Dynamic Characteristics And Vehicle-induced Vibration Response Analysis Of The Second Bridge Of Poyang Lake

With the emergence of extra long-span and light-thin structure bridges,the overweight problem of vehicle loads on the bridge is also becoming more and more serious,so the dynamic performance problems of the bridges are becoming more and more prominent.However,at present,there are relatively few literatures on the analysis of vehicle-bridge coupling vibration of cable-stayed bridges,especially there are few studies related to super-large-span composite beam cable-stayed bridges.Therefore,with the Poyang Lake Second Bridge as the subject background,it is meaningful to study the vehicle-bridge coupling vibration of the composite beam cable-stayed bridge.Taking the design example of the Poyang Lake Second Bridge as a research background,this paper makes a comprehensive analysis of the dynamic characteristics and vehicle-induced vibration response characteristics of the bridge.The specific work and research results are as follows:(1)Two large-scale general-purpose finite element analysis programs,ANSYS and midas Civil,are adopted.Three kinds of finite element models are established under the influence of the fineness of the model.Combining the calculation results of the dynamic characteristics of these three models,the dynamic characteristics of the full bridge are compared and analyzed.The results show that for this type of cable-stayed bridge,the fundamental frequency value of the vertical bending of the structure calculated according to the empirical formula in the code is smaller than the actual calculated value,and the rod-type cable-stayed bridge model established by ANSYS has fast calculation speed,simple model and effective,Can provide a reliable calculation model for the structural vibration response analysis of this type of bridge.(2)Combined with the actual situation of a wide variety of vehicle loads on highway bridges,in order to study the vibration response of cable-stayed bridges under the action of different vehicles,on the basis of the previous vehicle-bridge coupling theory,two-axis,threeaxis and five-axis vehicles are compiled.The vehicle-bridge coupling vibration equation numerically simulates the vehicle-bridge interaction under the influence of vehicle speed,road level,and lateral position of the vehicle.The results show that during the driving of the vehicle,the vertical displacement,bending shear stress and cable force of the bridge increase nonmonotonically with the increase of vehicle speed,but monotonically increase with the increase of acceleration,and with the increase of vehicle speed,each The fluctuation of the vibration response value at its equilibrium position is more and more obvious;the impact coefficient of the mid-span in the speed range of 10 km / h ? 120 km / h is three-axis car,five-axis car and two-axis car in order.The impact coefficient of the mid-span under the action of the three vehicles increases significantly with the increase of road roughness,and on the D-level road surface,the impact coefficient of the span of the bridge under the action of the three-axis vehicle and the five-axis vehicle exceeds 0.05,which is greater than the specification value..The difference in the lateral position of the vehicle has a greater influence on the vertical displacement value of the bridge.The closer the vehicle is to the centerline of the bridge deck,the greater the vertical displacement value and bending shear force,and the smaller the cable force.In addition,for each vibration response,the effect of eccentric load under the action of the three-axis vehicle is the largest,while that of the two-axis vehicle is the smallest.(3)By changing the structural parameters,the effects of different structural systems,auxiliary piers and cable spacing on the bridge's dynamic characteristics and vehicle-induced vibration response were studied.The results show that in terms of dynamic characteristics,the connection form between the tower and the pier does not significantly interfere with the vibration frequency and corresponding vibration mode of the bridge.Compared with tower girder consolidation and rigid frame systems,floating system cable-stayed bridges are more prone to longitudinal drift and lateral bending modes.In terms of vibration response,the original bridge semi-floating system showed good dynamic performance compared to other systems.Compared with the cable-stayed bridge without auxiliary piers,the mid-span displacement and cable force of the original bridge are smaller.In addition,the cross-sectional stress at the mid-span and the position of the fulcrum and the cable force of each cable increase as the cable distance increases.(4)Aiming at the characteristics of the semi-floating system cable-stayed bridge without longitudinal constraints,the longitudinal vibration response characteristics of the cable-stayed bridge under vehicle braking are studied.The results show that under vehicle operating conditions,when the vehicle travels to the bridge tower position and the mid-span 1/4 position,the displacement of the main beam end is larger than other positions.When the vehicle travels to the mid-span position,the main beam The longitudinal displacement of the beam end is the smallest,and this value increases with the increase of the vehicle speed.Under vehicle braking conditions,the sudden braking in the low-speed driving state is greater than the longitudinal displacement of the beam end caused by the sudden braking in the high-speed driving state.When the vehicle brakes at the 1 / 8th position of the mid-span,the longitudinal displacement of the bridge responds the most.When the vehicle brakes at the pylon or mid-span position,the longitudinal displacement of the bridge is significantly smaller than other positions.