Nodes

Nodes are the fundamental building blocks of any structural model. Think of them as the "joints" or "points" that define where structural members connect and where the structure interacts with the world.

What are Nodes?

In structural analysis, a node is simply a point in 3D space defined by X, Y, and Z coordinates. While members (beams, columns, braces) carry loads between points, nodes are those points themselves.

Nodes serve several critical purposes:

  • Connection points - Where two or more members meet and transfer forces between each other
  • Support locations - Where the structure connects to the ground or other fixed points (foundations, walls, etc.)
  • Load application points - Where point loads and moments are applied to the structure
  • Result locations - Where displacements, reactions, and other results are calculated

Every member in your model connects two nodes - a start node and an end node. Without nodes, members would have nowhere to begin or end.

Creating Nodes

Nodes are created automatically when you:

  • Click in Draw mode
  • Import geometry
  • Split members
  • Intersect members (right-click selected overlapping members)
  • Use Copy, Extrude, or Mirror tools

Node Properties

Select a node to view/edit its properties:

Position

  • X, Y, Z: Coordinates in the global system

Support Conditions

Each node has 6 degrees of freedom (DOFs):

  • DX, DY, DZ: Translations in X, Y, Z
  • RX, RY, RZ: Rotations about X, Y, Z

Common support types:

  • Free: No restraints (all DOFs free)
  • Pinned: Translations restrained, rotations free
  • Fixed: All DOFs restrained
  • Roller: One translation free, the other two restrained (rotations free) — allows sliding in one direction while resisting load in the other two
  • Spring: Elastic support with user-defined stiffness - useful for modelling soil springs or flexible foundations

Quick Support Assignment

The Properties panel provides preset support icons for quick assignment:

  • Fixed (FFFFFF) - All 6 DOFs restrained
  • Pinned (FFFRRR) - Translations fixed, all rotations free
  • Roller variants - One translation free, others fixed

Click on any icon to apply that support condition to selected nodes. You can also toggle individual DOFs using the 6-character code (F = Fixed, R = Released, S = Spring).

Spring Supports

Spring supports allow you to model elastic foundations, soil interactions, or flexible connections by applying a linear stiffness to any degree of freedom.

  • Translational Stiffness (tx, ty, tz): Measured in kN/m.
  • Rotational Stiffness (rx, ry, rz): Measured in kN·m/rad.

To assign a spring, toggle the desired degree of freedom to "S" in the node properties panel and enter the corresponding stiffness value. This is particularly useful for modelling elastic point supports or soil-structure interaction where a rigid support would be unrealistic.

Support Settlement

A support settlement (or prescribed displacement) tells the solver to move a supported node by a known amount, instead of holding it exactly where it was drawn. Common uses:

  • Differential foundation settlement — a soils report gives an expected settlement per column; check the resulting forces in the superstructure.
  • Pile or raft movement under load.
  • Construction tolerances — e.g., a column built 5 mm high inducing residual moments.
  • Thermal differentials imposing relative displacements between supports.

To apply a settlement, select a node and open the Settlement section in the properties panel (between Restraint and Loads). Enter a signed value for any DOF that is restrained (F):

  • DX, DY, DZ — translations, in your selected displacement unit (mm by default in metric, in by default in imperial).
  • RX, RY, RZ — rotations, in radians.

An input is only editable if its corresponding DOF is set to F. Released or spring DOFs cannot accept a settlement — restrain the DOF first. The 3D canvas shows a purple arrow at the settled node for translations and a magenta arc for rotations, with magnitude labels that respect the Display panel's label toggle.

Sign convention: a positive value moves the node in the positive global axis direction. A 10 mm settlement downward in Y is entered as -10.

Scope: in the current release, settlement is a model-wide boundary condition — it is enforced under every load combination. Per-combo settlements are not yet supported. Settlement works under linear static, P-Delta, and buckling analyses (where settlement-induced internal forces correctly feed the geometric stiffness). Modal frequencies are unaffected, since natural frequencies depend only on stiffness and mass — settlement is a static enforced motion.

Loads

When a node is selected, the Properties panel provides a Loads section with a quick-access button to open the Node Loads dialog for the selected node(s). This lets you quickly apply point forces and moments.

Constraints

Add or edit rigid diaphragms. See Rigid Diaphragms for details.

Nodes Table

Click the Nodes button in the ribbon to open the Nodes table. This provides a spreadsheet view of all nodes in your model where you can:

  • Set support conditions in bulk
  • Export node data

Node Labels

Toggle node labels in the Display panel (left sidebar). Right-click the Labels button to choose what to display: node IDs, member IDs, section IDs, or section names.