Experimental research on flexural behavior of reinforced concrete composite slab connected without gap

Ten simply supported slabs were tested under static loading to investigate the failure mode, stiffness, crack and bearing capacity of reinforced concrete composite slabs connected without gap. The tie-and-strut model of indirect lap of longitudinal reinforcement was used to analyze the quantitative relationship between lattice girder and longitudinal reinforcement. The research results indicated that the composite slab connected without gaps can be split easily along the interface between the old and new concretes, and that the bearing capacity of normal section and average stiffness were lower than those of cast-in-place slab. It was found that setting lattice girders across the seam could effectively control splitting failure and enhance the stiffness and bearing capacity perpendicular to the joint. When the distance between the lattice girder and the seam was equal to the thickness of the slab, splitting failure of specimens did not occur along the interface between the old and new concretes, and the bearing capacity of normal section was 6% lower than that of cast-in-place slab but 9%-18% larger than the calculated value. Design suggestions and construction requirements of the two-way composite slab connected without gap were proposed, based on the research results and the relevant national and international standards. © 2019, Editorial Office of Journal of Building Structures. All right reserved.