Analysis of RC Beams under Combined Torsion and Shear Using Optimization Techniques Evaluation of NBR 6118 and AASHTO LRFD Standards

Abstract

In this article, a novel calculation procedure using optimization techniques is proposed to compute the torsion–shear interaction curves for reinforced concrete (RC) beams. The calculation procedure is applied to NBR 6118 and AASHTO LRFD standards in order to evaluate their reliability. For this, some experimental results found in the literature and related to RC beams tested under combined torsion and shear, as well as results from the combined-action softened truss Model (CA-STM), are used for comparison. From the obtained results, AASHTO LRFD provisions are found to –be satisfactorily accurate. The NBR 6118 provisions are found to be consistent with the experimental results when the angle of the concrete struts is assumed to be variable or equal to the lower bound value of 30°, according to model II of the standard. For an angle assumed equal to 45°, according to model I of the NBR 6118 standard, the predicted strengths are found to be excessively conservative. The results demonstrate that formulating the analysis of RC beams under combined torsion and shear as an optimization problem, as proposed in this article, constitutes an alternative and efficient option. In addition, the generality of the proposed calculation procedure allows it to be applied to any design standard to compute the torsion–shear interaction curves for RC beams.