Axial behaviour of rc members repaired after fire exposure with frp sheets

This study aims to assess the effects of a severe fire on the axial behaviour of reinforced concrete (RC) columns and the efficiency of repair through external fibre reinforced polymer (FRP) jacketing after fire exposure. In the scope of the research, results of an experimental work including a total of six square RC columns with dimensions of 300 x 300 x 500 mm are presented. The specimens had four longitudinal reinforcing bars each having 20 mm diameter while lateral confinement was maintained using stirrups with a diameter of 10 mm and a spacing of 100 mm. Four of the specimens were subjected to fire in a fire facility following ISO-834 fire curve for 90 minutes whereas two of the columns were kept at room temperature as reference specimens. Two of the fire damaged columns were repaired using two layers of carbon FRP (CFRP) sheets while other two specimens were bare columns without CFRP sheets. The columns were tested under uniaxial compression to investigate the effectiveness of CFRP sheets in repairing fire damaged structural members. Test results indicated that fire exposure adversely affected the axial load resistance, stiffness and ductility of the columns. On the other hand, in case of FRP jacketing, axial load resistance was restored and ultimate deformation capacity was remarkably increased. Furthermore, experimental study showed that the use of FRP did not restore the column’s axial stiffness which was remarkably reduced after fire exposure.