Multi-factor Coupling Analysis Of Impact Coefficient Of Continuous Beam Bridge With Equal Span

Transportation integration development is an important part of Beijing-Tianjin-Hebei integration development strategy.However,due to the unbalanced development of history and other reasons,many bridges in Tianjin and Hebei have been built for a long time,and the physical damage of the bridge body has gradually deepened,which has caused great hidden dangers to the traffic safety of vehicles on the bridge.Because the impact of vehicles on bridges is the most important factor of bridge damage,it is very important to understand the change law of impact under different influencing factors and to fit the calculation formula of impact coefficient considering various influencing factors from the law.In this paper,based on wave theory and UM simulation software,the impact coefficients of equal-span continuous girder bridges are studied in terms of vehicle speed,vehicle weight,bridge fundamental frequency(bridge span length),headway spacing and other factors.According to the actual traffic conditions of bridges,the formulas for calculating the impact coefficients considering the combined effects of the above four factors are discussed for bridge designers and engineers.Technical staff reference.Firstly,the two-dimensional wave equation is deduced based on wave theory,and an example is used to analyze it.The advantages of dynamic analysis using wave equation are discussed by comparing the results of wave equation and finite element simulation.Then the vehicle-bridge coupling vibration simulation models of continuous girder bridge and simple-supported girder bridge are established by using ANSYS and UM software respectively.The impact coefficients of different vehicle types in two lanes are discussed from four angles of vehicle speed,vehicle weight,bridge fundamental frequency(bridge span length)and headway spacing.Finally,through regression analysis,the fitting formulas of impact coefficients of equal-span continuous girder bridges and simple-supported girder bridges considering the above-mentioned factors are given.According to the above research ideas,the impact effect of vehicle-bridge coupling is analyzed.It can be concluded that: 1)The calculation results of vehicle-bridge coupling of simply supported slab bridge by using two-dimensional wave equation are reliable;2)Through simulation calculation with UM software,it is known that the impact coefficient is affected by vehicle speed under different influencing factors,and the maximum impact coefficient is different for different vehicle types;3)The impact coefficients of continuous girder bridges and simply supported girder bridges increase with the increase of vehicle weight.The closer the fundamental frequency of the bridge approaches the natural frequency of the vehicle,the greater the impact coefficients of the bridge.Under these conditions,the impact coefficients of the continuous girder bridges formed by two vehicles are two times larger than that of the continuous girder bridges when one vehicle is driving;4)For continuous girder bridges and simply supported girder bridges,the maximum impact coefficient of traffic flow is determined by the maximum impact coefficient of vehicles with the greatest load on the bridge,whether in single or double lanes;5)The impact coefficient calculated by the fitting formula of continuous girder bridge considering various factors and the impact coefficient calculated by the fitting formula of simply supported girder bridge are more in line with the actual situation than the impact coefficient calculated by the standard formula.These two fitting formulas can be used as reference for bridge design.