Seismic performance of RC columns retrofitted using thick-hybrid-wall technique

This study examined the seismic performance of reinforced-concrete (RC) columns retrofitted using the thick-hybrid-wall (THW) technique with carbon fiber–reinforced panels (CFRPs). THW is a strength–ductility-type seismic retrofit technique developed to strengthen piloti-type RC buildings by incorporating additional concrete walls, steel plates, and high-strength bars called PC bars. Herein, six retrofitted specimens were tested under axial and lateral loads to evaluate their ultimate shear and flexural strengths, failure modes, and the experimental performance of the CFRPs. In this study, the CFRPs were used instead of the steel plates. Compared with steel plates, CFRPs offer advantages such as durability, light weight, high tensile strength, and construction simplicity. The additional wall length, bond performance of the rebars, presence/absence of PC bars, lateral confinement pressure, and axial force were the research variables. A theoretical equation for obtaining the demand flexural strength was developed, and the shear strength equation was modified, which resulted in an accuracy of > 95 %. Moreover, a model was developed to assess the interaction of the axial force with the shear and flexural strengths, which enabled the simultaneous evaluation of the shear and flexural strengths and prediction of the failure modes of the retrofitted columns. The test results indicate that the CFRP improves the lateral strength and ductility of the retrofitted columns; however, it does not exert a confinement effect on the compressive strength of concrete. The effects of the research variables on the seismic performance of the retrofitted columns were examined and the accuracy of the analytical models was validated experimentally.