Dynamic Response Of Cable-Stayed Bridge And Related Problems Based On Vehicle-Bridge Coupling

The development of the auto transportation turns toward to the direction of high speedand heavy load and the bridge to the direction of large span,light weight,flexibility,which makes the coupling effect of vehicle and bridge more and more obvious. Then, some problems will arise, such as the frequency variation of vehicle-bridge system and the dynamic response caused by the vehicle-bridge coupling system which will much greater than the static load. These problems will cause damage, fatigue and cracking of bridge structure and reduce bridge structure life, safety reliability and vehicle operating comfort. Based on the project financed by the National Natural Science Foundation of China, named "a three-dimensional coupled vibration analysis method of highway bridge based on cell automatic locomotive flow" (project approval number: 51208125), the dynamic response of cable-stayed bridge and related issues are discussed, the main contents are as follows:(1) Random flow simulation based on cellular automationThe cellular automata model is introduced to simulate the random flow on the highway bridge. The model considers the rules of vehicle operation and the vehicle lane changing rules in the lane, as well as the acceleration, deceleration, lane changing and overtaking of vehicles in the traffic flow. The random flow under different speed limit and traffic density is studied.The results are compared with the vehicle aerial chart in the literature to verify the correctness of the model.(2) Analysis of Vehicle-Bridge Coupled Vibration Based on Random Vehicle FlowBased on the FEM software ANSYS, the 3D vehicle-bridge coupled system is studied.The vehicles and bridge are modeled independently, APDL is used to consider the interaction between vehicles and bridge. Some factors are discussed for the vibration response of vehicle-bridge system, including traffic density and speed limit. The results show that the traffic density and speed limit have a great influence on the coupling response. The displacement of bridges with higher traffic occupanciesis significantly larger than lower traffic occupancies. With the increase of speed limit, the displacement of bridge is also increasing.(3) Time variant natural frequencies of a roadway bridge under Stochastic vehicle flowThe frequency equations of the beam - fixed mass system and the the beam-moving mass system under several boundary conditions are deduced. Comparing the frequencies between the beam - moving mass system and the beam - fixed mass system, the results reveal that the beam - moving mass system can be replaced by the frequency of the beam _ fixed mass system. Based on this conclusion, the time - varying frequency of the traffic - bridge system is studied based on the traffic flow. The first three vertical bending frequencies are summarized and the conclusions are as follows: The on-load frequencies of the bridge were less than the corresponding natural frequencies of the bridge.In general,with the increase of traffic density,the natural frequencies of the traffic-bridge system are reduced.(4) Reliability evaluation of cable based on vehicle-bridge couplingBased on the results of traffic flow-bridge coupling analysis, the stress time-history of the structural members are obtained. The stress histograms are obtained and the equivalent stress amplitude are calculated by the rain flow counting method. Based on the S-N curve and Miner theory, the fatigue life and fatigue reliability of the bridge are analyzed.The influence of the traffic density on the fatigue life and fatigue reliability of the cable are discussed in the paper.