Etabs Mass: Summary By Story

Which (ASCE 7, Eurocode, etc.) you're following

If you check both "Element Self-Mass" in the Mass Source and add a Dead Load pattern that already includes a Self-Weight Multiplier of 1.0, ETABS will double-count the structural steel or concrete weight. This leads to an artificially heavy building and overly conservative (but incorrect) seismic forces. Ignoring Wall and Column Splitting

It helps locate eccentricities between the Center of Mass and Center of Rigidity (COR), which cause unwanted torsional effects.

The story mass data is not just a number; it's the primary input for several critical aspects of seismic building design. etabs mass summary by story

If your story mass summary looks incorrect, check for these common modeling mistakes:

To get a "per story" breakdown in the Analysis tables, you usually need to have diaphragms assigned to your floor shells. If you want to verify the numbers , let me know: The building's total area Your typical dead load (PSF or kN/m²)

What are you using? (e.g., ASCE 7, Eurocode 8, NBC India) Are you dealing with rigid, semi-rigid, or no diaphragms ? Which (ASCE 7, Eurocode, etc

The mass summary by story is not just for documentation; it is used to diagnose potential modeling errors. A. Verification of Seismic Weight

If you use mesh refinement and have nodes between stories, ETABS follows two strict rules to assign mass at the story level:

The ETABS Mass Summary by Story table contains several key parameters. Understanding these definitions prevents misinterpretation during peer reviews or design checks. Column Header Definition The designated floor level defined in your story data. Mass X The story mass data is not just a

Weight). An error in the mass summary directly leads to an incorrect seismic force. Modal Analysis:

Navigate to the Model Explorer on the left side of your screen, or go to the top menu and select Display > Show Tables .

Which (e.g., ASCE 7-22, Eurocode 8) you are designing under?

Base shear depends directly on the structure's total seismic weight (

In most standard buildings with symmetric floor layouts, UX and UY will be equal or very close. Differences between UX and UY may indicate mass irregularities, eccentricities, or that the mass source is not defined consistently.