Story Better — Etabs Mass Summary By

Understanding the mass distribution of a building is the foundation of accurate seismic analysis. In ETABS, the "Mass Summary by Story" table is your primary diagnostic tool for verifying that your mathematical model reflects physical reality.

Detect "ghost mass" from accidental double-counting or modeling errors. Accessing the Data To find this specific table after running an analysis: Navigate to the . Expand Tables > Analysis Results > Structure Results . Right-click Mass Summary by Story and select Show Table . Key Columns to Analyze Significance UX / UY The total translational mass in the X and Y directions. Sum UX / Sum UY etabs mass summary by story better

Confirm the inclusion of the appropriate percentage of live loads. Understanding the mass distribution of a building is

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." Accessing the Data To find this specific table

Ensure you are checking the "Include Lateral Mass" option for seismic analysis.

If your Mass Summary by Story looks "wrong" compared to your manual hand calculations, check these three areas:

💡 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.