A Beam Constraint causes all of its constrained joints to move together as a rigid beam, i.e., it is infinitely stiff in transverse shear and bending, but not constrained in axial or torsional behavior. This constraint can be used to accomplish the following:
Connect structural-type objects (frame and shell) to solid-type objects (plane, asolid, and solid); the rotation in the structural object can be converted to a pair of equal and opposite translations in the solid object by the constraint.
Prevent bending deformation in frame objects.
The constraint must apply to at least two joints to have any effect on the model. It is intended to be used on a set of joints that lie along a straight line. If the joints do not lie along a straight line, the constraint will effectively restrain the joints against torsional rotation around the constraint axis, which is usually not desirable.
Use the following areas on the Beam Constraints form to make the appropriate entries:
Constraint Name. Use the default or enter a unique name for the constraint being defined.
Coordinate System. Choose the coordinate system in which the constraint axis (below) is being defined. If the constraint axis is automatic, the choice of coordinate system has no effect on the constraint.
Constraint Axis. The constraint equations will be written for a beam along the selected axis. If the joints lie along a unique straight line, it is usually best to choose Auto and let the program automatically determine the axis. This axis does not necessarily need to be parallel to a coordinate-system direction. If the joints are not colinear, or to force a particular direction, choose the axis in the chosen coordinate system that is parallel to the beam. For example, if the X axis is chosen, this constraint is equivalent to a body constraint in the same coordinate system with translations Y and Z and rotations Y and Z chosen.
If the Define menu > Joint Constraints command was used to access the Beam Constraints form, the defined constraint must be assigned to the joints.
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Access the Beam Constraints form as follows:
Click the Define menu > Joint Constraints command to display the Define Constraints form or select the joints to be assigned the constraint and click the Assign menu > Joint > Constraints command to display the Assign/Define Constraints form. Then do one of the following:
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