Node

Node#

This method is used to construct a Node which stores information about coordinates and mass at a single point. The assignment of mass is optional. Each node has Model.ndm coordinates (position in space) and Model.ndf degrees of freedom (displacement and, in 2D/3D frame models, rotation).

Model.node(tag, coords[, mass])#
Parameters:

  • tag – integer tag identifying node

  • coords – tuple of Model.ndm float coordinates

  • mass – tuple of Model.ndf lumped mass values per DOF (see Theory for units and interpretation)

Theory#

Nodes define the spatial discretization of the model: they carry coordinates (in the global system) and optional lumped mass. The number of coordinates is ndm (number of dimensions); the number of degrees of freedom per node is ndf (typically ndm for trusses, ndm + rotational DOFs for frames). See nodeDisp for the ordering of displacement components (u1, u2, u3, r1, r2, r3 in 3D).

Units. xara does not assume or enforce any unit system. All numeric inputs (coordinates, mass, forces, etc.) are unitless; the user must choose and maintain a consistent unit system throughout the model. See Units for predefined constants and supported systems.

Mass. When the mass argument is provided, it is a tuple of ndf values: lumped mass (or rotational inertia) per degree of freedom, in the mass units of the chosen system (e.g. kg in SI, slug in fps). For a 2D model with ndf=3, the first two values are translational mass for u1 and u2; the third is rotational inertia for r3. A value of zero means no mass or inertia for that DOF.

Example#

The following example adds two nodes to a Model with ndm=2 and ndf=3. Node 3 is at coordinates (168.0, 0.0), node 4 at (168.0, 144.0). Node 4 is assigned lumped mass (10.0, 10.0, 0.0): 10.0 for translational DOFs 1 and 2, and 0.0 for rotational DOF 3. Units are those of the user’s chosen system (e.g. kg in SI); see Units.

model.node(3, (168.0, 0.0))
model.node(4, (168.0, 144.0), mass=(10.0, 10.0, 0.0))

Code Developed by: fmk

Contents