Strengthening of fire-damaged bridge columns using CFRP fabrics

In recent years the introduction of CFRP composites for strengthening concrete structures has received considerable attention and popularity in structural applications. This is due to their high strength-to-weight and stiff-ness-to-weight ratios, high corrosion resistance, good fatigue behavior, and their ability to form and to shape to the existing structure. This paper presents the results of an experimental investigation on concrete specimens, both damaged and undamaged by elevated temperatures, then retrofitted with externally-bonded CFRP fabrics under axial compression. For this purpose, six identical experimental tests were carried out on 204 x 750mm RC columns and six identical plain cylinders 100 x 200mm. Four of the cylinders were subjected to high temperatures, but only two were confined with CFRP sheets. The experimental parameters included the number of CFRP sheet layers and damaged and undamaged concrete. The results of this experimental investigation indicate that CFRP can significantly increase the residual strength of undamaged columns and post-heated concrete cylinders. The test results also confirm that using CFRP fabrics is an effective way to restore some or even the full strength of concrete after damage by heating. The results compare well with the available codes and guidelines for strengthening.