Behavior of RC columns retrofitted with CFRP exposed to fire under axial load

Abstract

It has long been known that fire could dramatically reduce the characteristic strength of the reinforced concrete member. A significant effort has been devoted to study the effect of fire on the reinforced concrete members. Most of them were focused on evaluating columns’ fire resistance and provided some recommendations of structural fire resistance. Little attention was paid to the behavior of CFRP strengthened columns after fire.The main objective of the present work is to study the behavior of reinforced concrete CFRP strengthened columns exposed to fire under axial load experimentally. A furnace and a loading frame had been built to allow the application of the axial load driven from a hydraulic jack on the fired specimens at the same time. Fourteen CFRP strengthened columns with different protection layers subjected to 900°C for 30min and axial load at the same time according to ASTM were tested. It can be concluded that the some materials used for protection have low thermal conductivity and good resistance to fire, and CFRP materials used with a appropriate fire insulation can endure elevated temperatures of fire under service loads for more than 70min.Although increasing the coating thickness will increase the heat insulation, plain coating of more than 3.0cm thickness will not be able to stay in place without being reinforced with a suitable wire mesh.