嵌入式FRP加固钢筋混凝土梁的破坏机理及设计方法

Deterioration of materials, implementation of new design codes, increased loadings and functional change of structures have created more and more needs for strengthening/upgrading of existing civil structures. Fiber-reinforced polymer (FRP) composites have been widely used in the strengthening of civil structures, due to a number of important advantages including their excellent corrosion resistance and a high strength-to-weight ratio. In an externally bonded FRP system, however, the strength of FRP composites usually cannot be fully utilized as the failure of the strengthened structure is often controlled by debonding on FRP-to-concrete interfaces because of the relatively low bond strength between them. As an effective and promising alternative to the externally bonded FRP method, the near-surface mounted FRP method can significantly enhance the bond strength between FRP and concrete by inserting FRP into concrete covers, resulting in a remarkable increase in the strengthening efficiency. However, as a thorough and in-depth research on NSM FRP method is still lacking worldwide, its application for structure strengthening is significantly limited. Based on the previous research conducted by the applicants as well as existing studies by other research groups, the proposed project aims to clarify the behaviuor of RC beams strengthened with NSM FRP through a combined experimental, numerical and theoretical study, and thus establish the systematic design theory of RC beams strengthened with NSM FRP. The outcome of the proposed project will largely enrich the understanding and design theory of NSM FRP technique in the strengthening of RC structures and will strongly promote practical applications of this technique in our country.

材料性能退化、设计规范更新、使用荷载增加以及结构功能改变等因素给土木结构造成了大量的加固需求。纤维增强复合材料（简称FRP）由于具有耐腐、高强重比等优点而被作为加强材料广泛应用于结构加固中。在外贴FRP加固混凝土结构中，由于界面强度的限制，在许多情况下FRP材料的强度不能得到充分发挥。嵌入式FRP加固技术是对外贴FRP加固技术的发展，该技术通过把FRP材料内置于混凝土构件保护层而有效增加了界面粘结强度，从而显著提升了加固效果。但是国内外的相关研究严重不足，大大限制了该技术的实际应用。本项目在申请人前期相关研究以及其他已有研究的基础上，旨在通过试验研究、有限元分析和理论分析相结合的方法，探明嵌入式FRP加固混凝土梁的基本力学性能，从而提出嵌入式FRP加固混凝土梁的系统设计理论。本项目的研究成果将弥补国内外在嵌入式FRP加固混凝土结构设计理论方面的严重不足，对推动该技术在我国的应用有重大意义。

近二十年间，嵌入式纤维增强复合材料（FRP）加固混凝土结构技术受到了国内外学者的广泛关注和研究。虽然相关研究已经证明了嵌入式FRP抗弯和抗剪加固钢筋混凝土（RC）梁的优异性能，但剥离破坏仍在该类加固梁中频繁发生，严重制约了该项技术的加固效率。为了探究嵌入式FRP加固RC梁的剥离破坏机理及性能提升技术，本项目采用试验研究、数值模拟和理论分析相结合的方法，开展了系统且深入的研究，具体包括：（1）带锚固装置的嵌入式FRP-混凝土的界面粘结性能。通过14个带端部FRP锚固装置的嵌入式FRP-混凝土粘结结点剪切试验，证明了项目提出的端部FRP锚固装置可有效提升嵌入式FRP-混凝土界面粘结性能，并确定了最优的端部FRP锚固装置构型；（2）嵌入式FRP抗弯加固RC梁的力学性能。首先，通过21根足尺RC梁试验，研究了荷载分布对加固梁剥离破坏的影响，并探明了传统FRP U型箍和项目提出的新型埋入式FRP端部锚固装置对加固梁剥离破坏的抑制效果和机理。然后，建立了准确的嵌入式FRP抗弯加固RC梁有限元模型，并开展了大量数值参数分析。最后，基于参数分析结果提出了带U型箍锚固装置的嵌入式FRP抗弯加固RC梁剥离破坏强度模型；（3）嵌入式FRP抗剪加固RC梁的力学性能。首先，通过13根足尺RC梁试验，探明了项目提出的一种新型FRP锚固装置和一种新型嵌入式FRP抗剪加固装置对RC梁力学性能的提升效果和机理。然后，建立了准确的嵌入式FRP抗剪加固RC梁有限元模型，并开展了数值参数分析。最后，基于参数分析结果提出了带锚固装置的嵌入式FRP抗剪加固RC梁的强度模型。本项目揭示了嵌入式FRP抗弯和抗剪加固RC梁的剥离破坏机理，提出了能有效抑制加固梁剥离破坏从而提升其力学性能的锚固装置，并建立了加固梁准确的有限元模型以及强度模型。本项目研究成果为带锚固装置的嵌入式FRP抗弯和抗剪加固RC梁的工程应用提供了设计理论。