Flexural Behavior of Steel-UHPC Composite Beams with Waffle Slabs under Hogging Moment

This paper investigates the flexural behavior of steel-UHPC composite beams with waffle slabs (SUCBWS) under hogging moment. A three-point, reduced-scale flexural test was performed to investigate the effect of reinforcement ratio and partially filled UHPC in the compressive flange of the steel beam. The parameters, including the force ratio R, the laying length L-pfu, and thickness H-pfu of partially filled UHPC, were analyzed. A theoretical formulation was proposed to calculate the flexural capacity of SUCBWS under the hogging moment. The results show that the increase of reinforcement ratio and partially filled UHPC in the compressive flange of steel beam can improve the crack resistance and the flexural capacity of SUCBWS under the hogging moment. Force ratios of 0.22 and 0.48 are recommended for SUCBWS and partially filled steel-UHPC composite beams with waffle slabs (PFSUCBWS), respectively. It was also found that the reasonable laying length and thickness of partially filled UHPC should not be less than 0.5 times the clear span of the specimen (0.5l(0)) and 0.2 times the web height of the steel beam (0.2h(w)), respectively. The theoretical predictions based on the proposed formulas are in good agreement with the test results and numerical results.