This paper presents an analytical model for predicting the load-deformation relationships of concrete-encased steel stub columns
under axial compression. The model considers the concrete confinement effects, which increase the compressive strength of
confined concrete and reduce the web strength of structural steel, and the buckling of longitudinal steel reinforcements. The model
is applicable to the composite columns that use any doubly-symmetric structural steel shapes. After validated with previous test
data, the model is used to investigate the effects of design parameters on strength and ductility index of composite columns.
Moreover, a simplified equation for predicting the compressive strength of composite columns is proposed.