Shear behavior of large studs and novel bolted connectors in steel-UHPC composite beams

Abstract

With the gradual application of ultra-high performance concrete (UHPC), steel-UHPC composite bridges produce higher interfacial shear, which require larger diameter studs to avoid the group-stud effect of abundant small studs and accelerate the construction. Considering welding problems of larger studs, bolted connectors could be an alternative and benefit the replacement of composite bridges. The traditional bolted connector expressed early slip on the steel-UHPC interface due to the bolt-to-hole clearance, which reduced the composite action. To decrease the clearance, three novel bolted connectors involving a hinged bolt, a threaded-hole bolt, and a taper-sleeve bolt were proposed and tested along with large studs and traditional bolted connectors. The diameter of shear connectors ranged from 24 mm to 40 mm. Three failure modes were observed, in which the failure of the studs was significantly influenced by the welding quality. The shear capacities of the novel and traditional bolts with the same diameter were similar and unrelated to the bolt-to-hole clearance. The novel bolted connectors did not exhibit an early slip in load-slip curve and their stiffness was maximum 4.1 times that of the traditional bolt. The shear capacity and stiffness of shear connectors increased with their diameter. Six equations for predicting shear capacity and five equations for the shear stiffness of shear connectors were evaluated, the ductility of the studs and bolts were also assessed. The hinged bolt was evaluated to have a better comprehensive shear performance than other bolted connectors.