Fatigue Characteristics Analysis Of High-Speed Railroad Steel Pipe Concrete Tied Arch Bridge

With China’s economic development,new infrastructure has rapidly emerged nationwide.High-speed railroad bridges have garnered significant attention,particularly the prevalent use of steel pipe concrete arch bridges due to their favorable stressing properties.Statistics indicate that 80%-90%of structural damage is fatigue-related.Therefore,it is imperative to conduct further research on the fatigue characteristics of steel pipe concrete tied arch bridges subjected to reciprocating train forces.This research aims to ensure the operational safety of these bridges and identify key areas for future bridge maintenance.The technical approach of this paper is to select a high-speed railroad steel pipe and concrete tied arch bridge as the research object,and to evaluate the fatigue characteristics of this bridge based on the results of the static force check and fatigue calculation based on the numerical simulation method.The main research contents are as follows:（1）To establish a finite element model of a high speed railway steel pipe and concrete tied arch bridge,to perform static analysis of the bridge in all parts of the structure and to perform strength check calculations,and to compare the calculation results with the specification.（2）The vehicle load is applied to the bridge model with reference to the code and using two loading methods,and the stress simulation results of each part are compared to obtain the most stressful part of the bridge.（3）The bridges were loaded with standard fatigue vehicles by time-course analysis,and their stress performance under different working conditions was analyzed;the results were compared to further confirm the dangerous parts of the bridges and the fatigue loads.（4）A local model of the arch footing was established by Midas/FEA and loaded with fatigue load to obtain the fatigue life and damage degree of the local model.The fatigue life of each component of the arch footing under different stress levels was investigated by least squares regression analysis.Based on the above study,the strength calculation results of all parts of the bridge are in accordance with the specifications;the stress performance of each working condition and each part of the bridge is similar under two different vehicle loading methods;the arch foot and the beam end cross-section are the dangerous parts prone to fatigue damage;the fatigue numerical simulation analysis reveals the intrinsic connection between the fatigue life of the local model of the arch foot and the fatigue load stress level:fatigue life There is a strong negative correlation between the fatigue life and the maximum stress level S_max.When the stress level S_max≤0.40,the fatigue life is large and satisfies the infinite life use state,and no attention can be paid to the structural fatigue problem at this time;at 0.40<S_max≤1.00,the fatigue constant life decreases with the increase of stress level.When the fatigue stress level S_max>1.00,the fatigue life of the local model decreases by about 90%,and the degree of damage is larger.