| According to the limitation of existing energy dissipation braces,a novel friction damped self-centering cable(FDSC)is proposed,where the self-centering force is provided through pre-compressed disc springs and the seismic energy is dissipated through the friction device.Since the FDSC can only bear one-directional tension,the lateral seismic forces are resisted through two crossed FDSCs.In this way,the common buckling problem in energy dissipating braces could be avoided,and the structural configuration could be simplified.Moreover,the tendon in FDSC does not need to be tensioned in advance,so that the insufficient deformation capacity in existing self-centering energy dissipation cables is avoided,and the high strength and high elastic elongation of the material are fully utilized.For this novel friction damped self-centering cable,experimental research and seismic mitigation analysis are carried out in this paper,as follows:First,theoretical analysis and experimental research on the FDSC are conducted.The configuration and working principle of the FDSC are introduced,and the theoretical load-displacement curve is deduced.The cyclic loading test was conducted to verify the accuracy of theoretical derivation,where the theoretical and test results are in good agreement;the steel stranded wires with high strength and high elongation is the ideal tensile member for the FDSC,and disc springs has basically no residual deformation under cyclic loading so that they can be used as ideal re-centering component of the FDSC.Through reasonable design and adjustment of key parameters such as friction force,stiffness of disc springs and pre-compression force,etc.,the FDSC can effectively realize self-centering and energy dissipation.Secondly,the simulation analysis model of FDSC is established by using the ABAQUS finite element software and its user subroutine.The framework,the simulation model and the concept of the user subroutine are introduced.Based on the model,cyclic loading tests are simulated and parametric analysis is conducted.The result shows that the simulation and test results are in good agreement,and with the increase of friction and the stiffness of the FDSC,the energy dissipation capacity increases significantly;with the increasing of the stiffness and pre-compression of disc springs,the secondary stiffness(the stiffness after sliding friction occurs)and re-centering capacity of the FDSC significantly increase,respectively.Thirdly,a nine-story frame was reinforced by using the FDSC and the buckling restrained brace(BRB),respectively,and the nonlinear dynamic analysis under the 7-magnitude and 8-magnitude earthquakes were conducted on the frames before and after the reinforcement.It is found that the capability of the FDSC and BRB to reduce the maximum inter-layer drifts under small earthquakes is basically the same,while the FDSC behaves much better than the BRB in reducing the maximum inter-layer drifts under strong earthquakes.In the regard of reducing the residual deformation,the FDSC and BRB have similar capacity when the intensity of earthquake is small,but the FDSC performs much better than the BRB under strong earthquakes.Finally,taking the frame reinforced by using the FDSC and the BRB respectively for example,the maximum and residual story drift are taken as seismic demand parameters to determine the performance levels,and through the incremental dynamic analysis,seismic vulnerability curves under different performance levels are obtained through the regression statistical analysis of dynamic analysis results.It shows that the BRB and FDSC basically have the same capacity in reducing story drifts under moderate and frequent earthquakes;while,under the strong earthquakes,the capacity of FDSC in reducing maximum and residual story drifts is significantly higher than that of the BRB.Compared with the BRB,the FDSC can greatly reduce the residual deformation and improve the capability of anti-collapse of structures. |
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