Effect of steel tube thickness on the behaviour of CFST columns: Experimental tests and design assessment

In this paper, the results of experimental tests conducted on concrete-filled steel tubular (CFST) columns are presented. There is currently a deficit of data available that can be used to evaluate current guidance documents and provide assessment to improve their accuracy when considering the behaviour of CFST columns filled with high strength concrete. Thus, this paper aims to increase the volume of experimental data available with a series of groups of tests on stub CFST columns subject to axial compression. Among the specimens of the same group only one dimension changes, the steel tube thickness. The columns are filled with both normal and high strength concrete for comparison purposes. The use of high strength concrete in circular tubes increases the concrete contribution, but this effect does not fulfil in rectangular specimens where also the confinement is less effective than in circular CFST even when the former have thin steel tubes and high strength concrete. The specifications of four commonly used codes are discussed. Comparison of their predictions with the experimental data collected shows that AISC is conservative but EC4, DBJ and AS produce similar non-conservative predictions.