耐高温树脂基FRP筋嵌入式加固RC构件火灾下力学行为研究

Focusing on the ability inadequacy of fire resistance of the reinforced concrete (RC) components strengthened with near-surface-mounted (NSM) fiber-reinforced-polymer (FRP), which obstructs their application in building structures, this project proposes innovative ways which can improve the fire resistance of FRP-NSM strengthened RC components essentially and significantly via solving three scientific difficulties of three objects, bare FRP bars, embedded FRP bars and anchorage of FRP bars. The internal relationship between glass-transition temperature(Tg) of resin and the fire resistance of FRP will be determined, and the model of relationship between the effect of different high temperature and the residual strength and elastic modulus will be respectively established, based on the preparing of FRP bars with high temperature resistant resin matrix which has high Tg (HR-FRP bars) and measuring strain and temperature field of FRP bars utilizing high temperature resistant optic fiber in bare FRP bars and embedded FRP bars. Furthermore, digital image correlation measurement technique will be used in testing bond-slip relationship of FRP bar-adhesive-concrete, and the degradation of mechanical properties of anchorage will be studied. Furthermore, studies on RC slab members and beam members strengthened with NSM HR-FRP bars will be carried out, and their mechanical behavior under fire will be comprehensively investigated. The parameter table for fire resistance design, which consists of 5 parameters, will be proposed through theoretical analysis and numerical simulation according the experimental results. The investigation will be very conducive to the development of fire resistance design and performance quantitative evaluation of FRP-NSM strengthened RC components.

针对纤维增强复合材料（FRP）嵌入式（NSM）加固钢筋混凝土（RC）构件的耐火能力不足这一阻碍其在建筑结构中应用的瓶颈问题，项目重点解决材料和构件层面三个对象的关键科学问题，提出大幅提高FRP-NSM加固RC构件耐火能力的方法。通过采用高Tg温度树脂作为基体制备耐高温树脂基FRP筋，采用复合于FRP筋的耐高温光纤测试筋中应变和截面温度场，明确Tg温度与FRP筋耐高温性能的内在关系，建立耐高温树脂基FRP嵌入筋的残余强度和弹性模量与高温作用时间关系模型，运用图像数字相关技术测试FRP锚固件全场位移，建立锚固区FRP筋-黏结胶-混凝土界面高温黏结滑移关系，掌握FRP锚固区高温下力学性能退化规律，进而开展梁板构件火灾试验，研究耐高温树脂基FRP筋NSM法加固RC构件火灾下的力学行为，通过试验和理论研究及数值模拟建立抗火设计参数表，为FRP-NSM加固RC构件的抗火设计和耐火性能定量评估提供依据。

针对FRP嵌入式加固RC构件抗火性能不足的瓶颈问题，本项目提出了多种提升FRP筋嵌入式加固混凝土构件耐火性能的方法，从以下三个层面开展了系列研究。首先开发了耐高温树脂基FRP筋，揭示了其在高温中强度和弹性模量的退化规律；为可靠地得到高温中FRP嵌入筋的应变，提出了采用分布式光纤传感技术。其次，提出了一种低成本的设置铝合金管附加肋的方法，用以提高锚固区FRP筋与胶层或混凝土间的界面粘结性能，并开展了界面粘结试验。最后，开展了耐高温树脂基FRP筋嵌入式加固RC梁构件的抗火性能试验研究，验证了耐高温树脂基FRP筋在提升加固梁抗火性能方面的显著优势；通过带包覆层FRP筋嵌入式加固RC梁构件的抗火性能试验研究，验证了锚固区采用有机胶、非锚固区采用无机砂浆这种粘结剂布置方案的有效性。.研究结果表明，耐高温树脂基BFRP筋在350°C仍能保持70%左右的拉伸强度及95%以上的弹性模量；与普通乙烯基BFRP筋相比，耐高温乙烯基BFRP筋具有更好的耐高温性能。采用普通单模光纤即可进行高温环境中FRP筋应变和温度的监测，基于试验结果和已有模型拟合得到FRP嵌入筋的高温本构模型。附加肋能显著提高FRP筋与混凝土间的界面抗剪性能，于工程应用而言，附加肋将有助于减小结构中特殊位置处FRP筋的锚固长度。在耐高温树脂基BFRP筋嵌入式加固结构中设置局部防火保护措施是可行的，其耐火极限不低于甚至高于普通钢筋混凝土梁。当防火层达到25mm以上时，BFRP梁构件的耐火极限能达到2h以上。新的粘结剂布置方案充分结合了无机粘结剂和有机粘结剂的优点，可行并具有一定的经济性。若合理选用无机砂浆，无需对全长混凝土梁底进行隔热保护，依然能使加固梁的耐火极限不低于甚至高于普通钢筋混凝土梁的耐火极限。研究结论对FRP筋加固及增强混凝土结构均具有理论意义和实践指导价值。