Etabs Mass Summary By Story File

In fact, most convergence errors, unexpected mode shapes, and even incorrect base shears can be traced back to a single misunderstood line in this table.

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

Let’s dive into what those numbers actually mean, why ETABS sometimes lies to you (well, not lies , but misleads you), and how to use this table to save your design. In simple terms, the Mass Summary tells you how much weight is pushing down on each level of your building—and more importantly, how that weight moves sideways during an earthquake. In fact, most convergence errors, unexpected mode shapes,

Self-weight assignment.

If you’ve ever run a seismic analysis in ETABS, you’ve probably scrolled past the Mass Summary by Story table. It looks harmless enough—just a few columns of numbers under the Display > Show Tables > Analysis > Results > Structure Output menu. Let’s dive into what those numbers actually mean,

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).