Experimental Study on the Flexural Performance of Grooved-Connected Truss-Reinforced Concrete Composite Slabs

To address the conflicts between traditional composite slab reinforcement layouts and supports—which adversely affect construction quality and efficiency—and to fill the theoretical gap regarding end connections without projecting bars in terms of interface shear transfer, staged flexural behavior, and anchorage reliability, a grooved end-connection configuration for composite slabs is proposed. In this configuration, the longitudinal bars of the precast slab do not extend beyond the slab end. The precast slab end is formed with a recessed–protruding profile; the longitudinal bars are exposed within the groove, where additional reinforcement is pre-embedded (with a diameter not less than the area-equivalent of the longitudinal bars that would otherwise extend into the support). After erection, the additional bars are extended using straight-thread sleeves; short longitudinal bars within the groove are tied to the bottom longitudinal bars. Both the extended additional bars and the short longitudinal bars are anchored into the support by at least 5d and pass the support centerline. To evaluate the global flexural behavior of slabs with grooved end-connections, a two-span, full-scale specimen was tested under static loading. Failure characteristics, crack initiation and propagation, ultimate capacity, deflection, and ductility were investigated. The results indicate that, in the full-scale two-span test, the service load was 11.35 kN/m2 (approximately 13.5% higher than the design value of 10.0 kN/m2); the midspan deflection was about L/110 (smaller than the L/50 limit); the first cracking and the pronounced nonlinearity inflection point occurred at approximately 4.25 kN/m2 and ≥9.35 kN/m2, respectively; and the maximum crack width was 1.66 mm. The test was terminated prior to reaching the durability and deformation limits, after which the load was increased to 22.20 kN/m2. The specimen exhibited a ductile flexural failure governed by tensile reinforcement yielding; the top concrete did not crush, no shear failure was observed at the ends, and no delamination occurred at the composite interface, demonstrating favorable global flexural performance.