基于性能的FRP片材加固钢筋混凝土梁耐火性能评估与防火设计

Fiber-reinforced polymer (FRP) composites are widely used to strengthen existing reinforced concrete (RC) structures due to its many advantages such as the high tensile strength-to-weight ratio and excellent corrosion resistance. However, FRP composites have their own weakness mainly associated with the poor fire performance of the polymer matrix (usually soften at a warm temperature approaching to the glass transition temperature). Besides, the polymers are inherently combustible, and the fibers are usually oxidated or melt at elevated temperatures, leading to a significantly strength and stiffness degradations. Therefore, a proper approach for fire resistance evaluation and fire-insulation design of FRP-strengthened RC beams is very important and urgent for practical strengthening applications. ..The primary aim of this project is to develop a powerful computation tool to predict the fire performance of un-protected and insulated FRP-strengthened RC beams with the proposal and/or implementation of all necessary constitutive models for materials and interfaces, and to develop a performance-based design approach for predicting the fire resistance of FRP-strengthened RC beams. The temperature-dependent constitutive law of FRP laminates will be extablished based on the coupon tests of sheets and plates at different elevated temperatures. Standard fire tests on FRP strengthened RC beams in shear as well as the FRP flexurally strengthened RC beams with different anchorage behavior will be conducted to investigate the fire performance and failure model of insulated FRP strengthened RC beams. A finite elelment (FE) model will be proposed based on the proper descriptions of concrete, reinforcing steel, FRPs as well as their interfaces at elevated temperatures. Once the FE model is validated, an extensive parametric study will be conducted to investigate the effects of various design parameters on fire resistance of FRP strengthened RC beams, such as with/without fire insulation, fire load ratio, beam sectional dimensions, concrete cover depth, span-to-depth ratio, tension steel reinforcment. Based on the FE parametric study, a performance-based design approach will be developed for fire resistance evaluation of FRP-strengthened RC beams. Upon the completion of this project, an in-depth understanding of failure modes of FRP-strengthened RC beams under fire and powerful computation tools will be established; a performance-based design methodology will be developed to facilitate practical implementation. The project will open up a new area of research for the relevant international scientific committee and lead to a great potential for FRP strengthening applications in China and the rest of the world.

纤维增强复合材料（简称FRP）由于具有轻质、高强、耐腐蚀等特性而被做为外贴补强材料广泛应用于结构加固中。但外贴FRP加固技术存在一些自身缺陷：（1）胶粘剂的耐高温性能较差；（2）胶粘剂易燃烧以及纤维丝高温下氧化、熔化。因此研究FRP片材加固钢筋混凝土梁的耐火性能和设计方法具有重要的理论意义和实用价值。在现有研究的基础上，本项目通过高温下FRP片材材性试验、附加端部锚具的FRP抗弯加固梁以及FRP抗剪加固梁的耐火试验，探明高温下FRP片材力学性能劣化规律以及FRP加固梁火灾下反应和破坏模式。本项目将采用三维有限元分析和试验相结合的办法，建立系统的评估FRP片材抗弯、抗剪加固混凝土梁耐火性能的数值模型。同时将性能化抗火设计的思想引入到FRP片材加固混凝土梁耐火设计中，发展一种有效的基于计算的耐火设计方法，为现有加固结构耐火性能的判定、设计提供新途径。项目具有较强的理论研究价值和广泛的应用前景。

纤维增强复合材料（简称FRP）由于具有轻质、高强、耐腐蚀等特性而被作为外贴补强材料广泛应用于结构加固中。但是外贴FRP加固技术存在一些自身缺陷：（1）胶粘剂的耐高温性能较差；（2）胶粘剂易燃烧以及纤维丝高温下氧化、融化。因此研究FRP片材加固钢筋混凝土梁的耐火性能和设计方法具有重要的理论意义和适用价值。本项目进行了高温下FRP片材-混凝土界面剪切试验，建立了高温下FRP片材材料本构及FRP-混凝土界面粘结-滑移本构关系。在国际上首次建立高温下界面本构，用以表征界面剪力传递劣化机理。同时本项目进行了有防火保护FRP片材加固混凝土梁的耐火试验，研究不同防火保护方法、不同防火保护层厚度、FRP片材端部不同锚固措施对加固梁耐火极限的影响。建立的精细有限元模型较为精细地定义了高温下混凝土的塑性损伤和抗拉软化行为以及钢筋的抗拉刚化效应，同时精确地描述了高温下FRP片材力学性能劣化规律以及FRP片材-混凝土界面粘结退化机理，因而能准确预测加固梁火灾下的温度位移反应、破坏模式和材料应力应变历程。此外提出了基于性能的三等级耐火设计方法，并建立了简化温度场计算方法及未防火保护梁耐火极限简化计算公式以实现上述三等级耐火设计方法。上述三等级耐火设计方法已经被相关加固规程所采纳，产生显著的社会经济效益。