Research Description
Composite columns are generally installed in high-rise buildings and bridges. As well as
being smaller and lighter than conventional reinforced concrete columns, composite columns offer
high efficiency and ductility. In this research, experimental and analytical studies were carried out to
investigate the optimal distribution of the total steel area of the Concrete-Filled Hollow Steel Tube
(CFHST) columns; the experimental program included 20 CFHST columns. The main variables of
the experimental study were the distribution of the total steel cross-sectional area over the internal
concrete core (steel reinforcement) and the external steel tube, the cross-sectional shape, the widthto-breadth ratio t/b, and the presence or absence of shear connectors. In addition, using equations of
different codes, comparison was conducted between the experimental and analytical results. For a
constant steel cross-sectional area, the use of internal steel bars and external steel tubes, together with
the use of shear connectors, was found to exhibit a better ultimate load capacity, stiffness, and
ductility for the CFHST columns.
