Simcenter FEMAP 2019.1 has added support for explicitly defined Preload and Buckling STATSUBs in linear buckling analysis sets. Previously, multi-case buckling in FEMAP worked by setting up the desired number of static subcases with the defined load/constraint sets, then, upon export, a “synthetic” buckling case containing a STATSUB was written to the input file for each static subcase. Each synthetic buckling case would typically be exported with an ID Offset of 1000 from its corresponding static subcase.
While this approach worked well for single-case buckling, it was limited for multi-case buckling, given that a single static case could only be referenced by one buckling case. In other words, the same static solution could never be used more than once by different buckling cases with different constraint configurations. Furthermore, since buckling cases were generated “synthetically,” they could not be edited in the Analysis Manager. As a result, specifying certain requests or attaining a numbering scheme for buckling cases was locked to manual input, as the buckling cases don’t exist in the model database. Consequently, linear buckling input files that didn’t strictly adhere to FEMAP’s case control setup for linear buckling would seldom “round-trip” properly on import.
With explicitly defined STATSUBs, static solution selection for buckling cases has been simplified with STATSUB selection “interface” in the Analysis Manager. For a linear buckling analysis set, FEMAP subcases now have a “STATSUB” tree item that, when selected, brings up the “Subcase N STATSUB Options” dialog.
The dialog contains two lists – each populated with static subcases in the analysis set which are available to be “selected” by a buckling subcase as a Preload or Buckling STATSUB. The subcase that is selected as a Buckling STATSUB consists of the loading configuration used to compute buckling in the buckling subcase, while the preload case contains the load that will be applied to the structure prior to buckling being computed. Buckling cases can now be modified directly in the Analysis Manager, including labeling, numbering, output requests, order in the analysis set etc. With the new setup, all of these will be preserved on re-import of that deck (i.e., “Round Tripping”) into FEMAP. Also, with the addition of Preload STATSUBs, buckling cases can now include the effects of static stiffening by simply selecting a subcase containing the desired preload from the “Preload Subcase” list.
Please Note: In the initial release of FEMAP 2019.1, static cases created in the Analysis Set Manager will NOT have synthetically generated buckling cases exported for them for multi-case buckling. As a caveat, if your analysis set consists of several hundreds of cases that require computation of buckling, those cases would now need corresponding buckling cases defined in the analysis manager that point to them as a STATSUB. This will be addressed in the first maintenance update of FEMAP 2019.1, which will restore the synthetic generation of buckling cases for static cases that don’t have an associated case pointing to them as a STATSUB. In the meantime, an API was written that facilitates the generation of buckling cases in FEMAP to attain equivalent functionality to what was previously available. The API automates the generation of static and buckling cases for a buckling analysis set, with the STATSUBs appropriately defined for the buckling case. Simply select the load and constraint sets that you would like to use to compute buckling, and the API will do the rest. See the video below for a demonstration: