push-out test on low-density concrete filled stiffened steel tubular columns

In this work, both experimental and numerical analysis was carried out to determine the bond strength of stiffened circular concrete-filled steel tube (cfst) columns infilled with low-density concrete. push-out tests were carried out on 12 columns with an inner diameter of 150 mm and a height of 600 mm. the parameters varied are (i) thickness of steel tube (2.5 mm, 4 mm); (ii) infill concrete type (normal concrete—nc; light -dense concrete by partially replacing coarse aggregate with lightweight expanded-clay aggregates (leca)—lc; lc in which 40% of cement was replaced with ggbfs along with 1% of micro-steel fibers as the volume of concrete—lcgf); (iii) number and spacing of inner reinforcement stiffeners (4 stiffeners in a row with 37.5 mm c/c spacing and 6 stiffeners in a row with 25 mm c/c spacing). numerical analysis was performed using ansys software. comparisons were also drawn with the existing codes for cfst columns—en4, bs5400, as5100.6–2004, ansi/aisc 360-10, and aij. both experimental and numerical results revealed that the bond strength has increased in low-density concrete-filled steel columns. the increase in bond strength was more in specimens with a smaller (d/t) ratio and with a closely spaced inner stiffener. lc and lcgf as infill types have enhanced the bond strength up to 7% and 14%, respectively, than nc. thus, the low-density concrete could be cast as infill in stiffened cfst columns subjected to significant longitudinal shearing stresses to achieve enhanced bond strength