Properties of an innovative shear connector in a steel-concrete composite slab

Abstract The number of aging bridges in Japan is increasing, and steel-concrete composite slabs are commonly used in replacement work due to their durability and associated savings in construction time. Due to the limited capacities of existing bridge columns, replacement of the old bridge deck with a lightweight alternative is preferable. This study proposes an innovative steel-concrete composite slab with a thickness of 180 mm consisting of lightweight aggregate concrete (LWAC) and rectangular steel pipes (RSPs) as a new type of shear connector. The total weight could be reduced by about 20% from that of steel-concrete composite slabs. To investigate the shear properties of RSP, a push-out test was conducted on three specimens with static loading and five with fatigue loading. The static experimental results showed that the shear capacity of the RSPs could be determined by cracks, which occurred near the weld zone. Two failure patterns, RSP cracks and weld separation, were observed in the different specimens under fatigue loading. The static shear capacity was compared with the calculated results using different C-shaped and L-shaped channel specifications, and a headed stud number equivalent to one RSP was proposed. The S N curve of RSP was compared with that of the headed studs, and the fatigue performance appeared to be better than that of the studs when the shear stress was below 125 MPa. The changing trend in the slip rate and the normalised stiffness of the RSP when the fatigue loading cycles increased were investigated and formulated.