Study On Double-stage Yielding Buckling-restrained Braces And Their Damping Effect In Structures

In order to solve the problem that ordinary buckling-restrained brace（BRB）cannot dissipate energy under frequent earthquakes,scholars at home and abroad have proposed two-level yielding buckling-restrained braces to withstand earthquakes of different intensities.However,the existing two-level yielding buckling-restrained braces are faced with problems such as rapid weakening of stiffness and insufficient ductility.So,a double-stage yielding buckling-restrained brace（DYBRB）was proposed in this paper.The DYBRB was analyzed theoretically and numerically.And the DYBRB was applied to frame structure and latticed arch frame,and the damping effect of DYBRB on the two structures was analyzed.Firstly,the configuration and principle of DYBRB were explained,and the theories of DYBRB were investigated,besides,a three-fold line theoretical model of DYBRB was established.The hysteretic performance of DYBRB was analyzed by ABAQUS,and the accuracy of the theoretical formulas were verified through numerical analysis results.In addition,the key parameters affecting the hysteretic performance of DYBRB were analyzed,and reasonable suggestions were proposed.The results indicate that the theoretical formulas are accurate and they can be used in the preliminary design of DYBRB.The shear energy dissipation steel sheet and core plate in DYBRB can work well together.The ductility of DYBRB is large,and the hysteretic curves of DYBRB have a full shape,and the skeleton curves have obvious double-stage yielding characteristic.Secondly,three DYBRBs were designed by different principles,and they were arranged in steel frames.The seismic performances of the three double-stage yielding buckling-restrained braced frames（DYBRBF）were analyzed,and the optimal design principle was selected.In addition,the important parameters affecting damping effect of DYBRB were analyzed,and reasonable suggested values were given.The results indicate that the DYBRB designed according to the principle of equal yield strength can play a good role in energy dissipation under frequent and rare earthquakes,which reduces the seismic responses of the DYBRBF effectively,and gets the bestvibration reduction.Finally,the DYBRB was arranged in the lattice arch frame,and the damping effect of DYBRB was analyzed from the layout plan of DYBRB,connection position,design parameters,etc.The optimal layout and recommended values of design parameters were determined.On the basis of the optimal scheme,the seismic performances of the lattice arch frame with DYBRB were further analyzed under different earthquakes.The results indicate that the symmetrical and divergent center arrangement of DYBRB has the best damping effect.Under frequent and rare earthquakes,DYBRB can control the three-directional displacement peak of key points well in the upper chord and the whole structure.The displacement control in the z direction is better than that in the x and y directions.DYBRB can reduce the number of plastic members effectively,and improve the stress state of the whole structure,which lead to enhance the seismic performances of the lattice arch frame.