Title: Torsional Strength of Reinforced Concrete Members Failing by Crushing

Author(s): Allan Kuan, Evan C. Bentz, and Michael P. Collins

Publication: Structural Journal

Volume: 119

Issue: 6

Appears on pages(s): 233-244

Keywords: crushing; design; high strength; maximum torsion strength; shear; space truss; torsion

DOI: 10.14359/51736115

Date: 11/1/2022

Abstract:
The torsional strength of reinforced concrete members that fail by yielding of the reinforcement can be accurately predicted by design codes such as ACI 318-19 and the Canadian design standard CSA A23.3:19. However, these codes are relatively poor at predicting the strength of heavily reinforced members that fail by crushing. This paper presents a rational model which can predict the strength of such members. A key feature of the model is that the variation in torsional stresses through the thickness of a member is explicitly considered using stress block factors derived from the stress strain curve of the concrete. The model predicts the strength of 31 experiments with an average test-to-predicted ratio of 1.20 and a coefficient of variation (COV) of 14.4%. This is significantly better than the maximum torsion limits in ACI 318-19 (mean 1.62, COV 21.0%) and CSA A23.3:19 (mean 0.79, COV 41.1%). Simple equations suitable for design are presented.