D5.D.7.4 Clause 188.8.131.52(1) – LTB for rolled sections or equivalent welded section
The Finnish-NA provides the values for the terms λLT,0 and β factors given in clause 184.108.40.206(1) as follows:
For rolled doubly symmetric sections and hollow sections, use:
- λLT,0 =0.4 and β = 0.75
For welded doubly symmetric sections and hollow sections use:
- λLT,0 = 0.2 and β = 1.0
The Finnish NA specifies the following limits for choosing the buckling curves:
|Rolled double symmetric I- and H- sections and hot finished hollow sections.||
h/b ≤ 2
2 < h/b <3.1
|Welded double symmetric I- section and H- sections and cold-formed hollow sections||
h/b ≤ 2
2 < h/b < 3.1
The NA says that for all other cases the rules given in Cl 220.127.116.11 should be used. Hence even for rolled or welded doubly symmetric sections with h/b ratio ≥ 3.1, this implementation will resort to checks as per clause 18.104.22.168.
These equations and factors are then applied to equation 6.57 of SFS-EN 1993-1-1 to evaluate the Lateral Torsional Buckling reduction factor χLT.