Load Combinations

You can edit and add load combinations in the Structural Settings dialog.

Creating a Load Combination

Setting the Load Combination Type

Setting the Load Combination State

Setting the Load Combination Usage

Setting the Load Combination Name

1. Click Analyze tabLoads panel Load Combinations.
2. Click in the Load Combination table, and click Add.
3. Click in the Name field, and enter a name.
4. Click in the Edit Selected Formula section, and click Add in the same section.
5. Click in either the Case or Combination field to select a Case or Combination.
6. Click in the Factor field to enter a factor.

   Notice that the Name and Formula fields change in the Load Combination table.

7. Click Add again in the Edit Selected Formula section.
8. Click in the Case or Combination field to select a Case or Combination value.
9. Click in the Factor field to enter a factor.

   Notice that the Name and Formula fields change in the Load Combination section.

10. In the Type field of the Load Combination table, select either Combination or Envelope.

    Setting the load combination type to Combination, gives results (reactions and member forces) for a single load combination. Envelope gives maximum and minimum results on a group of load combinations.

11. In the State field of the Load Combination table, select either Serviceability or Ultimate.

    Setting the load combination state to Serviceability, reflects how a structure performs (deflection, vibration etc.) under normal or expected loading, whereas Ultimate states are based on the total capacity of a structure to safely resist extreme or ‘factored’ loads without failing (buckling, fracturing etc.).

12. Click in the Load Combination Usage field, and click Add.

    The load combination usage parameter is user defined (either gravity, lateral or combined).

    • Gravity Load Combinations include the vertical loads, both permanent or dead (self weight of the structure - floor, beams, columns etc.) and live loads based on occupancy (people on an office floor, boxes in a storage room, snow on a roof, etc.).
    • Lateral Load Combinations include the horizontal loads, both permanent or dead (soil resting up against a foundation wall) and live loads (wind against the face of a structure or the shaking of a structure from an earthquake).
    • Combined Load Combinations include varying degrees of both gravity and lateral loads in order to account for cases when structures are both occupied and experiencing wind or earthquake loads.
13. Click the Load Combination Name field to select a Combination to which to add a new Load Combination Usage.
14. In the Load Combination field, select the Load Combination to which a new Load Combination Usage is to be applied. This is achieved by clicking anywhere in the row of the Load Combination.
15. In the Load Combination Usage field, check the new Load Combination Usage that you want.

    Notice that as soon as a Load Combination Usage is checked, it applies itself to the selected Load Combination.

16. Click OK to exit the dialog.

Filtering load combinations generated by add-ins

By default, load combinations generated by add-ins are not displayed. To view them, select Show third-party generated combinations. However, they are not available for editing.