Etabs Mass Summary By Story Better Jun 2026

The exact coordinates of the Center of Mass (CM) for that specific floor.

, include 100% of dead load and a percentage (typically 25% or 50%) of live load in the mass source for seismic weight. Unit Conversion

. When viewed floor-by-floor, this allows the engineer to track the alignment of the building’s inertial center. If the COM shifts drastically from one floor to the next, it indicates a potential for high eccentricity and torsional shear, prompting a redesign of the lateral force-resisting system before the project advances too far. 4. Efficiency in Base Shear Calibration

Click on or look for specific mass tables depending on your software version. etabs mass summary by story better

The default is a starting point, not a finish line. A better mass summary is one that:

Mastering the table transitions your modeling from guesswork to verified engineering. By routinely checking this output against manual estimates, auditing your Mass Source inputs, and verifying torsional inertia, you ensure a rock-solid foundation for all subsequent lateral, dynamic, and seismic designs. To help tailor this guide further, let me know:

) under dead load cases to the total cumulative mass. These should align closely; a significant discrepancy often indicates unassigned masses. The exact coordinates of the Center of Mass

: Explicitly state how the mass was derived (e.g., element self-mass plus specified load patterns like 100% Dead Load and a percentage of Live Load).

This represents the floor's resistance to rotational acceleration. It is critical for tracking torsional behavior.

Merges self-weight and applied loads into one comprehensive narrative per story. 3. Direct Verification of Center of Mass (CM) When viewed floor-by-floor, this allows the engineer to

The primary benefit of the Story Mass Summary is its role in "Mass calculated manual" verification. By breaking down the weight floor-by-floor, you can easily compare ETABS’ output against manual calculations for:

You reach the roof. Here stands a tiny, lightweight acrobat.

An error in mass modeling—such as double-counting live loads or missing self-weight—will lead to incorrect design forces. The Best Way to Check Mass: Mass Summary by Story

Ensure that temporary partition loads or light architectural finishes are not duplicated in both the material self-weight and the superimposed dead load patterns.

Seismic design codes require you to calculate lateral forces based on individual floor masses and elevations. Reviewing the mass summary by story gives you clean, structured data for your external engineering worksheets. This simplifies your quality assurance checks for items like the Equivalent Lateral Force (ELF) procedure. How ETABS Assembles Story Mass