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Abstract The elastic stability of plane frameworks which are subjected to symmetric nodal loads had been studied often. Herein, the elastic buckling loads of different types of rigid frames (braced and unbraced portal frames, multistory frames and trapezoidal frames) subjected to concentrated loads moving along their beams are studied. In this case the elastic buckling loads of the frames are affected by the variation of load ratios on columns as well as by the presence of primary bending moments. Fixed as well as hinged base frames with various beam to column bending stiffness ratios, as well as various beam span to column height ratios, have been studied. The effect of the axial stiffness of the bracing elements is taken into account. The bracing elements are assumed to act in tension as well as in compression. Matrix displacement method of analysis has been used throughout this study. This method depends on forming the stiffness matrix of each member then assembling these matrices to form the overall stiffness matrix of the structure. The geometrical non-linear behaviour of the members is considered by introducing the trigonometrical buckling functions to modify the stiffness matrix of individual members. A computer program based on this method of analysis was developed. Several published cases were chosen in order to check the accuracy of the program results. Key Words: Structural Engineering ; Steel; Stability; Elastic Buckling; Rigid Frames ; Columns (Supports) ; Deformations; Variation of Loads; Primary Bending Moments |