Nowadays, application of FRP wraps is a common approach for strengthening columns. Various relationships have been proposed to determine the compressive strength of FRP confined concrete taking advantage of the confinement pressure. It should be noted that in some cases partial confinement is used due to some reasons. Therefore, the FRP confinement pressure differs with the case of continues confinement because of non-uniform distribution of confinement pressure. Therefore, modified relations for confinement pressure are required. Accordingly, in the present study, the authors try to propose a new and more accurate model for the confinement pressure of partially confined circular and square columns using experimental results and the Multi-Expression Programming (MEP).

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