Columns and shear walls span between two stories. ETABS automatically splits their mass, assigning half to the floor below and half to the floor above. Keep this in mind when comparing ETABS data to manual floor-by-floor calculations. Summary: A Better Workflow for Engineers
Typically, use 1.0 for Dead/SIDL and 0.25 for Live Load (depending on your local building code).
Go to Display > Show Tables > Analysis Results > Structure Output > Story Information > Mass Summary by Story . 3. Key Components of the Mass Table
Coordinates of the Center of Mass for the story (critical for identifying torsion). 4. How to Make Your Mass Summary "Better" (More Accurate)
Total Story Mass=Slab Mass+Beams/Columns Mass+Wall/Cladding Mass+FinishesTotal Story Mass equals Slab Mass plus Beams/Columns Mass plus Wall/Cladding Mass plus Finishes etabs mass summary by story better
If you want to troubleshoot a specific mass mismatch in your model, let me know: What you are currently running Your specified Mass Source definition settings
The ETABS Mass Summary by Story provides the (typically in ton-sec²/mm or kip-sec²/in) used for modal analysis (eigenvalue extraction) and equivalent lateral force (ELF) procedures. Understanding it correctly prevents underpredicting seismic demands.
Master the Mass Summary, and you will no longer wonder why your building twists unexpectedly or why your base shear seems low. You will know .
: Output values often require conversion; for example, dividing by 1,000 to match specific project units (e.g., from kg to Tonnes). Meshing Warning Columns and shear walls span between two stories
Mass moments of inertia; critical for capturing torsional effects.
Finally, a practical hallmark of a better engineer: . The Mass Summary typically reports in kg-s^2/m (metric) or kip-s^2/in (imperial). This is mass , not weight. To get weight (force) for base shear: $$Weight = Mass \times g$$
Confirm that "Lump Lateral Mass at Story Levels" is enabled to ensure masses are correctly aggregated at each floor for seismic analysis Coordinate System:
Here’s how to master the ETABS Mass Summary: Summary: A Better Workflow for Engineers Typically, use 1
To locate the data after running an analysis, follow this simple path in the software menu: Go to on the top menu bar. Select Show Tables . Expand the Analysis Results folder. Expand Structure Results .
Ensure you are checking the "Include Lateral Mass" option for seismic analysis.
The most common mistake is neglecting how ETABS calculates mass. By default, ETABS does not automatically know what to weigh. You must define a ( Define > Mass Source ).