: User-assigned point, line, or area masses to account for non-structural components like cladding or partitions. Specified Load Patterns : Often used for seismic calculations (e.g., Dead Load + Live Load) as per codes like 2. The Lumping Process
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
When the report loaded, the first line showed the total seismic weight per story. Maya read it like a heartbeat: lower floors carried more—concrete podiums, parking slabs, and heavy mechanical rooms—while the upper residential stories were lighter, filled with drywall and furniture assumptions. The variation was clear in the table: Story 1 held 1,200 kN, Story 2 had 1,000 kN, and by Story 12 it tapered to 650 kN. The building’s center of mass whispered its position: slightly offset toward the west because of the heavier stair core. etabs mass summary by story
ETABS determines story mass based on your definition ( Define > Mass Source ). Typical Mass Source Configurations
: The translational mass active in the global X and Y horizontal directions. : User-assigned point, line, or area masses to
) calculated for each floor, often verified against manual calculations. Proper Content for Documentation
). This value is the foundation for calculating the equivalent lateral force base shear. Torsional Irregularity Evaluation If the total mass is too low, the
Indicates a transition in building structure (e.g., changing from concrete to steel, or a setback). High Torsional Mass (RZ): High RZcap R cap Z values, even with low
In ETABS, the is a critical output table used to verify the total weight and mass distribution of a building for seismic and dynamic analysis. How to Access the Mass Summary Table To view the story mass data after running your analysis: Navigate to the Display menu. Select Show Tables .
…the Mass Summary by Story is where you will find the answers.