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National Advisory Committee for Aeronautics, Technical Notes - Stress Analysis of Circular Semimonocoque Cylinders with Cutouts by a Perturbation Load Technique

A method is presented for analyzing the stresses about a cutout in
a circular cylinder of semimonocoque construction. The method involves
the use of so-called perturbation solutions which are superposed on the
stress distribution that would exist in the structure with no cutout in
such a way as to give the effects of a cutout. The method can be used
for any loading case for whicthhe structure without the cutout can be
analyzed and is sufficiently versatile to account for stringer and shear
reinforcement about the cutout.

Stresses near a cutout in a semimonocoque shell can be much higher
than the stresses in the uniform shell some distance away from the cut—
out. The stress distribution in the neighborhood of cutouts in circular
semimonocoque cylinders is significant in the design of fuselages near
large Openings such as doors and in the determination of the most effi-
cient reinforcement to be used about these openings.

Same previous investigations relating to the problem of stress
analysis of cylindrical semimonocoque shells with cutouts were reported
in references 1 to 3. In reference A, Cicala discussed the limitations
of the analyses of references 1 to 5 - particularly the neglect of ring
flexibility — and introduced the idea that the effect of a cutout can be
reproduced.by superposing certain perturbation stress states on the
stresses which would occur in the shell without a cutout.

The problem discussed by Cicala in reference L is that of a cutout
in an infinitely long circular cylinder of semimonocoque construction.
Cicala's analysis is somewhat limited because it can be used only for
loading conditions which produce stringer stresses longitudinally anti-
symmetric about the center line of the cutout (for example, torsion),
and it cannot be used to determine the effects of coaming-stringer rein-
forcement.