The axial compression bearing capacity of reinforced recycled aggregate concrete filled square steel tube short column with dual constraints

This paper focuses on investigating the axial bearing capacity of Reinforced Recycled Aggregate Concrete (RRAC) Filled Square Steel Tube (RRACFSST) short columns. The research takes into account the double constraints of square steel tubes and steel cages, conducting a nonlinear simulation study on RRACFSST. The compressive bearing capacity of square steel pipe in nonlinear simulation is determined. The axial bearing capacity of RRACFSST short columns is analyzed using the limit analysis method and the Ferrule theory. A formula is proposed to calculate the axial bearing capacity of RRACFSST short columns, considering factors such as the width to thickness ratio of the steel tube, recycled coarse aggregate replacement rate, reinforcement ratio, and constrained effect coefficient. These influencing factors are also analyzed. The formula's accuracy and applicability are verified by comparing it with literature experimental values and finite element simulation values based on theoretical derivation. The research findings provide a theoretical basis for designing the axial compression bearing capacity of square steel tube RRAC short columns. Additionally, the study proposes a novel steel pipe-constrained RAC system, combining steel with RAC to enhance ductility, compressive strength, and seismic resistance, offering significant social and economic benefits.