Abstract
The use of Fiber Reinforced Polymer (FRP) composites for strengthening concrete structures has gained a lot of popularity in the past couple of decades. The major issue in the retrofitting of concrete structures with FRP is the accurate evaluation of flexural and shear strains of polymer composites at the bonding interface of epoxy and concrete. To address it, a comprehensive experimental study was planned and carbon fiber reinforced polymer (CFRP) composite was applied on the concrete surface with the help of adhesives. CFRP was used as an external mounted flexural and shear reinforcement to strengthen the beams. Flexural load tests were performed on a group of eight reinforced concrete beams. These beams were strengthened in flexural and shear by different reinforcement ratios of CFRP. The strain gauges were applied on the surface of concrete and CFRP strips to assess the strain of both CFRP and concrete under flexural and shear stresses. The resulting test data is presented in the form of load–deformation and strain values. It was found that the values of strains transferred to the FRP through the concrete are highly dependent on the surface tensile properties of concrete and debonding strength of the adhesive. The test results clearly indicated that the strength increment in flexural members is highly dependent on strain values of the CFRP.
Highlights
Reinforced concrete is one of the most widely used construction materials in the past, as well as in the modern world, due to its high compressive strength, fire and weather resistance properties.The majority of reinforced concrete structures that exist nowadays were designed and constructed based on old design codes and specifications
All beams that were retrofitted with Carbon Fiber Reinforced Polymer (CFRP) reinforcement showed better results than control samples in terms of peak load and mid-span deflection
All the beams under experiment were were strengthened with different CFRP reinforcement ratios
Summary
Reinforced concrete is one of the most widely used construction materials in the past, as well as in the modern world, due to its high compressive strength, fire and weather resistance properties. The majority of reinforced concrete structures that exist nowadays were designed and constructed based on old design codes and specifications Most of these concrete structures are more than fifty years old, and during their design life, with the passage of time, they are subjected to harsh environmental conditions, e.g., saltwater, deicing chemicals, and extreme temperature variations, resulting in strength reduction. When CFRP is applied to the concrete surface in the form of externally bonded flexural and shear strips, it results in debonding and sometimes premature failure of the CFRP concrete interface. This phenomenon becomes more critical at the mid-span and supports of a supported beam section [11,12,13,14,15]. The failure of CFRP-strengthened beams may occur due to flexural, shear, bearing, CFRP debonding, CFRP rupture and by the ripping of the concrete cover along with CFRP [16,17,18]
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