FRR栅格增强超高韧性水泥基复合材料加固混凝土结构的界面力学及设计理论

Reinforced concrete (RC) structures have traditionally been strengthened by section enlargement using concrete/cement mortar overlays, or by external bonding/bolting of steel plates. In recent years, these techniques have to a large extent been replaced by the technique of externally bonded fibre reinforced polymer (FRP) composites. The FRP strengthening technique has a number of advantages over the traditional techniques due to the high tensile strength-to-weight ratio and excellent corrosion resistance of FRP. However, FRP composites have their own weakness mainly associated with the poor fire performance (flammability, smoke generation and rapid degradation in mechanical properties) of the polymer matrix (usually an epoxy resin). Besides, moisture impermeability of the bonded FRP system is also a critical issue since the epoxy creates a sealed surface that may jeopardize the durability of the strengthening system. These weaknesses have greatly limited the application of the FRP strengthening technology particularly in buildings and moisture environments and compromise its attractiveness in many applications. For this reason, attempts have been made to develop inorganically (cement-based) bonded FRP system for strengthening of RC structures...The present project aims to develop an ultra high toughness cementitious composite (UHTCC) bonded FRP grid ("UHTCC-FRPG" hereafter for brevity) system for strengthening of existing concrete structures. The UHTCC-FRPG system possesses greatly improved fire resistance and durability than externally bonded FRP reinforcement and is advantageous over traditional overlays. The use of FRP grids together with UHTCCs to form a new composite provides an ideal combination of strength and deformability for the strengthening layer...The proposed UHTCC-FRPG system represents a significant forward step in the development of the externally bonded FRP strengthening technique as well as the traditional cement-based overlay technique. Upon the completion of this project, an in-depth understanding of the complex bond behaviour in the UHTCC-FRPG system and advanced modelling approaches will be established; a preliminary design theory will be developed to facilitate practical implementation. The project will lead to an attractive new method with a great potential for practical applications in China and the rest of the world and open up a new area of research for the relevant international scientific committee.

近年，由于FRP具有轻质高强及耐腐蚀等特性，利用外贴FRP片材加固混凝土结构在世界范围内得到广泛应用。但外贴FRP加固技术存在一些自身缺点：（1）FRP材料及胶粘剂的耐高温性能较差；（2）FRP的不透气性会引起FRP和混凝土界面在潮湿或冻融环境下的耐久性问题。因此，发展基于水泥基粘结剂的连续纤维加固技术已成为国际研究热点。本项目研究基于具有抗拉强化特性的FRP栅格增强新型超高韧性水泥基复合材料（英文简称"UHTCC"）的混凝土结构加固技术，综合应用试验研究、理论分析和先进的数值模拟，基于多层次的界面力学，澄清FRP栅格和混凝土构件之间通过UHTCC粘接层的剪力传递机理，建立基于FRP栅格增强UHTCC复合体系的混凝土构件的抗弯、抗剪加固以及混凝土柱包裹加固的分析方法和初步设计理论，为FRP加固混凝土结构的安全、使用、耐久性的更新设计提供新途径。

近年，由于FRP 具有轻质高强及耐腐蚀等特性，利用外贴FRP 片材加固混凝土结构在世界范围内得到广泛应用。但外贴FRP 加固技术存在一些自身缺点：（1）FRP 材料及胶粘剂的耐高温性能较差；（2）FRP 的不透气性会引起FRP 和混凝土界面在潮湿或冻融环境下的耐久性问题。因此，发展基于水泥基粘结剂的连续纤维加固技术已成为国际研究热点。本项目提出了一种基于具有抗拉强化特性的FRP 栅格增强新型超高韧性水泥基复合材料（英文简称“UHTCC”）的混凝土结构加固技术。围绕为实现其工程应用所需澄清的一些基础问题，对FRP栅格增强UHTCC的抗拉强化特性、FRP 栅格和混凝土构件之间通过UHTCC 粘接层的剪力传递机理，FRP 栅格增强UHTCC 复合体系的混凝土构件的抗弯加固、抗剪加固以及混凝土柱的包裹加固进行了大量的实验研究及理论分析。. 试验结果及理论分析表明，基于FRP-UHTCC复合体系的混凝土加固技术可有效抑制加固层和基体之间的界面剥离，提高FRP材料的利用率，改善加固后构件的强度和延性。本项目的实施，对基于FRP-UHTCC体系加固混凝土构件中的不同层次的破坏机理有了深入理解，建立了对应的承载力计算理论，并初步形成了基于FRP-UHTCC体系加固混凝土构件的设计方法，为基于FRP 加固混凝土结构的安全、使用、耐久性的更新设计提供了新途径。