Calculation of Load Distribution in Stiffened Cylindrical Shells Page: 5 of 70
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N.A.O.A. Technical Memorandum No. 866
the skin is taken into account by the addition of an ef-
fective width to the stringer sections. Under these as-
sumptions, in each of the sheet panels there is a con-
stant "shear flow"2 (t = e 7) to which correspond linear-
ly distributed normal forces in the longitudinal stiffen-
ers within the panels, while the transverse stiffener
walls are stressed by tangential peripheral loads, namely,
differences of the shear flows in the longitudinal direc-
tion. This state of stress agrees with the actual state -
the more closely the stronger the stiffeners an compared
with the skin. In the neighborhood of points of attach-
ment and cut-out portions, these are the relations which
generally exist. The roliability of the assumptions made,
which had previously been applied to the computation of
statically determinate systems (bending beams) is con-
firmed by tests. The assumption of constancy of the shear
in each of the panels in the longitudinal direction may,
in the case of curved shells, also be justified by the
fact that generally the flexural stiffness of the skin.
and stringers is small ~ompared to that of the transverse
stiffness of the bulkheads, so that within no panel can
important peripheral stresses aride .in the skin.
This simplified shell model corresponds to a lattico-
work, with redundant transverse frames in which the diago-
nals are replaced by shoot panols under shear. For (n - 1)
intermediate transverse frames, each of which is q-fold
statically indeterminate, the entire system with n string-
ers is [C(n - 1) (n - 3) + (n + l)q]-fold statically indo-
terminate, and there arc further additional redundancies
at points of attachment. The statically indeterminato
computation of the sunplifiod systom gives the force dis-
tribution "in the largo" and. the stress distribution in
the actual shell design nay then be estimated, taking into
account the constructional dotails. (Soo the numorical
oxamplo in section VI, 2.)
2. Principal Panel System
Longitudinal Forces as Static Rodundancios
Tho computation of the statically indeterminate nodel
shell procoods along linos similar to those developed by
the first author in previous papers on space frameworks
2The torm "Sohubfluse,n translated as n"shear flow," is
used consistontly in Gorman papers to denote.ehear stress
times skin thickness. (Translator)_ _ ___ ~ ____ 1 __
4
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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/m1/5/: accessed April 24, 2024), University of North Texas Libraries, UNT Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.