The Mass Summary by Story table provides a aggregated view of the mass calculated at each floor level. ETABS calculates this data based on your Mass Source definition. It lists the total mass, the center of mass, and mass moments of inertia for every story in your structure. 2. Key Output Parameters Explained
The is a quick yet powerful diagnostic tool. By ensuring the Mass Source is correctly defined—specifically by handling self-weight and live load percentages properly—engineers can trust the output table to verify the mass distribution essential for safe, accurate, and optimized seismic design.
) and compare it directly to the values in the ETABS table. The variance should ideally be under 5% to 10%. 3. Verify the Mass Distribution Trend Scan down the table from the roof to the base.
The you are noticing (e.g., zero mass, wrong center of mass, or unexpected values?)
The Mass Summary by Story is not merely a data table but the foundation of a building's seismic "identity." By meticulously reviewing these values, an engineer ensures that the mathematical model accurately reflects the physical reality of the structure, leading to a safe and optimized design.
ETABS provides a cumulative total from the top down. This is useful for checking overturning moments and total base shear.
The Mass Summary by Story report will display, showing the mass properties for each story in your building model.
The Mass Summary by Story report in ETABS summarizes the mass properties of a building model, including:
The program constructs the mass matrix based on the specified mass source, allowing it to accurately perform dynamic, spectral, and time-history analyses. Why is "Mass Summary by Story" Important?
) of a structure, which directly dictates the base shear calculation (
Understanding and validating the bridges the gap between raw CAD/BIM geometry and a mathematically sound structural model. By mastering this table, you guarantee that your lateral force-resisting systems are designed safely, economically, and exactly in accordance with modern building codes. If you want, I can:
When you review this table, you will typically find the following columns of data: The specific level or floor of the building. UXcap U sub cap X UYcap U sub cap Y
: Understanding mass distribution can provide insights into a structure's expected performance under lateral loads.
Compare the total weight (multiply mass by ( g )) against your hand calculation. If the ETABS total is 5,000 kN but your Excel sheet says 7,500 kN, you likely forgot to include cladding, finishes, or the live load percentage in the Mass Source.
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