Retrofitting of rc columns to enhance the seismic response of moment resisting frames

The gravity load designed or previous code designed buildings did not behave well during recent earthquakes on account of insufficient capacity and ductility. To lessen the seismic risk, special attention needs to be paid on such existing building stock. In this study, an attempt has been made to retrofit 3, 5, and 7 storey existing reinforced concrete (RC) buildings by means of RC jacketing. For this, different thicknesses of RC jacketing and column jacketing strategies were considered. The internal, external and full old columns of the case study structures were strengthened by applying 10, 15 and 20 cm thicknesses of RC jacketing. All structures were modeled as 2D RC frames having square columns using a finite element program. The seismic performance of the unretrofitted and retrofitted frame models were examined through the nonlinear static (pushover) analysis and nonlinear time history analysis. Capacity curve, base shear ratio, initial stiffness ratio, roof displacement versus time history, storey displacement, and inter-storey drift ratio were computed and discussed comparatively for each structural system.