Define Load Combinations for Composite Design Calculation
Load combinations in composite design can be created manually or imported from a regulatory file. Once defined in the Combinations tab, they are automatically recognized in the Composite Design tab, where they are applied for deflections, profiles, and fire verifications. Assignment to construction or final stages depends on the Stage for Composite parameter of each load case.
Contents
Step-by-Step Procedure
To configure the combinations for composite design calculation, follow these steps:
Step 1: Open the Combinations Dialog Box
You can access the Combinations dialog using either of the following methods:
- From the Menu: Go to Settings > Define Combinations
- From the Project Browser: In the Settings category, right-click Combinations and select Properties.
The Combinations dialog box will appear.
Step 2: Define Load Combinations in the Combinations Tab
Within the Combinations tab, you can define the necessary load combinations in one of two ways:
Option A – Automatically
- Click Load to load a regulatory combination file. The software will automatically generate all valid load combinations based on the selected code.
Option B – Manually
- Manually input each combination using the appropriate regulatory combination codes.
Step 3: Switch to the Composite Design Tab
After defining the combinations:
- Go to the Composite design tab in the Combinations dialog.
- The combinations created according to the composite regulation codes will be automatically recognized and loaded here. They will be used for deflections, profiles, and fire verifications.
Composite Design tab displaying automatically recognized load combinations
used for deflection, profile, and fire verification in composite analysis
Composite Design Tab Options
- Composite verification drop-down list - Defines the composite verification type:
- Construction Stage Deflections
- Final Stage Deflections
- Construction Stage Profiles
- Final Stage Profiles.
Each verification type has specific combinations available.
- Composite combinations list - Displays all combinations created according to the selected composite standards and used in composite calculation.
- Code column: Shows the corresponding combination code
- Type column: Specifies the combination type
- Duration column: Specifies the load duration
- Modify list: Opens the Combinations – Selection dialog box, allowing you to select which load combinations are used in the composite calculation.
Notes on Automatic Combination Assignment
When combinations are generated automatically, they are assigned to the four categories (Construction Stage Deflections, Final Stage Deflections, Construction Stage Profiles, Final Stage Profiles) using two filters:
- By Limit State Type
- SLS or ASLS - assigned to Deflections categories
- ULS or AULS - assigned to Profiles categories
- By Load Occurrence Stage
- Construction stage: The element behaves in a pre-composite state, with the steel section alone carrying all the loads while the concrete is still soft and lacks stiffness.
- Final stage: The element behaves in a post-composite state, with hardened concrete and steel sections working together as a composite section to carry the loads.
Stage for Composite Parameter
The combinations are divided between the two stages depending on the assignment of the load cases they contain. Dead load and live load cases include a Stage for Composite parameter in their properties. This parameter has three values:
- Construction stage
- Final stage
- Both stages.
The rules for filtering combinations are as follows:
- Assigned to Construction stage if:
- They include one or more load cases with Stage for Composite = Construction stage, and/or
- They include one or more load cases with Stage for Composite = Both stages,
- But they do not include any load case with Stage for Composite = Final stage.
- Assigned to Final stage if:
- They include one or more load cases with Stage for Composite = Final stage, and/or
- They include one or more load cases with Stage for Composite = Both stages,
- But they do not include any load case with Stage for Composite = Construction stage.
Notes
Combinations that contain both load cases with Stage for composite = Construction stage and with Stage for composite = Final stage are not assigned to any stage.
Combinations that do not contain any load case with the Stage for Composite parameter (e.g., dead or live load cases) are not assigned to any stage.
Load cases without the Stage for Composite parameter have no impact on whether the combination is filtered between the Construction stage or Final stage.
Stage for Composite parameter selection used to assign load cases to
Construction stage, Final stage, or Both stages in composite structure analysis
FAQ: Load Combinations for Composite Design Calculation
What is the Stage for Composite parameter in load combinations?
A: The Stage for Composite parameter determines whether a load case applies to the construction stage, the final stage, or both. It controls how combinations are assigned between pre-composite (steel-only) and post-composite (steel + concrete) behavior.
Why are some load combinations not assigned to any stage?
A: Combinations that contain both construction and final stage load cases, or that do not include any load case with the Stage for Composite parameter, are not assigned to a stage. These are excluded from stage-specific calculations.
Can I generate load combinations automatically instead of defining them manually?
A: Yes. You can click Load in the Combinations tab to import a regulatory combination file. The software automatically generates all valid load combinations according to the selected design code.
What should I do if my combinations do not appear in the Composite Design tab?
A: If combinations are missing, check that they were correctly defined in the Combinations tab and that each load case has its Stage for Composite parameter properly set. Without this assignment, combinations may not be recognized in the Composite Design tab.
Glossary
- Load Combination
- A formula combining multiple load cases with specific coefficients used for structural verification in composite design.
- Stage for Composite Parameter
- A property of load cases that specifies whether they apply to the construction stage, final stage, or both, controlling how combinations are assigned.
- Construction Stage
- The phase in composite design where the steel section alone carries the loads, as the concrete has not yet hardened.