Experiments on rectangular concrete-filled steel tubes loaded axially on a partially stressed cross-sectional area

The present paper aims to experimentally investigate the behaviour of rectangular concrete-filled steel tubular (RCFST) stub columns loaded axially on a partially stressed cross-sectional area. A total of twenty-two specimens, including thirteen partially loaded composite specimens, six partially loaded plain concrete reference specimens and three corresponding fully loaded composite specimens, were tested under concentric loads. The main parameters varied in the tests are: (1) depth-to-width ratio of the rectangular sections: from 1.2 to 1.8; (2) partial compression area ratio (concrete cross-sectional area to partial compression area): from 1.44 to 17.42; (3) steel wall thickness of top endplate: from 0 mm to 12 mm; and (4) shape of the bearing plate for partial compression: rectangular and strip. The test results showed that, while being loaded on partial cross-sectional area, RCFST stub column had a favourable bearing capacity and ductility compared with the corresponding plain concrete specimens. Simplified formulae were used for the prediction of the ultimate strength of CFST stub columns loaded on partial cross-sectional area.