Calculation of Load Distribution in Stiffened Cylindrical Shells Page: 51 of 70
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n.A.0.A. Technical Memorandum No. 86
which KS = 7.35 x 10".. This ease may also be interpret-
ed ith respect to the original dimensions as a reduction
in the bulkhead stiffness by.about 1/7. There has further
been computed the force distribution in the limiting case
of sheet rigid against shear.
Since the force group Yo is of "higher order" .(see
II, 2) than the convoxing group Xo, it reduced to soro
over a shorter shell length. The force distribution do-
pends only on the stiffness of the transverse stiffeners,
particularly if there is a strong end bulkhead at the load-
ing end. The dependence on the shear stiffness is consid-
erably groater, however, than in the case of the convexing
force group. As an approximating assumption for simplify-
ing the computation, it is accordingly permissible to neg-
lect the bulkhead deformations (KS wS = 0) in the static-
ally indoterminate computation for the simply symnatrical
force groups.
2. Computation of a Test Shell
The comnutation procedure developed will be applied
to a circular cylindrical 18-stringer shell, whose states
of stress under an applied bending and convexing force
group at 4 stringers, has been determinod experimentally,
as presented in detail i a simultaneously appearing papor
by E. Schapitz and G. Krunling. (Soo reference 1.) The
description of the shells and the method of conducting the
toots nmay therefore here be disponsod with. To further
limit ourselves to the computation of the longitudinal
stresses in the strincors before buckling of the skin.
takes placo, and compare then with the measured values.
aL) Aplication of a bending force roup.- The actual
arrangomont of the stringers is shown in figure Ja for
one quadrant. At stringors [7], [12, [3]), [16] , a puro
bending nomont about the transverse axis is applied by
four concentrated forces P. e consider first tho closod
shell without the cutaway portion at the loading sido and
idolize the syston to a 12-stringor sholl by combining
stringers [10] and [11] into one ptringoer 1 of double
the croso-soectional area. For the skin thickness thero in
assunod a uniform valuo of a = 0.06 cn and half the skin
10The stringor and bulkhead notations taken front the papor
by E. Schapits and G. Krnling are denoted by brackets.50
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Ebner, H. & Köller, H. Calculation of Load Distribution in Stiffened Cylindrical Shells, report, June 1938; (https://digital.library.unt.edu/ark:/67531/metadc63311/m1/51/: accessed April 25, 2024), University of North Texas Libraries, UNT Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.