Steel-concrete composite floors are a popular form of construction, which is reflected in a market share in excess of 70% for multi-storey steel-framed buildings in the UK. A key element in steel-concrete composite beams is the shear connector, which is critical in transferring the longitudinal shear force at the interface between the steel beam and the concrete slab. As well as resistance, the shear connector should possess sufficient ductility, which is defined by its slip capacity. Sufficient slip capacity enables the longitudinal shear to be redistributed between the connectors, which permits them to be equally spaced along the beam. The performance of shear connectors has been established from small-scale push test specimens and, apart from slight variations to their geometry, have hardly changed since their inception in the early 1930s. One of the most common forms of shear connector used in current construction is the headed stud. Design rules for headed studs are given in the composite steel and concrete standard Eurocode 4 which, as well as the UK, is currently being used by over thirty-four countries from around the world.
This talk will present the results from a research programme consisting of full-scale composite beam and companion push tests. The reason for the research was to investigate concerns that the ductility of headed studs used with modern trapezoidal floor decks was lower than expected by Eurocode 4. Comparisons of load-slip performance demonstrated that any brittleness exhibited is due to a deficiency in the standard push specimen rather than the shear connectors themselves. An improved test was subsequently developed, which better reflects the performance of headed stud connectors in beams. This improved push specimen is currently being implemented within the next version of Eurocode 4.