Go to the Selection of Modes tab next. It controls which modes are taken into account for the spectral analysis.
In the table, all 33 modes that were calculated for the modal analysis load case (LC5) are listed (see the Factors for Effective Modal Masses image). They are all activated by default. At the end of the table, you can see the overall sums of the ratios between Meff,i and ∑ M: 90.6% for fmeX and 93.7% for fmeY.
Use the
button to deactivate all modes less than 1% and, thus, deselecting minor relevant modes.
As a result, you will notice that the limit of 1% ('0.01' in the box to the right of the button) produces ratios for fmeX falling below the 90% rule. The limit must be adjusted: Enter 0.001 to reduce the limit manually.
The ratio between Meff,i and ∑ M now is 0.905 for fmeX and 0.936 for fmeY. 26 modes are sufficient for the analysis instead of 33.