An experimental study of the buckling of closely spaced integrally stringer-stiffened circular cylindrical shells under axial compression was carried out to determine the influence of stiffener and shell geometry, as well as mechanical properties of shell material, on the applicability of linear theory. Tests included 84 shells made of two different kinds of steel with completely different mechanical properties and 74 shells made of 7075-T6 Aluminum alloy. Agreement between linear theory and experiments was found to be governed primarily by shell geometry, Z, where for Z > 1000 values of “linearity” (ratio of experimental buckling load to the predicted one) of 70 percent and considerably above were obtained. Correlation with linear theory was also found to be affected by stringer area parameter (A1/bh) where for (A1/bh) > 0.45 the values of linearity obtained exceeded 65 percent and usually were much higher. No significant effect of other stiffener and shell parameters on the applicability of linear theory could be discerned for the specimens tested. The boundary conditions were found to be of importance and for some steel shells the inelastic behavior of the shell material was found to have a considerable effect on the linearity. Predictions of imperfection sensitivity studies could not be correlated with test results. By a conservative structural efficiency criterion all the tested stringer-stiffened shells were found to be more efficient than equivalent weight isotropic shells.

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