Experimental investigation on influence of sectional shape on deformation and bearing capacity of early-age concrete-filled steel tubular short columns under multi-level loading

The influence of continuous construction process on the mechanical properties of concrete-filled steel tube (CFST) is mostly considered by introducing an initial stress of steel tube, whilst the multi-level loading process as well as concrete shrinkage and creep at early age are neglected. In order to study the mechanical properties of early-age CFST under multi-level loading, axial compression deformation and ultimate bearing capacity tests of early-age square and circular CFST short columns under and after multi-level loading were performed respectively. The variations of deformation under different multi-level loading schemes as well as ultimate load bearing capacity after multi-level loading were analyzed. The results indicate that the creep deformations of both square and circular CFST under multi-level loading at early age are remarkable. The specimen deformation is significantly affected by the applied loading scheme. In addition, the deformation of circular specimen is found to be smaller than that of square specimen under the same loading condition. The impact of multi-level loading process on the bearing capacity of square and circular CFST short columns at mature stage is limited and can be neglected. The research outcome can serve as a reference for the deformation control and mechanical performance evaluation for CFST under continuous construction. © 2018, Editorial Office of Journal of Building Structures. All right reserved.