Flexural Behavior of Steel-UHPC-NC Composite Girders with Different UHPC-NC Interface Treatments

Abstract

The interface shear-resistant construction method between ultrahigh-performance concrete (UHPC) and normal concrete (NC) is critical to ensuring the overall collaborative work performance and structural safety of steel-UHPC-NC composite girders (SUNCGs). However, the influence of UHPC-NC interface construction on the flexural performance of SUNCGs has not yet been explored. In this research, a flexural test in the positive moment regions was first carried out to study the impact of different UHPC-NC interface treatments on the SUNCGs. The test results showed that SUNCGs exhibited excellent flexural performance and higher flexural capacity than the steel-NC composite girder. In contrast to the interface shear failure observed in the SUNCGs with 3 and 6 mm roughened UHPC-NC interfaces, the SUNCG with 6 mm roughness and adequate shear reinforcement at the UHPC-NC interface fully exerted the combined action of its composite slab and ultimately failed in plastic bending. Besides, a finite-element analysis was also performed to further study the effects of interface reinforcement ratios and interface cohesion parameters. Finally, theoretical formulas for evaluating shear characteristics and determining the minimum reinforcement ratio at the UHPC-NC interface were proposed. The test results validated the applicability of these formulas for the shear design of the UHPC-NC interface in SUNCGs.