Watch our user guide about How to use the Overall Imperfection Method to learn more.
Version: CS14.831
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Download model fileThe Overall Imperfection Method is an alternative way to carry out the buckling design for a structural member. With this method the buckling phenomenon is considered on the effect side of the equation, instead of on the resistance side, compared to the general method and the member check method. In the following video we explain the theoretical background for this calculation. After that we present application examples starting with the simplest ones, all the way to the most general case in a real-world building structure, showcasing the several extra capabilities and advantages of the Overall Imperfection Method.
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Contents
- Set design parameters
- Perform cross section check
- Examine the design results in the Section Module
- Stability design according to the general method
- Member check – stability design for members
- Serviceability check
Part 2 – Imperfection factors
The Eurocode EN 1993-1-1 offers basically two methods for the buckling verification of members:
(1) based on buckling reduction factors (buckling curves) and
(2) based on equivalent geometrical imperfections.
gateIntroduction
There are different ways to evaluate the stability of a structure. It is important to know the differences between those methods and the limits of applicability but it is also important to recognize the equalities in pure cases.
Methods of stability design
In Eurocode 1993-1-1, and so in Consteel, there are 3 methods to verify the stability of a model:
- Imperfection approach (described in Section 5.2 and 5.3)
The structural model is subjected to appropriate geometrical imperfections and after completing a second order analysis, only the cross section resistances need to be checked
- Isolated member approach ( described in section 6.3.1, 6.3.2 and 6.3.3)
The method is based on two essential simplifications:
- Structural member isolation: The relevant member is isolated from the global structural model by applying special boundary conditions (supports, restraints or loads) at the connection points which are taken into account in the calculation of the buckling resistance
- Buckling mode separation: The buckling of the member is calculated separately for the pure modes: flexural buckling for pure compression and lateral-torsional buckling for pure bending. The two effects are connected by applying special interaction factors.
- General method (described in section 6.3.4)
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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Download articleBadari, 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
In the second article of this series, Dr József Szalai of ConSteel Solutions demonstrates practical examples where the “General Method” of EN 1993-1-1 shows advantages compared to the conventional approaches.
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Download articleSzalai J. Practical application of the “General Method” of EN 1993-1-1 – New Steel Construction 2011
Clause 6.3.4 of EN 1993-1-1 describes a “General Method” for lateral and lateral torsional buckling of structural components, ideally suited to software applications. Although the UK National Annex places some limitations on the use of this method, it is possible that the approach will become more widely used.
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Download articleSzalai J. The “General Method” of EN 1993-1-1 – New Steel Construction 2011
The new versions of the EN 1993-1-1 (EC3-1-1) and the EN 1993-1-5 (EC3-1-5) standards have introduced the general method designing beam-column structures; see [1] and [2]. The design method requires 3D geometric model and finite element analysis. In a series of papers we present this general design approach. The parts of the series are the following:
- Part 1: 3D model based analysis using general beam-column FEM
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Download articlePapp F, Szalai J. New approaches in Eurocode 3 – efficient global structural design. Part 1: 3D model based analysis using general beam-column FEM. Terästiedote (Finnish Steel Bulletin), 5, 2010.
The new versions of the EN 1993-1-1 (EC3-1-1) and the EN 1993-1-5 (EC3-1-5) standards have introduced the general method designing beam-column structures; see [1] and [2]. The design method requires 3D geometric model and finite element analysis. In a series of papers we present this general design approach. The parts of the series are the following:
– Part 0: An explanatory introduction
Click the button bellow to download and read the full article.
Download articlePapp F, Szalai J. New approaches in Eurocode 3 – efficient global structural design. Part 0: An explanatory introduction. Terästiedote (Finnish Steel Bulletin), 5, Helsinki, 2010.