Reflects specified dead, live, and lateral load combinations automatically.
The "Mass Summary by Story" table is an indispensable tool in an engineer's ETABS workflow. By investing the time to understand its dependencies—from the foundational Mass Source definition to troubleshooting output discrepancies—you transform it from a simple data readout into a powerful diagnostic and optimization tool.
: Auto-meshing walls or slabs can sometimes lead to incorrect mass distributions. Manual meshing or ensuring all elements are properly connected to story nodes is recommended for precise results. Lumping Mass at Stories : Checking the option to "Lump Lateral Mass at Story Levels" etabs mass summary by story better
definition. This summary table is the primary diagnostic tool to ensure the software is "seeing" the weight as intended. By comparing the story mass against manual hand-calculations or architectural estimates, engineers can verify that self-weight, superimposed dead loads, and the appropriate percentage of live loads are being correctly converted into inertial mass. 3. Streamlined Center of Mass (COM) Tracking
: Indicates if the mass is assigned to a rigid or semi-rigid diaphragm. Reflects specified dead, live, and lateral load combinations
Mastering the ETABS Mass Summary by Story: Why It is Better for Structural Verification
This method calculates mass based on the loads defined in your model, which is the . It correlates directly with the building's actual weight. A key tip: the load combination 1.0DL + 0.5LL (Dead Load + 50% Live Load) is used in many codes, such as ASCE 7, to represent the effective seismic weight. Crucially, the 'From Loads' definition with DL+0.5LL was found to produce results closest to manually calculated values, accurately aligning with code recommendations (ASCE 7–10). : Auto-meshing walls or slabs can sometimes lead
Modern seismic codes require models to include a percentage of live loads and superimposed dead loads in the seismic mass. Tracking these manually across complex geometries is highly inefficient.
When using Element Self Mass , ensure that your Mass Source does not also have a "Dead Load" pattern activated with a self-weight multiplier of
The structural weight and mass distribution are the core pillars of seismic and dynamic analysis in ETABS. Understanding the table is not just a matter of pulling software data—it is a critical step in verifying that your building will behave exactly as intended during a lateral event.
While global totals provide a "big picture" view, the is the tool of choice for the meticulous engineer. It bridges the gap between complex finite element modeling and the practical requirements of building codes. By offering localized clarity, simplifying error detection, and enhancing the reliability of seismic data, it ensures that the digital twin behaves as closely as possible to the future physical structure.