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- BS EN 1993-1-1: 2005
- BS EN 1993-1-2: 2005
- BS EN 1993-1-4: 2006
- BS EN 1993-1-5: 2006
- BS EN 1993-1-8: 2005
- BS EN 1994-1-1: 2004
- BS EN 1994-1-2: 2005
- Other

Buckling lengths of columns: rigorous approach
(SN008)

The buckling length Lcr of a compression member is the length of an otherwise similar member with 'pinned ends' (ends restrained against lateral movement but free to rotate in the plane of buckling) which has the same elastic critical buckling load. In the absence of more accurate information, the theoretical buckling length for elastic critical buckling may conservatively be adopted. An equivalent buckling length may be used to relate the critical load of a member subject to non-uniform loading to that of an otherwise similar member subject to uniform loading. An equivalent buckling length may also be used to relate the critical load of a non-uniform member to that of a uniform member under similar conditions of loading and restraint.

Keywords:

6.3.1.3; effective length

Valid until:

Feb 2015

Created by:

SCI

Created on:

Feb 2006

BSI Approval:

Not reviewed by BSI

Critical axial load for torsional and flexural torsional buckling modes
(SN001)

For the following common cases, torsional and flexural torsional buckling will not give a lower mode than flexural buckling: Doubly symmetric I and H sections (provided that both flanges are restrained at positions of lateral restraint); Hollow sections. However, in some particular cases, the torsional buckling mode or the flexural-torsional buckling mode of an axially loaded member may correspond to a critical load lower than the one corresponding to the flexural buckling mode, especially for open sections. This document gives rules to determine the critical load for such cases.

Keywords:

6.3.1.4; Ncr; Ncrit

Valid until:

Jan 2015

Created by:

SCI

Created on:

Feb 2005

BSI Approval:

Not reviewed by BSI

Design of out of plane and transverse restraint systems for portal frames
(SN046)

Bracing is required to resist lateral loads, principally wind loads, and the destabilising effects of the imperfections defined in §5.3 of EN 1993-1-1. This bracing must be correctly positioned and have adequate strength and stiffness to justify the assumptions made in the analysis and member checks. It is essential to provide bracing that is both sufficiently strong and sufficiently stiff at all the points that are assumed to be restrained in the design calculations. This is especially true where the inner flange of the portal frame is in compression. Consequently, this document can only give general guidance, not detailed advice. The design criteria given in EN 1993-1-1 are summarised within this document.

Keywords:

5.3; 5.3.2; 5.3.3; portals

Valid until:

Jan 2015

Created by:

SCI

Created on:

Apr 2006

BSI Approval:

Not reviewed by BSI

Determination of moments on columns in simple construction
(SN005)

The method presented in this NCCI is applicable to steel framed buildings modelled as 'simple' according to EN 1993-1-8 §5.1.1 (2), in which the joints may be assumed not transmit any bending moment from the beams into the columns. The lateral stability of the frame must be provided by a system of bracing or by lift shafts and stair wells. Stability is not provided to any degree by the stiffness of the beam-to-column joints. The columns in this type of structure will primarily be loaded in axial compression, but 'nominal' moments due to the eccentricity of the beam-to-column joints should also be considered in design.

Keywords:

columns; simple construction; nominal moments; 6.3.3

Valid until:

Jan 2015

Created by:

SCI

Created on:

Apr 2005

BSI Approval:

Not reviewed by BSI

Determination of non-dimensional slenderness of I and H sections
(SN002)

This NCCI presents a method for determining the non-dimensional slenderness without explicit determination of Mcr. The basic, conservative method can be refined to take account of section geometry and bending moment distribution.

Keywords:

6.3.2; bending resistance; elastic critical buckling moment; Mcr; Mcrit; slenderness

Valid until:

Jan 2015

Created by:

SCI

Created on:

Mar 2005

BSI Approval:

Not reviewed by BSI

Effective lengths and destabilizing load parameters for beams and cantilevers - common cases
(SN009)

This NCCI presents values for the effective length parameter k and the destabilizing parameter D for beams and cantilevers with or without intermediate lateral restraints, for use with NCCI document SN004.

Valid until:

Mar 2015

Created by:

SCI

Created on:

Feb 2008

BSI Approval:

Not reviewed by BSI

Effective lengths of columns and truss elements in truss portal frame construction
(SN031)

This NCCI gives guidance on the determination of the effective length of columns in truss and column construction. It also provides rules to calculate the effective length for chord and bracing members in truss and column construction. In a welded lattice girder, chord and bracing members are partially fixed at the nodes, although the static calculation of the internal forces in the members is usually carried out assuming the joints to be pinned. As a consequence of this partial restraint, the value of the system length L may be reduced to obtain the effective buckling length Leff. The rules given below are partly based on EN1993-1-1 Annex BB.1 (Buckling of components in building structures). Detailed information about the structural stability of hollow sections is given in CIDECT publications and the relevant information is summarized in section 3. Rules for special cases taken from DIN 18800 are presented within section 4.

Keywords:

critical buckling lenth; effective length

Valid until:

Jan 2015

Created by:

SCI

Created on:

Apr 2006

BSI Approval:

Not reviewed by BSI

Elastic critical moment for lateral torsional buckling
(SN003)

This NCCI gives the expression of the elastic critical moment for doubly symmetric cross-sections. Values of the factors involved in the calculation are given for common cases. For a beam under a uniformly distributed load with end moments or a concentrated load at mid-span with end moments, the values for the factors are given in graphs.

Keywords:

Mcrit; lateral torsional buckling; 6.3.2.2; 6.3.2.3; C1 factor

Valid until:

Jan 2015

Created by:

SCI

Created on:

Apr 2005

BSI Approval:

Not reviewed by BSI

Elastic critical moment of cantilevers
(SN006)

This NCCI provides information for dealing with cantilever beams satisfying the following conditions: The beam has a uniform and doubly symmetrical cross-section; The beam is unrestrained except at support; The beam is torsionally restrained at support; Loads are applied normal to the beam to cause bending about the major axis; The line of action passes through the shear centre (applied at, above or below the shear centre); Favourable effect of the in-plane deflection not accounted for (beam assumed straight in the plane of loading at buckling); Normal force negligible.

Keywords:

Mcrit; lateral torsional buckling; C1 factor; 6.3.2.2; 6.3.2.3

Valid until:

Jan 2015

Created by:

SCI

Created on:

Jul 2005

BSI Approval:

Not reviewed by BSI

General method for out-of-plane buckling in portal frames
(SN032)

This NCCI clarifies the general method presented in §6.3.4 of EN1993-1-1 for verifying out-of-plane buckling of members in portal frames for which the methods given in § 6.3.1 to § 6.3.3 do not apply. The guidance is of particular relevance to non-uniform members or members with particular lateral restraint conditions.

Keywords:

portal; haunch; 6.3.4

Valid until:

Jan 2015

Created by:

SCI

Created on:

Dec 2005

BSI Approval:

Not reviewed by BSI

Initial design of non composite beams (GB)
(SN010a-EN-GB)

This document provides design graphs for the selection of Universal Beam profiles to be used as secondary beams (non composite beams). These graphs give the maximum span length versus the slab span, for various section ranges and steel grades. The lightest section is used for each range.

Keywords:

Beam design; 6.2.5; 6.2.6; 6.3.2

Valid until:

Feb 2008

Created by:

SCI

Created on:

Jun 2006

BSI Approval:

Not reviewed by BSI

Mono-symmetrical uniform members under bending and axial compression
(SN030)

This NCCI provides information for dealing with mono-symmetrical uniform members subjected to bending and axial compression satisfying the following conditions: The verification is restricted to the elastic behaviour of the member; The cross-section is symmetrical about the weak axis; The flanges and the web are made of the same steel grade; The loads create bending moments about the strong axis only; The axial load is expected to be applied at the centroid of the cross-section; The web is made of a solid plate of constant thickness; The effects of the fillet welds are not taken into account. Note 1: Such a mono-symmetrical cross-section is susceptible to torsional-flexural buckling. Note 2: This kind of cross-section can be found, for instance, in composite structures where the upper flange of the beam is connected to a composite slab by means of shear connectors. Then, the following calculations are required in the non-composite stage when the fresh concrete acts only as an external load. In this case, the smaller flange is generally mainly in compression. This kind of cross-section can be found also in welded cross-sections when a higher resistance to torsional-flexural buckling is needed for the member. In this case, the smaller flange is generally mainly in tension. Note 3: Cellular beams or beams made of two different hot-rolled profiles are not covered by this NCCI.

Keywords:

6.3.3; combined

Valid until:

Jan 2015

Created by:

SCI

Created on:

Dec 2005

BSI Approval:

Not reviewed by BSI

Sizing guidance - non-composite columns (H sections)
(SN012)

This NCCI provides design graphs for the selection of Euronorm H profiles to be used as columns in simple construction. The document may be used to make an initial selection of column sizes for internal and external columns over the full height of a building. The selection is based on estimated axial forces in the columns, the storey height and the chosen steel grade (S235, S275 or S355).

Keywords:

european profiles

Valid until:

Feb 2008

Created by:

SCI

Created on:

Mar 2006

BSI Approval:

Not reviewed by BSI

Sizing guidance - non-composite columns (UC sections)
(SN012a-EN-GB)

The document may be used to make an initial selection of column sizes for internal and external columns over the full height of a building. The selection is based on estimated axial forces in the columns, the storey height and the chosen steel grade (S235, S275 or S355).

Keywords:

multi-storey; 6.3; 6.3.1; 6.3.1.3; 6.3; Annex B

Valid until:

Jan 2015

Created by:

SCI

Created on:

Mar 2006

BSI Approval:

Not reviewed by BSI

Torsion
(SN007)

This NCCI provides guidance about the verification of a member subject to torsion. When a member is loaded by transverse forces whose resultant does not pass through the shear centre of the cross-section, the member is subject to stresses due to torsion. These stresses should be combined with those due to bending and shear forces. This NCCI gives some guidance for the verification of a member in torsion. It contains the equations to calculate the stresses due to torsion, and expressions for the calculation of the torsional properties concerning common profiles. References are given for more complex cases. This document deals with uniform members only.

Keywords:

6.2.3; 6.2.7

Valid until:

Feb 2015

Created by:

SCI

Created on:

Dec 2004

BSI Approval:

Not reviewed by BSI

Torsional and torsional-flexural buckling

Clause 6.3.1.4 describes torsional and torsional-flexural buckling. In some circumstances, these are the critical modes of buckling, for example for cruciform sections, or asymmetric sections with different restraints to each flange. This article in New Steel Construction describes the phenomena, and gives background to the checks.

Valid until:

Jun 2008

Created by:

NSC

Created on:

Jun 2008

BSI Approval:

Not reviewed by BSI

Verification of columns in simple construction – a simplified interaction criterion
(SN048b-EN-GB)

This NCCI proposes a new expression for the verification of columns that will avoid the calculation of k factors in Annexes A and B of EN 1993-1-1. For the design of columns in the following situations The column is a hot rolled I or H section, or rectangular hollow section; The cross section is class 1, 2 or 3 under compression; The bending moment diagrams about each axis are linear; The column is restrained laterally in both the y and z directions at each floor but is unrestrained between floors. Relates to: Simple Connections.

Keywords:

Eccentricity

Valid until:

Jan 2015

Created by:

SCI

Created on:

Mar 2006

BSI Approval:

Not reviewed by BSI