he aim of this paper is to determine the optimum amount of carbon fiber-reinforced polymer (CFRP) for strengthening columns in reinforced concrete (RC) frames suffering from weak column/strong beam condition. In this study, several parameters affecting the behavior of these frames including the level of columns’ axial force, Length and thickness of CFRP laminates are analyzed numerically. Nonlinear static analyses, employing three-dimensional finite element models are performed by an implicit method on 98 model frames having different length and thickness of CFRP and axial load. The results revealed improvements in both strength and ductility of the system when the columns of higher axial load were strengthened; while in strengthening of the columns under lower levels of axial load, the influence of CFRP was only observed in the strength of the system. An optimization method which takes into account the cost of the utilized material and the strength of the system was proposed, and the optimum CFRP length and thickness were determined.
