Square concrete section confined by FRP: ultimate strength prediction

During the last ten years, several studies have been devoted to understanding the behaviour of circular concrete sections confined by FRP. Less studies have dealt with square and rectangular sections, even if the problem is equally important, given the large amount of buildings with such sections that need to be retrofitted due to poor performance under vertical and horizontal actions. A numerical model was already proposed for the prediction of the stress-strain relationship. In order to implement such model in a design code framework, a mechanics-based equation has been developed and preliminary results are presented for the prediction of the ultimate strength of square sections confined by FRP. Since the model consider the corner radius influence, circular sections are automatically included as a particular case. The simplified model has been tested against a set of experimental values available in the literature: the comparison was satisfactory and its accuracy is discussed.