Etabs Mass Summary By Story Better ((top)) Review

The default ETABS Mass Summary is only as good as your assumptions. Many engineers open the table, see a number, and immediately proceed to design. This is a mistake.

: Include a check for Participating Mass Ratios (found under Analysis Results > Modal Results). Ensure that at least 90% of the mass is participating in the principal directions for seismic analysis. 4. How to Generate in ETABS

ETABS calculates mass as (Load Cases assigned as mass source) / g (acceleration due to gravity). By default, ETABS may only include self-weight and superimposed dead loads. It often ignores : etabs mass summary by story better

| Story | UTotal (ton-s²/m) | RTotal (ton-s²-m) | Verification Check | |-------|------------------|-------------------|--------------------| | Roof | 125.4 | 8,420 | ✅ Cladding + roof live 20% | | 5 | 210.2 | 12,150 | ✅ Partition added | | 4 | 210.5 | 12,140 | ✅ Uniform | | 3 | 210.3 | 12,160 | ✅ Uniform | | 2 | 211.0 | 12,170 | ✅ Slight increase from stair infill | | Base | 0.0 | 0.0 | ✅ No mass at fixity |

For underground structures or tanks, the mass of water and soil is significant. Assign these via Additional Mass or as a special load case with a multiplier of 1.0 in the mass source. Do not rely on DEAD for these. The default ETABS Mass Summary is only as

I can provide tailored steps to resolve your specific ETABS modeling challenges. Share public link

: Auto-meshing walls or slabs can sometimes lead to incorrect mass distributions. Manual meshing or ensuring all elements are properly connected to story nodes is recommended for precise results. Lumping Mass at Stories : Checking the option to "Lump Lateral Mass at Story Levels" : Include a check for Participating Mass Ratios

To get the most out of your ETABS mass summaries, implement these professional habits:

Loads applied to "null" areas (areas without a slab property) appear in reactions but are not added to the building's seismic mass. Cause: A null area has no structural stiffness, and its mass/loads are not automatically transferred to the diaphragm. Solution: You must explicitly assign a rigid diaphragm constraint to the null area. The diaphragm ensures the loads and mass from the null area are transferred to the lateral force-resisting system and included in the seismic mass.

Stop Guessing: How to Actually Use the ETABS Mass Summary by Story