Abstract
In the last two decades, the use of advanced composite materials such as Fiber Reinforced Polymers (FRP) in
strengthening reinforced concrete (RC) structural elements has been increasing. Research and design guidelines
concluded that externally bonded FRP could increase the capacity of RC elements efficiently. However, the
linear stress–strain characteristics of FRP up to failure and lack of yield plateau have a negative impact on the
overall ductility of the strengthened RC elements. Use of FRP laminates, which consist of either carbon, glass
fibers, and aramid fibers, changes the behaviour of the material to a non-linear behaviour. This paper aims to
study the performance of reinforced concrete beams strengthened by GFRP laminates. This paper presents an
experimental program conducted to study the behaviour of RC beams strengthened with glass fiber reinforced
polymer (GFRP) laminates. The program consists of a total of twelve T-beams with overall dimensions equal to
150 mm x250mmx3000mm. The beams were tested under cyclic loading up to failure to examine its flexural
behaviour. Different reinforcement ratios, fiber directions, locations and Glass fiber reinforced polymer (GFRP)
laminates were attached to the beams to determine the best strengthening scheme. Different percentages of steel
reinforcement were also used. An analytical model based on the stress–strain characteristics of concrete, steel
and FRP was adopted. Recommendations and design guidelines of RC beams strengthened by GFRP laminates
are introduced. The experimental test results showed that strengthening with GFRP significantly enhanced the
flexural responses of the specimens compared with the control specimen. The first cracking and ultimate loads,
energy absorption capacities, ductility and stiffness were remarkably enhanced. It was also confirmed that the
bond length of the strengthened reinforcement greatly influences the energy absorption capacities, ductility and
stiffness. The effect of the bond length on these properties is more significant compared to the amount of
strengthening reinforcement

Key words: Glass fiber reinforced polymer, Fiber directions, RC beams, Cyclic loading, FRP laminates, stress– strain characteristics