Axially Loaded Concrete-Filled Steel Tubes

This paper presents an experimental and analytical study on the behavior of short, concrete-filled steel tube columns concentrically loaded in compression to failure. Fourteen specimens were tested to investigate the effect of the steel tube shape and wall thickness on the ultimate strength of the composite column. Confinement of the concrete core provided by the tube shape was also addressed. Depth-to-tube wall thickness ratios between 17 <D/t< 50, and the length-to-tube depth ratios of 4 <L/D< 5 were investigated. Ultimate strength results were compared to current specifications governing the design of concrete-filled steel tube columns. Nonlinear finite-element models were developed and verified using experimental results. The analytical models were further used to investigate the adequacy of design specifications. Experimental results suggest that circular tubes offer substantial post-yield strength and stiffness, not available in most square or rectangular cross sections. Also observed by these results was that current design specifications were adequate to predict the yield load under most conditions for a variety of structural shapes.