Torsion Design Charts for Reinforced Concrete Rectangular Members

Abstract

This paper presents design charts constructed from the softened truss model to facilitate the torsional design of reinforced concrete rectangular members. These design charts comprise a normalized failure mode diagram and a strength contour diagram. Given a reinforced concrete rectangular section, the former diagram can be used to determine the corresponding failure mode and the latter one the strength. These diagrams are plotted on the plane of two newly defined reinforcement indices including the longitudinal and transverse steel indices, which are introduced so that the design charts are independent of the section dimensions, the yield strength of reinforcement, and the compressive strength of concrete. The accuracy of the proposed design charts in the prediction of the failure mode and the torsional strength is comparable to that of the softened truss model, as demonstrated in the presented example, whereas the design charts are more computation efficient for use by designers than the softened truss model.