Abstract
In this study, the generalized softened variable angle truss-model (GSVATM) is used to predict the response of reinforced concrete (RC) beams under torsion at the early loading stages, namely the transition from the uncracked to the cracked stage. Being a 3-dimensional smeared truss model, the GSVATM must incorporate smeared constitutive laws for the materials, namely for the tensile concrete. Different smeared constitutive laws for tensile concrete can be found in the literature, which could lead to different predictions for the torsional response of RC beams at the earlier stages. Hence, the GSVATM is used to check several smeared constitutive laws for tensile concrete proposed in previous studies. The studied parameters are the cracking torque and the corresponding twist. The predictions of these parameters from the GSVATM are compared with the experimental results from several reported tests on RC beams under torsion. From the obtained results and the performed comparative analyses, one of the checked smeared constitutive laws for tensile concrete was found to lead to good predictions for the cracking torque of the RC beams regardless of the cross-section type (plain or hollow). Such a result could be useful to help with choosing the best constitutive laws to be incorporated into the smeared truss models to predict the response of RC beams under torsion.
Highlights
In the second half of the last century, the Space Truss Analogy (STA) was successively refined in order to better predict the response of structural concrete beams under torsion.Nowadays, modern truss-based models can be considered reliable, comprehensive and unified analytical models
A STA-based model assumes that a reinforced concrete (RC) beam under torsion behaves like a cracked thin tube, where the external torque is resisted through a transversal circulatory shear flow
As for the other constitutive laws referred to Materials 2021, 14, 1260, different proposals of smeared constitutive laws for tensile concrete can be found in the literature
Summary
In the second half of the last century, the Space Truss Analogy (STA) was successively refined in order to better predict the response of structural concrete beams under torsion. Among the STA-based models that have been developed, one of the most commonly used and extended is the Variable-Angle Truss Model (VATM), which was originally proposed by Hsu and Mo in 1985 [3] This model incorporated for the first time smeared constitutive laws, or smeared stress (σ)—strain (ε) relationships, for both tensile steel reinforcement embedded in concrete and compressive concrete. The VATM was improved in order to reliably predict the response of RC beam under torsion for the low loading stages, namely the transition between the uncracked stage and the cracked stage This was achieved by incorporating into the model the contribution of the tensile concrete (neglected in the VATM) through an additional smeared σ—ε constitutive law in the perpendicular direction to the concrete struts. The number of reported experimental results in the literature for such beams is much higher than for other typologies such as PC beams or beams with a flanged cross-section
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