Multiple Vehicle-bridge Coupling Vibration Analysis Of Long-span Suspension Bridge

With the rapid development of China’s transportation industry,the increase of vehicle speed,load,and bridge span,the problem of vehicle-bridge coupling vibration has attracted widespread attention.At present,many scholars have carried out the corresponding research on the single vehicle-bridge coupling vibration of short span girder bridge,but there is still a lack of sufficient research on the multiple vehicle-bridge coupling vibration problem,especially for long-span suspension bridge.Therefore,the research on the latter is of great significance to the structure design,construction,operation,maintenance and management of long-span suspension bridge.In this paper,the multiple vehicle-bridge coupling vibration analysis of long-span suspension bridge is finished by using APDL,the parametric design language of ANSYS.Firstly,the principle of the finite element analysis on vehicle-bridge coupling vibration are introduced.Secondly,the ANSYS finite element model of the runyang suspension bridge is established,and the cables and suspenders’ initial internal force and the relevant dynamic characteristic parameters of the runyang suspension bridge are determined by static analysis and dynamic characteristic analysis.According to the results of dynamic characteristic analysis,girder end constraint conditions are modified,and the calculation results of finite element model are verified by the measured data.Then,the vehicle-bridge coupling parametric analysis under various working conditions is carried out based on the runyang suspension bridge finite element model.What’s more,the differences of analysis results between the moving force model and the moving single-axle vehicle model are compared,and the influence of vehicle weight,vehicle speed,vehicles number,vehicle distance,bridge damping ratio,central buckle on the girder’s dynamic response and impact effect are discussed respectively.Finally,the fatigue reliability of suspenders in different positions of long-span suspension bridges under the random traffic flow is studied,the fatigue reliability of suspenders is calculated,and the influence of vehicle-bridge coupling vibration effect and central buckle on the fatigue reliability of suspenders is discussed.The results show that:(1)There is a certain hidden danger in the impact effect evaluation only considering the basic frequency of the bridge,and the impact effect of different areas can not be simply measured by the midspan’s impact factor.(2)When evaluating the impact effect of the vehicle,the inertia force of the vehicle and the interaction between the vehicle and the bridge cannot be ignored.(3)The increase of the vehicle weight and the density of the traffic flow will increase the impact factor of the girder,but the impact factor of the girder will not increase monotonously and continuously when the vehicle speed increases.(4)The increase of the bridge damping ratio can generally reduce the impact factor of the girder.(5)The setting of the center buckle can effectively reduce the vertical displacement in most areas of the girder,and make the distribution of impact coefficient more uniform.(6)Under the simulation of two-way continuous random traffic flow,the fatigue reliability index of suspenders at 3L/8 and 5L/8 of the bridge is the lowest,which means the safety performance is the poorest.The fatigue reliability index of suspenders in most positions of the whole bridge can be improved by setting the central buckle in the suspension bridge midspan,and the fatigue performance improvement effect of suspenders at L/4 and L/2 is the best.