Rigid Connector
The Rigid Connector is a boundary condition for modeling rigid regions and kinematic constraints such as prescribed rigid rotations. The selected points will move as a single rigid object.
If the study step is geometrically nonlinear, the rigid connector takes finite rotations into account. The feature is similar to the rigid connectors in the Solid Mechanics and Shell interfaces. Rigid connectors from Beam, Pipe Mechanics, Shell, and Solid Mechanics interfaces can be attached to each other.
You can add functionality to the rigid connector through the following subnodes:
Applied Force (Rigid Connector) to apply a force in given point.
Mass and Moment of Inertia (Rigid Connector) to add extra mass and moment of inertia in a given point.
Spring Foundation (Rigid Connector) to add a translational or rotational spring or damper in a given point.
Coordinate System Selection
The Global coordinate system is selected by default. The Coordinate system list contains any additional coordinate systems that the model includes. Prescribed displacements or rotations are specified along the axes of this coordinate system. It is also used for defining the axis directions of the moment of inertia tensor of the Mass and Moment of Inertia subnode.
Center of Rotation
The center of rotation serves two purposes.
Select a Center of rotation Automatic, Centroid of selected entities, or User defined.
For Automatic the center of rotation is at the geometrical center of the selected points. The constraints are applied at the center of rotation.
For Centroid of selected entities a subnode for selection of the points is added to the Model Builder. The center of rotation is located at the centroid of the selected points, which do not need to be related to the points to which the rigid connector is attached. As a special case, you can select a single point, and thus locate the center of rotation at a certain point.
For User defined, in the Global coordinates of center of rotation XC table enter coordinates based on space dimension.
Once Centroid of selected entities is chosen, a default Center of Rotation: Point subnode is added.
Select the Offset check box to add an optional offset vector to the definition of the center of rotation. Enter values for the offset vector Xoffset.
The center of rotation used is the sum of the vector obtained from any of the input methods and the offset vector.
Prescribed Displacement at Center of Rotation
To define a prescribed displacement at the center of rotation for each space direction, select one or several of the available check boxes then enter values or expressions for the prescribed displacements. The direction coordinate names can vary depending on the selected coordinate system.
For 3D components: Prescribed in z direction u0z
Prescribed Rotation at Center of Rotation
Specify the rotation at the center of rotation. Select from the By list: Free (the default), Constrained rotation, or Prescribed rotation at center of rotation.
For 2D components, the Constrained rotation and Prescribed rotation at center of rotation is always about the z-axis, so no component selection is necessary.
Constrained Rotation (3D Components)
For Constrained rotation select one or more of the available check boxes to enforce zero rotation about the corresponding axis in the selected coordinate system:
Constrain rotation about x-axis
Constrain rotation about y-axis
Constrain rotation about z-axis
Prescribed Rotation at Center of Rotation
For Prescribed rotation at center of rotation enter an Angle of rotation φ0. For 3D components also enter an Axis of rotation Ω for the x, y, and z coordinates.
You can add a Harmonic Perturbation subnode for specifying a harmonic variation of the values of the prescribed displacements and rotations in a frequency domain analysis of perturbation type.
Location in User Interface
Context Menus
Ribbon
Physics tab with Beam selected: