Seismic behaviour of RC jacketed columns under different axial loads

Abstract

This study examines the flexural performance of reinforced concrete (RC) columns strengthened through a seismic jacket technique developed using a prefabricated steel bar unit that forms peripheral closed-hoops and supplementary V-ties, satisfying the design requirements of the ACI 318-14 seismic provisions. Three RC jacketed columns were prepared with a parameter of axial load levels and tested under a constant concentric axial load and cyclic lateral loads. Analytical approaches were also applied to examine the axial-load–moment interaction of the RC jacketed columns when considering the confinement effect provided by the jacket section and to investigate the applicability of the previous performance-based design models proposed for virgin seismic columns. The test results show that the developed jacket technique possesses a good potential in enhancing the flexural stiffness, strength, and ductility of deficient columns even under a high axial load. RC jacketed columns possess a higher ductility than that estimated using the ductility parameter model, regardless of the axial load level. Thus, the jacket section including the seismic details of a transverse reinforcement can be conservatively designed based on the axial-load–moment interaction and ductility parameter model for the moment and ductility enhancements required by deficient columns.