| Sector lead viscoelastic damper(SLVD) is a novel haunch brace damper which can be installed in beam-column joint. According to the damages of RC frame structure in earthquake, especially for structural collapses caused by the failure of beam-column joints, an approach to strengthen RC frame structure by using SLVD is proposed in this paper, subsequently the experimental research and finite element analysis of beam-column joint, frame unit, and the whole structure retrofitted by using SLVD are conducted, respectively.(1) Based on ABAQUS software, the nonlinear numerical simulation analysis of the tested frame joint is carried out, and numerical analysis results are compared with experimental results. The seismic performance of beam-column joint equipped with SLVD, along with its influence factors with different layout of SLVD, are analyzed. The analysis results show that the numerical analysis results of beam-column joint agree well with the corresponding experimental results; using SLVD to strengthen beam-column joint can improve its seismic performance, reduce the damage of concrete in beam-column joint, and make the crack far away the joint core area, which is helpful to realize the failure mechanism of “strong joint weak component”; SLVD layout form effects on seismic performance of joint; with the increase of number of SLVD, the bearing capacity and stiffness of joint magnify; the left and right sides symmetrical installation of damper can make the beam destruction area away from the core zone of the joint, which is in order to protect the joint; When SLVDs are installed on the top and bottom of the same RC beam at the same time, it is found that cracks are easy to form through the RC beam, which is disadvantageous to the protection of the joints. Combined with the simulation results, the layout of the SLVD reinforcement frame structure is proposed.(2) In order to study the influence of the design parameters of SLVD on the seismic performance of the reinforced RC frame, the 3 sets of 15 SLVD models were designed to strengthen the RC frame structure and the reinfoced performance was analysed. The analytical results show that while fan-shaped radius, lead core diameter, viscoelastic material width of SLVD increase,the initial stiffness, yield load, peak load of RC frame structure also increase, and after RC frame sructure reach the peak load, the bearing force level has nothing to do with lead core diameter. Among them, fan-shaped radius has the greatest impact on the seismic performance of the reinforced RC frame structure.With increase of the fan-shaped radius, concrete crack(plastic hinge) towards the direction away from the joint zone, which protects the frame joints. When the fan-shaped radius is too large, columns and beams hog seriously, left and right columns were destroyed shall avoid the fan-shaped radius is too large.(3) SLVD design parameters are numerous, the construction is complex, and the design process is cumbersome. In order to design SLVD reasonably, fan-shaped radius is selected as the basic parameter(viscoelastic material width B=2/3R, lead core diameter D=0.2R), and 7 different types of SLVD were designed. The restoring force curve of the damper is simulated by the finite element software ABAQUS, the restoring force curve of the numerical simulation and theory are compared. The results show that the restoring force curve of the numerical simulation is in good agreement with the theory, and dampers can be designed according to the theoretical formula. The numerical simulation analysis was carried out on frame struture with 7 different types of SLVD. The results show that the optimized SLVD can improve the initial stiffness, the calculational yield stiffness and the horizontal bearing capacity of the frame structure.(4) Two connection types between column and beam were proposed, U-shaped steel plate connection and box steel plate connection. Full scale RC frame specimens retrofitted by SLVD were conducted by cyclic loading test and numerical simulation. The experiment results shows that: after using SLVD to retrofit the RC frame, initial stiffness, horizontal bearing capacity, ductility and energy dissipation capacity of RC frame increases. Additionally, SLVD retrofitting method delays the appearance of plastic hinge, changes the failure mode of RC frame and transfer the plastic hinge far away from node area, which is beneficial to the formation of stronger column and weaker beam. These two connection types have little effect on the seismic performance of RC frame, which ensure the force transmit effectively via energy dissipation devices. Numerical simulation results are consistent with the experiments’, which verifies the reliability of finite element analysis.(5) Four-story teaching building retrofitted by SLVD was analyzed by finite element ETABS and PERFORM-3D. Before and after being retrofitted by SLVD, the time history of the structure is analyzed respectively under frequent earthquake and severe earthquake. The analysis results show that the method of RC frame retrofitted by SLVD provides a good reinforcement effect, which effectively increase the following seismic response, the floor shear force, interlayer displacement angle, vertex acceleration, column axial force, column shear force, column bending moments. Additionally, the appearance of plastic hinges is improved by this retrofitting method using SLVD. |
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