Comparative study on the behaviour of concrete reinforced with FRP and steel singly reinforced beams

Bakheit, Paul Charles Saki

Comparative study on the behaviour of concrete reinforced with FRP and steel singly reinforced beams

Master Thesis

2022

Abstract

Maintenance and repair of concrete infrastructure account for a large amount of financial resources. This is due to the deterioration of reinforced concrete through the corrosion of steel reinforcement. The depassivation of the steel creates an environment prone to chloride ingress and carbonation. This leads to steel corrosion and internal stresses which further exasperates the problem. Fiber Reinforced polymers can be an alternative to steel reinforced because it is considered to be chemically inert, high tensile-strength-to-weight ratio, high tensile-modulus-to-weight ratio, and high fatigue strength. Since it is chemically inert it will not undergo corrosion. Hence FRP will perform better in corrosive areas. The study aimed to investigate the behaviour of concrete reinforced with FRP. Its failure modes, crack width and patterns, and deformation of the reinforcing material. The experimental work consisted of testing a total of 5 simply supported beams, each tested under four-point loading until failure. One beam consisted of steel reinforcement, three beams consisted of the Carbon Fiber Reinforced Polymer (CFRP) reinforcement, the other beam had CFRP with an experimental anchorage. All the beams had the same cross section of 160mm x 250mm x 3040mm and designed to the same moment capacity. The FRP reinforced concrete beams and steel reinforced concrete beam failed through concrete crushing. This was expected for the FRP reinforced concrete beams but not the steel reinforced concrete beam. The FRP reinforced concrete beams exhibited extensive cracking in comparison to the steel reinforced concrete beams and significantly more deflection before failure. The maximum deflection produced by the FRP reinforced concrete beams was around 20mm more than the steel reinforced concrete beam. The large difference in values is because of the weak bonding between the FRPs and the surrounding concrete, also, the lower stiffness of the CFRCs in comparison to the SRC. The strain of the reinforcement inside the concrete showed that permanent deformation did not occur in the CFRP or steel. This was further supported by visually inspecting the reinforcement after the beams were loaded to failure. The maximum crack widths measured on the FRP reinforced concrete beams and the steel reinforced concrete beam was 2.5mm and 0.5mm, respectively. Horizontal cracks were observed at the depth of the FRP reinforcement which is attributed to a week bond between the FRP and concrete.

Keywords

Civil Engineering

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