A theoretical investigation of ultimate torque as calculated by truss theory and by the Russian ultimate equilibrium method

An analysis is given of the distribution of forces in reinforced concrete elements under pure torsion. It is assumed that the elements are under-reinforced and that failure is initiated by yielding of reinforcement. Two methods of calculation are taken into consideration, the space truss analogy and the ‘ultimate equilibrium method’ as adopted in the Soviet code. It is shown that the latter method will give the same results as the truss theory, provided that proper assumptions are made with respect to the form of the failure surface and the magnitude of the stirrup stresses at the smaller and the larger sides of the beam respectively.