Etabs Mass Summary — By Story Better

If the above is still not meeting your needs, use these power-user methods.

To get a better Mass Summary, you must stop using the default DEAD load case. You need to create a custom Mass Source.

To generate a professional Mass Summary by Story report in ETABS that is "better" than a basic data dump, you should focus on verifying the Mass Source and providing clear context for seismic design Draft Report Structure 1. Project Overview & Calculation Basis Mass Source Definition: Explicitly state the load patterns used (e.g., Dead Load + Live Load) Lumped Mass Logic:

Confirm that "Lump Lateral Mass at Story Levels" is enabled to ensure masses are correctly aggregated at each floor for seismic analysis Coordinate System: etabs mass summary by story better

Note the global origin used for Center of Mass (CM) and Center of Rigidity (CR) calculations CSI Knowledge Base 2. Story Mass Summary Table Extract this table by navigating to

Display > Show Tables > Analysis Results > Structure Results > Mass Summary by Story Cumulative Mass X (Sum to N) Total Mass

Check that the mass values are in the correct units (e.g., kilograms or tonnes); ETABS may require manual conversion (dividing by gravity if using weight units) 3. Torsional Sensitivity (CM vs. CR) For a superior report, include the Centers of Mass and Rigidity table to identify eccentricity Table Path: If the above is still not meeting your

Display > Show Tables > Analysis Results > Structure Results > Centers of Mass and Rigidity CSI Knowledge Base

Explain that the distance between CM and CR (eccentricity) directly influences the torsional shear on the building Fawad Najam 4. Quality Control & Verification Mesh Verification:

Mention if manual meshing was used for walls and slabs, as auto-meshing can sometimes lead to lumping errors CSI Knowledge Base Diaphragm Check: Confirm that Rigid Diaphragms If your mass summary shows different masses in

are assigned to all floors to ensure the story mass is reported accurately CSI Knowledge Base

If your mass summary shows different masses in U1 vs U2 for a symmetric plan, your diaphragms are likely semi-rigid or not assigned correctly. Better approach: Use Rigid Diaphragm for story mass checks.

For underground structures or tanks, the mass of water and soil is significant. Assign these via Additional Mass or as a special load case with a multiplier of 1.0 in the mass source. Do not rely on DEAD for these.