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National Advisory Committee for Aeronautics, Report - Restraint Provided a Flat Rectangular Plate by a Sturdy Stiffener Along an Edge of the Plate

A sturdy stifle-nor is defined as a stifiener of such pro-
portions that it does not safer cross-sectional distortion
when moments are applied to some part of the cross
section. When such a stiflener is attached to one edge
of a plate, it will resist rotation of that edge of the plate
by means of its torsional properties. A formula is gire-n
for the restraint coeficient provided the plate by such a
stifener.

In the calculation of the critical compressive stress
for flat rectangular plates as presented in references 1
and 2, it is necessary first to evaluate the restraint
coefficient along an unloaded edge of the plate. The
formula that must. be used to evaluate this restraint
will depend upon the characteristics of the structural
member or members which provide the restraint. In
references 1 and 2 it was'assumcd that the restraint was
provided by a specially defined elastic restraining
medium. As a result of this assumption, it was
possible to derive a general design chart for the calcu—
lation of the critical compressive stress that is, within
wide limits, independent of the structure which
provides the restraint.

On the assumption of perfect elasticity, both 6 and
D are constant for the plate and it. is necessary to
evaluate only 3.3. The detailed effect of loading beyond
the elastic range is considered in another section of
this paper.

The basic property of the elastic restraining medium,
as used in the theory of references 1 and 2 in the defini—
tion of e, is that rotation at one point of the medium
does not affect rotation atanother point of the medium.
In. many practical problems the elastic restraint is
provided by a stiffener, a plate, or some other structure
for which rotation at one point does affect rotation at
another point. Consequently, the evaluation of So in
any given problem must take into account the effect of
this interaction Within the elastic restraining structure.