Comparison of Three Methods for Calculating the Compressive Strength of Flat and Slightly Curved Sheet and Stiffener Combinations Page: 4 of 32
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N.A.SA. Technical Note No. 455 3
This method assumes complete independence of action
of the stiffeners but not of the sheet.
Method C.- Method C assumes the stiffener and effec-
tive width of sheet to behave as a column which fails by
bending normal to the plane of the sheet. The moment of
inertia and slenderness ratio of the combination of stiff-
ener and effective width of sheet are calculated and the
area of the combination is multiplied by the stress for a
column of these proportions.
This method assumes no independence of action of the
sheet and stiffener but rather a mutual action of the two.
COMPARISON OF OBSERVED AND PREDICTED COMPRESSIVE LOADS
FOR FLAT SHEET AND CHANNEL STIFFENER COMBINATIONS
In Table I are tabulated observed and predicted eom-
pressive' loads for the panels shown in Figure 2 tested
with flat ends. The loads observed in test were obtained
from Newell and the predicted loads were calculated as
outlined in Appendices A, B, and C.
The observed and predicted loads reoctrded in Table I
are plotted in Figure 3. It will be observed that for all
panel lengths with thin sheet and for short panels with
thick sheet there tends to be little difference between
the loads predicted by the three methods and that the ob-
served and predicted loads tend to be in good agreement.
For long panels with thick sheet, the loads predicted by
methods A and 3 err on the unsafe side by an amount which
increases with increase in both length of panel and thick-
ness of sheet, but the loads predicted by method C agree
very well with those observed in tests.
Because the tests were made with indefinite end con-
ditions (flat ends), any detailed consideration of small
differences between observed and predicted loads is not
justified. Conclusions will therefore be drawn with re-
gard to large differences only. .
Of the three methods for predicting the compressive
strength of flat sheet and stiffener combinations, method
C gives the best general agreement between observed and.
predicted loads for the specimens tested. 7or specimens
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Lundquist, Eugene E. Comparison of Three Methods for Calculating the Compressive Strength of Flat and Slightly Curved Sheet and Stiffener Combinations, report, March 1933; (https://digital.library.unt.edu/ark:/67531/metadc54181/m1/4/: accessed March 24, 2019), University of North Texas Libraries, Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.