ETABS automatically lumps mass at the story levels. If you have significant mass between floors, consider adding dummy levels or intermediate joints. Troubleshooting Common Discrepancies
The Center of Mass coordinates; compare these to the Center of Rigidity. How to Improve Your Mass Source Setup
Confirm the inclusion of the appropriate percentage of live loads. etabs mass summary by story better
💡 Always compare the Total Mass in the summary table to the Base Reaction for a dead load case. They should be identical. If they aren't, your mass source is likely missing a specific load pattern.
When you use ETABS for high-rise or complex structures, simply looking at the total mass isn't enough. You need to ensure the distribution aligns with the structural intent. Why Mass Summary by Story Matters ETABS automatically lumps mass at the story levels
Architects often provide cladding as a line load. Ensure these are applied to the perimeter beams and that the mass source is set to include "Specified Load Patterns."
If your Mass Summary by Story looks "wrong" compared to your manual hand calculations, check these three areas: How to Improve Your Mass Source Setup Confirm
Ensure you are checking the "Include Lateral Mass" option for seismic analysis.