Behavior and Reliable Design Methods of Axial Compressed Dune Sand Concrete-Filled Circular Steel Tube Columns

An innovative composite structural element, the dune sand concrete-filled circular steel tube (DS-CFCST) column combines the mechanical performance of concrete-filled steel tube (CFST) columns with the environmental and economic benefits of dune sand (DS) concrete. However, current experimental investigations into DS-CFCST columns’ axial compressive behavior are limited. This study conducts a numerical analysis to examine the effects of varying DS replacement ratios and the influence of confinement on DS-CFCST stub columns. Finite element (FE) analysis reveals that DS-CFCST stub columns exhibit reduced ultimate bearing capacity compared to CFST columns, primarily due to weakened confinement effects at higher DS replacement ratios. A parametric study investigated the impacts of various design parameters on the ultimate axial bearing capacity of DS-CFCST stub columns. A practical design formula, based on equilibrium principles and the FE model, was developed. This formula simplifies the prediction of the ultimate load-bearing capacity of DS-CFCST stub columns using the superposition method. Its accuracy was validated by comparing it with experimental data and FE results. Lastly, a reliability analysis was performed, showing the DS-CFCST columns’ reliability index sensitivity to variations in concrete strength, steel yield strength, steel content ratio, load effect ratio, load combination factor, and DS replacement ratio.