Strengthening of short circular columns using FRP materials - Determining the effect of confinement

Abstract

The paper is focused on strengthening of loadbearing reinforced concrete vertical members by composite materials. These modern materials are used more and more in the last years. Usage of the FRP fabrics as confinement has several advantages, however there are some uncertainties regarding the design (eg. determining the compressive strength of confined concrete and limit strain of confined concrete). An assessment of influence of the confinement on the elements (its load bearing capacity and ductility) is necessary for design. There is a large number of analytical formulas, standardized approaches and regulations, which specify the resulting influence of the confinement. The paper draws attention to the considerable dispersion between those obtained results. The paper presents an analysis of the influence of strengthening of reinforced concrete columns, which are confined with FRP fabric. The obtained theoretical results were compared with a real behaviour of several specimens. The short reinforced and confined concrete circular columns were used as the test specimens. The height-diameter ratio of the columns was set as 2:1, therefore an influence of slenderness to loadbearing capacity of the column can be neglected. Consequently, the influence of confinement can be maximized and the dispersion of results according to different methodologies can be emphasized.