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FixedLength

The Lagrange multiplier method can be used to define constraints. Extra storage is required for the so-called auxiliary border stiffness matrix. The constraint is satisfied exactly.

The FixedLength2D and FixedLength3D constraints behave similar to the Tie element, the nonlinear constraint is implemented via Lagrange multiplier method.

It shall not be used with global damping models in dynamic analysis since it alters the frequency distribution, leading to an unintended damping response. Only damping models that do not depend on system properties can be used.

Syntax

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fixedlength2d (1) (2) (3)
fixedlength3d (1) (2) (3)
constraint fixedlength2d (1) (2) (3)
constraint fixedlength3d (1) (2) (3)
# (1) int, unique constraint tag
# (2) int, node tag
# (3) int, node tag