You must have a completed analysis run (the lock icon should be closed). Navigate the Menu: Go to Display > Show Tables . Find the Specific Table: Expand Analysis Results . Expand Structure Results .
The translational mass active in the horizontal X and Y directions. This is calculated from your defined Mass Source.
Loads like lateral wind or soil pressure are forces , not masses . The summary will only include loads that have a vertical component and are assigned to the mass source. Review your diaphragm assignments to ensure mass is correctly lumped at the center of rigidity. etabs mass summary by story
The coordinates of the Center of Mass for that specific story.
: Check for directional links, non-linear properties, or asymmetric user-defined mass assignments. 3. Mass is Significantly Higher Than Hand Calculations You must have a completed analysis run (the
The accuracy of dynamic analysis in structural engineering is highly dependent on the correct definition and distribution of mass. ETABS (Extended Three-dimensional Analysis of Building Systems) provides a critical output called the "Mass Summary by Story." This paper explains the theoretical basis of mass summation in ETABS, differentiates between mass and weight, interprets the tabular output, and demonstrates how this summary is used for seismic load calculations (base shear), center of mass determination, and dynamic property verification (modal analysis).
In structural engineering, accuracy is everything. When designing a building for lateral loads—such as wind or earthquakes—the accuracy of your analysis depends heavily on how well you define and verify the building’s mass. Expand Structure Results
Compare modeled weight against manual calculations to meet quality assurance requirements.
: You likely forgot to define a Mass Source, or your Mass Source does not include element self-weight.