Behaviour of innovative stub columns utilising mild-steel plates and stainless steel tubes at ambient and elevated temperatures

This paper explores the behaviour of square and triangular fabricated stub columns consisting of Grade 316L stainless steel tubes and Grade 350 mild steel plates at ambient and elevated temperatures. The nominal dimensions of the stainless steel tubes were 31.8 and 38.1 mm diameters with 2 and 1.6 mm thicknesses, respectively. The plates had widths of 120 and 400 mm and a 3 mm thickness. Utilising all combinations of geometries, a variety of the fabricated stub columns were experimentally tested and their behaviour were compared with conventional square or triangular welded hollow sections utilising mild steel plates as well as single tubes. The experimental tests at elevated temperatures followed ISO834 curve and were performed under 70% of the column capacity given by the experimental tests performed at ambient state. The proposed fabricated sections defined above outperformed the conventional welded hollow columns under both room temperature and elevated temperature circumstances. The ductility of the sections was also increased by utilising stainless steel tubes. Furthermore, the results obtained from the experimental tests were compared with those given by finite element modelling whereas the accurate prediction of the failure modes was demonstrated.