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National Advisory Committee for Aeronautics, Technical Notes - Diagonal Tension in Curved Webs

The engineering theory of incomplete diagonal tension in plane
webs presented in NACA TN No. 1361+ is generalized in order to mate
it applicable to curved webs. Comparisons are given between
calculated and experimental results for a number of stiffened cylinders
subjected to torsional loads. The results indicate that the theory
predicts the stresses to about the same accuracy for curved webs
as for plane webs. The failing stresses in the stringers in curved.
webs were predicted conservatively in all cases.

Aeronautical practice in the design of stiffened sheet—metal
structures has long been to permit buckling of the sheet except for
such restrictions as may be imposed by aerodynamic considerations.
When the sheet is subjected essentially to shear forces, the state
of stress that exists after buckling has taken place is known as
diagonal tension. The theory of diagonal tension in plane (flat)
webs was developed in considerable detail by Wagner (reference 1)
for the theoretical limiting case of fully developed diagonal tension.
For the practical and more general case of partly developed plane
diamnal tension, theories of varying scope and. refinement have been
given by a number of authors. The engineering theory of incomplete
plane diagonal tension given in reference 2 is semiempirical but
is simple to use and has a wide scope.

A theory of diagonal tension in curved webs has also been given
by Wagner, again for the theoretical limiting case of fully developed
diagonal tension (reference 3). Because the curvature introduces
several complications, Wagner was forced to make more restrictive
assumptions in the theory of curved webs than in the theory of plane
webs. These additional complications have greatly retarded the
development of a theory of incomplete curved. diagonal tension. The
first attempt to develop such a theory was made by Wagner in reference 3,
where he suggested the assumption that the shear stress in excess of
the critical Value Tor is carried- by diagonal tension.