Axial compressive performance of reinforced sea-sand concrete-filled square stainless steel tubular stub columns

Owing to their exceptional durability, reinforced sea-sand concrete-filled (square) stainless steel tubular (RSCFSST) columns present a viable structural solution for coastal regions. Axial compressive tests were conducted on eight square RSCFSST short columns and two sea-sand concrete-filled (square) stainless steel tubular counterparts. The experimental results demonstrated that the incorporation of stainless steel rebars increased their axial compressive resistance, peak strain, and ductility by 4–13 %, 21–52 %, and 25–122 %, respectively. Notably, RSCFSST column filled with sea-sand concrete exhibited comparable axial compressive behavior to those columns utilizing normal concrete. A finite element model was developed to conduct the mechanism and parametric analyses. The mechanism analysis revealed that stainless steel outperformed carbon steel in improving both the peak strain and ductility of the composite columns. Parametric analysis indicated that increasing the concrete strength, 0.2 % proof strength of the steel tube, 0.2 % proof strength of stirrups, steel tubular ratio, or stirrup ratio significantly enhanced the axial compressive resistance of the RSCFSST columns. Finally, novel predictive methods were developed for estimating their axial compressive resistances and peak strains, demonstrating superior accuracy in predictions. • Axial compressive tests of 8 square RSCFSST stub columns were conducted for the first time. • No significant difference is observed between the use of sea-sand concrete and normal concrete in RSCFSST columns. • A finite element model for analyzing the behavior of square RSCFSST columns is proposed. • The RSCFSST column exhibits significantly higher peak strain and ductility compared to its RCFST counterpart. • Simplified methods are proposed to predict the axial compressive resistances and peak strains of RSCFSST columns.