ETABS usually focuses on horizontal inertia for seismic runs.
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. etabs mass summary by story
Negative values in mass summary. Problem: Load combinations that subtract loads (e.g., 0.9DL + 1.0WL) are incorrectly assigned to the mass source, or you have overturning with tension elements. Fix: Never use load combinations in the Mass Source definition. Use only primary load patterns. ETABS usually focuses on horizontal inertia for seismic runs
By mastering the Mass Summary table, you move from simply "running the model" to truly understanding the behavior of your structure. By reviewing the summary, you can quickly spot
: Always double-check your units (e.g., kg vs. tonf-s²/m) to ensure the values align with your manual seismic weight calculations. table directly to for further reporting?