalent damping ratio of the composite structure is suggested; the dynamic analysis of a composite structure is finished by using PKPM software, and given as an example to verify the rationality of the equivalent damping ratio’s formula. Besides, the equivalent damping ratio’s formula of the RC frame-shear wall structures is derived based on damping ratio’s formulas of the frame structure and the shear wall structure.(5) In this thesis, the full-scale seven-story RC frame-shear wall structure in the Japan-U.S cooperative test is given as an example, the nonlinear seismic response analysis of the RC frame-shear wall structure is finished by using the proposed equivalent damping ratio’s formula; the computing results and the test results are compared to verify the rationality of the equivalent damping ratio’s formula of the RC frame-shear wall structure; meanwhile, the nonlinear seismic response analysis of the RC frame-shear wall structure is also carried out by using other commonly used damping models, the influences of different damping models on the seismic response of the RC frame-shear wall structures are discussed. In order to further explore and compare the effect of damping models on high-rise RC frame-shear wall structures, a fifteen RC frame-shear wall structure is given as another example to compute its nonlinear seismic responses by using proposed equivalent damping model and other commonly used damping models.