Etabs Mass Summary By Story May 2026

The "Where is my Mass?" Mystery Here is the most common panic moment for engineers: "I assigned a 10-inch slab, beams, columns, and walls... so why does the Mass Summary show almost nothing on the roof?"

Self-weight assignment.

But when he ran the modal analysis, the building had massive torsion. He spent days adding shear walls. etabs mass summary by story

If you model a semi-rigid diaphragm, ETABS distributes mass to every joint in the slab. If you model a rigid diaphragm, ETABS lumps the entire floor’s mass at the Center of Mass (CM). The "Where is my Mass

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. He spent days adding shear walls