Study on seismic behaviour of concrete-filled steel tubular special-shaped columns

To investigate the seismic performance of prefabricated concrete-filled circular steel tubular T-shaped column–composite beam frame joints, six full-scale prefabricated T-shaped joint frame specimens were designed and fabricated. The experimental variables included loading direction and axial compression ratio. Their failure modes, hysteretic behaviour, energy dissipation capacity and stiffness degradation were analysed through low-cycle reversed loading tests. The results showed that the specimens failed at the beam ends by way of a plastic hinge mechanism, and the failure mode satisfied the design requirements of ‘strong column–weak beam’ and ‘strong joint–weak component’. Within a specific range, increasing the axial compression ratio enhanced the specimens’ load-bearing capacity, energy dissipation capacity and ductility, while increasing the shear force in the joint core area. Under the same axial compression ratio, specimens loaded along the flange direction exhibited energy dissipation that was 92.0, 71.0 and 58.9% higher than those loaded along the web, with displacement ductility coefficients increasing by 6.0, 13.0 and 29.6%, respectively. Under seismic loading, the energy dissipation capacity and ductility performance of the T-shaped joints in the special-shaped concrete-filled steel tubular column frames were superior when loaded along the flange direction.