If you have ever run a seismic analysis in ETABS, you have undoubtedly stared at the Mass Summary by Story table. It appears deceptively simple: a list of stories, masses in X, Y, Z, and a summation. Yet, for many engineers, this table is a source of quiet anxiety.
| Story | U1 (X) ton | U2 (Y) ton | U3 (Z) ton | | :--- | :--- | :--- | :--- | | Roof | 150 | 150 | 1000 | | 3rd Fl | 250 | 250 | 1200 | | 2nd Fl | 250 | 250 | 1200 | | Base | 200 | 200 | 1500 |
Is the mass correct? Did the software double-count the dead load? Why is the seismic weight different from the gravity takeoff? And most importantly— how can you get a better, more reliable Mass Summary?
Here is what you are looking at:
If you have ever run a seismic analysis in ETABS, you have undoubtedly stared at the Mass Summary by Story table. It appears deceptively simple: a list of stories, masses in X, Y, Z, and a summation. Yet, for many engineers, this table is a source of quiet anxiety.
| Story | U1 (X) ton | U2 (Y) ton | U3 (Z) ton | | :--- | :--- | :--- | :--- | | Roof | 150 | 150 | 1000 | | 3rd Fl | 250 | 250 | 1200 | | 2nd Fl | 250 | 250 | 1200 | | Base | 200 | 200 | 1500 |
Is the mass correct? Did the software double-count the dead load? Why is the seismic weight different from the gravity takeoff? And most importantly— how can you get a better, more reliable Mass Summary?
Here is what you are looking at:
