This and the next three slides are from the paper, "Optimization of stiffened panels in which mode jumping is accounted for" by David Bushnell, Charles C. Rankin, and Eduard Riks, AIAA 38th Structures, Structural Dynamics, and Materials Conference, AIAA Paper No. AIAA-97-1141, 1997, called "1997 modejump paper" in the next three slides.

This is Fig. 21 of the 1997 modejump paper. Shown here is an axially compressed single skin-stringer module of a metallic panel with uniformly spaced stringers of rectangular cross section. Symmetry conditions are applied along the two longitudinal edges of this single module model.

The nonlinear static equilibrium states displayed in this slide are from the first phase of a three-phase STAGS analysis of a panel that was previously optimized by PANDA2 with a mode-jumping constraint turned off (called "PANEL I" in the 1997 modejump paper).

The three phases of the STAGS analysis are:

1. initial nonlinear static analysis with STAGS load factor PA in the range 0 < PA < 0.7013

2. nonlinear transient analysis with STAGS load factor PA held constant at 0.7013

3. post-transient nonlinear static analysis with STAGS load factor PA in the range 0.7013 < PA < 0.943

Results from these three phases of the STAGS analysis are displayed on the next slide.

As shown on the next slide, STAGS predicts that the panel collapses at load factor, PA - 0.943. The load factor for which the panel was previously optimized by PANDA2 is the design load factor, PA = 1.0.

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