Fatigue performance of hybrid FRP-concrete-steel double-skin tubular beams incorporating PBL connectors

Hybrid double-skin tubular beams (DSTBs) integrate an outer fiber-reinforced polymer (FRP) tube, annular concrete and an inner steel tube, demonstrating excellent mechanical performance and corrosion resistance. Hybrid DSTBs with Perfobond (PBL) shear connectors have been used in real applications as bridge girders and arch bridges in which fatigue is an important issue. This study investigates the static and fatigue behavior of hybrid DSTBs with PBLs and compares them to the same beams with headed stub shear connectors. The test results indicate that hybrid DSTBs with a smaller number of PBLs (i.e., four) exhibited similar static and fatigue performance to those with a greater number of headed stud shear connectors (i.e., twelve), in terms of failure modes, development of cracks and slips, and fatigue life. The fatigue life of hybrid DSTBs decreases with the higher upper load limits. To ensure a fatigue life of 2 million cycles, the fatigue limits of hybrid DSTBs with PBLs and headed studs are 80% and 81% of the load corresponding to the yielding of steel tubes, respectively. The findings offer not only new experimental evidence for the structural advances of DSTBs, but also practical insights into their design optimization and potential application in bridges and other long-span infrastructure requiring durable and efficient load transfer.