> For the complete documentation index, see [llms.txt](https://docs.openbrim.org/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.openbrim.org/templates/steel-tub-girder-bridge-workflow/loading-stg/loads-stg/static-loads-stg/surface-load-stg.md).

# Surface Load \[STG]

**Surface:** User must choose either an arbitrary polygon or quadrilateral definition that was defined beforehand.

**Stage:** Choose the stage at which to apply the load.

**Fx:** Force in the longitudinal direction along the PGL.

**Fy:** Force in the direction perpendicular to the PGL.

**Fz (Gravity):** Force in the vertical direction. A positive value indicates a load in the global -Z or gravity direction. For usual loads(wearing surface loads - stay in place formwork loads), the user should input positive values.

**Mx:** Moment in the longitudinal direction along the PGL.

**My:** Moment in the direction perpendicular to the PGL.

**Mz:** Moment in the vertical direction.

{% hint style="info" %}
Although **Fz** is applied in the direction of gravity (positive values for **Fz** will correspond to the downward direction, as with gravity), **Mz** will have a positive direction relative to the **+Z** axis or, in other words, in the upward direction.
{% endhint %}

**Element \[Girder Top Flange/Girder Bottom Flange/Deck/Foundation]:** OpenBrIM distributes the defined surface loads to the chosen element nodes as nodal loads based on their respective tributary area. The tributary area of each node is automatically computed by OpenBrIM.


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