Load Combinations

Load combinations apply factors to load case results and sum them together, as required by structural design codes. This allows you to determine the worst-case design forces under various loading scenarios.

What are Load Combinations?

A load combination multiplies the results from each load case by a specified factor and sums them:

Combination Result = f₁ × LC₁ + f₂ × LC₂ + f₃ × LC₃ + ...

For example, the ASCE 7 combination 1.2D + 1.6L means:

• Multiply Dead Load results by 1.2
• Multiply Live Load results by 1.6
• Add them together

The factored results represent the design forces that structural members must resist.

Opening the Load Combinations Dialog

Click the Load Combos button in the ribbon toolbar to open the Load Combinations dialog.

Creating Load Combinations

The dialog displays a spreadsheet with:

• ID — A unique identifier for the combination
• Title — A descriptive name (e.g., "1.4D", "1.2D + 1.6L")
• Factor columns — One column for each defined load case, where you enter the multiplier

Adding a Combination

1. Type an ID and Title in an empty row
2. Enter factors for each load case you want to include
3. Leave factor cells empty or set to 0 for load cases not included
4. Click Apply & Close to save your changes

Example Combinations

Common Load Combinations (ASCE 7 LRFD)

The following are standard LRFD combinations from ASCE 7:

Common Load Combinations (AS/NZS 1170)

For Australian/New Zealand standards (ULS, Section 4.2):

Auto-Generate Combinations (Pro)

Pro users can automatically generate all required load combinations for a given design code. Click Auto-Generate in the toolbar to open the wizard.

How it Works

1. Select a design code (e.g., ASCE 7 or AS/NZS 1170)
2. Map your load cases to standard categories (Dead, Live, Wind, etc.). For directional categories like Wind and Seismic, you can select **multiple cases** simultaneously.
3. Configure **Mirroring** for directional cases if required.
4. Choose ULS, SLS, or both
5. Click Generate — the wizard creates every required combination permutation.

The wizard auto-detects category mappings from your load case names. Categories left unmapped are silently skipped (e.g., if you have no snow load case, snow combinations are excluded).

Directional & Mirroring Support

The wizard is designed to handle complex multi-directional loading in a single step:

• Multi-Directional Selection: If you have Wind X and Wind Z, select both in the Wind category dropdown. The generator will loop through both, creating a full set of combinations for each direction.
• ± Mirror Pattern: Enabling the ± Mirror toggle automatically generates both positive and negative variations of the load (e.g., 1.2D + 1.0Wx and 1.2D - 1.0Wx). This is essential for meeting code requirements for lateral loads without manual input.

Supported Design Codes

Generated combinations can be appended to your existing entries or replace them entirely.

Dialog Actions

The toolbar provides:

• Auto-Generate — Generate combinations from a design code (Pro)
• Download CSV — Export combinations to spreadsheet
• Copy — Copy to clipboard
• Save as Preset — Save for reuse
• Reload — Reload from model or presets

Viewing Combination Results

After running analysis, you can view factored combination results:

1. Enable a result view (Moment, Shear, etc.) in the left sidebar
2. Use the result selector dropdown in the left sidebar to choose a load combination
3. The displayed diagram shows the factored, combined results

You can switch between individual load case results and combined results at any time.

Envelope Results

When multiple load combinations are defined, you may want to find the maximum or minimum values across all combinations. This is called an "envelope" and helps identify the governing design forces.

Note: Envelope functionality is planned for a future release.

Best Practices

• Name combinations clearly using the factor notation (e.g., "1.2D + 1.6L")
• Include all combinations required by your governing design code
• Consider both strength (ultimate) and serviceability combinations
• For wind and seismic, remember to include both positive and negative directions
• Use presets to maintain consistent combinations across projects