Confinement effect on strength of concrete columns by using cold-formed steel tubes

Abstract

Enhancement of strength and ductility of weak concrete columns is continuously attempted and different methods are adopted. As the popular method, fiber reinforced polymer wrapping calls for precise quality control with skilled supervision, an alternate methods is being developed. Towards this, a methodology is proposed to confine concrete columns by using built-up tubes with cold-formed steel hat sections. This paper presents an experimental investigation on the confinement effect on axial strength of short concrete columns by using built-up. The performance of the columns is studied in terms of load-displacement behavior and failure modes and the results are compared with respective plain concrete columns. Critical failure modes; local crushing, vertical splitting of concrete followed by bulging of steel sections and rupture of the bolt are found out. The enhancement of the strength of the column is 38.64% to 56.61%. Based on the study, the existing expression for evaluating the confined strength of wall panels available in the literature is modified and validated with the results available in the literature. The modified expression predicts the axial strength of rectangular concrete columns confined with carbon fiber reinforced polymer wraps closer to the experimental results. It is inferred that the new method can be adopted as an alternative to the traditional methods for strengthening the weak columns.