Description
In the last decades, fiber-reinforced polymer (FRP) composites gained popularity in the field of structural engineering thanks to their high strength-to-weight ratio, limited corrosion in harsh environments, and permeability to electromagnetic fields. These composites are used as reinforcement of new concrete members as well as for strengthening of existing structures. For existing reinforced concrete (RC) buildings, different techniques are available to increase the strength and the stiffness of the existing elements. Among them, a promising technology consists in applying a compression force to the elements by using external prestressed FRP bars. This technique may provide concrete crack closure, thus reducing the exposure of steel bars to the environment.
In this paper, a thorough literature review is carried out to investigate the open issues that hinders the diffusion of this innovative technique. According to the literature, the main issue is the anchor systems that should guarantee high stress level into the composite material avoiding, at the same time, local ruptures. Another open issue is the percentage of ultimate tensile strength to apply to the composite bars. In fact, a high level of prestress tension may lead to premature failure. Finally, the exposure of FRP bars to the environmental conditions (e.g., high moisture level, presence of chemical agents, and high temperature) may lead to a decrease of the compression force applied to the RC element.
