Running Analysis

Once your structural model is complete, you can execute the finite element analysis to calculate displacements, reactions, and internal forces.

Before Running Analysis

Ensure your model meets these requirements for a successful analysis:

Checklist

  • ✓ All members have sections assigned — Members without sections have undefined stiffness
  • ✓ All members have materials assigned — Materials provide the elastic modulus
  • ✓ Sufficient supports — The structure must be stable (no rigid body motion)
  • ✓ At least one load case with loads — Either applied loads or self-weight enabled
  • ✓ No disconnected parts — All members should be connected

Minimum Support Requirements

For a stable 3D structure, you need to restrain:

  • 3 translations (prevent movement in X, Y, Z)
  • 3 rotations (prevent spinning about X, Y, Z)

A single fixed support provides all 6 restraints. For pinned supports, you typically need at least 3 non-collinear supports.

Model Health Check

Before running an analysis, it is recommended to use the Health Check tool. This automated system scans your model for common issues that could lead to analysis failure or inaccurate results.

To run a health check, click the Health Check button in the ribbon. The dialog will categorize issues into:

  • Errors (Red): Critical issues that prevent the analysis from running. These must be resolved first.
  • Warnings (Yellow): Potential issues that may affect accuracy or stability but won't block the analysis.

Note: If you attempt to run an analysis while your model has critical errors, the Health Check dialog will open automatically to show you what needs to be fixed.

Running the Analysis

Quick Run

  1. Click the button in the ribbon — the button label shows the currently selected analysis type
  2. Wait for the analysis to complete (a loading spinner appears)
  3. Check the status message

Changing Analysis Type

  1. Click the dropdown arrow next to the button
  2. Select the analysis type:
    • Linear — Standard first-order analysis (default)
    • P-Delta — Second-order analysis with geometric nonlinearity

The button label updates to reflect your selection. Next time you click it, it runs that analysis type.

See Analysis Types for details on when to use each method.

Analysis Status

After running the analysis, you'll see one of these outcomes:

✓ Success

The analysis completed successfully. Results are now available:

  • Result toggles in the left sidebar become active
  • You can view displacements, reactions, and force diagrams
  • The model shows a subtle indicator that results are valid

⚠ Warning

The analysis completed but with warnings. Results are available but should be reviewed carefully. Common warnings:

  • Members with no loads applied
  • Large displacements detected (may need P-Delta analysis)
  • Some load cases have no loads

✗ Error

The analysis failed. Check the error message for details. No results are available until the issue is resolved.

Common Errors

Unstable Structure (Mechanism)

The structure can move freely without developing internal forces.

Causes:

  • Missing or insufficient supports
  • Too many member releases creating a mechanism
  • Disconnected parts

Solutions:

  • Add more supports or restrain additional degrees of freedom
  • Check that all nodes are connected to at least one member
  • Review member end releases — pinned connections at both ends of all members at a joint creates a mechanism

Missing Section or Material

One or more members don't have required properties assigned.

Solutions:

  • Select all members without sections (they may be displayed differently)
  • Assign sections and materials via the Properties panel
  • Use the Members table to review all member properties at once

Singular Stiffness Matrix

A mathematical error indicating the stiffness matrix cannot be inverted.

Common causes:

  • Collinear nodes with pin connections (creates a mechanism)
  • Zero-length members
  • Members with zero stiffness properties
  • Insufficient global restraints

Solutions:

  • Check for overlapping or duplicate nodes
  • Verify member connectivity at joints
  • Ensure supports prevent all rigid body motion

Analysis Did Not Converge

For iterative analyses (Linear or P-Delta), the solution didn't stabilize.

Common causes:

  • Structure is at or near buckling load
  • Very large deflections relative to member lengths
  • Numerical instability from extreme stiffness ratios

Solutions:

  • Try Linear analysis first to understand the behavior
  • Reduce applied loads to check if the structure is overloaded
  • Review structure for stability issues

Results Become Stale

After a successful analysis, results may become "stale" if you modify the model:

  • Adding, moving, or deleting nodes or members
  • Changing section or material assignments
  • Modifying loads or load cases
  • Changing support conditions

Stale results remain viewable but may not reflect the current model. Re-run the analysis to update results.

Usage Limits

Anonymous Users: Limited to 3 analysis runs per day. Sign up for a free account to remove this daily limit.

Free Accounts: Unlimited daily runs, but models are limited to 20 nodes.

For larger models (unlimited nodes), upgrade to the Pro plan.

A dialog will appear if you reach any of these limits.

Performance Tips

For best analysis performance:

  • Use a modern browser — Chrome, Firefox, or Edge (latest versions)
  • Stable internet connection — Analysis runs on our servers
  • Reasonable model size — Very large models take longer to transfer and solve
  • Close unnecessary tabs — Frees up browser resources

What Happens During Analysis

When you click Run:

  1. Model preparation — Your model data is packaged for the solver
  2. Server transfer — Data is sent to our analysis server
  3. FEA solution — The finite element equations are solved
  4. Results transfer — Results are sent back to your browser
  5. Visualization — Results are displayed on your model

The entire process typically takes a few seconds for typical models.