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.

Premature fatigue cracking in the tube-gusset plate connection of longitudinal diaphragms has been observed in long-span cable-stayed bridges, resulting in undesirable stress distribution of the decks and costly repair efforts. Based on field inspection and finite-element (FE) simulation, this paper presents a diagnosis of the fatigue damage, and it is found that under the vehicle loads the connections are subjected to large stress cycles and significant stress concentration exists around the cope holes. The secondary stresses caused by bending result in different degrees of cracking among the eight locations of the diaphragm within a chamber. To mitigate such damage, several retrofit measures, including plug welding at the slot end, crack-stop holes, welded plates, and bolted channels, were applied. According to field observation and FE simulation, it is found that although the plug welding, crack-stop holes, and welded plates may slightly mitigate the cracking, they cannot significantly elongate...

This paper investigated the stress distribution of an adhesive layer for GFRP–steel bonded joints under 22.48 kN tensile loading using a three-dimensional numerical simulation. Firstly, a stress analysis of three paths was conducted, and after comparison, path II (through the middle layer of the bonding layer) was adopted as the analyzing path. Furthermore, a systemically parametric study of the effects of the FRP stiffness (i.e., elastic modulus and thickness), bonding length, adhesive thickness, and adhesive modulus was conducted. For the joints with different FRP elastic moduli, the minimum value of normal peeling stress was calculated as −3.80 MPa by the FRP for 10 GPa, showing a significantly severe stress concentration of FRP for 10 GPa. An analysis of the von Mises stresses proved that the increase in FRP stiffness could reduce the stress concentration of the adhesive layer effectively. The study of the effect of bonding lengths indicated that a more uniform peeling stress distribution could result from the longest bonding size; the largest peeling stress of 6.54 MPa was calculated for a bonding length of 30 mm. Further parameter analysis showed that the stress concentration of the adhesive layer could be influenced by the FRP thickness, bonding thickness, and elastic modulus of the adhesive layer.

Fiber-reinforced polymer (FRP)-retrofitted concrete structures are extensively utilized, and they have attracted growing research interest due to their combined performance in marine environments. To investigate the effect of seawater exposure, a total of 20 single-shear GFRP (glass-FRP)-bonded concrete structures were tested. Three corrosion conditions, i.e., exposure to single-salinity and triple-salinity seawater through wet–dry cycles as well as continuous immersion in triple-salinity seawater, were simulated and tested. The minimum shear strength (13,006 N) was tested using specimen B150-T-DW-90, which was cured in triple-salinity seawater with wet–dry cyclic exposure. The results of the shear strengths, load–displacement curves, interfacial shear stresses, and fracture energies indicated that seawater exposure degraded the bonding strength of the GFRP–concrete interface. Notably, the wet–dry cycles in triple-salinity seawater resulted in the most significant interface degradation, which could exacerbate with prolonged exposure. By introducing a parameter, the residual coefficient α, a new strength calculation model for GFRP–concrete exposed to a seawater environment was proposed and discussed.