Fatigue Reliability Analysis Of Steel-concrete Composite Girder Bridge Based On The Vehicle-bridge Coupling Vibration

Steel-composite beams have the advantages of light dead weight,high stiffness,high strength and good ductility,etc.Since the 1950 s,steel-composite beams have been widely used in the bridge field.Steel-concrete composite girder bridge is affected by external factors such as vehicle load during its service.in the service process of steel-concrete composite girder bridge,the fatigue cracking phenomenon may occur in the design reference period,and even cause the collapse of the bridge.Therefore,considering the coupling vibration between the vehicle and the bridge,it is necessary to analyze the fatigue service life of the steel-concrete composite girder bridge according to the fatigue reliability theory,so as to provide theoretical support for the steel-concrete composite girder bridge in normal service under certain fatigue reliability index.Based on the engineering background of Fu Tu Yu Bridge,the fatigue reliability of the key structural details of the mid-span section of steel-concrete composite girder bridge under the coupling action of vehicle and bridge is studied as follows:(1)Fatigue vehicle model in AASHTO bridge design code is adopted to establish vehicle vibration equation and bridge vibration equation.Vehicle-bridge coupling vibration equation is established through displacement coordination condition and force balance condition,and Newmark-β method is used to solve vehicle-bridge coupling vibration process.Matlab software is used to simulate the roughness of the bridge deck,and the roughness analysis samples are obtained.(2)The finite element models of Fu Tu Yu bridge and American bridge design code are established by using ANSYS to simulate the whole process of standard fatigue vehicle from the upper bridge to the lower bridge.(3)The stress time history and stress amplitude of the key structural details of the mid-span section under vehicle vibration load were studied.The limit state equation was obtained based on the Miner linear cumulative damage criterion,S-N curve and structural reliability theory.The relationship between the fatigue reliability index of the key structural details of the mid-span section and the service life of the bridge was calculated.(4)The influence rules of bridge deck irregularity,overloaded vehicles,vehicle speed and annual traffic volume growth rate on fatigue reliability of bridge are analyzed,the relationship between the fatigue reliability index of different key structural details and the service life of the bridge under different operating conditions is obtained.