Effect of corroded reinforcement on capacity of square reinforced concrete columns confined with FRP sheets under eccentric loads

Abstract

Steel corrosion is one of the primary causes which significantly degrade the load-carrying capacity and FRP (fibre reinforced polymer) strengthening efficiency of FRP-strengthened reinforced concrete columns under eccentric loading. However, this issue has not been studied comprehensively and systematically in the literature. Particularly, there has been no study on the strengthening efficiency of basalt FRP (BFRP) which is becoming popular due to its excellent performance and affordable price. This study experimentally investigates the effect of corrosion level of reinforcement by mass (0%, 15% and 30%), relative eccentricity (e/h = 0.125 and 0.375), type of FRP (CFRP and BFRP) and FRP thickness (1 or 3 layers) on the load-carrying capacity and deformation of corroded-reinforcement reinforced concrete (RC) columns. The experimental results showed that steel corrosion reduced the load-carrying capacity of the unstrengthened RC columns up to 23% and this degradation increased with the corrosion level. Both CFRP and BFRP have proven excellent strengthening efficiency since the capacity of the FRP-strengthened corroded-reinforcement RC columns increased up to 47%. Particularly, the strengthening efficiency of BFRP sheets was slightly lower than that of CFRP sheets (<7%). On the other hand, the increase of the relative eccentricity from e/h = 0.125 to e/h = 0.375 reduced the strengthening efficiency of FRP. In addition, a semi-empirical model was proposed to predict the capacity of corroded-reinforcement RC columns strengthened with FRP under eccentric loading. The predictions match well with the experimental results with a small coefficient of variation.