After running modal analysis, ETABS provides "Modal Participating Mass Ratios." For a valid model, the sum of modal mass ratios in the X and Y directions must exceed 90% of the total mass from the Mass Summary. If not, the analyst must add more modes.
: Elements meshed between story levels might not have their mass lumped correctly to the nearest story. etabs mass summary by story
Ensure your Dead Load pattern has a self-weight multiplier of 1, so the program automatically includes the weight of beams, columns, and slabs. 5. Exporting for Documentation After running modal analysis