复材栅格/喷射ECC加固受火后钢筋混凝土受弯构件的界面力学及设计方法

针对火灾后爆裂混凝土结构的修复难题，本项目提出了一种新颖的复材栅格/喷射ECC(FRP Grid-Reinforced ECC Shotcrete，简称FGRES)加固技术，有效提升受损结构的承载能力，实现“二次”安全使用和延寿目的。将针对此开展一系列研究：①材料方面，研发可喷射ECC的优化配合比，探究复材栅格在ECC基体中的粘结行为及抗拉强化特性；②界面方面，开展剪切试验研究混凝土受火损伤程度和表面处理方法对FGRES-混凝土界面粘结的影响机制，建立多层次数值模型探究复材栅格和受火损伤混凝土间通过喷射ECC粘结层的多层次界面传力机理，建立界面本构模型；③构件方面，通过试验、数值模拟和理论分析，明晰FGRES加固受火后钢筋混凝土受弯构件的破坏机理和受力性能，建立相应的抗弯加固设计方法。本项目力图研发一种新颖的加固材料体系、解决核心科学问题，为受损结构的性能提升和延寿提供经济有效的技术手段。

This project aims to explore an innovative strengthening system made of FRP grid-reinforced ECC shotcrete (FGRES) for repair of fire-damaged RC members, especially to solve the rehabilitation problem of such members with explosive concrete spalling after fire exposure. The proposed strengthening system is expected to enhance the load-carrying capacities of fire-damaged RC members efficiently and to extend their lifetime. A series of material tests will be conducted to find out the optimized mix design of ECC shotcrete. The bond behavior between the FRP grid and the ECC substrate will be examined through the pull-out tests, and the tension stiffening model of the FGRES overlay will be proposed based on the experimental and numerical studies on the tensile specimens. A number of shear tests will be carried out to investigate the effects of the concrete damage level after fire and the surface treatment method of damaged concrete on the interfacial bond behavior between the FGRES overlay and the concrete substrate. Then, a multi-layer numerical model will be developed to explore the bond interaction between the FRP grid and the fire-damaged concrete through the spraying ECC. Based on the experimental and numerical results as mentioned earlier, a bond-slip model will be proposed to accurately describe the bond behavior of the FGRES overlay and the fire-damaged concrete substrate. Also, the failure modes and the load capacity enhancements of the FGRES-strengthened fire-damaged beams and slabs will be clarified through the full-scale bending tests, the numerical simulations and the theoretical analyses. In addition, the strengthening design method will be established for the fire-damaged beams and slabs strengthened in flexural using the FGRES system. In conclusion, this project attempts to develop an innovative strengthening system for repair of fire-damaged RC members. The critical issues related to the bond mechanisms and the failure modes of FGRES-strengthened fire-damaged RC flexural members will be extensively studied to achieve a cost-effective means for the performance enhancement and the service life extension of damaged structures.