Fatigue reliability analysis for suspenders of a long-span suspension bridge considering random traffic load and corrosion

For suspension bridges, suspenders are critical load transferring components that connect girder to main cable, the safety of the suspenders conduces to maintain the structural integrity of the bridge. The cyclic stress and corrosion environment are the main reasons for the failure of suspenders. To evaluate the fatigue status of suspenders under the combined action of traffic load and corrosion, this paper presented a time-variant fatigue reliability analysis framework based on in-site measured traffic data and corrosive deterioration model for suspenders. First, the refined vehicle parameter models are established by statistical analysis. An elaborate random traffic flow model that involves car-following theory and Monte-Carlo method is developed. Then, a practical FEM-based method is used to simulate vehicle induced response time history. The fatigue loading effects, namely equivalent stress range and corresponding cyclic number are subsequently obtained. Finally, the time-variant fatigue reliability for suspenders considering corrosion and traffic growth is evaluated. A case study was performed for suspenders of an in-service sea-crossing suspension bridge in China. The results indicate that corrosion and growing traffic density would greatly shorten the service life of suspenders of a suspension bridge, among which corrosion has the most significant influence. Fatigue reliability index of the shortest critical suspender at 1/2 mid-span of the case bridge would lower than target value at the 18th service year in the most serious marine corrosion environment, which resulted in references for suspender maintenance and replacement.