Joint - Restraints

Form: Joint Restraints

A joint restraint is the same as a joint support. It is a rigid connection of the joint to the ground. Restraints are specified independently for each degree of freedom at a joint. Restraints are always applied in the joint local coordinate system. By default, this is the same as the Global coordinate system, i.e., joint local axes 1, 2, and 3 are the same as the global axes X, Y, and Z, respectively. If necessary, use the Assign menu > Joint > Local Axes command to specify the local axes for selected joints.

Tip: To impose a specified displacement at a joint degree of freedom, first restrain that degree of freedom using the Assign menu > Joint > Restraints command. This is because displacement loads are actually specified for the ground, and the restraint will force the joint to move with the ground. See Assign - Joint Loads - Displacements.

Select a set of joints to be assigned the same restraints. Other types of objects can be selected because they will not be affected by this assignment.
Click the Assign menu > Joint > Restraints command to access the Joint Restraints form.
- Restraints in Global Directions check boxes. Check the boxes next to the degrees of freedom to be restrained. Uncheck the boxes for degrees of freedom that should not be restrained. These assignments will overwrite any previous assignments of restrained and unrestrained degrees of freedom for the selected object(s).
- Fast Restraints. Use the Fast Restraints buttons to quickly check the restrained degrees of freedom for common restraint conditions:

Fully supported: All degrees of freedom are restrained.

Pinned: All three translational degrees of freedom are restrained.

Roller: Only the vertical (translation 3) degree of freedom is restrained.

Fully free: All degrees of freedom are unrestrained.

After using one of the Fast Restraints buttons, if necessary, modify the individual degrees of freedom by checking or unchecking the appropriate boxes.

Example: Assignment of joint restraints is demonstrated in Problem D, Problem E, Problem F, Problem M, Problem N, Problem P, Problem Q, Problem S, Problem U, Problem V, and Problem Z.