Dear Colleagues,
I am seeking technical guidance regarding persistent convergence failures in ETABS during Nonlinear Time History Analysis (NLTHA) for a 20-story reinforced concrete building, specifically related to nonlinear hinge modeling.
---
Project Context:
Objective: Extract interstory drifts and displacements under seismic loading using NLTHA for detailed performance and damage assessment.
Software: ETABS vXX (please replace with your version).
Building: 20-story RC frame structure.
Ground Motions: Scaled real records per target spectrum.
Nonlinear Hinges:
Assigned per FEMA guidelines.
Hinges placed near member ends.
Using M3 hinges for beams and P-M2-M3 for columns.
---
The Issue:
The analysis consistently fails to converge, with the solver either:
Halting at ~X% progress, or
Exhibiting large displacements and instability prior to stopping.
From my investigation, the core issue appears to stem from:
Potential mismatch in hinge properties (rotation capacities, backbone curves).
Hinge placements or effective lengths.
Incompatibility between hinge definitions and the building’s stiffness/mass distribution under the applied ground motions.
---
Steps Already Attempted:
Verified hinge locations and types.
Reduced ground motion scaling and time step (dt = X sec).
Adjusted solver tolerances and maximum iterations.
Ran modal analysis to check mass participation ratios.
Simplified the model incrementally, but convergence issues persist once hinges are activated.
---
Request for Guidance:
If you have experience with large-scale ETABS NLTHA using nonlinear hinges, I would greatly appreciate insights on:
1. Recommended strategies for hinge property calibration to ensure numerical stability.
2. Common pitfalls in hinge placement or effective length consideration for convergence.
3. Recommended solver settings (tolerances, iteration caps) for NLTHA with nonlinear hinges.
4. Whether using default FEMA hinge definitions (vs. user-defined) may improve stability in practice.
5. Any workflow you use to debug hinge-related divergence systematically.
---
Additional Information:
If needed, I can provide further details regarding:
Material properties and section dimensions.
Specific error messages or screenshots from ETABS analysis.
Ground motion details and scaling approach.
---
I appreciate your time and any guidance you can provide to help resolve this issue efficiently while maintaining model fidelity under seismic NLTHA.
Thank you in advance.
I am seeking technical guidance regarding persistent convergence failures in ETABS during Nonlinear Time History Analysis (NLTHA) for a 20-story reinforced concrete building, specifically related to nonlinear hinge modeling.
---
Project Context:
Objective: Extract interstory drifts and displacements under seismic loading using NLTHA for detailed performance and damage assessment.
Software: ETABS vXX (please replace with your version).
Building: 20-story RC frame structure.
Ground Motions: Scaled real records per target spectrum.
Nonlinear Hinges:
Assigned per FEMA guidelines.
Hinges placed near member ends.
Using M3 hinges for beams and P-M2-M3 for columns.
---
The Issue:
The analysis consistently fails to converge, with the solver either:
Halting at ~X% progress, or
Exhibiting large displacements and instability prior to stopping.
From my investigation, the core issue appears to stem from:
Potential mismatch in hinge properties (rotation capacities, backbone curves).
Hinge placements or effective lengths.
Incompatibility between hinge definitions and the building’s stiffness/mass distribution under the applied ground motions.
---
Steps Already Attempted:
Verified hinge locations and types.
Reduced ground motion scaling and time step (dt = X sec).
Adjusted solver tolerances and maximum iterations.
Ran modal analysis to check mass participation ratios.
Simplified the model incrementally, but convergence issues persist once hinges are activated.
---
Request for Guidance:
If you have experience with large-scale ETABS NLTHA using nonlinear hinges, I would greatly appreciate insights on:
1. Recommended strategies for hinge property calibration to ensure numerical stability.
2. Common pitfalls in hinge placement or effective length consideration for convergence.
3. Recommended solver settings (tolerances, iteration caps) for NLTHA with nonlinear hinges.
4. Whether using default FEMA hinge definitions (vs. user-defined) may improve stability in practice.
5. Any workflow you use to debug hinge-related divergence systematically.
---
Additional Information:
If needed, I can provide further details regarding:
Material properties and section dimensions.
Specific error messages or screenshots from ETABS analysis.
Ground motion details and scaling approach.
---
I appreciate your time and any guidance you can provide to help resolve this issue efficiently while maintaining model fidelity under seismic NLTHA.
Thank you in advance.
