Behaviour of RC columns strengthened by steel caging under combined bending and axial loads

The steel caging technique is used to strengthen RC columns all over the world, as it has been shown to be effective, economical and easy to apply. Most studies carried out to date on this strengthening technique have focussed on isolated sections of columns subjected to axial loads. This paper deals with an experimental study on the behaviour of RC columns strengthened by steel caging under combined bending and axial loads. Full-size specimens were laboratory tested and the beam–column joint was also simulated. Two different types of element were used to solve the strengthening in the zone nearest to the joint. These were: (1) capitals welded to the steel cage in contact with the beam and (2) steel tubes joining the cage on both sides of the joint. The results obtained show that the technique described considerably increases the resistance and ductility of columns strengthened in this way. The results are compared with those that could be obtained with the proposal of Eurocode No. 4 and also with the results of two other similar studies.

Research highlights
► The paper deals with an experimental study on the behaviour of RC columns strengthened by steel caging.
► This study considers the influence of the beam–column joint.
► The results obtained show that the strengthening technique increases the resistance and ductility.
► The results obtained are compared with those that could be obtained with other proposals.