Abstract
This paper concerns an investigation on six large-scale Steel Fiber Reinforced Concrete (SFRC) beams tested in pure torsion. All beams had longitudinal rebars to facilitate the well-known space truss resisting mechanism. However, in order to promote economic use of the material, the transverse reinforcement (i.e. stirrups/links) was varied in the six large scale beams. The latter contained either no stirrups, or the minimum amount of transverse reinforcement (according to Eurocode 2), or hooked-end steel fibers (25 or 50 kg/m3). Material characterization were also carried out to determine the performance parameters of SFRC. The results of this study show that SFRC with a post-cracking performance class greater than 2c (according to Model Code 2010) is able to completely substitute the minimum reinforcement required for resisting torsion. In fact, the addition of steel fibers contributes to significantly increase the maximum resisting torque and maximum twist when compared to the same specimen without fibers. Moreover, SFRC provides a rather high post-cracking stiffness and a steadier development of the cracking process as compared to classical RC elements. This phenomenon improves beam behavior at serviceability limit state. The experimental results are critically discussed and compared to available analytical models as well as with other tests available into the literature.
Highlights
Reinforced Concrete (RC) structures in practice are rarely subjected to pure torsion
Consideration on the torsional response of beams composed of Steel Fiber Reinforced Concrete (SFRC) cannot be fully exhaustive. To bridge this lack of information, this paper presents a series of pure torsion tests on SFRC beams with longitudinal reinforcement and without stirrups alongside a full suite of material characterization tests
Comparisons have been made between a sample with no stirrups nor fibers, one with the minimum classical reinforcement and the remaining four containing steel fibers
Summary
Reinforced Concrete (RC) structures in practice are rarely subjected to pure torsion. Materials and Structures (2021) 54:34 of the phenomena governing the torsional behavior of RC members, the study of specimens subjected to pure torsion represents an important and unavoidable starting point The latter becomes even more significant for practice when considering the high amount of transverse reinforcement required in beams subjected to low torsional moments. The response of RC beams strengthened with innovative materials and subjected to torsion have recently been reported [13,14,15] All these tests confirm that, after first cracking, the shear stresses that develop as a result of the induced torsion are unable to be resisted unless a suitable mechanism is formed, which enables the transfer of stress across a cracked section. These models usually consist of diagonal compressive struts and tie elements (i.e., stirrups and rebars), which are formed to redress equilibrium and enable stresses to be transferred within the cracked sections [19]
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