Nodes

Two types of nodes are available; structural and non-structural.

Structural nodes
Are all those to which an element, of whichever type, is attached to. In fact, in SeismoStruct it is not possible to run an analysis of any type if a node that has been defined as "structural" does not feature at least one element connected to it. Put in other words, structural nodes are all those to which degrees-of-freedom are assigned and then included in the assemblage of stiffness matrix and load/displacement vectors.

Non-structural nodes
On the other hand, are nodes that are not to be considered in the solution of the structure but are instead usually needed to define the orientation of local axes of certain types of elements (as described in element connectivity). No elements of any type can be attached to this type of nodes and whilst it is obvious that structural nodes can also be used as a reference point in the definition of these local axes, it usually results much more simple and clear to reserve this role to their non-structural counterparts. The user is referred to the global and local axes systems chapter for a deeper discussion on this subject. By default, non-structural nodes do not result visible on the 3D plot of the model, a condition that can be easily modified through a change in the display settings.

As in all other modules, the user is capable of adding new nodes (also in the graphical input mode) and removing/editing existing selected ones. Nodes can be sorted according to their names or their x-, y- or z- coordinates. If the user clicks once on the header of the corresponding column, ascending sorting is adopted, whilst if a second click is employed, the nodes become sorted in descending fashion (see module editing functions for further details on data sorting).

The Nodes module features also an incrementation facility with which the user can create new nodes through "repetition" of existing ones. This is done by first selecting a set of nodes that will serve as the base for the incrementation, then specifying the increment in the name and coordinates of the node(s), and finally deciding on the number of "repetitions" to be carried out. To better understand this automatic node generation tool, let us consider an example:

1. Selected existing nodes
   node10: (0, 0, 3)
   node20: (5, 0, 3)
2. Incrementation parameters
   Name increment: 100
   x-increment: 5
   y-increment: 0
   z-increment: 3
   repetitions: 3
3. Automatically generated nodes
   node110: (_5, 0, _6) [from "repetition" 1]
   node120: (10, 0, _6) [from "repetition" 1]
   node210: (10, 0, _9) [from "repetition" 2]
   node220: (15, 0, _9) [from "repetition" 2]
   node310: (15, 0, 12) [from "repetition" 3]
   node320: (20, 0, 12) [from "repetition" 3]

Notes

1. One element editing feature that might come very useful to users is the ability to change a co-ordinate type of a large number of nodes through a single operation, by making a multiple selection and opening the Edit dialog box. This can be very handy, for example, when one needs to change the y-coordinates of all nodes of a frame that is to be moved into a different position in space.
2. A maximum number of 50000 nodes may be defined.
3. It is noted that when users define non-structural nodes with very large coordinates, and then activate visualisation of such nodes, the model will inevitably be zoomed-out to a very small viewing size. To avoid such a scenario, users should (i) bring the non-structural nodes closer to the structure, (ii) disable visualisation of the latter or (iii) zoom-in manually every time the 3D plot is refreshed.