Loading Composite Members

Composite beam checks and design involve analysis of the members for both construction and final stages and for multiple limit stages (strength and serviceability). For this reason, some consideration is required to properly set up load cases and combinations, as well as a load class. The load class is required so that all stages and limit states can be considered and checked simultaneously.

Note: As of SCIA Engineer 17.0, the load combinations and the load class needed for composite design can be generated automatically. Load cases are automatically put into combinations based on the stage to which they are set. Self-weight load cases are created automatically, so at minimum, a final stage load case should be created and added to the project.

Load Case Setup

For each load case, the stage in which the load is intended to occur must be specified using the drop-down menu under Stage for composite analysis model. The options for the stages are “Construction stage”, “Final stage – long term”, and “Final stage – short term.” Putting a dead load (i.e. Action type = permanent) in the construction stage means it may occur in both construction and final stages.

Automatic Load Combinations and Result Class Setup

Load combinations and a result class containing these combinations can be created automatically.

In the project data, under the loads tab, is the option to generate code combinations automatically. If this check box is activated, design method can be selected.

Prior to version 18.0, the option to generate combinations is found in the 'Composite Setup' as described below:

In the composite setup, the option for Generate composite combinationscan be set to ASD or LRFD to generate combinations according to the respective design method or be set to NO to not generate combinations automatically.

If combinations are set to be generated automatically, they will be generated when analysis is run. Additionally, a result class which contains the generated combinations is also created automatically.

Manual Load Combinations and Result Class Setup

Load Combination Setup

Once all load cases have been created, combinations containing these load cases must also be created.

The design methodology under Type must also be specified for the combination. The supported design methodologies for composite strength checks are ASD and LRFD.

At least four combinations should be created: one for the construction stage strength (or ultimate) check, one for the construction stage serviceability check, one for the final stage strength (ultimate) check, and one for the final stage serviceability check. The design method for the strength checks must be consistent. The design method for the serviceability checks may differ from the strength combinations. It's recommended to always use ASD combinations for serviceability checks.

The load combinations can be given any name, but all load cases in the construction combinations must be from the construction stage and at least one final stage load case must exist in the final combinations. By correctly setting up load combinations the program can automatically determine for which stage the load combination is intended and can use the combination correctly for designing the member.

Load Class Setup

A load class is automatically generated if load combinations are generated automatically.

After load cases and combinations have been created as specified above, the load combinations must be put into a load class. It is important that the class contains the four required combinations.

To add combinations to the class, simply click New and add the combinations:

Note: Self-Weight Load Cases and Their Use in Combinations

In the composite setup there is the option to 'use fresh concrete weight in construction stage.'

If this option not checked, there will be only one automatically created self-weight load case which contains all self weights. This self-weight case is a permanent load set to construction stage so it may be included in both the construction and final stages and should be included in construction and final stage combinations. This is the default and recommended setting. It should be used unless the wet weight of concrete in the construction stage is meant to be considered.

If this option is checked, there will be three automatically created self-weights. These three self- weights include:

• Self-weight excluding weight of concrete from composite deck - A permanent load set to construction stage so it may be included in both the construction and final stages. It should be included in both construction and final stage combinations.

• Self-weight of fresh concrete from composite deck - A variable load set to construction stage. It should only be included in construction stage combinations.

• Self-weight of dry concrete from composite deck - A permanent load set to construction stage so it may be included in both the construction and final stages, however, it should only be included in final stage combinations.

By default, the composite concrete self-weights are named using the same name as the non-concrete self-weight followed by “_fresh concrete” or “_dry concrete” for the fresh and dry concrete weights, respectively.

Self-weights should always be assigned to the Construction stage.