Numerical Study of RC Columns Strengthened by the Combination of Steel Strips and CFRP Sheets

The carbon-fiber-reinforced polymer sheets (CFRP) and steel jackets are typically used for strengthening of the concrete columns. In the current study, a new approach is considered for the columns retrofitted applying those materials simultaneously. The effect of hybrid methods on the performance of columns under lateral loading is investigated numerically. For this purpose, the numerical models are verified using valid laboratory tests on the columns confined with FRP or steel jackets. Strengthening methods of concrete columns in the present study include the combination of a CFRP layer of different thicknesses and a steel cage, which is made as a complete steel jacket or the combination of L-shaped sections with steel bands. The results show that the concurrent use of steel jacketing and CFRP wrapping techniques increase the bearing capacity of the column, up to 4 times the bearing capacity of the unreinforced column. The alternative steel jackets composed of the connection strips lead to better performance in terms of the increasing strength, as well as the ease of execution. Ultimately, it should be noted that the presence of carbon fibers reduces the ductility of the studied columns.