Analysis of longitudinal shear behaviour for composite steel and concrete slabs

The strength of composite slabs depends mainly on the strength of contact between the steel sheeting and concrete. In the article a method of analyses for strength of the horizontal section of the composite slabs based on the theory of built-up bars, which gives one an opportunity to assess strength and the rigidity of contact is presented. The proposed method evaluates the influence of both plastic deformations of the concrete layer and cracks in the concrete on the rigidity of this layer and of the whole slab as well. Performed investigations in deformations and strength of the contact between steel sheeting and concrete allowed one to explore the behaviour of the contact from the start of loading up to the failure. During contact testing, influence of pre-compression forces on deformations and strength of the contact were investigated. The strength of horizontal section in 6 fragments of composite slab with ‘Holorib’ type profiled steel sheeting was investigated experimentally. In tests the thickness of concrete layer of the slab and concrete strength varied. Theoretical calculations for the strength of a horizontal section of experimental slabs were made in this investigation. Calculations were performed according to the method proposed by us with the application of the method of built-up bars. In calculations, rigidity of the contact between steel profiled sheeting and concrete as well as equivalent rigidity of a concrete layer with cracks were evaluated. Experimental and theoretical results of the strength of the horizontal section in composite slabs were compared. Comparison of results revealed that their agreement was sufficiently good.