Seismic strengthening of rectangular reinforced concrete columns using fiber reinforced polymers

In recent years, fiber-reinforced polymers have been widely utilized to improve the seismic performance of deficient RC columns. In this study, the flexural behavior of CFRP strengthened rectangular RC columns with plain bars and insufficient confining steel was investigated. Five specimens, representing a typical deficient building column with poor transverse reinforcement detailing and low concrete strength, were tested under cyclic displacement excursions and constant axial load. The beneficial effect of CFRP anchor dowels and the FRP confinement ratio on the ultimate drift ratio of the specimens was assessed. It was found that an increase in the confinement ratio enabled the column to sustain higher ultimate drift capacities for the strengthened columns. Furthermore, an appropriate configuration of CFRP anchor dowels resulted in a better seismic behavior compared to the CFRP retrofitted column without any dowels. Subsequently, a simplified drift based design equation was proposed for FRP retrofit design of deficient rectangular columns.