Interaction Diagram of Rubberised Concrete Filled Square Hollow Sections

Rubberised concrete utilises waste material, prevents resource extraction and improves concrete ductility, however at the cost of reduced strength and stiffness. The performance of thirty rubberised concrete-filled single-skin steel tubes under combined loading conditions were systematically investigated and comparisons against six steel hollow tubular columns and beams were made. The experimental program consisted of three rubber replacement ratios, 0%, 15% and 30%, three load eccentricities and four tube sections with section slenderness (b/t, width/thickness) of 18 to 50. The results showed that the confined rubberised concrete and the restrained steel tube improved strength and ductility of the composite section. The rubberised concrete was more effective in delaying the premature buckling failure of the steel tube compared to the more brittle normal concrete. The rubberised concrete with 15% rubber replacement ratio showed a good balance of strength and ductility. The interaction diagrams obtained from the experiments and theoretical calculations were constructed and compared. The behaviours of the rubberised concrete filled steel tubes could be accurately predicted using existing design guidelines and safe designs can be produced. This study demonstrated the possibility of using rubberised concrete as a cost-effective solution to problems that require high moment and deformation capacity, such as the roadside barriers and columns in buildings located in seismic active zones.