Concrete Beams in Bending, Torsion and Shear

The results of tests on 18 rectangular reinforced concrete beams subjected to combined bending torsion and shear are reported. The principal variables were the ratio of twisting to bending moment, the transverse shear force, and the reinforcement configuration. The beams failed by one of three different modes which were characterized by the formation of a hinge adjacent to one face of the beam and yielding of the reinforcement adjacent to the face opposite to the hinge. In beams subjected to a constant twisting moment and a varying bending moment, failures with the hinge located adjacent to the bottom face occurred in the region subjected to the lowest bending moment and failures with the hinge located adjacent to the top face occurred in the region of highest bending moment. Idealized failure surfaces are defined and expressions for the strength of these beams are derived using an equilibrium approach. The results are presented both in tabular form and in interaction diagrams. Good correlation is obtained between the predicted and observed mode of failure and strength.