Since the CPU cost of using the warping DOF is very small, we actually recommend using it in all BEAM188 and BEAM189 models. The warping will only be detected if you 1) set KEYOPT(1)=1 to activate the warping and 2) restrain that DOF somewhere. If you just activate it, but never restrain it, the warping will not be shown. Some sections show more warping than others. For most cross sections, a torsional load will cause the cross section to twist. In many cases, this is not a big deal – i.e., the error will not be too large. However, for thin walled sections (I beams, channels, etc.), warping can be important. Incidentally, circular (round) shapes do not warp. Torsion causes warping, but many combinations of loading and beam section can cause torsion. For example, a transverse shear load applied at the mid-span of an open “C” section (fixed at each end) which is not applied at the shear centre will cause the beam to twist. We do warn the user that if a section of the beam structure were to go plastic, we do not recalculate the torsional shear distribution on cross sections in the deformed configuration. Instead, we recommend modelling such scenarios with solid elements.