Strength and Ductility of Axially Loaded RC Short Columns Confined with CFRP and GFRP Wraps

Abstract

With the evolution of technology, construction industry has witnessed enormous advancement in the production of concrete and construction materials. Such materials have helped the community to produce structures that consume less energy, environmental friendly, have less carbon foot print and are more durable with longer life expectancy. However, old buildings that didn't follow the latest technology are no longer considered to have the previous qualities. In addition, they are no longer considered safe due to the deterioration of the concrete, steel or both. As a result, researchers continued to investigate different types of materials that can best strengthen and rehabilitate aging concrete structures and render them safe. In this investigation, RC short columns have been strengthened with CFRP and GFRP wraps to increase their load carrying capacity and enhance their ductility. Thirty columns were tested - fifteen of them were normally designed, i.e., they have the minimum number of transverse reinforcement and the other fifteen were under designed, i.e., their transverse reinforcement is less than the minimum. The parameters investigated were the type of material used for strengthening and the number of layers of CFRP and GFRP used for wrapping the columns. Comparison of gains of axial strength and ductility are presented in this research. It is observed that the axial load capacity of the columns has increased, in the average, by 9.44 % and 24.56% when wrapped with one and two CFRP layers, respectively while it has increased with, in the average, by 8.06% and 17.68% when wrapped with one and two layers of GFRP layers, respectively. It is also observed that the ductility of the columns has increased when wrapping with one or two layers of CFRP. It is also observed that the Ductility of the columns has increased by 2.06% and 8.15% when wrapped with one and two layers of CFRP, respectively while it has increased by 11.77% and 52.67% when wrapped with one and two layers of GFRP layers, respectively. It can be concluded from this study that CFRP wraps enhances the axial load capacity more than GFRP wraps while GFRP wraps enhances the ductility more than the CFRP wraps.