Effects of partial shear connection of curved in plan composite steel-concrete beams under combined flexure and torsion

Methods for the ultimate load analysis and design of straight composite steel-concrete beams in flexure are well-established, and solutions can be obtained with relative ease. However, there are situations in which a composite beam is subjected to torsion, such as members that are curved in-plan and edge beams. The concrete slab and the steel beam contribute to the torsional strength and stiffness of a composite beam, but this composite action is usually ignored in design codes of practice, which leads to conservative designs. Partial shear connection is commonly used in the design of floor systems, and this is also ignored in the design of composite beams for combined flexure and torsional actions. This paper investigates the ultimate strength of composite steel-concrete beams which are curved in-plan. Eight composite beams with realistic dimensions comprising of a universal steel beam and a concrete slab were tested to failure. Four beams had full shear connection, with the other four having partial shear connection, and the beams were subjected to a concentrated load applied at the mid-span of the simply supported beams, whose ends were restrained against twist rotation. Based on the experimental results, the behaviour of the beams was assessed in terms of member strength, stiffness and ductility. The increase in the torsional moment capacity in the presence of flexure was also demonstrated and quantified. Beams with partial shear connection were shown not to experience a reduction in their torsional strength in comparison with beams with full shear connection.