Generalized Softened Variable Angle Truss Model for RC Hollow Beams under Torsion.

Luís Bernardo

doi:10.3390/ma12132209

Abstract

In recent studies, a new softened truss model called Generalized Softened Variable Angle Truss Model (GSVATM) has been proposed to compute the full torsional response of reinforced concrete (RC) rectangular solid beams under pure torsion. In this article, the GSVATM is extended to cover RC hollow beams under torsion. The modification of the calculation procedure, in order to account for the specific behavior of RC hollow beams for low loading levels, as well as the final solution procedure, is presented. The theoretical predictions from the extended GSVATM are compared with experimental results of RC hollow beams under torsion found in the literature. Good agreement is observed between the experimental and theoretical results, for both high and low loading levels.

Highlights

One of the most comprehensive and used analytical toll to model the behavior of reinforced concrete (RC) beams under torsion is the Space Truss Analogy (STA)
The general design rules of current codes of practice include orientations to assess structural beams for both the service and ultimate loads, specific design rules for torsion are still mainly focused on the ultimate limit state
Such experiments were especially designed as highly controlled to accurately record the behavioral stage of the beams prior to cracking, as well as the cracking torque and the corresponding twist. With these additional experimental results, it was possible for Jeng to calibrate some parameters of the constitutive relationships for concrete in tension and compression used in the original model, in order to consider the specific behavior under torsion of RC hollow beams [14]

Summary

Introduction

Jeng in 2015 [14] proposed a modified calculation procedure to refine the SMMT, which was previously proposed by Jeng and Hsu in 2009 [8] for RC solid beams under torsion. Jeng carried out a series of additional experiments on RC hollow beams under torsion (5 hollow beams with thin walls and 4 hollow beams with thick walls), which enabled to increase the number of available experimental data Such experiments were especially designed as highly controlled to accurately record the behavioral stage of the beams prior to cracking, as well as the cracking torque and the corresponding twist. A similar calculation procedure as the one previously referred is implemented to modify the GSVATM, with the aim to unify the model for both RC rectangular solid and hollow beams.

Thickness of the Shear Flow

Constitutive Relationships for Concrete

New Calculation Procedure for the GSVATM

Reference Beams

Comparative Analyzes

Conclusions