Flexural behaviour of concrete-filled thin-walled steel tubes with longitudinal reinforcement

![CDATA[Concrete filled steel tubes (CFTs) are efficient members in structural applications including bridges, buildings and piled foundations and their use in the building industry is increasing. To date their primary use has been in axial applications, with the design methodology based on theory and tests of columns under loads applied axially or at relatively small eccentricities. Limited in to research into the behaviour of CFTs subjected to large eccentricities or loading in pure flexure have been conducted, with preliminary experimental investigation suggesting that stiffness of composite members tending towards that of the tube at relative low loads. An ongoing research program on the flexural behaviour of CFTs is being undertaken at the University of Western Sydney with a particular emphasis on thin-walled steel tubes that can provide an economical form of construction. In this paper, the results from additional experimental work will be presented with a particular emphasis on the stiffness of the members when subjected to flexural loading. The experimental work to date has demonstrated that even in composite specimens where there is negligible end slip; the stiffness of the specimens under pure flexure tends to the stiffness of the bare steel tube. A numerical model will also be presented that can accurately generate the bond/slip relationship of the concrete within the steel tubes and consequently the behaviour of the specimens modelled. From the experimental results and the numerical model some guidelines for the design of concrete filled tubes subjected to primarily flexural loading will be presented.]]