Experimental study on straight composite beams subjected to combined flexure and torsion

Acceptable methods of ultimate load analysis and design for composite steel–concrete beams are nowadays readily available. However, in the case when a composite beam is curved in plan under vertical loading or an edge beam, the beam is subjected to a state of combined flexure and torsion. Previous studies have shown that current methods of using flexure–torsion interaction equations for reinforced concrete beams cannot be directly applied to composite steel–concrete construction. Moreover, partial shear connection which has been commonly used in composite steel–concrete construction has not been previously addressed in studies on flexure–torsion interaction. Therefore, this paper provides results from several test programmes to support the view that in the presence of flexure, there will be an increase in the torsional moment capacity but the flexural capacity does not increase in the presence of torsion. In addition to these experimental results, a model has been provided to allow for the design of combined flexure and torsion.