Sumo Wind Loading

Posted1 July 2022

Sumo has a wind loading feature that can be applied as an area load to selected load-bearing elements. The area load is automatically reduced to a line load applied to the loaded elements. The “Loaded Elements” dialog within the wind load’s properties palette, allows you to choose which elements must be loaded.

Figure 1 : Area wind load properties, indicating “Loaded Elements” dialog box.

Within the “Loaded Elements” dialog, you can choose the elements that needs to be loaded. The selected loaded elements will automatically adjust the applied line load’s magnitude to be equivalent to that of the applied area load.

The below examples indicate the difference in adding the wind load to a roof structure’s purlins, as well as rafters.

Loaded elements being the purlins:

Figure 2 : Loaded elements linked to the structure’s purlins.

Figure 3 : Equivalent line loads added to purlins of the structure.

Loaded elements being the rafters:

*Figure 4 : Loaded elements linked to the structure’s rafters.*

Figure 5 : Equivalent line loads added to rafters of the structure.

Before applying the wind load to your structure, the following restrictions must be considered:

Elements must be on the same plane. The wind load area is defined as a 2D plane, and only elements in this plane can be loaded.
Elements must start or end on the defined load’s area edge, or outside – but not inside. Elements beginning/ending within the defined area are automatically excluded. A typical example of this, will be cross bracing elements that is added to the structure. These cross bracing elements will not be loaded, and the load will be added onto the rafters, or purlins, which will sit on the perimeter of the area load.
Loaded elements can’t be connected to each other. For example, you can either load the columns, or load the beams, but not both.
Only tri-angular or four-sided polygons can be defined for the wind load area.

You can define the wind code in the “Loads” ribbon and its associated location-specific wind parameters:

Figure 6 : Loads ribbon, indicating the location of the global wind load settings.

The equivalent load is calculated and applied with a default Cp.net value of 1.0 (Cp.net = Cpe + Cpi). The Cp.net value can be adjusted within the properties palette, according to each load requirement, which will in return, automatically adjust the added area load magnitude.

Figure 8 : Area wind load properties palette indicating the chosen Cp.net value and the resultant area load.

The Wind Load Properties have several more adjustments that you can make. For more info, see our YouTube video about the application of wind loads within Sumo.

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