# Modelling of intersecting shapes in SCIA Engineer with the “cut-out” tool

Date:
Sunday, 1 March, 2015
Region:
International

A structural engineer is sometimes confronted with geometries that are more complex than a flat slab on some columns: this can be the case for organic shapes, for intricate steel joists, etc.

SCIA Engineer offers a very practical and powerful tool to handle intersecting shells of any shape.

We will illustrate this below, on a joint at the intersection of 4 steel tubes.

## Modelling the tubes

In this case, the geometry was first defined by usual linear (beam) elements. This makes it easy to define the coordinates in 3D and adjust the lengths of the tubes. There are then several ways to create the tubes as shell elements:

a. Direct modelling with the shell options from the Structure service, using the surface of the tubes as snap points

b. Using Predefined Shapes, and rotating / scaling the tubes to align them with the 1D members

## Creating intersections

As each tube has been modeled independently, there is no connection between them at first.
This connection can be easily created using the “Connect nodes/edges to members” command from the Geometrical manipulations toolbar or the “Intersection” command from the Structure service.

## Removing unwanted parts

Once the intersections have been created, the “Cut-Out” tool can be used to remove unwanted parts. In this case, we will remove only the penetrating parts. It would also be possible to create holes on the main tube in the same way.

## Mesh generation with refinements

A basic mesh can then be generated with an average mesh size.

One can see that the mesh nicely follows the intersections and is perfectly connected.
In order to get accurate results where they matter most, it is possible, as a next step, to create local refinements along the intersections (Calculation, mesh > Local mesh refinements).

In this example, the new “elastic mesh” was used in order to get a smooth transition between one mesh size and the other.

With these tools, we hope that you will be able to apply SCIA Engineer to an even wider range of projects. An inspiring example is the project “Repair and revise of dust collection line” by GSG-Georgsmarienhütte Service Gmbh:

We’re looking forward to your entries in this year’s User Contest!