Postbuckling of Stiffened Panels Using Strut, Strip, and Finite Element Methods

Postbuckling results are presented for isotropic stiffened panels loaded in compression. Comparisons are made between single-bay and double-bay e nite element (FE) models (where “ bay” denotes a repeating portion, between supports, in the load/length direction ) and a new strut model, following a Shanley-type approach, for single-bay and multibay panels. The strut model has been incorporated within the strip program VIPASA with CONstraints and OPTimization (VICONOPT) to design a multibay example panel with postbuckling reserve of strength in its skins, assuming linear elastic material properties. The panel has been shown by VICONOPT to have a stiffener buckling failure mode when an overall sinusoidal imperfection causing increased stiffener compression is present. The failure is cone rmed by the double-bay FE model, which is shown to be an imperfect representation of the multibay case. Single-bay analysis using the strut model shows good agreement with the single-bay FE results. The VICONOPT code is able to design a metallic panel of realistic dimensions and loading using 50 strip elements (compared with the 9600 shell elements required by the e nite element model ) but cannot correctly account for material nonlinearity. The important phenomenological difference between postbuckling of single-, double-, and multibay panel models are indicated.

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