Seismic Performance Study Of Cable-stayed Bridge With Pre-pressed Disc Springs Self-centering Energy Dissipation Brace

Large-span cable-stayed bridges generally adopt floating systems or semi-floating systems in the longitudinal direction.The longitudinal displacement of the main girder is relatively large under earthquakes.The transverse bridge generally adopts a fixed connection,and the bridge tower is subjected to greater force under the earthquake.In response to this problem,this paper proposes a new type of seismic mitigation device,pre-pressed disc spring self-centering energy dissipation(PS-SCED)brace,which is used to control the seismic responses of cable-stayed bridges.The simplified analysis model of PS-SCED brace is established and the effectiveness of this model is verified by comparing with the test.The longitudinal and transverse seismic performances of the cable-stayed bridge with the braces are studied,and the main research contents are as follows:(1)A simplified analysis model of PS-SCED brace is established in ABAQUS according to the principle of superposition.Two test cases of the brace are simulated and the energy dissipation capability,the bearing capacity and the secant stiffness between simulation and tests are compared.Results show that the numerical simulation results of PS-SCED brace using the simplified model agree well with the test results,the maximum bearing capacity error is less than 16%and the total energy dissipation error is less than 8%and the secant stiffness is less than 14%.It is verified that the simplified brace model is effective to describe the behaviors of PS-SCED brace.(2)The longitudinal seismic performances of the cable-stayed bridge with elastic cables,viscous dampers and PS-SCED braces are compared and analyzed to study the influence of the different connection mode between tower and girder on the seismic responses of cable-stayed bridge.Results show that the displacement of main girder can be reduced by using the elastic cable devices between the tower and girder,but the base shear force and moment of tower will be increased.Using the PS-SCED brace between the tower and girder can reduce the displacement of main girder and base moment of tower,but will increase the base shear force of tower.The viscous damper has better control effects on the base shear force and moment of tower and the displacement of girder than the first two,which can control the base shear force and moment of tower force and girder displacement of cable-stayed bridge well.(3)The seismic performance of cable-stayed bridge with PS-SCED braces installed at the end of girder is studied.Results show that the control effect of PS-SCED brace which is installed at the girder end is less than that installed between the tower and the girder.But it can also reduce the girder displacement,improve the internal force of the tower,control the displacement of tower,and basically eliminate the residualdisplacement of the girder,which has a good self-centering effect on the girder after earthquakes.(4)A transverse seismic system of cable-stayed bridge with PS-SCED brace is proposed and a parameter design method for the brace is developed and the time history analyses of the fixed pier-girder system and the seismic mitigation system with braces are carried out due to earthquakes.The seismic performance of the braced system is studied from the aspects of the seismic responses at key locations,the energy dissipation capabilities,etc.Results show that PS-SCED brace can effectively control the transverse displacement of the girder and prevent the collision between the girder and the bridge tower.Compared to the original bridge consolidation system,the additional PS-SCED brace reduces the base shear force of pier by a maximum of 41%,the base moment of pier by a maximum of 55%,and reduces the base shear of the tower by about 15%and the base moment by 17%.At the same time,the displacement and strain of the tower are reduced,the internal force of the bridge tower is improved and the protective effect of the tower is better.The brace dissipates about 40%of the seismic energy and reduces the hysteretic energy dissipation of the cable-stayed bridge.The brace has a better self-centering effect and the residual displacement of the girder at the position of tower is reduced by more than 60%compared with the consolidation system and the floating system.