Circular columns confined with FRP: Experimental versus predictions of models and guidelines

This paper presents results of an experimental investigation on half-scale concrete columns retrofitted with externally bonded fiber reinforced polymers (FRP). It then reviews six selected confinement models and three North American design guidelines for circular columns retrofitted with FRP and provides an in-depth comparison between experimental test results, models predictions, and values obtained using the guidelines. The comparison, which is carried out in terms of the confined to unconfined strengths, but also in terms of the gain in the load carrying capacity, considers the following parameters: The FRP confinement ratio, the unconfined concrete strength, and the elastic and mechanical properties of FRP. The results of this investigation indicated that for columns made of lower strength concrete, existing models and guidelines overestimate the confined concrete strength, and hence, the load carrying capacity of the columns.