The "Mass Summary by Story" table is more than just a data output; it is a vital diagnostic and design tool. By understanding how to define your mass source, where to find the table, and how to interpret its data, you can ensure your seismic loads are applied correctly, your building's dynamic properties are accurately captured, and your design is compliant with relevant codes. Checking this data should be a standard step in the quality assurance process of every ETABS project.
| Story | U1 Mass (kN-s²/m) | U2 Mass (kN-s²/m) | R3 Mass (kN-s²/m-rad) | | :--- | :--- | :--- | :--- | | Roof | 85 | 85 | 12,500 | | Story4 | 110 | 110 | 18,200 | | Story3 | 110 | 110 | 18,200 | | Story2 | 110 | 110 | 18,200 | | Story1 | 115 | 115 | 19,000 | | Base | 0 | 0 | 0 | etabs mass summary by story
The running total of the building's mass from the topmost story down to the current story. The bottom story row displays the total mass of the structure. The "Mass Summary by Story" table is more
Indicates if a rigid or semi-rigid diaphragm is assigned. If no diaphragm is assigned, the mass is treated as lumped at the joints. | Story | U1 Mass (kN-s²/m) | U2
Note: To avoid doubling your dead load mass, do not check both "Element Self-Mass" and include the "Dead Load" pattern in the specified multipliers unless your dead load pattern explicitly excludes self-weight. How to Extract the Mass Summary by Story Table
ETABS automatically calculates the volume of beams, columns, slabs, and walls, multiplying them by their material density.
Codes require that you accumulate 90% of the total building mass in the modes you consider for response spectrum analysis.