Axial stability and equivalent slenderness design of four-limb CFST latticed columns

In order to investigate the axial compression behavior of four-limb concrete-filled steel tubular latticed columns, experimental and numerical studies were conducted. The varied experimental parameters including height-to-width ratio, lacing member dimensions, and cross-sectional size. The experimental results indicated that all specimens exhibited yielding of limb steel tubes and crushing of concrete cores, while lacing steel tubes remained elastic at the peak load. Significant global bending was observed in the slender column, and the slender column showed a notable reduction in stiffness and a 5% decrease in ultimate load compared to the stub column with identical cross-section. Finite element models were developed and validated against experimental results. A parametric analysis was then conducted to expand the database and quantify the influence of key parameters included height-to-width ratio, steel ratio, material strength of limb, confinement coefficient, and cross-sectional sizes of lacing steel tubes on axial compressive strength and φ-H/h curve, which shows the relationship between stability coefficient (φ) and height-to-width ratio (H/h). The accuracy of existing methods in current design codes for determining the ultimate strength for such members was evaluated. Based on this assessment, an optimized formula for calculating the equivalent slenderness ratio and stability coefficient was proposed.