Partial Shear Interaction in Deconstructable Steel-Concrete Composite Beams with Bolted Shear Connectors

Abstract

With the emergence of structural design paradigms that focus on sustainable and low-carbon engineering structures, the implementation of a life-cycle building analysis inevitably involves the issue of deconstructability. Con-ventional steel framed buildings that are composite with concrete slab floors utilise the symbiotic advantages of the concrete being subjected to compression and the steel being subjected to tension, that is realised through the use of welded headed stud shear connectors to carry the shear force at the steel-concrete interface. Clearly, at the point of deconstruction, welded stud connec-tors embedded in the concrete slab are highly problematic. To circumvent this deconstructability obstacle, the use of high-strength bolts as shear connectors is proposed in this paper, being installed in pre-drilled holes in the steel top flange and in precast concrete slab units. A mechanics-based model is developed in which the interface shear is resisted initially by the friction caused by preload in the bolts with full interaction, followed by a condition in which the bolts slip in their pre-drilled holes and then finally bear against the holes in the slab and steel joist in a more conventional fashion. The concept is illustrated by a simple physical model. 1 Introduction Bolted shear connectors provide a simple means to ensure deconstructability in com-posite steel-concrete beams, as the bolts can be removed and the slabs and steel joists then reused at the end of the design life of a steel framed building with composite flooring systems. Since fabrication tolerances require oversized clearance holes for the bolts, they need to be pre-tensioned so that the ensuing friction at the interface provides resistance to the shear flow force at that location, ensuring composite action at service load levels. Despite the attraction of this alternate shear connector technology, its reporting in the published literature is scanty. Dallam and Harpster (1968) reported testing of bolted shear connectors in work performed for the Missouri Transport Department,