LAUSR

Abstract An experimental study was performed on thin-walled concrete-filled steel tubular (CFT) columns. In practical applications of CFT columns, the use of high-strength steel non-compact or slender section is expected to grow because thin plates are advantageous in steel production and economy. Thus, the present study focused on evaluation of the axial load-carrying capacity of rectangular CFT columns with high-strength steel (grade 800) slender section. The test parameters were the yield strength of steel, the width-to-thickness ratio of steel plates, and the use of stiffeners. Five specimens were tested under monotonic axial-compression loading. Although elastic local buckling occurred in the high-strength steel slender sections, unlike the expectation, the specimens exhibited significant post-buckling reserve strength, exceeding design code predictions. The specimens strengthened with vertical stiffeners showed enhanced performance, attaining the plastic capacity of the composite section. To investigate the characteristic behaviors such as steel local bucking and concrete confinement, nonlinear finite element analysis was performed on the specimens. The experimental and numerical results showed that the steel peak stress is affected by the lateral expansion of the crushed concrete, and the peak stress of the high-strength concrete is generally lower than the cylinder strength. On the basis of the results, a modified fiber analysis model and a simplified strength equation were proposed.