If we are talking about the warping constant, then I believe it is usually neglected for closed sections (or in your case solid sections) since the warping constant is usually quite small relative to the torsion constant "J". The same is not true for open sections, where both the warping constant and torsion constant are used to determine the member (buckling) capacity of beams subject to bending.
Similar to Trenno, my experience is with Australian codes only.
Cw is defined in the Canadian Standard CSA S16.1 as the "warping torsional constant" and is used in the formula for the critical elastic moment of an unbraced member, when computing the resisting moment of a laterally unsupported member.
I recently designed a flat plate to act as a beam (about it's major axis). In regards to finding the member capacity, I assumed Iw = 0 in the following equation.
ok, thanks. When I get into the office I will scan the page and post it. (we had a bit of snow overnight, so it will be slow drive to work...guess you don't have that problem in Australia...my niece lives in Sydney)
