Experimental and numerical study of stirrup-confined concrete-filled L-shaped steel tube stub column under axial compression

In this paper, three concrete-filled L-shaped steel tube (CFLST) stub columns subjected to axial compression were tested, with one normal CFLST stub column and two stirrup-confined specimens. The investigation focused on the effect of the equivalent stirrup ratio on ultimate bearing capacity, axial compression stiffness, ductility factor, and strain ratio of the columns. 3D finite element (FE) models of the specimens were constructed and verified against the tests results and data from literature Parametric analysis was carried out to analyze the influence of different section length-width ratios, steel ratios, material strength grades, and equivalent stirrup ratios on the ultimate bearing capacity. Additionally, the confinement effect of stirrups on the core concrete was analyzed. By generalizing the stress nephogram of the core concrete at the ultimate state and considering the equilibrium of forces, a formula was proposed for calculating the ultimate bearing capacity of the stirrup-confined CFLST stub column under axial compression using the superposition method. The accuracy of the proposed formula was demonstrated by comparing its results with experimental results, FE model results, and those proposed by other scholars.