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Application of a Numerical Procedure to Stress Analysis of Stringer Reinforced Panels

A numerical procedure, as well as the underlying theory
and assumptions, is presented for the calculation of the
stringer stresses and shear stresses in reinforced panels.
The method may be applied to all panel problems in which
the loads may be considered acting in the plane of the sheet.

Examples are given to illustrate the use of the
method for axially loaded panels with and without rectan-
gular cut-outs and for the covers of box beams with and
without rectangular cut-outs.

The results of this procedure are compared with the
experimental data and the approximate engineering methods
of analysis of previous NACA papers from which the problems
are obtained.

Several papers have been written on the stress analysis
of sheet-stringer panels loaded axially or as the cover of
box beams. (See referencesl and 2.) The solutions
presented in these papers are generally sufficiently
accurate for most practical cases of construction and
loading but are not readily applicable to more general
cases in which the cross section varies and the loads
are arbitrarily distributed.

In the present paper a numerical procedure for the
_stress analysis of flat-sheet and stringer combinations
of arbitrary construction and loading is presented and
applied to axially loaded panels and to the reinforced
covers of box beams. The basic theory of the procedure
was originally developed in reference 5. Comparisons are
given of the results obtained by the numerical procedure
of the present report and the results obtained by the
approximate analyses and experimental results of
references 1 and 2.

The numerical procedure parallels that of Southwell's
relaxation method and Cross's moment-distribution method
(references 4 and 5) but is so given in the present report
that the reader need have no previous knowledge of these
techniques. The equations obtained in reference 3
are solved by a relaxation procedure, whereas in the
present paper a direct solution of simultaneous equations
is used.