Imperfection measures of eigen- and periodic modes of axially loaded stringer-stiffened cylindrical shell

Abstract: The influence of initial geometric imperfections in the shapes of eigenmodes and peri-odic modes on the load-carrying capacity of a steel stringer-stiffened cylindrical shell subject to axial compression is studied. For comparison of the influence of different shapes, the imperfec-tions are normalized by an integral–energy measure, which is considered as an alternative to the commonly applied amplitude. The shell dimensions are chosen out of the set of 24 small-scale specimens tested between 1981 and 1984 at Imperial College in London. Published results of statistical analysis of measured imperfection surfaces of the set are employed for checking their conjectured relationship to the normalization of imperfections by the energy measure. The study is finite element method (FEM)-oriented; the numerical model is checked by application of two FEM codes