| Sign | What to check | |------|----------------| | 1. Negative eigenvalues | Unrestrained rigid body motion – missing constraints. | | 2. Modal period > 4 sec (for stiff frame) | Overly flexible or missing shear walls. | | 3. Large accidental torsion warning | Irregular plan – check eccentricity. | | 4. Zero stiffness in one direction | Beam disconnected from column. | | 5. Drift ratio > 2% but small base shear | Soft story or P-Delta instability. | | 6. High axial force in slender column | Likely buckling – run nonlinear analysis. | | 7. Story shear discontinuity | Check diaphragm assignment or column overwrites. |
1. Model → 2. Assign (9 checks) → 3. Analyze → 4. Detect (7 signs) → 5. Debug → 6. Forensics (4 tools) → 7. Redesign or Certify csi etabs 974
| Sign | What to check | |------|----------------| | 1. Negative eigenvalues | Unrestrained rigid body motion – missing constraints. | | 2. Modal period > 4 sec (for stiff frame) | Overly flexible or missing shear walls. | | 3. Large accidental torsion warning | Irregular plan – check eccentricity. | | 4. Zero stiffness in one direction | Beam disconnected from column. | | 5. Drift ratio > 2% but small base shear | Soft story or P-Delta instability. | | 6. High axial force in slender column | Likely buckling – run nonlinear analysis. | | 7. Story shear discontinuity | Check diaphragm assignment or column overwrites. |
1. Model → 2. Assign (9 checks) → 3. Analyze → 4. Detect (7 signs) → 5. Debug → 6. Forensics (4 tools) → 7. Redesign or Certify
