Upgradation of gravity load designed sub-assemblages subjected to seismic type loading

In the present study, a methodology based on strength hierarchy has been proposed for upgradation of original gravity load designed (GLD) reinforced concrete (RC) structures. Exterior beam–column joint of an RC structure has been considered as the target sub-assemblage and the target strength of the deficient sub-assemblage was decided from that of a seismically designed ‘Ductile’ one. Three different types of upgradation schemes were investigated where shear- and flexural-strengthening were provided by Fiber Reinforced Plastics (FRP) and weak joint region of ‘GLD’ sub-assemblage was upgraded by steel plate jacketing. The original (‘GLD’-, ‘NonDuctile’-, ‘Ductile’-) and upgraded-sub-assemblages were investigated under repeated reverse cyclic loading. It was observed that the ‘GLD’ specimen seized to function under reverse loading and subsequent improvements, though not optimal, were observed from ‘NonDuctile’ and ‘Ductile’ specimens. It was further found out that the upgraded specimens showed considerable improvement in strength deterioration, stiffness degradation and energy dissipation. Further, the upgraded specimens with adequate energy dissipation could even be able to shift the plastic hinge from the joint face into the beam which was not observed even in original ‘Ductile’ specimen. The upgraded schemes are simple, practically feasible and efficient as well.