Fatigue strength of welded transverse stiffener joints under variable amplitude loading

Long life fatigue tests are carried out using 2 m long plate girder specime ns with transverse stiffeners, under constant amplitude loading and two typ es of typical variable amplitude loading. Fatigue cracks are initiated from the fillet weld toe at the top and bottom ends of the stiffeners; which ar e the compression and tension areas of the girder, respectively. Fatigue cr acks in the tension area of the girders lead bottom flanges to failure, whi le those in the compression area are arrested in the vicinity of the weldme nt. Fatigue failure life of all specimens satisfies the Japanese standard c ategory code D with a sufficient margin under constant and variable amplitu de loading. Miner's law, either with or without cut-off limits, cannot eval uate the difference in fatigue life under two types of variable amplitude l oading, but it can be estimated accurately by variable amplitude fatigue cr ack propagation analysis using fracture mechanics concepts. (C) 1999 Elsevi er Science Ltd. All rights reserved.