Etabs Mass Summary By Story Instant

: Converts assigned loads (e.g., Dead Load + a percentage of Live Load) into mass by dividing the weight by the gravitational multiplier ( ). For example, codes like IS 1893:2016 often require Dead Load plus Live Load depending on load intensity. 4. Mass Lumping Mechanics

| Pitfall | Consequence | Fix | | :--- | :--- | :--- | | | Ignored live load and SDL; unconservative base shear | Define custom mass source (Dead + SDL + % Live) | | Duplicated Mass | Artificially high seismic forces | Check for overlapping shells or duplicate area loads | | Zero Rotational Mass | No torsional periods; inaccurate mode shapes | Assign diaphragm constraints to all floors | | Mass at Pinned Base | Building wants to lift off during analysis | Release base restraints or ignore (static only) | etabs mass summary by story

U1 mass is huge, but U2 mass is near zero. Problem: In-plane diaphragm is assigned only to beams in one direction, or shell elements are not properly meshed. Fix: Check Assign > Diaphragm for each story. All floor elements must be assigned to a diaphragm name (e.g., "D1"). : Converts assigned loads (e

: The translational mass assigned to each story in the global X and Y directions, respectively. Mass Lumping Mechanics | Pitfall | Consequence |