warping constan

huangyhg

warping constant
can anyone explain what the warping constant cw is and how it is calculated?
this is discussed in roark's formulas for stress and strain- section 9.3 in the 5th edition.  it also includes formulas for the cw and for k (which appears to be j in the aisc books).  it may take some juggling around with the fillet radius to make the j work out right.
find a copy of the aisc design guide 9 (
by the way, "for doubly symmetric i-shapes with rectangular flanges, cw = iy*ho^2/4", where ho = distance between the flange centroids.  this from section f2 of the new aisc code.
simply put the warping constant for torsion is analogous to the moment of inertia for bending.  it describes how well the flanges will resist warping.
just refer to "cold-formed steel design manual", you'll find the formula to calculate these constants for many kinds of shapes.
cordially yours
i thought the torsional resistance factor k or r was the counterpart to i, not cw.
you are correct k or r (i think it's called j too?) describes how well the entire section will resist torsion.
in addition to torsion for wide flange (or other open-sections) significant warping stresses can develop in the extremities (ie the flanges) cw is a factor that describes how well the flanges resist warping.
while the entire section does technically warp, for i sections the amount the web warps in insignificant compared to the flanges.