Etabs Mass Summary - By Story Fixed

ETABS solves the eigenvalue problem, [K]ϕ = ω²[M]ϕ , to extract the structure's natural frequencies (ω) and mode shapes ϕ. The [M] matrix is built directly from your mass source. The accuracy of your modal analysis is therefore a direct reflection of the accuracy of your Mass Summary by Story data. This is why a significant oversight in modeling (e.g., forgetting a heavy mechanical penthouse) or an incorrect mass source definition can lead to completely erroneous dynamic properties.

Perhaps the most critical column in the Mass Summary table is the location relative to the Center of Rigidity (CR) . While the CR is often calculated separately, the Mass Summary provides the precise location of the resultant inertial force for each floor.

Checks the box to include the weight of beams, columns, and slabs based on material density.

Which (e.g., ASCE 7, Eurocode 8) are you design for? Are you dealing with a torsional irregularity warning? Do you need help setting up the Mass Source definition? 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.

Understanding Mass Summary by Story in ETABS In structural engineering, the Mass Summary by Story

Engineers check this table to ensure the Total Weight matches their manual calculations for base shear. If the total mass is too low, the calculated seismic forces will be underestimated, leading to unsafe design. B. Identifying Torsional Issues ETABS solves the eigenvalue problem, [K]ϕ = ω²[M]ϕ

The software automatically calculates mass based on structural geometry and material density.

Generating the mass summary by story in ETABS is a straightforward process:

the structural period in modal analysis? This is why a significant oversight in modeling (e

The is an output table in ETABS that aggregates the total calculated mass of your structure on a floor-by-floor basis.

: Confirm that the mass decreases or changes logically from the roof down to the base.