For P-Delta analysis, ETABS uses the Weight column. If you check "Include P-Delta" in load cases, verify the gravity load summation matches your mass summary.

In the world of structural engineering, few outputs are as critical—yet as frequently misunderstood—as the . When preparing a building for earthquake analysis, the first question every engineer asks is: "How much does my building actually weigh?"

If you use Rigid Diaphragms, your Mass Summary will show a single point mass at the CM. This is fine for simple boxes. But if you have a podium slab or a building with a hole (an atrium), using a rigid diaphragm will overestimate torsion because mass is artificially concentrated.

: Often 0.25 (25%), though this varies by code and occupancy (e.g., higher for storage).

, the total mass (seismic weight) determines the lateral force.

But when he ran the modal analysis, the building had massive torsion. He spent days adding shear walls.

Weight is 2x larger than hand calculation. Cause: The Mass Source includes "Self Mass" AND "Loads" simultaneously. Fix: In Define > Mass Source , if using "From Loads", ensure "Self Mass and Additional Mass" is NOT checked. ETABS will double count if both are active.

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Etabs Mass Summary By Story Hot! Jun 2026

For P-Delta analysis, ETABS uses the Weight column. If you check "Include P-Delta" in load cases, verify the gravity load summation matches your mass summary.

In the world of structural engineering, few outputs are as critical—yet as frequently misunderstood—as the . When preparing a building for earthquake analysis, the first question every engineer asks is: "How much does my building actually weigh?" etabs mass summary by story

If you use Rigid Diaphragms, your Mass Summary will show a single point mass at the CM. This is fine for simple boxes. But if you have a podium slab or a building with a hole (an atrium), using a rigid diaphragm will overestimate torsion because mass is artificially concentrated. For P-Delta analysis, ETABS uses the Weight column

: Often 0.25 (25%), though this varies by code and occupancy (e.g., higher for storage). When preparing a building for earthquake analysis, the

, the total mass (seismic weight) determines the lateral force.

But when he ran the modal analysis, the building had massive torsion. He spent days adding shear walls.

Weight is 2x larger than hand calculation. Cause: The Mass Source includes "Self Mass" AND "Loads" simultaneously. Fix: In Define > Mass Source , if using "From Loads", ensure "Self Mass and Additional Mass" is NOT checked. ETABS will double count if both are active.