This paper investigated degradation of flexural bond of a ribbed carbon fiber reinforced polymer (CFRP) bar in ultra-high-performance fiber reinforced concrete (UHPFRC) after exposure to elevated temperatures. For this purpose, the mechanical properties of UHPFRC and thermal properties of CFRP bars after exposure to elevated temperatures were investigated, and a total of 16 groups of hinged beams were fabricated with variables of embedment length (4, 10, 20, and 40), bar type and exposed to elevated temperatures (200 °C, 300 °C, 400 °C, 600 °C). The mechanical properties of UHPFRC increased until elevated temperatures reached 400 °C and it was shown that the reduction of the ultimate tensile strength of CFRP bars were not notable after exposure to elevated temperatures of up to 300 °C. The ultimate moment of ribbed CFRP bars after exposure to elevated temperatures at 200 and 300 °C was similar. After exposure to an elevated temperature of 400 °C, it decreased by about 29–63 % compared to non-heated specimens, with bar rupture. Although similar decomposition temperatures of ribbed and sand coated CFRP bars occurred, the residual flexural bond strength of the ribbed CFRP bar was larger than that of the sand coated CFRP bar after exposure to elevated temperature at 400 °C. In addition, a relatively lower reduction of bond strength occurred in RC-40ED-400 compared to RC-10ED-400 and RC-20ED-400. Based on the test results, development length with consideration of degradation of developed tensile and normalized bond strength of CFRP bars were proposed, and it was found that the required development length of ribbed CFRP bars after exposure to elevated temperatures at 400 °C increased by 294 % compared to ambient temperature.

中文翻译：

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暴露于高温后 UHPFRC 中 CFRP 棒的弯曲粘合降解


本文研究了超高性能纤维增强混凝土 (UHPFRC) 中带肋碳纤维增强聚合物 (CFRP) 棒在暴露于高温后的弯曲粘合降解情况。为此，研究了UHPFRC的力学性能和CFRP筋在高温下的热性能，并制作了总共16组嵌入长度变量（4、10、20和40）的铰接梁，棒型并暴露于高温（200°C、300°C、400°C、600°C）。 UHPFRC 的机械性能在高温达到 400 °C 之前一直增加，并且表明，在暴露于高达 300 °C 的高温后，CFRP 棒材的极限拉伸强度的降低并不明显。暴露于 200 和 300 °C 高温后，带肋 CFRP 棒的极限力矩相似。暴露于 400 °C 的高温后，与未加热的样品相比，其强度降低了约 29-63%，并出现棒材断裂。尽管带肋和涂砂CFRP筋的分解温度相似，但在暴露于400℃高温后，带肋CFRP筋的残余弯曲粘合强度大于涂砂CFRP筋。此外，与 RC-10ED-400 和 RC-20ED-400 相比，RC-40ED-400 的粘合强度降低相对较小。根据试验结果，提出了考虑CFRP筋拉伸强度和归一化粘结强度退化的开发长度，结果发现，在暴露于400℃高温后，带肋CFRP筋所需的开发长度增加了294 % 与环境温度相比。