Abstract: Traditional effective length and the modified effective length methods are presented, and the limitation in the application of modified effective length approach is outlined. Based on the story buckling approach of frames, a universal slenderness for a frame story is defined. A large number of frames are analyzed to acquire their limit loads by utilizing ANSYS. Residual stresses and initial geometric imperfections are considered. The limit loads are correlated with the universal slenderness. It is found that when the universal slenderness is intermediate, there exists an unfavorable interaction between sway buckling and non-sway buckling of frames. The universal slenderness and the story-based stability coefficient are modified to consider this interaction, and formulae based on the column curves in the Code GB50017 are suggested to predict the stability coefficient of the story.