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12.06: Numerical analysis of stainless steel, concrete encased and carbon steel double skin tubular stub columns

The use of stainless steel as formwork for concrete columns provides several benefits for the structure, including the high corrosion resistance, durability, fire resistance, ease of maintenance and high aesthetic value. The use of composite systems in columns has been a major breakthrough in bridges and viaducts. A particular advantage of the composite columns is the reduction of cross sectional area, speed of construction, easy maintenance and material saving when compared to conventional reinforced concrete structures. These advantages are related to the idea that the columns are concrete filled eliminating the use of forms and the need for extra steel reinforcing bars. The investigated system adopts a second carbon steel tube inside the primary stainless steel tube composing the structural system made of concrete‐filled double skin composite tube columns (CFDSCT). This study aims to develop numerical models, using the finite element method and considering geometric imperfections. The structural behaviour was assessed through a nonlinear analysis and was later compared to compressive tests performed in the laboratory. After the completion of the numerical models calibration, a parametric analysis was performed to investigate the influence of parameters like the diameter, thickness and height of the stainless steel tube (outer) while its results were also compared to predictions made by traditional design equations.