In this paper, an iterative quasi-Newton procedure based on the Regula-Fals
i numerical scheme is proposed for the rapid sectional analysis and design
of short concrete-encased composite columns of arbitrary cross section subj
ected to biaxial bending. The stress resultants of the concrete are evaluat
ed by integrating the concrete stress-strain curve over the compression zon
e. Exact integral expressions of the stress resultants for both polygonal a
nd circular subsections are derived, and these are used to achieve an effic
ient and accurate analysis. The stress resultants of the encased structural
steel and the steel reinforcing bars are obtained using the fiber element
method. A particularly important feature of the present method is the use o
f the plastic centroidal axes of the cross section as the reference axes of
loading in the iterative solution process. This ensures the convergence of
the solution process for all cross-sectional conditions. Numerical example
s are presented to demonstrate the validity, accuracy, and capability of th
e proposed method.