In designing cylindrical structure such as chimney-stacks, as well as storage tanks, it is very important to accurately predict the buckling strength and collapse strength of axially compressed cylindrical shells, especially with initial imperfections. This paper investigates the effects of large initial imperfections on the buckling and collapse strength of axially compressed cylindrical shells, utilizing the finite element analysis. Main conclusions obtained from this study are as follows; (1) The effects of large initial imperfections, such as several times of shell thickness, are clarified. (2) The larger the ratio of radius to thickness of shells (R/t) are, the more sensitive to the initial imperfections the buckling strength of cylindrical shells are. (3) The circumferential buckling mode number gets large according as R/t ilarge or magnitude of imperfection gets large. (4) In the case of small imperfection, the axial length of imperfection when the cylindrical shell has the smallest buckling strength is 4√Rt. But in the case of large magnitude imperfection, it becomes larger than 4√Rt.
