Mass Summary By Story Better Hot! | Etabs

The default ETABS Mass Summary by Story is often misunderstood. To make it —meaning more accurate, transparent, and useful for seismic design (ASCE 7, UBC 97, or IS 1893)—you need to move beyond the default settings.

If you haven't assigned a rigid diaphragm to your floors, the mass summary might not accurately represent the floor-level mass distribution, leading to incorrect seismic load distribution. 5. Summary Checklist for Accurate Mass Ensures correct inputs ( Verify Floor Area Ensures slabs are modeled correctly. Inspect Table Data Look for unexpected zeros or massive jumps in mass. Check Ensure mass is centered correctly, not skewed. Compare with Total Does the sum of story masses match the total building mass? etabs mass summary by story better

4. Perfect Alignment with Code-Based Lateral Load Procedures The default ETABS Mass Summary by Story is

table is generally the superior and more reliable choice for extracting the total seismic weight of a structure. Direct Comparison: Story Mass vs. Diaphragm Mass Mass Summary by Story Diaphragm Mass Summary Scope of Mass mass assigned to the story (slabs, beams, columns, walls). Check Ensure mass is centered correctly, not skewed

If your "Mass Summary by Story" doesn't match hand calculations, here's a systematic approach to diagnose the issue:

A foolproof way to cross-check your "better" mass summary is to look at the from a static Load Case that includes the mass source loads with g = 386.4 in/s² .

By mastering the ETABS mass summary by story feature and incorporating the tips and best practices outlined in this article, engineers can take their structural analysis and design skills to the next level, creating better buildings that are safer, more efficient, and more sustainable.