The present time design of R/C columns, which is based on intentional collapse mode, is dependent on ductility. In this paper, the effect of various bond properties of longitudinal bar on behavior of R/C columns is investigated. Six R/C columns with three types of longitudinal bar's bond properties were tested under cyclic lateral load while simultaneously being subjected to constant axial load. Test results indicate that the collapse modes of R/C columns are affected by bond properties of longitudinal bar.
