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The 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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A warehouse bulding model to learn more about the critical temperature feautre
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The calculation of the critical temperature is available in Consteel since the release of version 14. As an introduction of this feature, we prepared a video that gives some theoretical background on the topic, and demonstrates its usage in Consteel. It is shown how to prepare the model, how to execute the analysis and design, and how to create documentation about the critical temperature results.

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Consteel 14 is a powerful analysis and design software for structural engineers. Watch our video how to get started with Consteel.

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Consteel 14 is a powerful analysis and design software for structural engineers. Watch our video how to get started with Consteel.

Contents

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.

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Introduction

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:

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

       The method is based on two essential simplifications:

  1. 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
  2. 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.
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In everyday practice frames of pre-engineered metal buildings are often designed as 2D structures. Industrial buildings often have partial mezzanine floors, attached to one of the main columns, to suit the technology. Additionally, such buildings often have above the roof platforms for machineries.

When it comes to seismic design, as long as seismicity is not deemed to be a strongly controlling factor for final design, the mezzanines are just attached to the same type of frames as used at other non-seismic locations and are locally strengthened, if necessary. Only the horizontal component of the seismic effect is considered in most of the cases.

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The main objective of the research paper is to present the technical and economical results obtained for standardized structures with small and medium spans. The obtained results can represent a starting point for designers as well as for investors, who intend to build single storey steel structures. According to the research, there have been identified a series of interrelated factors which may represent sources of savings in the optimization process. The authors highlight the work strategy in creating standardized structural systems that will improve product performances. The paper analyzes three standardized configurations including the following structural solutions: frame structures made of hot rolled beams and columns, thin-walled frame structures and structures using trusses and rectangular hollow sections columns. All configurations have been analyzed using Consteel 7.0 design software, for Bucharest region, loads evaluation being performed according to the current standards. Free height of the building varies between 4.00m and 6.00m, bay between
4.00m and 5.00m, and the span between 8.00m and 12.00m. The article presents the principle of the structural configurations and gives reference charts in order to estimate the steel consumption per square meter, aiming structural performance in what concerns price per square meter and execution time.

Click the button bellow to download and read the full article. (ROU)

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Zs Nagy, A Jurcut, A Pop, I Mois: Technical and economical performance of thin-walled steel structures vs. Hot rolled profiles, Tendințe actuale în Ingineria structurilor Metalice, Lucrările celei de-a Xiii-a conferințe naționale de Construcții metalice, București, 21-22 noiembrie 2013

The authors will describe in the following pages the reasons why the project of the Multi-functional Sports Hall from Cluj Napoca is attractive. The main lines of the building are: a hall with a capacity of 7000 seats, a structure dominated by precast concrete elements, a long span roof and an advanced analysis of the connections, all well-kept into the limited funds. The roof solution consists in using steel space trusses made out of square hollow sections (SHS). The truss has a clear span of 63.90m, a total length of 76,10m, a maximum height of 4,00m that is reduced on the length of the structural
element, and a triangular cross section being 3,60m wide. Global stability checks and specific local stability problems were performed and are exposed in the following paper. For the fabrication of the space truss, welded joints between the SHS profiles were designed. As a result of the fact that for characteristic failure checks of the welded TT and KK joints analytical methods are based only on a semi-empirical formulae, developed for Φ=90 degrees (the angle between the diagonal planes), for the design of joints finite element modelling was used. Good agreement between the results of the developed finite element joint model and the analytical method for TT and KK joints has been found, even though the semi-empirical formulae are applied for the analysed truss which had Φ=50 degrees.

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Kiss Z, Karoly B, Toader Nicu, Nagy Zs: A long span structure in Romania – IABSE Kolkata Symposium 2013