Stimulating Equivalent Geometric Imperfections for the Numerical Buckling Strength Verification of Axially Compressed Cylindrical Steel Shells

Abstract

A geometrically and materially nonlinear analysis with imperfections included (GMNIA) is currently the most sophisticated and perspectively the most accurate method of a numerical buckling strength verification. By this way, equivalent geometric imperfections, which have to cover the influence of all deviations from the nominal data of the resistance parameters, are fundamental. The problem of consistent equivalent geometric imperfections includes the problems of their shape and size. It is recommended to start from the failure modes of the perfect structure in order to get imperfection patterns, which are unfavourable with respect to buckling resistance, relevant referring to manufacture and easy to use. The influence of the imperfection length is not sufficiently attended in the present design codes. It is proposed to use the full wave length of the ideal ring buckling mode as the imperfection length of the equivalent geometric imperfection for the basic buckling case of the axially compressed cylindrical shell. Finally, proposals are made for consistent equivalent geometric imperfection amplitudes of this buckling case.