Experimental study on shear performance of prefabricated HSS-UHPC composite beam with perfobond strip connectors

High-strength steel (HSS)-to-ultra-high performance concrete (UHPC) composite beams are highly competitive in prefabricated bridge constructions. This paper employs a four-point loading system to evaluate the load-bearing mechanism of prefabricated HSS-UHPC composite beams under shear loadings. Five large-scale composite beam specimens are prepared and tested, with variations in parameters such as steel plate perforation form, arrangement of perforated plate, UHPC slab width, and presence of slab tapered haunches. The composite beams' failure modes, shear stiffness, load-deflection behavior, strain profiles, and interfacial slippage characteristics are presented and discussed. Experimental results indicate that the prefabricated HSS-UHPC composite beams exhibit large shear stiffness and favorable ductility, and the composite beams with tapered haunches demonstrate a 26.9 % higher shear stiffness than those without. However, this improvement is accompanied by a 26.8 % reduction in initial cracking load, attributed to the upward movement of the neutral axis. Replacing circular holes in the perforated steel plate with puzzle-shaped openings increases the shear stiffness and ductility of the composite beam by 79.0 % and 47.4 %, respectively. Additionally, the adoption of double-row perforated plates further improves the shear performance of the composite beam due to the more intensive layout of PBLs in shear-span regions. The study also examines the applicability of existing codes and typical shear capacity formulas to HSS-UHPC composite beams and proposes a predictive model to calculate the shear capacity of the beams accurately. The proposed equations provide a reasonable methodology for determining the shear resistance of such composite beams.