Combination classes (ASCE 7)

Having created your combinations you classify them as: Construction Stage, Gravity, Lateral, Seismic or Modal Mass.

Note: If generated via the Combinations generator they are classified for you automatically.

Then (where applicable) you indicate whether they are to be checked for strength or service conditions, or both. You also have the option to make any of the combinations inactive.

Construction stage combination

A Construction Stage load combination is only required for the purpose of designing any composite beams within the model. It is distinguished from other combinations by setting its “Class” to Construction Stage. Typically this combination would include a loadcase of type “Slab Wet”, (not “Slab Dry”), other loadcases being included in the combination as required.

Note: The Slab Wet loadcase type should not be included in any other combination.

Gravity combination

These combinations are considered in both the Gravity Sizing and Full Design processes.

They are used in the Gravity Sizing processes as follows:

Design Concrete (Gravity) - concrete members in the structure are automatically sized (or checked) for the gravity combinations
Design Steel (Gravity) - steel members in the structure are automatically sized (or checked) for the gravity combinations.
Design All (Gravity) - all members in the structure are automatically sized (or checked) for the gravity combinations.

They are also used during the Full Design processes as follows:

Design Concrete (All) - concrete members in the structure are automatically sized (or checked) for the gravity combinations.
Design Steel (All) - steel members in the structure are automatically sized (or checked) for the gravity combinations.
Design All (All) - all members in the structure are automatically sized (or checked) for the gravity combinations.

Lateral combinations

These combinations are not used in the Gravity Sizing processes.

They are used during the Full Design processes as follows:

Design Concrete (All) - concrete members in the structure are automatically sized (or checked) for the lateral combinations.
Design Steel (All) - steel members in the structure which have not been set as Gravity Only are automatically sized (or checked) for the lateral combinations.
Design All (All) - all concrete members and all steel members which have not been set as Gravity Only are automatically sized (or checked) for the lateral combinations.

Seismic combinations

These combinations are only considered during the Full Design process. They are not used in the Gravity Sizing process.

Modal mass combinations

For modal analysis, you are required to set up specific “modal mass” combinations. Provided these combinations are active they are always run through the modal analysis.

Note: It is always assumed that all loads in the loadcases in the combination are converted to mass for modal analysis. You are permitted to add lumped mass directly to the model.