When using Element Self Mass , ensure that your Mass Source does not also have a "Dead Load" pattern activated with a self-weight multiplier of
A "better" Mass Summary is not just a number—it is a deliverable. You should export the table and compare it to your design basis.
Unlike the Mass Summary by Diaphragm table, which only includes mass associated with specific diaphragm assignments, the story summary captures every ounce of mass (columns, walls, beams, and slabs) assigned to that story level.
Here’s how to master the ETABS Mass Summary: etabs mass summary by story better
The culprit?
Always verify the active units (e.g., kg, kN, or kips) before exporting the table to Excel to avoid catastrophic scaling errors.
: It allows for a quick manual comparison against estimated building weights (e.g., Dead Load + % Live Load) to ensure no significant loads were missed. When using Element Self Mass , ensure that
ETABS only includes mass for elements physically modeled. If you have a heavy parapet, signboard, or mezzanine drawn as a line load—did you convert it to a mass? Model heavy non-structural components as point masses ( Assign > Shell/Area > Additional Mass ).
A percentage of (typically 0.25 for storage areas, or 0.0 for standard residential/office spaces depending on code clauses). 2. Perform a Manual Hand Calculation
Seismic design codes require you to calculate lateral forces based on individual floor masses and elevations. Reviewing the mass summary by story gives you clean, structured data for your external engineering worksheets. This simplifies your quality assurance checks for items like the Equivalent Lateral Force (ELF) procedure. How ETABS Assembles Story Mass Here’s how to master the ETABS Mass Summary: The culprit
To help tailor further structural optimization strategies, what specific or lateral force-resisting system are you currently designing? Share public link
Compare total calculated mass against initial estimates in seconds. 2. Seamless Integration of Mass Sources
Select a standard, repeatable story in your building. Manually calculate its total dead weight:
Modern seismic codes require models to include a percentage of live loads and superimposed dead loads in the seismic mass. Tracking these manually across complex geometries is highly inefficient.
The portion of the floor mass assigned directly to a rigid or semi-rigid diaphragm.