Fatigue crack detection and evaluation in a welded steel girder highway bridge

Fatigue-induced cracking is a common failure mode in many steel bridges reaching their original design life. These aging bridge structures have experienced increasing traffic volume and weight, deteriorating components, as well as a large number of stress cycles. This paper presents a case study of fatigue assessment of an interstate highway steel bridge through real time monitoring under traffic. The bridge is a single-span, composite steel I-girder structure with K-type cross frame diaphragms. The study also included numerical analysis using 3D global and local finite element models. Based on the simulated traffic flow, statistical dynamic responses such as displacements and stress-ranges of bridge girders were studied for the cause of fatigue cracks that occurred in some cross frame connections. Meanwhile, long-term field monitoring has also been conducted. Based on the information from field tests, simulated numerical analytical results were verified. Thus, the performance of highway bridges under truck load can be predicted in a more realistic way to estimate the fatigue performance of highway bridges.