Experimental investigation for structural parameter effects on fatigue behavior of rib-to-deck welded joints in orthotropic steel decks

Various fatigue cracks occurred in orthotropic steel decks have been reported in the last decade. The fatigue cracks initiated at the weld root of the fillet weld of rib-to-deck plate were investigated in this study. The fatigue behaviors were investigated by performing 19 full-scale fatigue tests, which conducted on six types of orthotropic steel decks with different structural parameters. The fatigue cracking patterns and their influence factors were discussed by comparing the crack propagation angles, crack lengths and depths of the cracked section. Meanwhile, the cracking mechanism and stress responses around root tip were analyzed by establishing elastic finite element models, and verify with fatigue tests results. The results of the experimental analysis demonstrated that fatigue cracks did not occur where the stress ranges were purely compressive, it was considered the welded joint might under the low tensile residual stress so that the effective stress range was reduced. Similarly, the magnitude of tensile stress range would play a decisive role during the root crack propagation. It was found that increasing the penetration rate had the beneficial effect of preventing root cracking. There was also a significant improvement in the fatigue durability when the deck plate thickness was increased from 12 mm to 16 mm. Finally, some special treatments in welded joint such as: the grinding at weld toe could avoid crack at toe but might lead to a deeper root crack, and the press straighten could be an effective treatment for preventing root cracks propagating in depth.