Seismic retrofitting of damaged exterior beam–column joints using fibre reinforced plastic composite–steel plate combined technique

A conventional gravity load design philosophy for reinforced concrete (RC) structures has been slowly replaced by seismic design since the 1970s. But, till recently, capacity design and ductile detailing were not strictly implemented in practice in many developing countries which are prone to seismic hazard. In the present study, performance of exterior beam–column joints designed based on ductile and non-ductile philosophy has been studied under cyclic load. It is found that although the incorporation of ductile detailing has considerably improved the seismic behaviour of the structural component, it could not assure the damage propagation in a safe zone. Moreover, in both specimens, the main damage has been concentrated in the joint zone irrespective of ductile detailing. Further, the damaged specimens were adequately repaired and suitably retrofitted using fibre reinforced plastic and steel plate and tested again under the same cyclic load. The retrofitted ‘NonDuctile’ specimen, as proposed in this study, could not only be able to regain its original performance (in terms of strength deterioration, stiffness degradation, energy dissipation), but has also shown improved performance in comparison to the original ones which is ideally desirable as well. Further, the retrofitted ‘Ductile’ specimen has shown a promising aspect of the proposed retrofitting strategy for seismically damaged components.