内嵌CFRP加固钢筋混凝土梁的抗火性能试验研究

Study on the Fire Behavior of RC Beams Strengthened with Near-surface Mounted CFRP Reinforcement

碳纤维增强复合材料(CFRP)被广泛地应用于钢筋混凝土结构加固。由于碳纤维增强复合材料的高温力学性能较差,外贴CFRP加固体系存在耐火性能不足的缺点。由于锚固性能、黏结性能和延性等方面的优势,嵌入CFRP法(NSM)被越来越广泛地应用于钢筋混凝土梁的加固工程。由于外覆混凝土层和黏结材料的保护,CFRP免于暴露在外部恶劣环境之中,从而具备抵抗火灾的可能。为了了解NSM加固梁在高温下的力学性能,笔者进行了11根碳纤维加固梁和1个对比梁的ISO834标准火灾试验。研究了4个主要因素,即加固方法(嵌入式/外贴技术)、胶黏剂的种类(环氧树脂/氯氧镁水泥)、防火材料(超薄膨胀型涂料/厚型涂层)和防火保温模式(楔入/单面/三面)对梁的高温力学性能的影响。试验结果表明,采用适当的防火保护并选择有效的黏结材料,内嵌CFRP加固钢筋混凝土梁可以达到普通钢筋混凝土梁的耐火水平。该研究为嵌入CFRP加固钢筋混凝土梁的耐火性能设计提供了依据和参考。

Although carbon fiber reinforced polymer （CFRP） has been widely used in the retrofitting andstrengthening of concrete structures, the externally bonded （EB） CFRP strengthening system is foundvulnerable in fire resistance. The near surface mounted CFRP technique becomes increasingly popular due toits specific advantages over EB system, such as a better anchoring capacity of the CFRP, better bondcharacteristics and more ductile behavior. Moreover, the near surface mounted CFRP reinforcement isprotected by concrete cover from environment impact, making it possibly superior in fire resistance. To figureout the fire resistive capacity of the near surface mounted CFRP system, 11 CFRP reinforced concrete beamsand one unstrengthened reference beam were heated to failure under ISO834 standard fire with constant loads.Four main factors were studied, i.e. strengthening technique （near surface mounted/externally bonded ）,adhesive （epoxy/magnesium oxycbloride cement）, fire protection materials （thin intumescent fire retardantcoating/thick fire retardant coating） and the location of fire protection （notch protection/single-sidedprotection/three-sided protection）. Test results indicate, with appropriate fire protections, RC beamsstrengthened with CFRP can reach the equal fire resistive capacity of normal RC beam. The study provides ascientific basis for fire design of NSM strengthening in practical engineering.