Suspenders are crucial load-bearing members of suspension bridges, and they are prone to fatigue damage under repetitive vehicle and wind loads. Field observation shows that short suspenders at the midspan or the ends of bridges may be more vulnerable. This study investigated the influence of using rigid central clamps on the fatigue performance of short suspenders, and two finite-element models of a long-span suspension bridge, with and without central clamps, were developed for comparison. Results show that central clamps can significantly mitigate the bending stress of short suspenders by reducing the relative motion between cables and the girder. Although wind-induced stresses of suspenders are smaller in amplitude than those induced by the vehicle load, the wind loads also contribute significantly to fatigue damage of suspenders because of the large number of stress cycles. Based on a vehicle-load model and the wind spectrum developed from field-monitored data, a fatigue life evaluation procedure was developed, and the fatigue lives of suspenders of the bridges with and without central clamps were calculated, respectively. Results suggest that when there are no central clamps, suspenders may have fatigue lives shorter than the design value.

Suspenders are critical force transmission components in suspension and arch bridges, which connect the girder to the main cable/arch. Field inspection indicates that short suspenders at the midspan or the ends of a bridge may be more prone to fatigue damage under cyclic traffic loads when coupled with the effects of corrosion. The damage has been frequently observed to occur at the lower ends of suspenders. To evaluate the safety of suspenders, a stochastic time-variant reliability assessment method is proposed, where the time-variant model for deterioration of steel wires and probabilistic critical limit states based on crack depth and failure area are integrated, so as to consider the combined effect of corrosion and cyclic loading. A case study on the suspenders of the Jiangyin Yangtze River Bridge was performed in which a finite-element analysis was conducted in conjunction with a comprehensive traffic model. The time-variant reliability indices of the short suspenders were obtained according to the proposed method, which resulted in recommendations for suspender maintenance and replacement.

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.