scope:

Description of Driving Event:

The basis of the Z1 ITS modeling strategy in the preliminary and conceptual design phases was a simplified beam element representation of the primary structure bulkheads and panels. This facilitated rapid, automated beam based stress analysis of the primary structure and decreased the design cycle time as well as manpower loading. The same model was used for both (1) the design dynamic-coupled load analysis and (2) the pre-test model and static test prediction analyses.

The pretest model analysis model produced poor correlation with the model test data. The correlation was improved by remodeling critical bulkheads and panels in greater detail using shell elements for the basic web and shell/beam elements for the upstanding ribs & flanges. Solid elements were also used where "plate" proportions did not exist. The increased fidelity of the post-test model led to improved correlation with the static test as well. However, the changes made to the model have forced a re-evaluation of the internal stresses both because of the change in model response and/or load paths. This re-evaluation came long after the design of the hardware was finalized and manufacturing completed. Any adverse findings from this re-evaluation could lead to costly retrofits or undesired limitations on hardware use during operations.