Rib-to-deck joints of orthotropic steel decks (OSDs) in steel bridges are susceptible to longitudinal fatigue cracking, which often results in considerable repair costs as well as traffic interruption. To mitigate such cracking, a strengthening method using externally bonded fiber-reinforced polymer (FRP) angles was investigated. Seven OSD specimens were tested and subjected to pure bending to evaluate the effectiveness of the strengthening. The influences of different FRP materials, adhesives, and angle dimensions on the fatigue lives of rib-to-deck fatigue details were experimentally studied. It is demonstrated that the proposed method can significantly reduce the hot-spot stress ranges in the vicinity of welded details and elongate their fatigue lives. Ductile adhesive with higher strength and angles with longer legs would help improve the fatigue performance by delaying the occurrence of debonding between angles and OSD specimens. It is also observed that carbon FRP angles are more effective than glass FRP ones, due to their higher elastic modulus. Besides, FRP angles with stiffeners can further increase the fatigue life of the details due to the additional stiffness, if debonding could be avoided or delayed. Finally, numerical analysis validated the beneficial effect of different FRP-based strengthening measures on the stress intensity factors at crack tips. This study provided a reference to the design and application of externally bonded FRP angles in the strengthening of weld details in OSDs.
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