This is due to the ability of flanged and plain cruciform to resist lateral-torsional buckling, allowing development of efficient plastic resistance, over longer unbraced lengths when compared to conventional shapes.
Analysis results show the ability of flanged and plain cruciform to resist lateral-torsional buckling over longer unbraced lengths, allowing development of efficient plastic resistance.
Lee, "Lateral-torsional buckling
of I-girder with corrugated webs under uniform bending," Thin-Walled Structures, vol.
From the paper , the lap edge single section was considered as critical in purlin design and lateral-torsional buckling becomes critical when in the case of laterally unrestrained purlins.
The strength requirements , plastic and lateral-torsional buckling behaviour  of single cold-formed channels bolted back to back, were investigated.
Structural safety of rolled and welded beams subjected to lateral-torsional buckling
, Journal of Civil Engineering and Management 16(2): 172-178.
2009) and lateral-torsional buckling capacity (Hindman et al.
(2005), which showed that the NDS specifications for bracing against lateral-torsional buckling are typically conservative.
AISC presents the lateral-torsional buckling by the following Eq:
Lateral-torsional buckling of beams is presented in EN 1993-1-1 Eurocode 3: Design of Steel Structures.
 developed an analytical approach to estimate the critical elastic moment in order to compute the final design lateral-torsional buckling
resistance moment in special truss-reinforced composite steel-concrete beams.
However, for deeper beams due to the high level of strain concentration at the RBW area and excessive lateral-torsional buckling
of the beam web (which was due to the increase in the depth of the voids), the efficiency of this method reduced and the modified connection did not achieve adequate connection's strength and ductility.