Steel brace design to EC3

Tekla Structural Designer
2021
Tekla Structural Designer

Steel brace design to EC3

Design method

Unless explicitly stated all brace calculations are performed in accordance with the relevant sections of BS EN 1993-1-1:2005 (Ref. 1) (herein abbreviated to EC3) and the associated National Annex.

A basic knowledge of the design methods for braces in accordance with the design code is assumed.

Classification

No classification is required for braces in tension.

Braces in compression are classified according to Table 5.2 as either: Class 1, Class 2, Class 3 or Class 4.

Class 4 sections are not allowed.

Axial tension

An axial tension capacity check is performed according to clause 6.2.3.(1)

The following points should be noted:

  • Clause 6.2.3 (3) - is not considered

  • Clause 6.2.3 (4) - is not considered

  • Clause 6.2.3 (5) - is not considered

Axial compression

An axial compression capacity check is performed according clause 6.2.4.(1)

Compression buckling

If axial compression exists, the member is also assessed according to clause 6.3.1.1(1) for flexural buckling resistance about both the major and minor axis i.e. Nb,y,Rd and Nb,z,Rd over the buckling lengths Lyy and Lzz and where required the torsional, or flexural-torsional buckling resistance, Nb,x,Rd.

For single and double angles (both equal and unequal) there is also a compression buckling check about the v-v axis, over the buckling length Lvv. For single angles, Lvv is the system length L, while for double angles Lvv is L/3.

All section types are checked for flexural buckling. It is only hollow sections that do not need to be checked for torsional and torsional-flexural buckling.

Different effective length factors can be applied for flexural buckling in the major and minor axis. For single and double angles an effective length factor can also be applied in the v-v axis. The default effective length is 1.0L in all 3 cases. You are expected to adjust the effective length factor (up or down) as necessary.

The torsional and torsional flexural buckling effective length factor (1.0L) can not be changed.

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