The portal frames composed of tapered welded I-shaped structural members play important roles in the industrial buildings. The application of the relatively thin plates and the optimized fabrication makes these structures being competitive against the light truss structures at least in the range of 24–36 meters span. Competition has resulted in lesser selfweights using thin plated slender cross-sections, which are sensitive to local buckling. However, the development of structures concerning local buckling was delayed in Hungary by the conservative specifications of the MSz 15024 standard. The application of the new EN 1993 standard may cause radical development in the design of tapered structural elements with relatively thin plates. This paper introduces the methods as well as the advantages of the new design methodology.

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The EN 1993 Part 1-1 (EC3-1-1) has introduced a new approach (called the “General Method”) to perform lateral-torsional buckling (LTB) assessment of beam-column structural components on the basis of elastic stability analysis. In the last years great research investigations went into the development of the method, see for instance [11,12] and also into the improvement of appropriate design software that is suitable to include the method and applicable for practical solutions [10]. The general objective of this paper is to review this issue from the point of view of the practice and contribute more effectively to understanding and resolving issues in the fields of practical application of the General Method. It is essentially significant to define the minimal analysis tools for the practice which are required for the accuracy of the method but on the other hand simple enough to make the modeling and calculation efficient. The paper briefly presents the theoretical background and the practical application of the elastic stability analysis of beam-columns that is necessary for the accurate evaluation of the General Method. The elastic stability analysis is verified by benchmark examples and also by shell finite element analysis. The application of the design method is demonstrated in the field of irregular structural members, especially web-tapered members and frames. The paper analyses the new theoretical results in the field of LTB of webtapered members that have led to prohibitive statements in some National Annex for EC3-1-1 concerning the segment method in the analysis of these members. It is shown that a comprehensive design method that is based on an appropriate segmented model and the General Method is efficient as well as reliable for conceptual design and with some restrictions also for detailed design.

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