Do not trust the number until you complete this checklist.

| Symptom | Likely Cause | Fix | | :--- | :--- | :--- | | Mass at roof is too high | Penthouses, water tanks not modeled as separate stories | Assign point mass or model as a dummy story | | Mass is negative or zero | Invalid constraint or bi-axial hinge | Check Display > Show Undeformed > Joints for errors | | Cumulative mass changes after analysis | Mass source relies on load-dependent deflection (e.g., nonlinear) | Use linear static for mass source | | Mass differs between ETABS and Excel takeoff | Line loads, area loads not converted to mass | Convert all Uniform Loads to Mass via Assign > Area Loads > To Mass |

When working with ETABS, a powerful software for structural analysis and design, understanding the mass distribution of a building is crucial for ensuring its stability and performance under various loads, including seismic and wind loads. The Mass Summary by Story report in ETABS provides engineers with essential data to assess how mass is distributed across different stories of a building. In this post, we'll delve into the significance of the ETABS Mass Summary by Story, how to interpret it, and why it's vital for structural engineering projects.

) to obtain true mass, or adjusting units (e.g., dividing by 1,000) for standard reporting. 4. Verification Checklist Center of rigidity - ETABS - CSI Knowledge Base