Experimental study on concrete columns confined with external FRP

Abstract

It is known that confinement with FRP (fibre reinforced polymer) jackets is a useful reinforcement technique to improve the strength and ductility of concrete columns subjected to axial compression loads, especially in those that have a circular cross section. This strengthening method is less effective for elements with square or rectangular sections in which, unlike the circular ones, the FRP confinement is not uniform. However, concrete columns with non-circular cross section are very common in construction, so it is essential to be able to estimate adequately the ultimate capacity of the reinforced element depending on the shape of the section. Most of the international guidelines for the design and calculation of this type of reinforcements recognize this circumstance and incorporate a shape factor, although there is no unanimity in their proposals. This paper presents the preliminary results of an experimental study on intermediate-sized concrete specimens reinforced with FRP jackets. Special attention is paid to two parameters related to the section shape that have an important impact on the efficiency of the reinforcement on rectangular sections: the aspect ratio of the cross section or relationship between the sides of the concrete section (b/d) and the radius of curvature of the corners (Rc). This work is part of a research project that includes a larger experimental program with full-scale tests.