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Issue: incorrect sum of masses

Issue

The sum of masses does not correspond to hand calculation (IGE17-176ANJGZ6, IBE17-99AL6L7D)

The user simply compares the sum of masses provided in the eigenfrequency calculation protocol with the sum of loads and reactions provided in the linear calculation protocol. In theory, if the masses and the loads match, the loads should be equal to the masses multiplied by the acceleration of gravity g.

Total load calculated from the mass in the eigenfrequency calculation protocol:

Total load given in the linear calculation protocol:

Difference:

Explanation

Several factors can affect the masses used in the calculation and, therefore, the correspondence between loads and masses:

• property modifiers allow to alter separately the mass and the self-weight of structural members
• masses directly attached to rigid supports are completely ignored in the dynamic analysis
• the self-mass of structural members directly attached to rigid supports is affected similarly (portion of the member close to the support)

For more information, see Validation of modal analysis: sum of masses

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