The surface generator is a calculation tool that will distribute a surface load (given in kN/m²) to a selection of bars resulting in a line load (kN/m).
To use this feature:
- Select at least two bars that will carry the load.
The selected bars must be in the same plane, but they don’t have to form a closed circumference. - Click on
.
The following dialogue appears:
- Diamonds searches for all the possible surfaces to be defined between the selected bars. Using the visual representation, you can verify their position.
- Diamonds supposes that the load acts on the orange areas.
You can click on an area to deactivate it. It will then be shown in grey. Diamonds doesn’t apply loads to grey areas.
- It is assumed that only the selected bars, that are drawn in black in the image above, will carry the load.
You can click on a bar to deactive it. It will then be shown in grey. Grey bars won’t help carry the load.
- Diamonds supposes that the load acts on the orange areas.
- In the next part of the dialogue, define the size and direction of the force on the surface.
- Should the load be applied either perpendicularly to the plane of the selected bars or along one of the global axes. Each colour refers to an axis of the global coordinate system at the bottom right of the model window. The arrows indicate the direction of a positive load.
- If you choose a force on surface load along the global coordinate system, you also need to specify whether the inserted value is a value per m² of the surface (
) or per m² of the horizontal surface (projected 
).
- How does the surface load generator on bars work?
To convert a surface load into a line load, a dummy surface (= the yellow surfaces you see in the dialog above) is divided into triangles. This process is called triangulation.
Next, Diamonds determines the centre of gravity for each triangle as well as the load 
on it.
It will also divide the surrounding bars, to which the load will be diverted, into several small bars whose nodes are numbered from 1 to j.
Then Diamonds calculates the distance
between each of these points and the centre of gravity of a triangle. With that it becomes possible to calculate for each point of the bar, which part 
of the load will be diverted to this specific point using:
![\[F_{i}=P\cdot \frac{\frac{1}{d_{i}}}{\sum _{j}\frac{1}{d_{i}}}\]](https://support.buildsoft.eu/wp-content/ql-cache/quicklatex.com-aebf4db14f20f3a8104c521b65e21e82_l3.png "Rendered by QuickLaTeX.com")
What ensues that the major part of the load is diverted to the points closest to the triangle in question.
Once the procedure has been applied to all triangles, Diamonds can evaluate the total load for each point.
The last stage consists of converting loads on discrete points into a distributed load on the bar. - Precision of triangulation
You can change the amount of triangles in the triangulation with the slider, but for practical use, the default value (slider completetly to the left) is sufficient. - You can visualize the triangulation by checking the corresponding box.
- Above we explained how this function works. At a certain point, Diamonds will divide the surrounding bars, to which the load will be diverted, into small bars. The number of small bars can be imposed by you and will determine how the load distribution on the surrounding bars looks like.
Number of subdivisions for loads: 1 (recommended) Number of subdivisions for loads: 8 This results in a constant line load over the entire bar. This results in a parabolic line load over the entire bar. This is theoretically the most correct load distribution, but it will take long to distribute the load and it will result in a heavy model. Therefore we don’t recommend it. 
