Concrete columns confined with CFRP wraps

Today, there is an increasing use of fiber reinforced polymer (FRP) composites in civil engineering as reinforcement of existing structures. In particular, FRP composites offer higher strength and Young’s modulus than traditional steel devices, also easy handling and installation, excellent resistance to corrosion and they can be plastered after application. When FRP wraps are used to confine compressed pillars, the effective contribution of the composite cannot be accurately evaluated because it begins to work as the stress state of the member grows. In the present paper, some theoretical relationships available in literature and in current international design guidelines, regarding the evaluation of confinement effect on wrapped concrete columns, are analyzed and compared with experimental test results. Based on these considerations, we propose a new formula that is in good agreement with the experimental test results that were produced for the purpose and reported both in the present paper and in a previously published research study. Although empiric, the proposed formula is able to reproduce the structural response of wrapped specimens and the failure mode as observed in the experimental tests.