Lateral torsional
buckling may occur in an
unrestrained beam. A
beam is considered to
be unrestrained when its
compression flange is free
to displace laterally and
rotate. When an applied
load causes both lateral
displacement and twisting
of a member lateral
torsional buckling has
occurred. Figure 1 shows
the lateral displacement and twisting experienced by a beam when lateral torsional buckling occurs.