Research On Vehicle-Bridge Coupling Vibration Of Multitower Partially Cable-stayed Bridge

With the continuous development of the transportation industry,highway vehicles are gradually developing in the direction of heavy load and high speed,bridge spans are getting larger and larger,bridge structures are getting thinner and lighter,and the problem of vehicle-bridge dynamic interaction has become more prominent.The safety of bridge structures under the load of moving vehicles has always been a concern of scholars and engineers.Especially for some cable-stayed bridges that have only been developed in the past 30 years,people’s research has focused more on static in the construction phase.For force analysis and seismic analysis during the completion of the bridge,there are relatively few studies on the vehicle-bridge coupled vibration of some cable-stayed bridges,and most of them are researches on the vehicle-bridge coupled vibration of railway partial cable-stayed bridges.To this end,this paper uses an actual five-tower partial cable-stayed bridge as the engineering support.Based on a numerical recursive analysis method with approximate initial conditions,the dynamic response and power amplification factor of each component of the bridge when single-row vehicles and multiple-row vehicles pass by are expanded.The main work and conclusions are as follows:(1)Based on the engineering construction drawings,ANSYS was used to establish a three-dimensional bridge finite element analysis model,the first ten modes and frequencies of the bridge were obtained,and its natural vibration characteristics were analyzed.(2)Three commonly used models of ordinary cars,trucks and trucks are selected,and the structural dynamic response and power amplification factor of a single vehicle passing through the bridge are calculated and analyzed under multiple working conditions.Taking into account the influence of factors such as vehicle model,vehicle weight,vehicle speed,bridge deck grade,cable tension,and bridge structural system,the results show that the impact of vehicle model on structural dynamic response is mainly reflected in vehicle weight.As the vehicle weight increases,the structure The dynamic response also increases;the influence of vehicle speed on the dynamic response of the structure does not show obvious regularity.In contrast,as the level of bridge deck flatness decreases,the dynamic response of the structure increases significantly.By increasing or decreasing the cable force of the full bridge by the same extent,it is found that with the increase or decrease of the cable force,the dynamic response of the structure and the dynamic amplification coefficient do not show a monotonous increase or decrease.Fluctuate within a certain range.The influence of the bridge structure system on the dynamic response of the bridge is obvious.Under the same conditions,the dynamic displacement and bending moment of the rigid frame system with the tower beam and the pier are smaller than the continuous beam system.(3)Based on the calculation results of static load loading efficiency,calculate and analyze the dynamic amplification factors of the towers,beams,and piers when the static load loading efficiency is maximum for single-row and multi-row vehicles,and compare the dynamic amplification factors in the current bridge design specifications.The comparison of coefficient values shows that if only single-row vehicle loading is used in the analysis of vehicle-bridge coupled vibration,on the one hand,the calculation result of the power amplification factor will be too large;on the other hand,due to the single-vehicle loading effect and the design lane The load loading effect is quite different.If the calculated value of the dynamic amplification factor is compared with the standard value,it is not convincing and does not match the actual situation.Therefore,when selecting the vehicle loading method,it should be determined in conjunction with the design lane load effect in the specification,and strive to achieve the same or similar static load effect as the design lane load in the layout of the loaded vehicle.In addition,the dynamic amplification coefficients of different components are different.If a method of uniformly adopting a dynamic amplification coefficient value for the full bridge in the specification,the dynamic impact effect of a certain component may be underestimated,which is not conducive to the force of the structure.To be safe,it is recommended that different components adopt different dynamic amplification factors to consider the dynamic impact caused by the vehicle load when designing the bridge.