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National Advisory Committee for Aeronautics, Technical Notes - Experimental Investigation of the Strength of Multiweb Beams with Corrugated Webs

The results of an experimental investigation of the strength of
multiweb beams with corrugated webs are reported. Included in the inves-
tigation were two types of connection between the web and the skin. A
comparison between the structural efficiency of corrugated—web and
channel-web multiweb beams is presented, and it is shown that, for a
considerable range of the structural index, corrugated-web beams can be
built which are structurally more efficient than channel—web beams.

Attention has been directed to the use of corrugated webs in thin—
wing construction as a means of reducing stresses associated with nonuni-
form temperature distribution in a structure. Compared with more conven-
tional webs, a corrugated web can offer only a slight restraint to thermal
expansion of wing skins.

Upon closer examination of the prOperties of corrugated sheet as a
web, it appears that other advantages over more conventional webs can be
realized. Corrugated.webs, because of their high moment of inertia, are
capable of supplying very stiff deflectional and rotational restraints to
a skin if an adequate connection is made. In addition, information exists
which indicates that corrugated sheet is very efficient in carrying shear
loads (refs. 1 and 2).

The purpose of the investigation herein described.was to evaluate
experimentally the ultimate bending strength of corrugated—web beams at
room temperature and to acquire an indication of their structural
efficiency.

Nine three-cell multiweb beams with corrugated.webs were fabricated
for this investigation. The beams were divided into two groups which
differed principally in the type of the connection between the corrugated
webs and the skins.

The.first group (beams l to h, table I) had web-skin connections
which provided only a negligible restraint_to thermal expansion of the
skin. The connections were made with an individual clip angle between
the web and the skin at each corrugation crest. (See fig. 1(a).) In
the second group (beams 5 to 9, table I) some of the desirable thermal
characteristics were sacrificed in an attempt to improve_the load—
carrying ability of this type of beam. gThe individual clip angles were
replaced by continuous angles (see fig. l(b)) which will offer a small
restraint to expansion of the skin if the beams are subjected to a non-
uniform temperature distribution.