|
||
|
|
||
There exists a set of rules that are followed when nodes or 1D members change their position. The rules, for example, guarantee that an undefined state of geometry or otherwise forbidden situation won’t arise once the move operation has been carried out.
SCIA Engineer uses two types of nodes: absolute and linked. If a modification function is carried out with a part of a structure model, the result will depend on the type of nodes that are included in the structure part being moved. The differences may occur for move of separate nodes as well as for move of whole 1D members (and of course, for move of both nodes and 1D members at the same time).
The rules that are applied during move operations are given below. The rules are divided into two separate parts. The first one deals with move operation that includes nodes only. The other part describes that rules that are followed when either 1D members or 1D members and nodes together are being moved.
When an absolute node or several absolute nodes are moved, the 1D member(s) connected to the node before the move operation remains connected also after the operation. It is not possible to "tear" the node out of the 1D member. This feature may be used to e.g. rotate, shorten, or prolong a 1D member.
If all the nodes relating to a particular 1D member are selected for the move operation, the result is the move of the whole 1D member. This feature can be therefore deliberately used for the repositioning of 1D members.
An absolute node can be moved to an arbitrary new position. The connected 1D member follows the move of the node and, as a result, the 1D member connected to the moved node may change its orientation or length or both. A curved 1D member may also change its curvature.
A linked node can be moved in two ways. First, it may be moved the same way as an absolute node. Second, it can be shifted in a way so that it remains bound to the 1D member it relates to. The latter result is achieved if nodal co-ordinates are modified in the property table.
When a 1D member is being moved to a new location, it may remain attached to the rest of the model (with simultaneous distortion of the model) or it may separate from the remaining part of the model. Which variant actually happens depends on the type of connection between the moved and unmoved 1D members (See below).
If the 1D member that is being moved is connected to the attached 1D member s by means of linked nodes, the connection remains unchanged and the ends of the connected 1D members move together with the moved 1D member. That means that the attached 1D members may change its orientation, size, curvature, or both.
If the connection between the moved and attached 1D members is NOT made via linked nodes, the 1D member that is being moved is separated from the structure.
If a 1D member is placed to a new location, the program verifies whether some unattached nodes would not remain in the original 1D member location. If so, such nodes are automatically moved together with the 1D member. If not, the 1D member is moved and new end nodes are automatically created for the 1D member in its target location.
If the 1D member end nodes in its target location fit into some of the existing nodes, the existing nodes are assigned as the end nodes of the 1D member and no new nodes are created.
For more information about nodes read chapter Nodes.
Practical examples of node type influence
Let’s assume a simple plane frame consisting of two columns and a horizontal beam.
As the first step, let’s consider that the right hand column is connected to the horizontal beam by means of a linked node. The linked node is marked by the short double line drawn at the connection of the members.
Now, let’s move the horizontal beam up and right. The result can be seen in the figure below. The right hand column has remained connected to the horizontal beam, has inclined to the right and has changed its length. On the other hand, the left hand column has stayed in its original position without any change. There is no linked node on the horizontal beam in the point of connection with this column.
In the second step of the example, let’s assume that the linked node is missing also at the connection of the horizontal beam with the right hand column. Consequently, when the beam is moved (again up and right), both the columns undergo no change at all (see the figure below).
