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The paper presents the influence of the diaphragm effect on the behavior of pitched roof portal frames, having Z purlins and corrugated sheeting as cladding. The paper highlights the stabilizing effect in terms of αcr on portal frames by taking into account the lateral constraints ensured by a typical cladding system – Z purlins with one layer of sheeting panels. The purpose of the paper is to make a comparison between the simplified design model of a portal frame, where the supports simulating the purlins are considered with infinite axial rigidity and a portal frame design model where the calculated stiffness of the cladding for the lateral supports is introduced manually. The obtained results highlight the importance of the diaphragm effect and refer to the variation of the load multiplication factor αcr for main structural elements. The fundamental objective of this research is to develop a relatively fast checking procedure, easy to use in the current design process, by including the diaphragm stiffness in the analysis of the pitched roof portal frame. Using Abaqus, simplified calculation procedures are validated by complex FEM models.

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Nagy Zs., Popp A., Moiș I., Ballok R.: Stressed skin effect on the elastic buckling of pitched roof portal frames. Eighth International Conference on ADVANCES IN STEEL STRUCTURES 2015

A two-part paper has been written to summarise the main results of a comparative study on the design provisions currently adopted in Europe (EU) and the United States (US) for steel storage pallet racks. In part 1 (Discussion and general comparisons), key features of the verification procedures for thin-walled cold-formed members as well as of the design alternatives permitted by the EU and US rack codes have been discussed, pointing out the most relevant similarities and differences. The present part 2 applies six design alternatives to medium-rise pallet racks unbraced in the longitudinal direction. In particular, the proposed research outcomes are based on the design of 216 racks differing for configurations, geometry of components and degree of rotational stiffness of beam-to-column joints and base-plate connections. Results are presented and compared directly to each other in term of safety index in order to allow for a concrete appraisal of the most relevant differences between the considered design methods, highlighting also the influence associated with the approaches to modelling the geometric imperfection effects. Finally, Appendix A presents a complete design example to be used as benchmark for researchers and designers, where all the discussed design options are applied.

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Bernuzzi C., Draskovic N., Simoncelli M.: European and United States approaches for steel storage palletrack design. Part2:Practical applications 2015

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In this paper a numerical study is presented which examines a steel frame with two different finite element programs. Stability failure is more frequent in a lot of cases than strength failure hence it is important to focus on these failure modes: global, in-plane-, out-of-plane -, lateral-torsional- and local buckling. Three models were used with different elements such as shell elements and 7 DOF beam elements. 7 DOF beam elements were used in the first model, shell elements were used in the other two. The first of the shell models gave too much local buckling shapes therefore it was improved with local constraints and that is the third model where global buckling shapes can be examined. There are three different procedures to calculate the resistance: (i) the general method, (ii) the method of the reduction factors, and (iii) the simulation. The analysis results of the different programs and design methods were compared to each other and to the manual calculation based on the Eurocode 3 standards.

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Tóth A. , Joó A.: Comparative study of steel frame modelling levels and Eurocode based design methods, “Model Validation and Simulation” – Graduate Courses for Structural Engineering Applications, Bauhaus Summer School 2015

After introducing the Eurocode standards several theses have been published on the now much-discussed phenomenon of lateral-torsional buckling of steel structural elements under pure bending. According to that, researchers are working on the development of such new design methods which can solve the problems of the design formulae given by the EN 1993-1-1. This paper gives a detailed review of the proposals for novel hand calculation procedures for the prediction of LT buckling resistance of beams. Nowadays, the application of structural design softwares in practical engineering becomes more common and widespread. Recognizing this growing interest, the main objective of our research work is the development of a novel, computer-aided design method. In this paper, the details of a general type stability design procedure for the determination of the LT buckling resistance of members under pure bending are introduced. Here, the theoretical basis of the proposed method is clarified, the calculation procedure is detailed and some results for the evaluation of the appropriateness of the method are also presented. Based on the evaluations it can be stated that the new, general type design method is properly accurate and has several advantages on the stability check of beams under bending

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Badari, B., Papp, F.: On Design Method of Lateral-torsional Buckling of Beams: State of he Art and a New Proposal for a General Type Design Method. Periodica Polytechnica Civil Engineering 2015

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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Szalai J, Papp F. Theory and application of the general method of Eurocode 3 Part 1-1. 6th European Conference on Steel and Composite Structures. Edited by Dunai L at al. 2011

Stability analysis and design have always played a key role in the process of verification of steel structures. The possible analysis methods and design procedures have a long history with plentiful literature providing various proposals for the engineers. This paper concentrates on the use of different types of eigenvalue analysis as a simple and powerful tool for stability design. Nowadays almost all the engineering software products have some kind of eigenvalue analysis options so these tools are easily available for the practicing engineers providing them a deeper look on the structural behavior. Various types of application possibilities are reviewed and new methods are proposed supporting the most up-to-date standard procedures of different levels from the isolated member design to the partial or global structural stability design. The suitable theoretical (both mathematical and mechanical) background is developed and the numerical procedure is implemented. The technique is applicable for a wide range of structural types and stability problems making the automatic effective length calculation possible in general without the use of any iterative process or tabulated values for certain cases. An application example is presented showing the comprehensiveness of the methods, and special efficiency indicators are presented in order to supply information about the adequacy of the applied design method.

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Szalai J. Use of eigenvalue analysis for different levels of stability design. International Colloquium on the Stability and Ductility of Steel Structures. Edited by Batista E at al. 2010