Dynamic Responses Analysis Of A Long-Span Cable-Stayed Bridge Under Running Trains Based On SIMPACK Software

At present,long-span cable-stayed bridges have been applied more and more due to their long span capacity,well performance against winds and large integral stiffness.It is of great theoretical and practical significance to study their dynamic characteristics under moving train vehicles and the running safety and comfort of vehicles on bridges.Taking the Hutong long-span cable-stayed bridge under construction as the engineering background,the coupling vibration of the train-bridge system is numerically analyzed based on the multi-body dynamic calculation platform Simpack and the bridge FE software Midas.The main research contents are as follows:(1)A whole bridge FEM is established according to the engineering background,load criteria,sectional parameters and constraints of the Hutong Yangtze River Bridge.The modal ananlysis is then carried out and the natural frequencies and their modes are obtained.(2)The CRH2 train vehicle model is established by the multi-body dynamics.The modal ananlysis is carried out.The numerical results are compared with those of the classical vehicle dyanmics.The results show that the vehicle model in this paper is with a high accuracy.(3)The data exchange between the train and the bridge model is realized by the whole process iteration method.According to the actual operation conditions,the dynamic responses of the vehicles and the bridge are calculated when the train passes through the bridge at the design speed of 200 km/h under single-train,double-train,tri-train and four-train running conditions.The results show that the vertical displacement of the bridge is much affected by the train gravity loading and increases with the increasing numbers of the vehicles on the bridge.The train live load has a few influences on the cable forces,and the maximum amptitude of cable force is about 3%of the initial value.Compared with different operation conditions,the maximum lateral and torsional responses of the bridge appears under the double-train running in the opposite direction and tri-train running condition.When the train passes through the bridge on different track,the closer the track is to the center line of the bridge section,the greater responses of the bridge,the smaller responses of vehicle.(4)Based on the theory of multi-flexible body,the DOFs reduction and the substructure analysis are carried out,and the flexible car-body is generated.The rigid-flexible train model is then established by combining the flexible car-body and the rigid bogies.The coupled train-bridge vibration is analysed to investigate the influence of the car-body flexibility on the dynamic responses of the bridge and the runnability of the train.The results show that the car-body flexibility has little influence on the dynamic response of bridge and the same to the derailment factor,lateral wheel/rail force and the offload factor.However,it much affects the vertical/lateral acclerations and Sperling factors,which decreases the running stability and riding comfort of the train on the bridge.The vertical acceleration spectrum of the car-body has more high-frequency components close to the natural frequencies while the low-frequency components changes a little.The main frequencies in the vibration spectra of the flexible car-body are more than those of the rigid car-body.The vibration characteristics of the car-body can be described more fully by adopting the flexible model,which is well in line with actual situation.