Experimental and Numerical Study on Flexural Behaviors of Steel-UHPC Composite Beams under Hogging Moment

The cracking resistance was a significant factor influencing the design load of composite beams. According to previous studies, the cracking load reached only 14–40% of the ultimate load when steel-UHPC composite beams in the hogging moment, and the risk of cracking remained. A new perfobond rib shear (PBL) connector was proposed further to improve the cracking resistance of steel-UHPC composite beams. Bending behaviors were researched by analyzing the crack distribution, failure mode, and load-deflection curve for composite beam. At failure, the steel beam flange buckled significantly, and three cracks penetrated through the UHPC board at the pure bending section. Additionally, the excellent slip resistance of the new PBL connector was validated in a push-out test. The failure mode of the push-out specimens was the fracture of the perforated reinforcement. During the push-out test, no cracks were observed on the UHPC boards. Besides conducting experiments, exploring the influence of the headed stud and new PBL connector on the composite beam by numerical analysis. The numerical results proved that the new PBL connector could release tensile stresses in the UHPC slabs and enhance the cracking properties of composite beams.