Structural behaviour of fibre reinforced plastic reinforced concrete

Abstract

Rapid advances in construction materials technology have taken place in these recent years. A relatively new concept is the use of fibre reinforced plastics as a construction material. Over the past decades steel has been the primary reinforcing material used in reinforced concrete structures. However, it is susceptible to corrosion when exposed to adverse environmental conditions, such as humidity, contamination from sea water and other aggressive substances. An effective approach, to eliminate the corrosion problems in steel reinforced structures is to use fibre reinforced plastic rebars as a substitute to the steel rebars. The mechanical and physical properties of fibre reinforced plastics vary from the conventional steel reinforcement. Such properties include; high strength-to-weight ratio, low modulus of elasticity and noncorrosive, non-magnetic and non-conductive properties. The most common fibre types used are glass, carbon and aramid. Of these three, glass fibres have proved to have the greater potential in civil engineering applications mainly because of their relatively low cost, compared to the other two fibres. Because of this fact, glass fibre reinforced polymer rebars were used in this study. The aim of this study was to investigate the flexural behaviour of GFRP reinforced beams. In this study, twelve beams were tested, nine of which were reinforced with GFRP rebars, whilst the other three were reinforced with conventional steel rebars. Comparison between the behaviour of GFRP reinforced and steel reinforced beams was made. Two modes of failure were observed, namely the compression and tension mode of failure. Both failure modes were brittle; however the tensile failure mode in the GFRP reinforced beams resulted in a more sudden and catastrophic failure, when compared to the compression failure mode. The main variable in this experimental program was the reinforcement ratio. It was noted that deflections and concrete strains were influenced by the reinforcement ratio. Strains at the upper most fibre of the concrete were measured by means of strain gauges. Strains at different locations along the rebars were also measured. The experimental results obtained from the tests were then examined against suggested equations by researchers and published guidelines.