Etabs Mass Summary By Story Access
Mass summary matches hand calculation. Modal analysis can proceed.
The should generally exhibit a lower mass compared to standard floors due to lighter live loads and absence of upper-level vertical columns/walls.
When you open the table, you will see several standard columns. Understanding exactly what each column represents is vital for proper data interpretation.
A quick glance at the cumulative mass helps verify if you are working in kips, tons, or kilograms. C. Calculating Eccentricity etabs mass summary by story
The software automatically calculates the weight of modeled beams, columns, and slabs based on material density. Additional Mass: Any manually assigned mass.
Alternatively, you can access it via the top menu: Display > Show Tables > Analysis Results > Structure Results > Mass Summary by Story . 4. Interpreting the Table Columns
Unlike simple gravity takeaway, this summary specifically focuses on (force/acceleration), which is the primary driver of inertial forces during an earthquake. Mass summary matches hand calculation
Alternatively, you can find it in the output text file ( .OUT ) generated after analysis.
The Mass Summary is your best detective tool. Here are four common mistakes it catches:
You defined mass source from load patterns but forgot to assign any load pattern to the roof diaphragm. Or, you used a rigid diaphragm but the beams are not connected to the diaphragm constraint. When you open the table, you will see
The distribution of mass across stories directly dictates mode shapes and periods. A top-heavy model will produce longer periods and higher overturning moments. By reviewing the summary, you can quickly spot if a penthouse or water tank mass was accidentally omitted.
In a standard seismic analysis, the story-by-story report is the most practical tool.
The table in ETABS is far more than just a collection of numbers—it is the foundational footprint of your building's dynamic behavior. By taking ten minutes to export this table, check its distribution trend, and cross-reference it with a quick manual calculation, you can catch critical modeling mistakes before they compromise your design. Thorough mass verification guarantees a safer, highly optimized, and structurally sound building design.
