Rapid repair of severely damaged reinforced concrete columns under combined axial compression and flexure: An experimental study

Reinforced concrete (RC) columns are in general subjected to combination of axial compression and bending loads. A rapid repair technique for effectively restoring the original strength and stiffness of severely damaged RC columns under combined bending and compression loads is investigated. In total, six RC columns are tested under uniaxial eccentric compression at an eccentricity (e) to depth ratio (d) of 0.63. The columns are initially subjected to severe damage corresponding to a concrete compressive strain (εc) of 0.0035. Damaged columns had buckling of longitudinal reinforcement and concrete crushing. After severe damage, the columns are repaired with three different techniques using (i) quick set cement grout mortar (QS), (ii) near surface mounting (NSM) of CFRP laminates and (iii) hybrid FRP strengthening using a combination of NSM and external bonding (EB) of CFRP fabric. The specimens are tested under high ratio of eccentric compression (e/d = 0.63) in a displacement controlled mode. The performance of different repair techniques under eccentric compression is compared with the similar specimens tested under concentric compression. Test results revealed that hybrid FRP strengthening is very efficient in fully restoring the original strength and failure displacement under combined compression and bending loads. Only NSM strengthening is found to be very efficient under eccentric compression than in concentric compression