Structural strengthening and seismic retrofitting of corrosion-damaged concrete structures

在地震区，钢筋混凝土结构的延性至关重要。以往的研究表明，钢筋因腐蚀而失去延性，可能发生突然破坏，危及结构安全。随着复合材料在强化应用中的广泛应用，由于复合材料的脆性和可能的过早脱粘，人们对强化后截面延性的潜在损失感到担忧。***本程序提出了一种新的技术，以加强腐蚀损坏的钢筋混凝土结构，而不影响其延性。该技术的基础是使用由玄武岩纤维制成的特殊配方纤维增强混凝土（称为玄武岩MinibarsTM），同时使用外部粘合纤维增强胶凝基质（FRCM）系统来加固受损部分。该方法结合了玄武岩纤维混凝土（BFRC）和纤维混凝土（FRCM）的特点，以恢复受损构件的强度和延性。***将进行两个主题，每个主题由实验室测试，数值或分析建模和现场应用组成。主题1包括对腐蚀损伤的连续RC梁在凹区和凹区分别用BFRC修复和/或用FRCM加固。本主题将研究可能影响梁在单调和疲劳载荷下的性能的各种参数。将特别注意塑性铰的形成、转动能力和梁的延性。主题2涉及用BFRC和/或FRCM对地震缺陷和腐蚀损坏的混凝土柱进行改造。柱将受到循环横向荷载，以模拟地震荷载。研究包括腐蚀程度、配筋率和细节、FRCM的类型和体积分数以及BFRC的特性等参数。***该计划还将解决拟议的强化技术的耐久性问题。强化后的试样将暴露在进一步的腐蚀中，以评估所提议的技术的可持续性。此外，将开发一种新的有限元模型来模拟FRCM与衬底之间的界面行为；在测试过程中难以评估的行为。该模型将在混凝土混合物中加入玄武岩纤维的使用。拟议的项目还将与魁北克交通部讨论是否可能使用不同的FRCM系统进行现场试验，以加强选定桥梁的受损部件。预计拟议的技术将延长国家基础设施的使用寿命，同时具有显著的社会经济效益。该计划将为实践工程师提供一种创新技术，以保持我们基础设施的可持续性。

Ductility of reinforced concrete (RC) structures is crucial in seismic regions. Previous research has shown that steel bars lose their ductility due to corrosion and abrupt failure may occur, thus jeopardizing the structure's safety. With the wide use of composites in strengthening applications, concerns about the potential loss of section's ductility after strengthening are raised due to the brittle nature of composites and their likely premature debonding. ***This program proposes a novel technique to strengthen corrosion-damaged RC structures without compromising their ductility. The technique is based on strengthening the damaged sections with externally bonded Fabric-Reinforced Cementitious Matrix (FRCM) systems while using specially formulated fiber-reinforced concrete made with chopped basalt fibers known as basalt MinibarsTM. The proposed technique combines the features of FRCM and those of basalt-fiber reinforced concrete (BFRC) to restore the strength and ductility of the damaged member. ***Two themes, each consisting of laboratory testing, numerical or analytical modeling, and field applications will be conducted. Theme 1 comprises an investigation on corrosion-damaged continuous RC girders repaired with BFRC and/or strengthened with FRCM in both the hogging and sagging regions. This theme will examine various parameters that are likely to affect the performance of the girders under monotonic and fatigue loading. Special attention will be given to the formation of plastic hinges, the rotational capacity, and the ductility of the girder. Theme 2 involves the retrofitting of seismically-deficient and corrosion-damaged concrete columns with BFRC and/or FRCM. The columns will be subjected to cyclic lateral loads to simulate seismic loading. Parameters such as the corrosion level, reinforcement ratios and details, the type and volume fraction of FRCM, and the characteristics of BFRC will be investigated. ***The program will also address the durability of the proposed strengthening technique. Specimens will be exposed to further corrosion after strengthening to assess the sustainability of the proposed technique. In addition, a novel finite element model will be developed to simulate the interfacial behavior between FRCM and the substrate; a behavior that is difficult to assess during the tests. The model will incorporate the use of basalt fibers in the concrete mix. The proposed program will also be discussed with the Ministry of Transportation in Quebec for the possibility of conducting field trials using different FRCM systems to strengthen damaged elements in selected bridges. It is expected that the proposed technique will extend the service life of the nation's infrastructure, while having significant socio-economic benefits. The program will provide practicing engineers with an innovative technique that will maintain the sustainability of our infrastructure.