Large deflections in reinforced concrete (RC) beams under different loadings can cause cracking of walls and damage to nonstructural components. The long-term deflection of RC beams is one of the design issues that must be accurately controlled by designers to satisfy serviceability requirements. Flexural strengthening is one of the ways to deal with this phenomenon of excessive deflection in RC beams. Nowadays, using Fiber-Reinforced Polymers (FRP) is a common method for strengthening and rehabilitation of RC structural members. In recent years, many researches have been performed on the deflection and effective moment of inertia of RC beams strengthened with FRP bars, but investigations on the effective moment of inertia of RC beams reinforced with FRP sheets by EBR method are relatively limited and the need for further studies in this regard is felt. The current design codes use simple and approximate methods to calculate deflection of these structural elements, but to prevent their unexpected behavior under service and ultimate load, more precise relationships are needed. Estimation of deflections under the service load level requires the effective moment of inertia of the beams. Various studies have been conducted to determine the relationships for the effective moment of inertia of RC beams strengthened with FRP sheet, but the results showed that the accuracy of the existing relationships is not acceptable. In this research, using an evolutionary algorithm called multi-expression programming (MEP) and a database of experimental results collected from literature, a relation for the effective moment of inertia of such beams has been proposed. Comparison of the accuracy of the propose model with other existing relations proves higher accuracy of the suggested model

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