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National Advisory Committee for Aeronautics, Technical Notes - Handbook of Structural Stability Part II-Buckling of Composite Elements

The local buckling of stiffener sections and the buckling of plates
with sturdy stiffeners are reviewed, and the results are summarized in
charts and tables. Numerical values of buckling coefficients are presented
for longitudinally compressed stiffener sections of various shapes, for
stiffened plates loaded in longitudinal compression and in shear, and for
stiffened cylinders loaded in torsion. Although the data presented consist .
primarily of elastic-buckling coefficients, the effects of plasticity are .3
discussed for a few special cases.

The buckling behavior of simple plate elements is described in
parts I and III of this "Handbook of Structural Stability" (refs. 1 and
2). Structural components often consist of two or more simple plate
elements so arranged that the buckling stress of each is increased as a
result of the support provided by contiguous neighbors. Such composite
elements are termed stiffeners because they are frequently used to stiffen
a plate in order to increase the buckling stress. A compact stiffener is
described as tsturdy" when it is not subject to local buckling and there-
fore only the axial, bending, and torsional rigidities of the stiffener
influence the behavior of the plate-stiffener combination under a specified
loading. The data presented in this report on the buckling of stiffened
plates pertain to sturdy stiffeners.

The report begins with a discussion of calculation of local buckling
stress of stiffening elements. Stiffener structural shapes in common use,
such as Z-, channel, and hat sections, have been analyzed for buckling
and charts are presented to facilitate buckling-stress computations. For
sections which buckle elastically, failure may occur at loads considerably
in excess of buckling. Failure, or crippling, of stiffening elements is
treated in reference 3.

When the proportions of a stiffener are such that it is sturdy with
respect to the plate which it is stiffening, it acts essentially as an
elastic restraint to the plate. It may assist in the resistance to load,
as do the spanwise stiffeners in a wing cover, or it may behave primarily
as a support, such as a transverse rib.