It is proved that fiber orientation significantly affects the confinement of fiber-reinforced polymer (FRP) wrapped concrete members. The inclination of fiber relative to the hoop direction reduces confinement effectivity. In addition, most available models for peak stress and ultimate strain of confined concrete fail to provide accurate estimations for FRP-wrapped concrete in such cases. Accordingly, the main objective of the present study is to suggest modification factors that can be applied to the existing predictive models in the case of inclined fiber orientation and improve their prediction accuracy. For this purpose, a database of experimental results on FRP-confined concrete columns with inclined fiber orientation from previous studies have been collected. Then, by using an evolutionary algorithm, modification factors were proposed to incorporate the effect of fiber orientation. Applying these modification factors to the existing stress and strain models for FRP- confined concrete cylinders leads to a more accurate estimation of the behavior of FRP-confined columns with inclined fibers.

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