Torsional strength of reinforced concrete beams

A simple method for predicting the ultimate strength and mode of failure of reinforced concrete beams subjected to pure torsion is presented. This method is an extension of a recently developed method for predicting the strength of membrane elements subjected to pure shear that was also applied to beams subjected to combined shearing forces, bending moments, and axial loads. The torsional strength is related to the amounts of transverse and longitudinal reinforcement and to the concrete strength. To check the adequacy of this simple method, the calculated strength and mode of failure are checked against the experimental results of 66 beam tests available in the literature, and good agreement is found. The simplicity of the method is illustrated by an example.Key words: beams, building codes, mode of failure, reinforced concrete, shear, strength, torsion.