Structural strengthening and seismic retrofitting of corrosion-damaged concrete structures

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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.