عنوان مقاله [English]
For design purposes, the stability of any structure being designed is of paramount importance. The fact that it is possible to perform an analysis on a space structure, which shows that the stresses in that structure are all below those permissible for the materials used in its construction, is, in itself, no guarantee that when the structure is loaded it will not collapse. In order to determine this, it is necessary to find out if the structure is stable under the action of the applied loads. The secondary paths, especially in unstable buckling, can play the most important role in the collapse of the structure. In this paper, an attempt is made to automatically calculate the bifurcation path of shallow lattice domes. This calculation is performed in a two--stage analysis of the space structure,
without introducing any geometrical imperfections. The method is implemented in a combined materially and geometrically nonlinear finite element analysis computer program, based on an incremental iterative
Newton--Raphson solution procedure. In the first stage analysis, the proportional live load factors, at which critical points occur, are determined and the primary path is obtained. In the second stage analysis, the perfect structure is led towards the lowest bifurcation path, using the technique described in the paper. The resulting theoretical predications are verified by existing experimental observations on a model dome.