Accuracy of Rotation-Angle of Softened Truss Model for Reinforced Concrete Beams under Pure Torsion

The Rotating-Angle of softened Truss Model (RA-STM) by Thomas T. C. Hsu and Y. L Mo, developed for predicting the post-cracking torsional behavior of reinforced concrete beams up to the ultimate torsional strength, takes account two of Equilibrium equations and the softened constitutive equations for concrete struts in bending and compression. In this paper, the ultimate torsional strength and failure modes of 10 beams were observed by using RA-STM. Specimens have different yield strength of torsional steel and the ratio of amount of reinforcement to the maximum amount of reinforcement of ACI 318-R14. Especially a correct behavior prediction of the specimens using high-strength reinforcement or having the maximum amount of reinforcement of ACI 318-R14(/,) is important as design codes including the ACI 318-14 design code and Eurocode 2 limit the yield strength and the maximum amount of torsional reinforcement in order to avoid the brittle failure and induce torsional tension failure. Index Terms - Rotating-Angle of Softened Truss Model, ultimate torsional strength, high-strength reinforcement, failure mode