Axial compression behavior of GFRP‐waste stone dust alkali slag concrete‐steel double‐skin tubular columns with circular outer and square inner

To explore the fundamental mechanical mechanisms of the GFRP‐waste stone dust and alkali slag concrete‐steel double‐skin tubular columns (DSTC‐SCs) , 15 composite columns were designed. The effects of parameter changes, like the thickness of GFRP and steel tubes, the hollow ratio, and loading methods, on the axial compression mechanical behavior of DSTC‐SCs were clarified. Additionally, mechanical performance indicators of the composite columns, such as failure characteristics, bearing capacity, and load–displacement curves, were acquired. The findings show that the change in the substitution rate of waste stone powder in the waste stone dust alkali slag concrete has a substantial influence on the axial compression performance of the columns. When the substitution rates of waste stone powder for slag and fine aggregates are 16% and 30%, respectively, the overall axial compression performance indicators of DSTC‐SCs are relatively optimal. As the hollow ratio of the columns rises, the bearing capacity decreases significantly. Based on the ultimate equilibrium theory approach, taking into account the non‐uniform confinement effect of the square steel tubes in the composite columns, an effective sectional confinement coefficient k 0 was introduced, and the calculation formula for the axial compression bearing capacity of DSTC‐SCs was derived.