Abstract Past research has used synthetic fiber (SY.F) and steel fiber (ST.F) for decades to advance concrete mechanical characteristics, including shear, tensile, and flexural strengths. Nevertheless, there is limited information concerning the torsional concrete reinforced with SY.F and ST.F performance. This research aims to explore the torsional performance of hollow reinforcement concrete beams reinforced with various fiber types. The fiber content of 1% with three different lengths of SY.F, 19, 38, and 57 mm, along with 13 mm of ST.F, was used. Two specimens were cast with normal concrete without using fibers as control beams and four hollow beams with ST.F and SY.F. To use a pure torsional load on the tested samples, an innovative test method was employed. The twisting angle of tested beams was calculated at each interval of the load as well as the first crack load and failure load. Outcomes illustrated that the utilizing of SY.F and ST.F in the reinforced concrete beams (RCB) enhanced the overall performance under torsional load compared to the control beam behaviors. This enhancement in the performance was relative to the fiber type and length. For the first cracking load, the tested beams reinforced with the ST.F and SY.F of 19 and 37 mm lengths showed approximately the same value. Also, the beam reinforced with the SY.F length of 55 mm exhibited the highest first cracking load value, among other tested beams. As the fiber length increases of SY.F, the ultimate load capacity was raised by 4.7, 9.4, and 21.9% for beams cast with 19, 37, and 55 mm fiber length, respectively. For the ST.F reinforcement concrete beam, the ultimate load capacity was raised by 5.5%. Therefore, due to the significant impact of SY.F on the torsional performance, it is recommended using SY.F with normal concrete.

中文翻译：

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合成/钢纤维增强空心混凝土梁抗扭强度试验研究

摘要 几十年来，过去的研究一直使用合成纤维 (SY.F) 和钢纤维 (ST.F) 来提高混凝土的力学特性，包括剪切、拉伸和弯曲强度。然而，关于用 SY.F 和 ST.F 性能增强的抗扭混凝土的信息有限。本研究旨在探讨各种纤维类型增强的空心钢筋混凝土梁的抗扭性能。使用三种不同长度的 SY.F、19、38 和 57 毫米以及 13 毫米的 ST.F 的 1% 纤维含量。用普通混凝土浇筑两个试件，不使用纤维作为控制梁，用四个空心梁浇筑 ST.F 和 SY.F。为了在测试样品上使用纯扭转载荷，采用了一种创新的测试方法。计算各荷载间隔下受试梁的扭转角以及初裂荷载和破坏荷载。结果表明，与控制梁行为相比，在钢筋混凝土梁 (RCB) 中使用 SY.F 和 ST.F 提高了扭转载荷下的整体性能。这种性能增强与光纤类型和长度有关。对于第一次开裂荷载，用 19 和 37 毫米长度的 ST.F 和 SY.F 加固的测试梁显示出大致相同的值。此外，在其他测试梁中，用 55 毫米 SY.F 长度加固的梁表现出最高的首次开裂载荷值。随着 SY.F 纤维长度的增加，19、37 和 55 毫米纤维长度浇铸的梁的极限承载能力分别提高了 4.7、9.4 和 21.9%。对于 ST。F钢筋混凝土梁，极限承载能力提高5.5%。因此，由于SY.F对扭转性能的影响很大，建议在普通混凝土中使用SY.F。