Experimental study on the performance of shear connections between local UHPC slabs and GFRP girders

This paper proposes a novel fiber-reinforced polymer (FRP)-concrete hybrid system with local ultrahighperformance concrete (UHPC) in key parts to accelerate construction and reduce the cost of UHPC. Fifteen push-out specimens were tested to investigate the shear behavior of the UHPC-FRP hybrid interface embedded with bolts in a local UHPC slab. The parameters varied were the local UHPC width, types of concrete slabs, bolt diameter, bolt number and bolt embedding length in concrete. Push-out test results showed that (1) the increase in bolt embedding length substantially reduced the bearing capacity, with a maximum reduction of 25.8%; (2) the interfacial bearing capacity and rigidity increased significantly with increasing bolt diameter, while the excessive diameter may cause the failure of GFRP flange shear-out; (3) the increase of the number of bolts improved the interface performance, but decreased the efficiency of a single bolt utilization; (4) the employment of local UHPC increased the slip stiffness by 16.9%, which had similar shear performance to that of the whole UHPC slab; (5) further changing the local UHPC width had little effect on the shear performance of the push-out specimens. Finally, the calculation method of the bolt shear bearing capacity considering the influence of the embedded length was proposed by modifying the existing formula.