MDX Software - FAQ #3<BR><BR>

How is the lateral moment from curvature in a flange, between braces, determined?<BR>
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Lateral moment at a brace is qL**2/12, where q is the distributed
    force on the side of the flange at the brace from warping torsion. The value of "q" is the primary moment M divided by radius of curvature R and the depth of the girder between flanges (q=M/Rd).
Also see LRFD C4.6.1.2.4b.

    L is the average of straddling unbraced lengths.

    The segment of flange between braces is viewed as a fixed-end beam
    having qL**2/12 as the fixed-end moment at each end (q different at
    each end), and a parabolic distribution of lateral moment between
    ends.  The parabolic distribution of lateral moment between braces
    can be determined by statics using these known end moments and the
    trapezoidal distribution of q between the braces.

    Two checks are made, one using the length between braces as the beam     segment and the other using the entire span.  The latter can be suppressed as     a check if the user assumes temporary construction bracing or curvature is     sufficient to prevent this behavior.
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