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Subsection 3.10.1: Prescribed Nodal Degrees of Freedom Up Section 3.10: Boundary Section Subsection 3.10.3: Rigid Nodes

### 3.10.2 Fixed Nodal Degrees of Freedom

Degrees of freedom that are fixed (in other words, constrained, or are always zero) can be defined using the fix boundary condition:
<bc type="fix" node_set="set1">
<dofs>x,y,z</dofs>
<bc>

The node set must be defined in the Mesh section.
The fix boundary condition can be assigned to multiple degrees of freedom of the node set and the list of degrees of freedom is defined via the dofs parameter.
Although the prescribe element with a value of zero for the node tags can also be used to fix a certain nodal degree of freedom, the user should use the fix element whenever possible, since this option causes the equation corresponding to the constrained degree of freedom to be removed from the linear system of equations. This results in fewer equations that need to be solved for and thus reduces the run time of the FE analysis.
Subsection 3.10.1: Prescribed Nodal Degrees of Freedom Up Section 3.10: Boundary Section Subsection 3.10.3: Rigid Nodes