The is far more than a routine output table. It is the structural engineer’s first line of defense against incorrect seismic modeling. By understanding how mass is calculated—from the mass source definition to the lumping onto diaphragms—you can diagnose hidden errors, validate your model’s behavior, and confidently proceed to response spectrum analysis.
When reviewing the table, the most immediate metric is the vertical consistency of mass per story. A building follows the laws of physics; typically, lower stories have larger masses due to bigger column sections, thicker shear walls, and heavier floor plates, tapering off as the building rises.
These coordinates tell you where the "weight" of the floor is centered. If these are far from the geometric center, you’ll have high accidental torsion. etabs mass summary by story
: The gravitational force associated with that story's mass. Critical Setup Requirements
: If you choose "Specified Load Patterns" and include Dead Load (multiplier = 1), uncheck "Element Self Mass" to prevent duplication. Conclusion The is far more than a routine output table
When you open the table, it typically contains the following columns. Let’s break down each one:
To ensure your mass summary is accurate, check these settings: When reviewing the table, the most immediate metric
The should generally exhibit a lower mass compared to standard floors due to lighter live loads and absence of upper-level vertical columns/walls.
ETABS distinguishes these very strictly, similar to SAP2000. The relationship is:
Which (ASCE 7, Eurocode, etc.) you're following
If you include "Element Self Mass" in the checkboxes and also include a Dead Load pattern that contains self-weight, ETABS may double-count the structure's structural weight. Keep "Element Self Mass" checked, but ensure your added load patterns only account for superimposed loads. Engineering Check: Manual vs. Software