Experimental study on fatigue strength of trapezoidal corrugated-web steel girders based on hot spot stress method

• Static and constant amplitude fatigue tests were conducted on four groups (a total of 20) of trapezoidal corrugated-web steel girders (TCWGs). • The normal stress distribution in the flange and the hot spot stress concentration factor (SCF) at S-point (the location of fatigue crack initiation) of TCWGs were measured in detail. • The fatigue failure modes, fatigue crack at S-point, and crack propagation processes of TCWGs were investigated. • A unified fatigue design S-N curve, based on the hot spot stress range, was proposed for TCWGs with different geometric parameters. Corrugated-web steel girders (CWGs) significantly reduce the use of transverse stiffeners and avoid the fatigue problems associated with the web, in contrast to flat-web girders (FWGs). However, alterations in the web profile induce an uneven normal stress distribution in the flange, introducing an additional fatigue problem. This study experimentally investigates the static and fatigue behaviours of 20 trapezoidal corrugated-web steel girders (TCWGs) with four groups of different geometrical dimensions under a four-point bending load. Static test results indicate that in cross-sections with parallel and inclined web folds, normal stresses in the flange exhibit a linear variation along the width direction in both constant bending and combined bending-shear regions. Reducing the corrugation angle and length, and increasing the corner radius, contributes to a decrease in the stress concentration of TCWGs. Fatigue test results reveal that, among the 20 TCWGs showing fatigue failure, 85% of the initial cracks originate at the S-point in the tensile flange, while the remaining specimens exhibit cracks at the web weld toe. Varied crack propagation processes were observed at different crack initiation points. Cracks originating at S-point first progress along the flange thickness and width, eventually propagating upward along the weld to a minor height on the web. For cracks originating at the weld toe on the web, propagation does not proceed along the flange thickness and width initially; instead, it penetrates through the web thickness and propagates diagonally along the web height direction to a certain distance. Finally, utilising the hot spot stress range, a combined regression of the fatigue test data from this study and other studies was performed to propose the design S-N curve (log N = 12.645-3logΔ σ hs ) for TCWGs experiencing S-point fatigue failure. This curve can be applied to calculate the fatigue strength of TCWGs with varying geometrical dimensions.