The object of the research are short, thin-walled columns with an open top-hat cross section made of multilayer laminate. The walls of the investigated profiles are made of plate elements. The entire columns are subjected to uniform compression. A detailed analysis allowed us to determine critical forces and post-critical equilibrium paths. It is assumed that the columns are articulately supported on the edges forming their ends. The numerical investigation is performed by the finite element method. The study involves solving the problem of eigenvalue and the non-linear problem of stability of the structure. The numerical analysis is performed by the commercial simulation software ABAQUS®. The numerical results are then validated experimentally. In the discussed cases, it is assumed that the material operates within a linearly-elastic range, and the non-linearity of the FEM model is due to large displacements.

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Article citation info: (*) Tekst artykułu w polskiej wersji językowej dostępny w elektronicznym wydaniu kwartalnika na stronie www.ein.org.pl IntroductionThin-walled load-carrying structures are characterized by high strength and rigidity as well as low weight. Given the above properties, these structures are widely applied not only in the aerospace and automotive sectors, but also in designs where low structure weight is crucial. A disadvantage of thin-walled structures is that they are prone to loss of stability under compressive or shearing loads [2, 3, 9, 13, 21-25, 28, 29]. Nonetheless, thin-walled structural elements can operate even after their stability loss provided that they do it in the elastic range [11,14,21,27]. These structures are particularly sensitive to geometric inaccuracies, which is critical regarding their use. For this reason, they must be precisely manufactured to prevent premature loss of stability. Uniform thin-walled plates are relatively cheap to produce, yet they can carry relatively low loads due to their low flexural rigidity. When subjected to compression, these plates lose stability even under small loads. With common methods for improving load capacity such as the use of stiffeners or ribs, the form of a structure is not only considerably modified, but its weight can increase, too. However, there is a way in which load capacity of thin-walled structures can be greatly improved while the structures themselves can be used as both carrying structures and elastic elements. This can be done by forcing these structures to operate in a higher buckling mode (flexural and torsional). To do so, it is necessary to make a cut-out in the plate and slightly displace the vertical zone in the opposite direction. This displacement will be realized in a special frame -so that the jump on basic mode was impossible. In this way, the plate acquires the desired characteristics, i.e. stable operation in the post-buckling range.Issues of the stability and post-buckling behaviors of plate structure with all sorts of holes was described in [19], where you can find a very comprehensive review of the literature on this issue. At that work as the author of the earliest elaboration, in numerical terms, is given Pennington Vanna [16], who as first considered the problem of the stability of elastic uniaxially compression plate with a cut-out. The article presents the results of FEM calculations and compared to the results of experimental studies. The earliest post-buckling behavior analysis of plate structures with cut-out are reported in [18]. A major contribution brings the works [15,17,20,30], where are considered the postcritical states and limited carrying capacity of this type of structures. Not encountered of research, where was investigated plate structures with cut-out and in which attempted to force of the higher flexural and torsional mode deformation of the structure.In the researched load-carrying structure, one can clearly distinguish a vertical zone where this thin-walled element undergoes com...

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