Seismic Isolation Analysis Of Long Span Continuous Girder Bridge In High Intensity Area

Long span continuous beam bridge has many advantages,such as large span capacity,reasonable force,large stiffness,simple structure,mature construction technology,few expansion joints.It is widely used at present,and the span length has a tendency to increase continuously.In order to avoid the excessive additional internal force of concrete shrinkage and temperature deformation,only one fixed support is set in one connection.Under the longitudinal earthquake action,the seismic force of the superstructure is transferred to the foundation through the fixed piers,and the design of the pier body is difficult.In view of this,this paper takes a long span continuous beam bridge(50+8 × 100+50)m as the background of intercity engineering,three kinds of seismic isolation schemes are put forward,the seismic isolation mechanism and the effect of isolating and isolating are studied systematically.(1)read a lot of literature,analyze the main damage forms of bridge seismic damage,summarize the commonly used seismic isolation devices and parameter values of continuous girder bridges.(2)taking a long span continuous beam bridge(50+8 ×100+50)m as the research object,the whole bridge dynamic calculation model is established by Midas civil,the self vibration characteristics and main characteristics of the bridge are analyzed and summarized.(3)aiming at the vibration reduction scheme of the friction pendulum bearing,the friction pendulum element is used to simulate the constitutive relation of the friction pendulum support,and the effect of the friction coefficient u and the surface radius R on the bottom moment of the bridge pier and the relative displacement of the pier beam is analyzed by using the nonlinear time history analysis method.The optimal reference value is given and compared with the general support scheme.Reduce the effect of isolation.(4)aiming at the damping scheme of liquid viscous dampers and common bearings,the Maxwell model is used to simulate the constitutive relation of liquid viscous dampers.The effect of damping coefficient C and damping index alpha on the pier bottom bending moment and the relative displacement of pier beams is studied by using the nonlinear time history analysis method.The seat scheme contrasts the effect of shock isolation.(5)in view of the shortcomings of the first two schemes,a combination of liquid viscous dampers and friction pendulum supports is proposed,and the influence of the layout angle of liquid viscous dampers on the longitudinal and lateral shock isolation effects of the bridge is systematically analyzed.Through statistical analysis,the mechanical parameters of friction pendulum bearing and liquid viscous damper are obtained.The merits and demerits of the three kinds of seismic isolation schemes are evaluated.