Investigations on Efficiently Interfaced Steel Concrete Composite Deck Slabs

The strength of the composite deck slab depends mainly on the longitudinal shear transfer mechanism at the interface between steel and concrete. The bond strength developed by the cement paste is weak and causes premature failure of composite deck slab. This deficiency is effectively overcame by a shear transferring mechanism in the form of mechanical interlock through indentations, embossments, or fastening studs. Development of embossment patterns requires an advanced technology which makes the deck profile expensive. Fastening studs by welding weakens the joint strength and also escalates the cost. The present investigation is attempted to arrive at a better, simple interface mechanism. Three types of mechanical connector schemes are identified and investigated experimentally. All of the three shear connector schemes exhibited full shear interaction with negligible slip. The strength and stiffness of the composite slabs with shear connectors are superior about one and half time compared to these of the conventional reinforced concrete slabs and about twice compared to these of composite slabs without mechanical shear connectors. The scheme2 and scheme3 shear connector mechanisms integrate deck webs and improve strength and stiffness of the deck, which can effectively reduce the cost of formworks and supports efficiently. 1. Introduction Cold formed profiled steel sheets with embossments are widely used for composite floor decking systems in multistoried steel buildings wherein they remain permanently placed as an integral part of the floor system. The metal sheet performs as the formwork for concreting and as the primary tension reinforcement. The composite deck flooring results in faster construction and lighter floors. It also performs as a good ceiling surface and a convenient ducting for routing. Additional steel in the form of reinforcing bars or welded wire fabric needs to be provided for taking care of shrinkage, temperature, and the negative bending moment at supports. In composite slabs, the composite action between two dissimilar materials like concrete and steel is developed by bonding at the interface of two materials. The cement paste develops weak surface bonding and it is not sufficient to retain the composite behaviour. In addition surface bonding between concrete and metal deck requires shear connectors at the interface of the two materials. These shear connectors are normally the embossments in the deck sheets. These embossments are in typical pattern unique to each profile. These embossments develop friction as well as mechanical