Prefabricated steel-concrete composite beams with distributed Y-shaped connectors embedded in UHPC: experimental investigation and analytical model

The concept of prefabricated steel-concrete composite beams (PSCCBs) in bridge engineering provides innovative insights into the design of composite beams. To further enhance the interfacial shear behavior and overall flexural performance, improve construction quality, and reduce material usages of steels, a novel PSCCB with distributed Y-shaped connectors embedded in ultra-high-performance concrete (UHPC) was proposed. To investigate the flexural performance of PSCCBs with distributed Y-shaped connectors, bending tests were performed by varying degrees of shear connection and connection types. The failure modes, deflections, interfacial slip, vertical separation, and strain distributions of main cross-sections were discussed. Then, a universally applicable flexural stiffness model for PSCCBs with different configurations of shear connectors was proposed using the energy equivalence method, with the effect of interfacial slip properly considered. The test results indicated that PSCCBs with distributed Y-shaped connectors exhibited typical flexural failure and superior resistance to interfacial slip and vertical separation. The flexural stiffness of the PSCCB with Y-shaped connectors and a degree of shear connection of 0.66 was 12.0% larger than that of the steel-concrete composite beam (SCCB) with traditional continuously arranged perfobond rib (PBL) connectors. The PSCCB with a lower degree of shear connection but a larger area of UHPC shear pocket in the pure bending section exhibited 31.5% higher ductility than the SCCB with traditional continuously arranged PBL connectors. The universally applicable theoretical model accurately predicted the flexural stiffness of PSCCBs, providing valuable guidance for the design of PSCCBs.