ANALYSIS OF DEFLECTIONS UP TO FAILURE OF COMPOSITE STEEL FIBERREINFORCED CONCRETE SLABS

Analysis of experimental and theoretical results of investigation into deflection of composite steel-concrete slabs is presented in the paper. Profiled steel sheeting (Holorib type) and steel fiber-reinforced concrete were used for specimens. For two slabs, the layer of concrete was reinforced with steel fiber, whereas the rest of them were not reinforced. Slabs were tested under static short-term load. The experimental investigation revealed that the use of steel fiber in composite slabs was effective. The meanings of deflections under the action of the bending moment M ≈0.6MR (where MR is the bending moment at failure of the slabs) were by 16–18% lower in the slabs with a steel fiber-reinforced concrete layer than in the slabs with a common concrete layer. The deflection of composite slabs directly depends on the rigidity of the shear bond between the profiled steel sheeting and the concrete layer. The method for the deflection analysis in composite slabs is based on the built-up bar theory. Influence of a cracked concrete layer on the deflection of the structure and plastic deformation in the compression zone of this layer are evaluated by this method. Furthermore, it evaluates the stiffness of separate layers and the stiffness of the shear bond between the profiled steel sheeting and the concrete layer. Experimental investigation was performed for determination of the shear characteristic for the bond between the steel sheeting and the concrete layer. Therefore, specimens were made of the same concrete mixture as that of the slabs. Theoretical analysis of deflection for the composite slabs was made. When the value of the bending moment is close to the service load M ≈0.6MR, agreement of the results of analysis with the experimental ones is sufficiently good. Ratio of the theoretical values to the experimental ones varies within the limits of ωobs / ωcall=1.01–1.03 for slabs with a usual concrete layer, and the ratio of ωobs/ ωcall=0.99–1.02 for slabs with a concrete layer reinforced with steel fiber.