Understanding Mass Summary by Story in ETABS In structural engineering, the Mass Summary by Story
Decoding the ETABS Mass Summary by Story: The Foundation of Seismic Design
In the realm of structural engineering, few outputs are as deceptively simple yet critically important as the ETABS Mass Summary by Story. While novice users might scroll past this table on their way to flashy deflection diagrams or rebar contours, experienced engineers know that this summary is the first checkpoint for structural sanity.
This measures the mass distribution relative to the vertical axis. It is the governing factor for the building's torsional (rotational) response. Center of Mass (CM):
- Sanity Check: Does the total weight make sense? (e.g., a 5-story office building typically weighs between 80–100 psf. If the total implies 300 psf, something is wrong).
- Distribution: Does the mass decrease as you go up the building? (It usually should, as column and wall weights reduce with height).
- Location: Is the Center of Mass roughly in the geometric center of the floor plate? If it is near the edge, verify your loading pattern or rigidity distribution.
- Go to Define > Mass Source.
- Option 1 (Recommended for seismic): "From self and specified mass."
- Option 2: "From load patterns."
Etabs Mass Summary By Story (2026)
Understanding Mass Summary by Story in ETABS In structural engineering, the Mass Summary by Story
Decoding the ETABS Mass Summary by Story: The Foundation of Seismic Design
In the realm of structural engineering, few outputs are as deceptively simple yet critically important as the ETABS Mass Summary by Story. While novice users might scroll past this table on their way to flashy deflection diagrams or rebar contours, experienced engineers know that this summary is the first checkpoint for structural sanity.
This measures the mass distribution relative to the vertical axis. It is the governing factor for the building's torsional (rotational) response. Center of Mass (CM):
- Sanity Check: Does the total weight make sense? (e.g., a 5-story office building typically weighs between 80–100 psf. If the total implies 300 psf, something is wrong).
- Distribution: Does the mass decrease as you go up the building? (It usually should, as column and wall weights reduce with height).
- Location: Is the Center of Mass roughly in the geometric center of the floor plate? If it is near the edge, verify your loading pattern or rigidity distribution.
- Go to Define > Mass Source.
- Option 1 (Recommended for seismic): "From self and specified mass."
- Option 2: "From load patterns."
