Fatigue tests of slender-web hybrid plate girders under combined moment and shear

Fielding, David Joseph, 1944-
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Fatigue tests of thirteen slender-web welded hybrid plate girders are described. The girders were tested under loading that produced a maximum flange stress of 50 ksi and a shear stress of about 12. 5 ksi. The girder flanges were constructional alloy steel with a minimum yield point of 100 ksi, and the webs were carbon steel with a minimum yield point of 36 ksi. The objectives of this investigation were: (1) to obtain fatigue data for hybrid girders and (2) to determine the effects on fatigue life of the test parameters: (a) flange stress range, (b) web slenderness ratio β (ratio of web depth to thickness), and (c) transverse stiffener length. From the test data a relationship is indicated between flange stress range and fatigue life in the form of an S-N curve. It is concluded that the shorter stiffeners investigated were detrimental to fatigue behavior due to their inability to actually stiffen the web. It was further found that girders with lower web depth to web thickness ratios develop cracks at the compression flange-to-web connection later than the girders with higher ratios.