Etabs Mass Summary By Story -

You can use this as a template or a direct submission for a course or technical report.

2. Theoretical Background

2.1 Mass vs. Weight in ETABS

• Weight ($W$): Force due to gravity ($W = m \cdot g$). Used for gravity load combinations and P-Delta effects.
• Mass ($m$): Inertial property ($m = W/g$). Used for dynamic analysis (eigenvalue extraction, time history).

1. Open your model in ETABS.
2. Go to the "Analyze" menu and select the type of analysis you want to run (make sure you've assigned masses appropriately).
3. Run the analysis.
4. After analysis, go to "Results", then select "Story" or similar options depending on the ETABS version.
5. Look for a "Mass Summary" or similar report.

Using the Summary for Modal Analysis

Before running response spectrum or time history analysis, check the Participating Mass Ratio (found in the Modal Analysis Tables). If your U1 and U2 participating mass ratios do not sum to at least 90% (per most codes), your building has insufficient modes captured. etabs mass summary by story

The Mass Summary by Story is essential for: You can use this as a template or

Check Mass Distribution: Confirm that the mass decreases or changes logically from the roof down to the base. Weight ($W$): Force due to gravity ($W = m \cdot g$)

Cumulative Center of Mass: The center of mass for the entire structure from that story upward. 3. Why This Data Matters A. Seismic Base Shear Verification

What is Mass Summary by Story?

Method 3: Direct File Output (F2K Text File)

After analysis, open the .log file or the .f2k text file. Search for STORY MASS. This raw data is useful for scripting or batch verification.