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: