Frame structures with either pinned or fixed joints are frequently used in aerospace applications as the primary structure supporting light secondary panels or other structural assemblies. In the analysis of such structural designs it is very often necessary to consider loading conditions for which the deflections are large enough to cause significant changes in the geometry of the structure so that the equations of equilibrium must be formulated for the deformed configuration. In the present paper the general analysis for large deflections of frame structures is presented using the concept of discrete element idealization. The solution for deflections and stresses is presented as a step-by-step matrix method based on load increments and is particularly suitable for computer programming. As a bi-product of the large deflection analysis the eigenvalue equations for structural stability are also formulated. The theoretical results of the nonlinear, large deflection matrix solution are compared with the exact analytical results for a square frame. In addition, the results for deflections of a six-bay truss and buckling of columns with either constant axial load or gravity loading are also presented. The computer program listing and instructions for the preparation of input data are included.

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