D5.D.6.4 Clause 6.3.2.3(1) – LTB for rolled sections or equivalent welded section

The FR-NA provides equations to evaluate the λ_LT,0 and α_LT factors given in clause 6.3.2.3

For rolled doubly symmetric sections use:

{\bar{λ}}_{L T, 0} = 0.2 + 0.1 \frac{b}{h}

α_{L T} = 0.4 - 0.2 \frac{b}{h} {\bar{λ}}_{L T}^{2} \geq 0

Note: Since EN 1993-1-1:2005 limits the value of λ_LT,0 to 0.4, STAAD.Pro limits λ_LT,0 to a maximum value of 0.4.

For welded doubly symmetric sections use:

{\bar{λ}}_{L T, 0} = 0.3 \frac{b}{h}

α_{L T} = 0.5 - 0.25 \frac{b}{h} {\bar{λ}}_{L T}^{2} \geq 0

For other sections:

λ_LT,0 = 0.2

α_LT = 0.76

And for all sections, β = 1.0

These equations and factors are then applied to equation 6.57 of NF EN 1993-1-1 to evaluate the Lateral Torsional Buckling reduction factor χ_LT.