Unified Softened Membrane Model for Torsion in Hollow and Solid Reinforced Concrete Members: Modeling Precracking and Postcracking Behavior: Fid-Bau Portal

Unified Softened Membrane Model for Torsion in Hollow and Solid Reinforced Concrete Members: Modeling Precracking and Postcracking Behavior

Jeng, Chyuan-Hwan

Abstract

The softened membrane model for torsion (SMMT) was the first rational theory to incorporate the precracking and postcracking torsional behavior of solid RC members. A series of theoretical and experimental investigations were conducted in Taiwan to extend the SMMT to hollow RC members. This paper proposes a generalized SMMT based on the results of these investigations, determines the constitutive relationships of concrete for thin- and thick-walled hollow RC members, and develops a unified SMMT theory for hollow and solid RC members. The proposed SMMT for hollow RC members (SMMT-H) is also employed to derive a rational $T_{c r}$ and $θ_{c r}$ formula for such members, completing a unified set of noniterative rational $T_{c r} - θ_{c r}$ formulas for both hollow and solid RC members. In the experiment, the proposed SMMT-H analyzed the torsional responses of the specimens reasonably well, and predicted the cracking points and precracking torque-twist curves almost perfectly. The proposed rational formula for hollow RC members, which accurately predicted the $T_{c r}$ and $θ_{c r}$ of the specimens, is an almost-perfect simplification of the SMMT-H in terms of $T_{c r}$ and $θ_{c r}$ . A numerical example illustrating the simple application of this formula is presented.