The torsional capacity of R/C beams is considered in this paper. On the basis of Batti and Almughrabi theory, a new general formula is proposed. Accordingly to their theory, this formula takes into account that stirrups influence the concrete torsional capacity because of their involvement in the aggregate interlock. A large number of previous test results, available in the literature (87 beams), has been considered to determine a few coefficients, by minimizing the coefficient of variation of the experimental-to-theoretical torsional capacity ratio. The obtained contributions of concrete and reinforcement on torsional capacity have both a sound physical meaning, which was not the case of the original Batti and Almughrabi’s expressions. The theoretical results obtained with the proposed formula have been compared with the torsional capacities provided by other already available formulae and by some design codes. It is shown that the proposed formula is very efficient, since the computed capacities are very close to the test results and - on the whole - much closer than other well known formulae.
