Fatigue Damage Analysis Of RC Arch Bridge Under Vehicle-Bridge Coupling Vibration

In the whole transportation system of China,reinforced concrete bridges dominate,accounting for about 90% of the total number of bridges.Reinforced concrete arch bridges are widely used in the southwest of China because of their low cost,great bearing potential and convenient construction.In recent years,due to the rapid economic development and the rapid development of transportation industry in China,the operating environment of highway and bridge has changed greatly,the level of vehicle load has increased significantly,and the fatigue problem of bridge structure has become increasingly prominent.Therefore,in the first chapter of the General Design Code for Highway Bridges and Culverts,the design and service life of integral structure and partial components of bridges are specifically specified,but no speci fic estimation method is given.The bridge is subjected to long-term repeated action of vehicle loads during the whole service period.Vehicle-bridge coupling vibration under vehicle loads is the main cause of bridge fatigue damage.Therefore,fatigue damage analysis of reinforced concrete arch bridges under vehicle-bridge coupled vibration conditions has very important theoretical significance and practical value.The main contents of this paper are as follows:(1)The modal synthesis method is selected as the analysis method of vehiclebridge coupling.Based on the principle of mode superposition,the modal dynamic equilibrium equation expressed in the regular coordinates of bridge structure is obtained.The dynamic equilibrium equation of a two-axle 7-DOF space vehicle model is established based on the D’Alembert principle.The mass matrix,stiffness matrix and damping matrix of the vehicle model are obtained.Finally,the dynamic equilibrium equation of vehicle-bridge coupling is deduced.(2)The methods of fatigue analysis and the cumulative theory of fatigue damage are summarized and compared.The Palmgren-Miner linear cumulative damage theory can be applied to the fatigue damage analysis of reinforced concrete arch bridges.Based on the experimental study of reinforced and concrete materials,the S-N curves of the two materials in the fatigue analysis of reinforced concrete arch bridges are determined.(3)The formulation method of vehicle load spectrum is studied,and the vehicle load spectrum suitable for fatigue analysis in this paper is determined.Based on the mathematical model of random traffic flow obedience,a program for generating random traffic flow is developed by Monte Carlo method in MATLAB.Two loading modes are provided for bridge fatigue damage analysis.(4)With the help of ANSYS,the finite element model of the arch bridge is established,and the modal analysis of the bridge is carried out,and the key section of fatigue analysis is determined.Three kinds of fatigue vehicle models in the fatigue vehicle load spectrum are established by the vehicle-bridge coupling analysis program Dynlab,and the vehicle-bridge coupling vibration analysis is realized.Based on the S-N curve of steel bar and concrete and the principle of linear fatigue cumulative damage,the fatigue damage calculation and residual life prediction of reinforced concrete arch bridge are finally realized.Finally,the factors affecting vehicle-bridge coupling vibration are discussed.