| With the improvement of China’s comprehensive national strength and the development of domestic railway transportation,the spans of railway bridges are also growing as well,in practical projects,railway lines will inevitably need to cross great valleys and wide rivers,and put forward higher requirements for the span of railway bridges.As a number of key projects such as Sichuan-Tibet railway are about to be implemented,many railway suspension bridges will be put into practice.However,characteristics of suspension bridge like small stiffness,prominent geometric nonlinear characteristics and highly susceptible to wind load threaten the safety of train operation and bridge structure.In view of this,it is necessary to study the safety of railway suspension bridge under adverse wind load and research on coupling effect and analysis method of wind-train-bridge of railway suspension bridge.This paper,based on the engineering example of Jinshajiang railway suspension bridge,explores the coupling analysis method and interaction characteristics of the wind-train-bridge coupling effects,and analyzes the parameters of external excitation,and explores the influence of different speed and wind speed on the dynamic response of the wind-train-bridge coupling system.The main research contents and conclusions are as follows:(1)For the situation that explicit expression of unstressed length of cable segment cannot be gotten in the cable basic equation,a dichotomy method is proposed to solve the unstressed length of the cable segment according to the monotonicity of the basic function of the cable segment.The method is simple in principle,few code,readable and highly accurate.It avoids the problems of no solution and complicated programming when using continued fraction numerical method or searching algorithm.Based on the calculation principle of cable shape finding of suspension bridge with segmented catenary theory and the numerical iterative method of influence matrix,a two dimensional cable shape finding calculation software is developed.A example is used to verify the correction of software and the results show that once the unstressed lengths of cables obtained by the software are used to build the finite cable element cable model,the displacement of the model can be control under 1mm.According to the file characteristics of input file of ABAQUS,the function of automatically generating ABAQUS input file is developed,which can automatically export the cable result to ABAQUS input file,so as to quickly build cable finite element model in ABAQUS,which greatly improves the modeling efficiency.(2)Based on the general finite element software,the static analysis model of Jinshajiang railway suspension bridge is established,and the geometric nonlinear static analysis of the structure is carried out.The longitudinal displacement of IP point on the top of the pylon is controlled within 1 mm,and the longitudinal horizontal force of the main span and side span is balanced,which verifies the accuracy of the static analysis model.On this basis,the influence of the orthotropic steel deck of the plate-truss composite structure on the respect of longitudinal force is explored.The vibration characteristics of the finite element model of Jinshajiang railway suspension bridge are analyzed.The first mode of the structure is the transverse swing of the stiffening girder,the frequency is 0.21 hz,the second mode is the vertical bending of the stiffening girder,the frequency is 0.34 hz,and the first ten modes of the structure are both transverse and vertical bending of the stiffening girder,which shows that the lateral bending resistance and vertical bending resistance of the structure are weak.Lateral oscillation is easy to occur under lateral wind load.(3)The fluctuating wind speed time history of each wind field simulation point on the stiffening girder of the suspension bridge is calculated by the string wave synthesis method.The aerodynamic three component coefficients of the bridge structure and the train of several working conditions are obtained by the numerical wind tunnel technology.The wind load time history of each wind field simulation point on the bridge and the train is obtained according to the wind load calculation theory.(4)Analyzing wind-train-bridge coupling effects through self-made software or ANSYS+SIMPACK are most commom ways now,but it is difficult for others to reproduce the analysis process for self-made software method and it is hard to consider geometric nonlinearity,this paper studies on how to establish wind-train-bridge coupling system of suspension bridge which considers its geometric nonlinearity through general CAE software ABAQUS.Use restart method to transfer standard static analysis result to the explicit analysis to take the static analysis equilibrium state of the bridge structure as the basis of the dynamic analysis of the vehicle-bridge coupling.Abaqus Python secondary development technology is used to batch wind load time history of trains and each simulation point of bridge.Hertz contact property is used to simulate the wheel rail contact relationship through surface to surface contact method,separation between wheel and rail is allowed.So far,the establishment of the coupling analysis system of wind-train-bridge based on ABAQUS is completed.(5)Wind-trian-bridge coupling effects under different working conditions are analyzed to explore dynamic response of trains and bridge when trains run on single line and double lines,the result shows: vertical acceleration and vertical wheel-rail force will increase rapidly when trains enter or leave the bridge,once the trains run faster,this problem becomes more serious.When the trains run into the bridge at the speed of 200km/h or 300km/h,the instantaneous vertical acceleration and wheel load reduction rate of the train exceed the code’s limit.When the train speed is reduced to 100km/h,train’s acceleration and wheel load reduction rate meet the code’s requirements,under all working conditions,the acceleration values of bridge structure are within the safe range. |
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