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SCIA Engineer recognises primarily two types of nodes:
an absolute node,
a linked node.
It is important to understand the differences between the two types as the type of node can have a significant influence on the model properties and behaviour and it also affects functions used for the modification of model geometry.
An absolute node is defined by its "absolute" position, or we can say absolute co-ordinates, in space.
An absolute node is used to define end-points of members (e.g. 1D members).
A linked node is usually defined by its position, or we can say relative co-ordinate, on a 1D member.
As the term "linked" suggests, a linked node is used to "link" two entities together.
On the screen, a linked node is marked by a unique graphical symbol. The linked node mark looks like a pair of short parallel lines drawn in a node.
In order to show an example, let’s assume a simple plane frame consisting of two vertical columns and a horizontal beam connecting heads of the two columns with a short cantilever on one side.
Column B1 has two end-nodes N1 and N2. Both nodes are absolute.
Column B2 has two end-nodes N3 and N4. Node N3 is absolute, node N4 is linked and is bound (linked) to beam B3.
Horizontal beam B3 has three nodes N2, N4, and N5. Nodes N2 and N5 are absolute. Node N4 is linked is related to beam B3.
The linked node N4 guarantees that column B2 is connected to beam B3 and that internal forces in any of the two beam 1D members are transferred into the other one. This configuration represents the state usually required in practice.
To demonstrate what happens if the linked node is not applied, let’s consider the sample structure as shown in the following figure.
The structure here is very similar to the previous one. However, there exists a seemingly small difference and the difference leads to significant consequences.
Column B2 has two end-nodes N3 and N4. And both nodes are absolute.
Horizontal beam B3 has just two end-nodes N2 and N5 which are both absolute.
Because there is no node lying on horizontal beam B3 in the place where column B2 intersects with this horizontal beam, the two 1D members do not have a single common node and are not connected to each other. Both the 1D members would act as separate structures and not as a single column-beam unit.
The differences between the two node types concerning modification functions (such as move, rotate, etc.) are given in chapters describing the modification functions.