The aim of present work is to investigate the characteristics of interactions of different buckling modes of flat-bar stiffened panels. Literature-based and rules-based expressions for assessing buckling strength of stiffened plates are studied. Energy method is employed for the analyses of selected buckling modes of stiffened plates including plate buckling, torsional buckling, web buckling and interactions of them when either plate or stiffener or both are under compression. Results are compared with numerical solutions using finite element method and available expressions to identify the applicability and accuracy of selected expressions for certain conditions. It is found that some of the given expressions for buckling analyses of stiffened plates have limited applicability.