Abstract Extensive experimental investigation was conducted to evaluate the performance of fiber reinforced concrete (FRC) beams that have been externally strengthened with and without preloading in flexure using carbon fiber reinforced polymer sheets. Steel, synthetic and hybrid fibers (mix of steel and synthetic fibers) with a volume fraction of 0.5% were added to the concrete matrix to prepare 15 beams. Test results show that the addition of all fibers types improved the flexural capacity, crack initiation and propagation, stiffness, post cracking behavior, deflection and ductility of the beams. Hybrid fibers was found to improve the ductility of the FRC beams by 4 times when compared to the control specimen without fibers. Furthermore, preloading before strengthening of concrete beams without fibers led to increase of the ultimate capacity by about 120%. Preloading caused improvement in elastic stiffness of the beams by 33.4%, 23.5% 17.6 for steel, synthetic and hybrid fibers, respectively. While strengthening increased the elastic stiffness for all beams and up to 65.3%. However, for the FRC beams there was no significant improvement in the ultimate capacity from those strengthened without preloading. Applicability of ACI 440 equations to predict the capacity of fiber reinforced concrete beams was also investigated.

中文翻译：

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预压CFRP增强纤维混凝土梁的性能

摘要 进行了广泛的实验研究，以评估使用碳纤维增强聚合物片材在弯曲预加载和未预加载的情况下进行外部加固的纤维增强混凝土 (FRC) 梁的性能。将体积分数为 0.5% 的钢、合成纤维和混合纤维（钢和合成纤维的混合物）添加到混凝土基体中以制备 15 根梁。测试结果表明，所有纤维类型的添加都提高了梁的抗弯能力、裂纹萌生和扩展、刚度、开裂后行为、挠度和延展性。与不含纤维的对照样品相比，发现混合纤维将 FRC 梁的延展性提高了 4 倍。此外，无纤维混凝土梁在加固前进行预压使极限承载力提高了约 120%。对于钢、合成纤维和混合纤维，预加载使梁的弹性刚度分别提高了 33.4%、23.5% 和 17.6。在加强的同时，所有梁的弹性刚度增加了 65.3%。然而，对于 FRC 梁，与没有预加载的加强梁相比，极限承载力没有显着提高。还研究了 ACI 440 方程在预测纤维增强混凝土梁的承载力方面的适用性。对于 FRC 梁，与没有预加载的加强梁相比，极限承载力没有显着提高。还研究了 ACI 440 方程在预测纤维增强混凝土梁的承载力方面的适用性。对于 FRC 梁，与没有预加载的加强梁相比，极限承载力没有显着提高。还研究了 ACI 440 方程在预测纤维增强混凝土梁的承载力方面的适用性。