For a stiffened panel with a flange (such as a T or and I), HyperSizer does local buckling analysis of the "Spacing Span" object, which includes both the Open Span between the flanges, and the flange/facesheet bonded region.

In the current software, HyperSizer creates an ABD matrix which is equivalent to the spacing span region. This ABD matrix includes the effects of the eccentricity between the bonded region and the open span, and therefore includes non-zero B terms. HyperSizer then does a buckling analysis of this region assuming a rectangular plate with the equivalent ABD terms.

The boundary conditions on this buckling analysis are Simple on all edges, therefore the rotational restraint of the stiffener is not included in this analysis.

Because the buckling analysis includes both the open span and the bonded retion, the width for this local buckling analysis is equal to the stiffener spacing, or the distance from the middle of one web to the center of the next.