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Title: Cover Spalling in Reinforced Concrete Beams Subjected to Pure Torsion

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

Publication: Structural Journal

Volume: 120

Issue: 5

Appears on pages(s): 109-120

Keywords: design; reinforced concrete; softening; space truss; spalling; torsion

DOI: 10.14359/51738839

Date: 9/1/2023

Cover concrete plays an important role in the torsional behavior of reinforced concrete members because the resulting shear stresses are concentrated in these areas. Modeling its behavior is difficult due to: 1) compression softening; and 2) the possibility of spalling at high loads. Traditional approaches, which only consider one effect or the other, are limited in their ability to model the ultimate strength and torque-twist response of members over a wide range of cover thicknesses. This paper presents a mechanics-based model which can predict when torsional spalling occurs and quantify its effect on a member’s strength and stiffness. Its application within a nonlinear analysis framework and a design procedure based on ACI 318-19 is shown. Using the proposed model together with existing compression-softening models results in improved strength predictions of 187 pure torsion tests found in the literature.