Composite connections at perimeter locations in unpropped composite floors

Of all new multi-storey buildings in the UK, approximately 40% use composite floor construction. This type of construction is structurally efficient because it exploits the tensile resistance of the steel beams and the compressive resistance of the concrete slabs. This composite action allows shallower steel beams to be used because of the increased flexural strength and stiffness. Research has shown that more savings, approximately 25% on weight or depth of individual beams, can be achieved if composite connections are adopted. With such connections, increased, moment of resistance can be achieved by introducing dedicated slab reinforcement, which acts like an additional row of bolts in an extended end plate. However, the use of composite connections is not widespread. This is due in part to two problems addressed herein. Firstly, the existing composite connections design and detailing rules can currently only be used with beams that are propped during construction, whereas unpropped construction is generally a preferred and more economic construction method. For applications where it is important to minimise beam depth, even if this is at the expense of heavier perimeter columns, practical details are also required for single sided moment resisting connections. In order to investigate these problems, a test was carried out at the Building Research Establishment, UK, on a full-scale unpropped sub-frame that incorporated a novel exterior column connection. The results of this test, with an emphasis on the exterior column connection, are presented in this paper.