## Constraints tests

Constraints tests check various constraints capabilities, such as

• join node to node connections check explicit node to node and dof to dof connections as well as automatic detection of node to node connections.

• linc linear constraint equations.

• 'Rigid beam element' connections and 'force-moment distribution element' connections.

## 1. Node to node coupling tests with join

The tests couple pairs of nodes of a mesh with the join command and the node or dof options.

Shell tests are specifically designed for B2000++ and the 5 DOF MITC shell elements: Except if both nodes have a similar normal, the solver automatically assigns 6 DOF nodes for nodes linked with join.

## 2. DOF to DOF coupling tests with linear constraints

The tests check the linear constraint equation capabilities with the linc command. The test couples 2 independent meshes with a linear constraint equations. Each structure consists of a cantilever beam modelled with beam elements. A single equation is defined, linking the v-displacement of the tip node a cantilever beam 1 (branch 1) to the v-displacement of the tip node b of cantilever beam 2 (branch 2). Thus, the equation is of the form va = vb or, va - vb = 0

In the MDL language, the above equation is specified as follows, considering that DOF 2 of the beam mid-node (node 55 of branch 11) is linked to DOF 2 of node 11 of branch 22 (a node with the same coordinates as node 55 of branch 11):

linc
equation 2 0.0 11 55 2 1.0 22 11 2 -1.0
end

 MDL file linc1/constraints/linc/beam.mdl Test case size Small

The solution is equal to the one obtained with beam element rotation end releases set accordingly: One beam element attached to the beam model mid-node must remove rotations (see MDL element option node_rot_dofs in MDL file beam1.mdl). The deformed shape is displayed below: