Do not trust the number until you complete this checklist.
Export a concise, professional table directly into your final structural calculation report. How to Access the Table in ETABS
A "better" Mass Summary is not just a number—it is a deliverable. You should export the table and compare it to your design basis.
The "Mass Summary by Story" is a tabulated report in ETABS that lists the calculated mass (or weight) at each floor level based on the defined Mass Source . etabs mass summary by story better
If you use From Self and Specified Loads , the self-weight multiplier is typically 1.0 . But if you accidentally set it to 0 , you lose the entire slab and beam mass. Double-check this.
Mention if manual meshing was used for walls and slabs, as auto-meshing can sometimes lead to lumping errors CSI Knowledge Base Diaphragm Check: Confirm that Rigid Diaphragms
Let’s discuss your favorite verification techniques in the comments! Do not trust the number until you complete this checklist
Drawing overlapping shell elements causes ETABS to calculate duplicate volumes, which inflates the self-weight and story mass at that level. 3. Vertical Element Assignment
If you'd like to dive deeper into the technical side, I can help you with: The for mass source. How to export this data to Excel for faster reporting.
The next time you run ETABS, spend 15 minutes on the Mass Summary. Compare it, question it, and improve it. Your future self—and the building's occupants—will thank you. You should export the table and compare it
Ensure that the sum of the effective modal masses in the X and Y directions equals at least 90% of the total mass listed in your Story Mass Summary. If they don’t match, your structure is either too flexible (need more modes) or your constraints (rigid diaphragms) are preventing proper mass participation.
| Red Flag | Fix | |----------|-----| | Mass at base (Foundation) | Exclude from lateral mass unless basement walls provide restraint | | Sudden drop in mass at top story | Missing penthouse/cladding mass | | RTotal zero for all stories | Assign rigid diaphragm – mass moment computed from floor plan | | Identical mass for Ux and Uy but building is asymmetric | Add point masses to reflect actual distribution |