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Intersection of two shells

The problem of intersection of two shells (or plates) is divided into two separate problems:

1. calculation of the intersection (i.e. the intersection curve),

2. removal of the part (called cut-out) that should not be considered in the calculation (if such a part exists).

Procedure to generate the intersection of two shells

1. Input the 2D members (shells, plates, walls).

2. If you want to limit the action on selected 2D members only, select the required ones.

3. Call function Modify > Connect members / nodes or Structure > 2D member components > Intersection .

4. The program calculates the intersection of all defined 2D members (the function connects also nodes to 1D members and 1D members to 2D members).

Procedure to define the cut-out (i.e. to define the part of a shell that should be removed from the model)

1. In you have not done so yet, define the intersection – see above.

2. Start function Structure > 2D member components > Cut-out.

3. Select the shells you want to process and confirm the selection with [Esc].

4. The program highlights individual parts of the selected shells. The boundaries of the parts are defined by the shell edges and by the generated intersections.

5. Select the parts that should be removed and confirm with [Esc].

6. The program draws a cut-out symbol around the border of the selected part(s).

Note: The function cut-out is ment to use only on curved members where no opening is possible to input.

Example

Let’s demonstrate the procedures on a simple example of two intersecting semi-cylinders that may represent an intersection of two corridors.

Define the shells.

Call function Modify > Connect members / nodes ([]) to generate the intersection curves.

They may be better seen in the plan view (the black curves).

When you rotate the view, you may see that even though the intersection has been generated, both shells remain unchanged, i.e. it is not possible to pass from one corridor to the other one.

Now call function Structure > 2D member components > Cut-out and select both shells. Then select three end-outs.

When you confirm the selection, the program removes the selected parts from the calculation model. To verify it, generate the FE mesh and display it.

When you rotate the view, you may see that it is possible to freely pass from one corridor to the other.

Note: In SCIA Engineer terminology, the cut-out is an extra entity added to the shell (it is called Additional Data, or Add Data). The removed part of the shell is not removed from the graphical scene, the shell still remains unchanged, and is drawn AS IS. The cut.-out is drawn as an additional entity relating to the shell.

It means that if you display rendered surfaces (or rendered middle plane) of the shell, the removed part (the cut-out) is still displayed.

In order to see the final shape with cut-outs removed, it is necessary to switch off the rendering and display the generated finite element mesh. See the example above.

Examples

The enclosed images show a practical application of shell intersections and cut-outs.

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