Mechanical Behavior of Stirrup-enhanced Improved Welded Concrete Filled L-shaped Steel Tubular Stub Columns under Axial Compression

In this paper, we conducted the axial compression test on one improved welded concrete filled L-shaped steel tube (IWCFLST) stub column and two stirrup-enhanced IWCFLST stub columns. The experimental results indicate that the stirrup-enhanced IWCFLST stub columns exhibit better compressive mechanical properties. The stirrups can increase the axial compressive load-bearing capacity by up to 35% and the ductility coefficients by 77%. The impact of the equivalent stirrup ratio on the axial compression mechanical behavior was investigated. Three-dimensional (3D) solid finite element (FE) model of the specimens was constructed by ABAQUS. Parametric analysis was performed and the restriction action of IWCFLST stub column under axial compression was studied. The numerical study revealed the working mechanism of stirrups, steel tubes on concrete, while direct confinement of concrete elevates its axial stress level. Considering the shape and the stirrups, the axial compression ultimate load-bearing capacity design method of the IWCFLST stub column was proposed, providing data support for the promotion and application of special-shaped CFST columns.