Abstract Despite many advantages provided by fiber-reinforced polymer (FRP) bars, their low resistance against fire has been an important barrier for their widespread application in reinforced concrete (RC) members. Studying the post-fire performance of concrete structures reinforced with FRP bars can be beneficial in understanding the structural safety and estimating the serviceability conditions after a fire incident. Since little information is available in the literature in this regard, especially for high-strength concrete (HSC) and fiber-reinforced concrete (FRC), this research attempted to investigate the flexural behavior of HSC beams reinforced with glass fiber-reinforced polymer (GFRP) bar and steel fibers after exposure to elevated temperatures. The variables under consideration consisted of the applied temperature (20, 250, 400, and 600 °C), volume ratio of steel fibers (0 and 1%), and reinforcement ratio (0.314 and 0.872%). Following the quasi-static four-point flexural test on the heated and non-heated beam specimens, various parameters involving the load-carrying capacity, load-deflection relationship, cracking pattern in terms of the number and width of cracks at service and ultimate loads, and ductility of the beams were examined. It was found that exposing the beams to 250 °C reduced their load-carrying capacity negligibly and exposing them to 400 °C increased their residual load-carrying capacity notably while exposing them to 600 °C led to severe degradation in their flexural capacity. Further, the effectiveness of steel fibers on the behavior of beams with the lower reinforcement ratio was not significant; however, as the reinforcement ratio of the beams and applied temperature increased, steel fibers properly demonstrated their ability in improving the load-carrying capacity and reducing deflection at service load. By evaluating prediction relationships provided by codes and other researchers against the experimental results observed in this research, ACI 440.1R-06 and ACI 440.1R-15 codes were found to be able to predict deflection under service conditions with proper accuracy. Ultimately, for capturing the load-deflection relationship of heated and non-heated beam specimens, an analytical model was developed using the sectional analysis method, which was able to predict the experimental results appropriately.

中文翻译：

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FRP筋增强钢纤维高强混凝土梁加热后弯曲性能评价：试验和分析结果

摘要 尽管纤维增强聚合物 (FRP) 钢筋具有许多优点，但它们的低耐火性一直是其在钢筋混凝土 (RC) 构件中广泛应用的重要障碍。研究用 FRP 钢筋加固的混凝土结构的火灾后性能有助于了解结构安全性和估计火灾事故后的可使用性条件。由于这方面的文献资料很少，特别是对于高强度混凝土 (HSC) 和纤维增强混凝土 (FRC)，本研究试图研究用玻璃纤维增​​强聚合物 (GFRP) 增强的 HSC 梁的弯曲行为) 暴露于高温后的棒材和钢纤维。所考虑的变量包括应用温度 (20, 250, 400, 和 600 °C)、钢纤维的体积比（0 和 1%）和增强比（0.314 和 0.872%）。在对加热梁和非加热梁试样进行准静态四点弯曲试验后，各种参数包括承载能力、载荷-挠度关系、在使用和极限载荷下裂纹数量和宽度方面的裂纹模式，并检查了梁的延展性。研究发现，将梁暴露于 250 °C 时可忽略不计地降低其承载能力，将其暴露于 400 °C 会显着增加其残余承载能力，而将其暴露于 600 °C 会导致其抗弯能力严重下降。此外，钢纤维对低配筋率梁行为的影响不显着；然而，随着梁的配筋率和应用温度的增加，钢纤维在提高承载能力和减少使用载荷下的挠度方面适当地展示了其能力。通过根据本研究中观察到的实验结果评估代码和其他研究人员提供的预测关系，发现 ACI 440.1R-06 和 ACI 440.1R-15 代码能够以适当的精度预测使用条件下的挠度。最终，为了捕捉加热和非加热梁试样的载荷-挠度关系，使用截面分析方法开发了一个分析模型，能够适当地预测实验结果。钢纤维正确地展示了它们在提高承载能力和减少使用载荷下的挠度方面的能力。通过根据本研究中观察到的实验结果评估代码和其他研究人员提供的预测关系，发现 ACI 440.1R-06 和 ACI 440.1R-15 代码能够以适当的精度预测使用条件下的挠度。最终，为了捕捉加热和非加热梁试样的载荷-挠度关系，使用截面分析方法开发了一个分析模型，能够适当地预测实验结果。钢纤维正确地展示了它们在提高承载能力和减少使用载荷下的挠度方面的能力。通过根据本研究中观察到的实验结果评估代码和其他研究人员提供的预测关系，发现 ACI 440.1R-06 和 ACI 440.1R-15 代码能够以适当的精度预测使用条件下的挠度。最终，为了捕捉加热和非加热梁试样的载荷-挠度关系，使用截面分析方法开发了一个分析模型，能够适当地预测实验结果。发现 1R-15 代码能够以适当的精度预测使用条件下的挠度。最终，为了捕捉加热和非加热梁试样的载荷-挠度关系，使用截面分析方法开发了一个分析模型，能够适当地预测实验结果。发现 1R-15 代码能够以适当的精度预测使用条件下的挠度。最终，为了捕捉加热和非加热梁试样的载荷-挠度关系，使用截面分析方法开发了一个分析模型，能够适当地预测实验结果。