Rate of Reinforcement Corrosion and Stress Concentration in Concrete Columns Repaired with Bonded and Unbonded FRP Wraps

Abstract

Experiments were conducted to assess the effect of using bonded and unbonded glass and carbon fiber–reinforced polymer (FRP) wraps to strengthen corrosion-damaged, reinforced-concrete (RC) columns. The effect of wrapping on the rate of corrosion and strain concentration on the FRP wrap was investigated through an accelerated corrosion test. The results indicated that wrapping reduced the mass loss in the reinforcing bars by 33–46% after 130 days of accelerated testing. Both glass and carbon wraps were equally effective in slowing down corrosion. Although unbonded wraps reduced stress concentrations in the FRP, they were slightly less effective in reducing the corrosion rate than bonded wraps. Finite-element (FE) analysis of the experimental specimens was performed to verify the effect of bonded and unbonded FRP wraps on the strain concentration obtained from experimental tests. The FE results confirmed that the strain concentration around a corroding bar reduced when the wrap was unbonded. Because the strain concentration on the bonded wraps at the laboratory-scale FE model was of concern, a large-scale RC column was modeled to assess the effect of strain concentration around a corroded bar in real bridges.