D5.D.3.5 Clause 6.3 – Buckling resistance of members

The D-NA introduces a new clause 6.3.0, which in turns requires the checks as per clauses 12.1.2.2, 12.13.2 and 12.1.4.2 of NEN 6771 to be applied.

Clause 12.1.2.2 (NEN 6771)

This clause in NEN 6771 determines the relative torsional slenderness and is given as:

λ_{θ, r e l} = \sqrt{\frac{N_{c; u; d}}{F_{E; θ}}}

Where:

N_c;u;d = A·f_y;d

A = area of section
f_y;d = the yield stress
F_E;θ is the Euler-torsion formula

This value of slenderness is to be used to calculate the modification factors used in section 6.3 of EC-3.

Clause 12.1.3.2 (NEN 6771)

This clause works out the relative torsional-flexural buckling slenderness for compression members. The relative torsional-flexural buckling slenderness is given as:

λ_{t k, r e l} = \sqrt{\frac{N_{c; u; d}}{F_{E; t k}}}

Where

N_c;u;d = A·f_y;d

A = area of section
f_y;d = yield stress
F_E;tk is the Euler torsional buckling strength

Clause 12.1.4.2 (NEN 6771)

Buckling lengths of rotationally restrained bars with intermediate spring supports.

Note: STAAD.Pro does not allow for these end conditions, specifically. The effective length factors may be used to accommodate this requirement.