Why do reaction forces not sum to zero in an Inertia Relief analysis with a superelement?
The documentation states that the sum of the reaction forces in a IRLF calculation
should be zero. For the attached model that uses a matrix50 element this is not true. Here is development's explanation of the non-zero reaction forces
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I reported this in Defect 54555, but development found that it was not an error. The condensed mass matrix of your Substructure is not representative of the mass of the model with the current location of the Master DOF in the model. With a slight modification of the input data (by selecting additional MDOF at the 'bounding box' of the of model) the reaction forces are near zero. The documentation has been modified at 11.0 to include the possibility that this may be necessary to obtain zero reaction forces in an inertia relief analysis. Verifying that the reaction forces are near zero in an inertia relief analysis is a good check on the adequacy of the Master DOF specification. |
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