Torsional Strength of R/C Beams Containing Rectangular Openings

Abstract

A method for predicting the torsional strength of a reinforced concrete beam containing a rectangular opening is developed using the principles of limit analysis. A simple yield criterion for yielding under combined bending and torsion is employed. The applicability of the method is limited to openings in which the chords are subjected to predominant bending and torsion, while the shear force at collapse is less than 2/3 of the ultimate shear force. Such openings are characteristically long, and a suitable length parameter to use is the ratio of ultimate bending moment to ultimate shear force of chords. The proposed method is easier to apply than other available methods because it requires only some hand calculations beyond the computation of ultimate values of bending moment, torsion, and shear force of the chords using standard methods. Comparison with available test results shows that the proposed method provides consistently good predictions.