How many mode shapes do I need to consider for an earthquake analysis?
In the module RF-DYNAM Pro you find those values together with the frequencies in the Dynamic Load Cases (DLCs) in a tab called 'Mode Shapes', please see attached picture. You can check whether or not you calculated a sufficient number of eigenvalues before starting the calculation, it might be that you have ti increase the number of eigenvalues.
After calculation you find the effective modal masses and the factors in Table 5.7 5.7 Effective Modal Mass Factors.
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Dynamic analysis of natural frequencies and mode shapes of member, surface, and solid models
Seismic and static load analysis using the multi-modal response spectrum analysis
Dynamic and seismic analysis including time history analysis and multi-modal response spectrum analysis