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Abstract

Influence of geometric imperfections of mast shaft in form of initial mast span curvatures both on internal forces status in the structure elements as well as on those elements effort, which is particularly important at the design stage, was analysed based on an example of certain specific mast. The calculations were performed taking into account L/1000 imperfections equal to the permissible assembly deviations as per [1], and L/500 equal to initial imperfections as for uniform built-up columns according to [2]. Remarks and final conclusions have practical meaning and can be useful in design practice.

Abstract

The present paper is devoted to the numerical analysis and experimental tests of compressed bars with built-up cross section which are commonly used as a top chord of the roof trusses. The significant impact on carrying capacity for that kind of elements in case of out-of-plane buckling is appropriate choice of battens which are used to provide interaction between separate members. Linear buckling analysis results and nonlinear static analysis results, with material and geometrical nonlinearity, are presented for the bar with built-up cross section which was used as the top chord of the truss made in reality. Diagonals and verticals which are supports for the top chord between marginal joints were replaced by the elastic supports. The threshold stiffness (minimum stiffness) for the intermediate elastic supports which ensures maximum buckling load was appointed for the beam and shell model of the structure. The magnitude of limit load depended on length of the battens was calculated for models with initial geometric imperfections. The experimental tests results for the axially compressed bars with builtup cross section and elastic support are presented.

Technology Publishing House, Poznan (in Polish). 5. Chybinski M., Rzeszut K., Garstecki A. (2013), Snap-through phenomenon of imperfect steel structures, Proceedings of International Conference Design, Fabrication and Economy of Metal Structures , Miskolc, Hungary, Springer-Verlag. 6. Garstecki A., Rzeszut K. (2009), Modeling of initial geometrical imperfections in stability analysis of thin-walled structures, Journal of Theoretical and Applied Mechanics , 47(3), 667–684. 7. Gosowski B. (1999), Spatial bucling of thin-walled steel-construction beam-columns with

initial geometric imperfections of steel frames in advanced analysis”, Journal of Constructional Steel Research, 98, pp 167-177, 2014. 10.1016/j.jcsr.2014.02.016 29. L. Simões da Silva, L. Marques, C. Rebelo, “Numerical validation of the general method in EC3-1-1 for prismatic members”, Journal of Constructional Steel Research, 66, pp 575-590, 2010. 10.1016/j.jcsr.2009.11.003 30. L. Simoes da Silva, R. Simoes, H. Gervasio, “Design of Steel Structures, Eurocode 3: Design of Steel Structures, Part 1-1: General Rules and Rules for Buildings”, ECCS Eurocode Design Manual