Axial compression and load-carrying performance of rectangular UHPC-filled stainless-steel tubular short columns

Fifteen rectangular ultra-high-performance concrete (UHPC)-filled stainless-steel tubular (UHPCFSST) columns were designed and tested under axial compression to explore the axial compression performance and loadcarrying effect. The variables included the cross-sectional size and wall thickness t of the stainless-steel tubes. Failure modes can be categorized into two types: bulging and oblique shear failures. The stress-strain curves can be classified into two categories based on the hoop confinement coefficient (xi s). The test specimens exhibited significant compressive size effects and excellent post-peak ductility. A quantitative analysis was conducted on the sensitivity of the parameters affecting the load-carrying capacity. As the cross-sectional steel ratio alpha increases, the strength index SI exhibits a growing trend. The specimens with high xi s experience a greater increase in the axial load-carrying capacity of the stainless-steel tubes. A predictive model for the axial load-carrying capacity of rectangular UHPCFSST columns was established with high accuracy and rationality. A quantitative evaluation of the load-carrying effect was conducted using a multilevel extension evaluation model, the results indicated that with an increase in the cross-sectional size, the multilevel extension grades exhibited a decreasing trend.