Experimental investigation of the bending behavior of ribbed composite slabs with UHPC liner

This study proposes a ribbed composite slab incorporating a UHPC liner and investigates its flexural performance through comparative tests considering three parameters: the presence of the UHPC liner, liner thickness, and arrangement of core materials. The flexural mechanisms were analyzed in terms of load-bearing capacity, flexural stiffness, and overall composite performance, and a three-stage calculation method for short-term flexural stiffness under service conditions was developed. The research results demonstrate that the flexural behavior of this type of composite slab is comparable to that of cast-in-place slabs; however, the UHPC liner provides superior tensile resistance, effectively sharing the tensile stress of the longitudinal reinforcement during loading, thereby significantly enhancing the load-bearing capacity and flexural stiffness. For slab thicknesses of 210 mm and 230 mm, the ultimate load-bearing capacity of ribbed composite slabs with a 20 mm UHPC liner increased by 15.22 % and 24.55 %, respectively, compared with specimens without a liner. Moreover, the 230 mm thick ribbed composite slab exhibited slightly better flexural performance than the 210 mm thick cast-in-place slab. Further analysis revealed that the thickness of the UHPC liner and the number of longitudinal tensile reinforcements in the ribs are important factors influencing flexural performance. Based on these characteristics, it is recommended that the short-term flexural stiffness of ribbed composite slabs be calculated using simplified cross-sectional models that separately account for the cracking states of conventional concrete and the UHPC liner.