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Fatigue Performance Test and Numerical Analysis of Composite Girders with CSW-CFST Truss Chords

Composite girders with corrugated steel webs and concrete-filled steel tubular (CSW-CFST) truss chords are a new type of structure and have been used in bridges. To study the fatigue performance of these composite girders, model tests and numerical analysis were conducted, and the results compared with those for composite girders with corrugated steel webs and steel tubular (CSW-ST) truss chords. The results indicated that concrete-filling the chords constrained chord radial deformation and relieved hot-spot stress in the intersecting weld zones of composite girders with CSW-ST truss chords by 18.5–60.1%. The crack growth rates along both depth and length directions in composite girders with CSW-CFST truss chords were lower than those of composite girders with CSW-ST truss chords during the crack propagation and failure stages. Under the same fatigue load, concrete-filling the chords increased the fatigue life of composite girders with CSW-ST truss chords by 61.5%. Under the condition that there is no fatigue design S-N curve, the fatigue design S-N curve given in API can be used to evaluate the fatigue life of composite girders with CSW-CFST truss chords with a deviation of less than 17.4%.