Concrete beam subjected to shear and torsion: a comparison between the Brazilian Standard Code NBR 6118, ACI and AASHTO Provisions


Most of torsion studies available are relative to pure torsion, arising from the exclusive application of a torsion moment in a concrete beam. This situation, however, is only possible in laboratories. In practice, the vast majority of twisted beams are subjected to the combination of shear forces and torsion, which gives rise to a more complex state of stress to be analyzed. The purpose of this paper is to present the provisions of the ACI Codes, AASHTO and NBR Standards related to shear and torsion, and compare some results with experimental data from Rahal & Collins [3]. It is shown that if the recommended value of 45° is used for the angle of the compression strut, the ACI provisions for shear-torsion interaction give similar results compared to NBR, but these results are very conservative. If the lower limit of 30° is used, the results obtained using both codes are less consistent. This paper concludes that using the recommended value of 36° derived from the AASHTO provisions, some consistent and more accurate results are obtained.