Analysis On Seismic Response Of Long-span Suspension Bridge And Its Control

Long span suspension bridge has been developed rapidly in recent years because of its excellent span ability and beautiful shape.It is a flexible structure with long natural vibration period.If a large earthquake occurs,or the long period component of the seismic wave is close to the natural vibration period of the suspension bridge,it is easy to produce resonance phenomenon,which often poses a threat to the safety of the structure.Taking Runyang Yangtze River Bridge with a span of 1490 m as the research background,the bridge model is established by ANSYS finite element software.On the basis of seismic response analysis,the shock absorption control analysis of long-span suspension bridge based on viscous damper and mild steel damper is carried out.The main contents and conclusions are as follows:(1)Finite element modeling and dynamic characteristics analysis of long span suspension bridge.By using ANSYS finite element software,the dynamic characteristics of the structure are analyzed by to analyze the dynamic characteristics of the structure.The results show that the fundamental frequency ratio of the central buckle model is larger than that of the central buckle model,and the setting of the central buckle can appropriately improve the longitudinal stiffness of the structure.(2)Seismic response analysis of long span suspension bridge under uniform excitation.Three different seismic waves are selected,and the two models are used to analyze the seismic response under consistent excitation.The results show that the response results are affected by seismic baud property and seismic wave input direction.The setting of rigid central buckle limits the longitudinal displacement of the main beam and improves the longitudinal stiffness of the structure,but increases the shear force of the main beam.(3)Seismic response analysis of long span suspension bridge considering traveling wave effect.Three kinds of ordinary seismic waves and three kinds of long-period seismic waves are selected and input along the longitudinal direction of the main beam.The traveling wave effect of the model with central buckle is analyzed by using the large mass method.The results show that the seismic response of long period seismic wave is larger for the flexible structure of long span suspension bridge,and the seismic response of suspension bridge fluctuates greatly in the low visual velocity range after considering the traveling wave effect.With the increase of apparent velocity,the response value is close to the corresponding value of uniform excitation.(4)Analysis of the damping effect of two kinds of damping devices on long-span suspension bridges.Based on the longitudinal input of long-period seismic wave,the vibration control analysis of long-span suspension bridge with consistent excitation and considering traveling wave effect is carried out by using viscous damper and mild steel damper.The optimal parameters of the two shock absorbers are given by parameter sensitivity analysis.The results show that the two shock absorbers have good shock absorption effect,but the internal force of suspension bridge structure will be increased to a certain extent,among which the shock absorption effect of soft steel damper is relatively better.