A Study of the Shear Behavior of Concrete Beams with Synthetic Fibers Reinforced with Glass and Basalt Fiber-Reinforced Polymer Bars

Buildings Pub Date : 2024-07-11 DOI:10.3390/buildings14072123

Isabela Oliveira Duarte, N. Forti, L. L. Pimentel, A. E. Jacintho

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Abstract

The use of synthetic materials with high corrosion resistance in a concrete matrix yields structures that are more durable and suitable for use in aggressive environments, eliminating the need for frequent maintenance. Examples of such materials include glass (GFRP) and basalt (BFRP) fiber-reinforced polymer bars (FRP). Due to the low modulus of elasticity of these bars, concrete elements reinforced with FRP longitudinal rebars tend to exhibit cracks with wider openings and greater depths compared to those reinforced with steel rebars, which diminishes the element’s shear resistance. The addition of discontinuous fibers into the concrete aims to maintain stress transfer across the cracks, thereby enhancing the shear capacity and ductility of FRP-reinforced structures. This study evaluates the impact of fiber addition on the shear resistance of concrete beams reinforced with FRP rebars. An experimental investigation was conducted, focusing on the partial and complete substitution of stirrups with polypropylene macro fibers in concrete beams reinforced with FRP longitudinal rebars and stirrups. This research examined beams reinforced with glass (GFRP) and basalt (BFRP) fiber-reinforced polymer bars. For the initial set of beams, all stirrups were replaced with synthetic macro fibers. In the subsequent set, macro fibers were added to beams with insufficient stirrups. Although the complete replacement of GFRP and BFRP stirrups with polypropylene macro fibers did not alter the brittle shear failure mode, it did enhance the shear resistance capacity by 78.5% for GFRP-reinforced beams and 60.4% for BFRP-reinforced beams. Furthermore, the addition of macro fibers to beams with insufficient stirrups, characterized by excessive spacing, changed the failure mode from brittle shear to pseudo-ductile flexural failure due to concrete crushing. In such instances, the failure load increased by 18.8% for beams with GFRP bars and 22.8% for beams with BFRP bars.

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用玻璃纤维和玄武岩纤维增强聚合物棒增强合成纤维混凝土梁的剪切行为研究

在混凝土基体中使用具有高耐腐蚀性的合成材料，可使结构更加耐用，适合在侵蚀性环境中使用，无需经常维护。此类材料的例子包括玻璃纤维增强聚合物（GFRP）和玄武岩纤维增强聚合物（BFRP）。由于这些钢筋的弹性模量较低，与使用钢筋加固的混凝土构件相比，使用 FRP 纵向钢筋加固的混凝土构件往往会出现开口更大、深度更深的裂缝，从而降低构件的抗剪能力。在混凝土中加入非连续纤维的目的是保持裂缝间的应力传递，从而提高玻璃钢加固结构的抗剪能力和延展性。本研究评估了添加纤维对 FRP 钢筋加固混凝土梁抗剪性能的影响。研究人员进行了一项实验调查，重点是在使用玻璃钢纵向钢筋和箍筋加固的混凝土梁中，用聚丙烯大纤维部分和完全替代箍筋。这项研究考察了使用玻璃纤维增强聚合物（GFRP）和玄武岩纤维增强聚合物（BFRP）钢筋加固的梁。在第一组梁中，所有箍筋都用合成大纤维代替。在随后的一组研究中，在箍筋不足的梁上添加了大纤维。虽然用聚丙烯大纤维完全替换 GFRP 和 BFRP 箍筋并没有改变脆性剪切破坏模式，但它确实提高了 GFRP 加固梁的抗剪能力，GFRP 加固梁的抗剪能力提高了 78.5%，BFRP 加固梁的抗剪能力提高了 60.4%。此外，在箍筋不足（间距过大）的梁中添加大纤维后，由于混凝土破碎，梁的破坏模式从脆性剪切破坏转变为假韧性弯曲破坏。在这种情况下，使用 GFRP 杆件的梁的破坏荷载增加了 18.8%，使用 BFRP 杆件的梁的破坏荷载增加了 22.8%。

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