Strengthening of square concrete columns with composite materials. Investigation on the FRP jacket ultimate strain

An accurate estimation of the effective ultimate strain of the FRP jacket is crucial to determine the values of strength and ultimate strain of FRP confined concrete. However, this is one of the main aspects not yet resolved by the theoretical models. Published design recommendations differ on this aspect, particularly in the case of non-circular sections. In this work, an experimental program carried out on 38 square section concrete specimens confined with FRP is presented. The results show a great influence of the radius of rounding of the corners on the behaviour of FRP confined square columns. The experimental values of effective ultimate strain are compared with the recommended values given by design guidelines.