Imperfection Sensitivity Analysis of Structures in the Plastic Range

Initial imperfections in initial configuration, material properties, initial deflection, or remaining stress are well known to cause deterioration of buckling strength of imperfection sensitive structures. The importance of considering the plastic deformation in presence of imperfection has long been recognized. The plastic buckling imperfection sensitivity has received a greet deal of attention in the past [1, 2, 3]. Yet a systematic treatment, analogous to the Koiter’s imperfection sensitivity law for elastic systems, is not available for structures in the plastic range. In this paper, the imperfection sensitivity of a simple beam structure in the plastic range is analyzed in detail to investigate the mechanism of such behaviors. The variations of live loads applied to the model are interpreted as imperfections. Asymptotic imperfection sensitivity formulas are introduced to describe these variations when the structures are in the plastic range. The introduced formulas are validated numerically for a wide verity of imperfection patterns in loading to demonstrate the usefulness of the proposed formulas. References