Enhancement in the Load-Carrying Capacity of RC Rectangular Columns Adopting CFRP and GFRP

Abstract

There exist various techniques for retrofitting of reinforced concrete structural elements that have undergone damage. The use of FRP wrapping is one of the retrofitting techniques to enhance the load-carrying capacity of reinforced concrete (RC) columns (up to 20% increase). In this work, enhancement of axial load-carrying capacity of distressed RC columns adopting CFRP and GFRP was carried out. An RC column having a cross-sectional dimension of 400 mm × 600 mm and a height of 4 m is considered for this study. The RC column considered for the study was initially designed using concrete having a compressive strength of 30 N/mm2. Eventually, due to erroneous mixing and placing of concrete in the site, it resulted in the concrete in the column to have developed a lower compressive strength of 25 N/mm2. This distressed RC column eventually tends to have a lower load-carrying capacity due to a reduction in the compressive strength of concrete. This RC column is retrofitted using fibre-reinforced polymer (FRP) composites by wrapping the column to restore its original load-carrying capacity through the confinement provided by the FRP wrapping. The FRP composites considered in this study are carbon fibre-reinforced polymer (CFRP) and glass fibre-reinforced polymer (GFRP) fabrics wrapped around the distressed RC column with the application of epoxy. The design and estimation of quantity of the retrofit using CFRP and GFRP are adopted based on ACI codal provisions (ACI 440.2R-08). It was learnt by carrying out the design of the retrofit for the distressed RC column, the number of CFRP and GFRP layers obtained for wrapping are five numbers and ten numbers, respectively. From this study, it is learnt that CFRP is better when compared to GFRP in terms of enhancement in strength and load-carrying capacity of the distressed RC column with a lesser number of layers of wrap.