FrameSolver 2D Workflows: From Setup to Simulation

FrameSolver 2D: Common Problems and Fixes

Overview

FrameSolver 2D is a structural analysis tool used for modeling and solving planar frame problems. This article covers frequent issues users encounter and provides targeted fixes to get reliable results quickly.

1. Convergence failures

• Cause: Nonlinear elements, large displacements, or overly stiff constraints cause iterative solvers to diverge.
• Fixes:
  1. Reduce load increments: Apply loads in smaller steps or use incremental load control.
  2. Use line-search or damping: Enable solver options for line search or damped iterations.
  3. Check boundary conditions: Ensure supports aren’t over-constraining the model (remove redundant restraints).
  4. Improve mesh/element distribution: Refine elements where gradients are high; avoid extremely long thin elements.

2. Unexpected zero or NaN results

• Cause: Division by zero, singular stiffness matrices from mechanisms, or invalid material properties.
• Fixes:
  1. Verify material and section values: Ensure nonzero stiffness (E, A, I) and no negative densities.
  2. Check for rigid-body modes: Add appropriate supports or connect floating parts with small stiffness springs.
  3. Inspect input files for syntax errors: Look for misplaced delimiters or missing fields that can create invalid numerical entries.

3. Incorrect boundary condition behavior

• Cause: Misinterpreted support definitions or local vs global axis confusion.
• Fixes:
  1. Confirm coordinate system: Ensure supports are defined in the same coordinate system used for geometry.
  2. Use visual checks: Display reaction forces or apply a simple test load to validate support behavior.
  3. Avoid duplicate constraints: Remove overlapping supports defined on the same node.

4. Large displacement vs small displacement mismatch

• Cause: Using small-displacement formulation when geometry changes are significant.
• Fixes:
  1. Switch to large-deformation analysis: Enable geometric nonlinearity (GNL) or update the geometry during iteration.
  2. Apply incremental loading: Combine with load stepping to track nonlinear response.

5. Poor element performance (locking, shear distortion)

• Cause: Choice of element type unsuitable for slender or thick members; coarse mesh.
• Fixes:
  1. Change element formulation: Use reduced-integration or higher-order beam elements if available.
  2. Refine mesh near stress concentrations: Add more nodes/elements in critical regions.
  3. Use shear correction factors: Enable or adjust if supported by FrameSolver 2D.

6. Strange modal/frequency results

• Cause: Mass matrix definition errors, unconstrained rigid-body modes, or negative eigenvalues from incorrect stiffness.
• Fixes:
  1. Check mass distribution: Ensure masses and densities are assigned correctly and consistently.
  2. Remove rigid-body freedoms: Add minimal constraints or use algorithmic elimination of rigid modes.
  3. Re-run with different eigen solver: Try shift-and-invert or another method if available.

7. Visualization discrepancies (deformed shape scaling, missing loads)

• Cause: Post-processor display settings or mismatched units.
• Fixes:
  1. Verify units: Confirm consistent units for geometry, loads, and material properties.
  2. Adjust display scale: Use automatic scaling or set an appropriate scale factor for deformations.
  3. Ensure load visibility: Toggle load display options; check that loads are assigned to correct nodes/elements.

8. Slow solve times

• Cause: Excessively fine meshes, inefficient solvers, or dense output requests.
• Fixes:
  1. Use sparse solvers: Switch to a sparse matrix solver if available.
  2. Reduce DOFs: Collapse unnecessary nodes, use symmetry, or apply substructuring.
  3. Limit output frequency: Request results only for key steps or modes.

9. File import/export errors

• Cause: Unsupported formats, corrupted files, or mismatched coordinate origins.
• Fixes:
  1. Standardize formats: Export/import via common exchange formats (e.g., DXF/CSV) with checked headers.
  2. Re-center geometry: Translate geometry to origin if units or origins differ.
  3. Validate files in text editor: Look for non-ASCII characters or truncated lines.

10. Solver crashes or unexpected exits

• Cause: Memory limits, numerical overflow, or software bugs.
• Fixes:
  1. Increase memory/stack limits: Adjust application or OS settings where possible.
  2. Run smaller test cases: Isolate the issue by progressively simplifying the model.
  3. Update software/patches: Ensure you’re on the latest stable release; report reproducible crashes to support with minimal example files.

Quick troubleshooting checklist

1. Confirm units and material properties.
2. Visualize supports, loads, and mesh.
3. Run a simple sanity test (single beam).
4. Enable incremental loading and GNL if needed.
5. Switch solvers or refine mesh selectively.

When to contact support

If you’ve followed fixes above and can reproduce the issue with a minimal model, gather: minimal input file, screenshots, solver log, and system specs — then submit to support.

Closing note

Apply fixes progressively: start with units/materials, validate boundary conditions, then adjust solver and mesh. This ordered approach isolates root causes faster and reduces trial-and-error.