Page Comparison

{hidden-content}
*TO DO:*
* Migrate Body vs. Equal constraint-test problem 1 from migration1d to Constraint test problems.
{hidden-content}

\\

An *equal constraint* is applied to [joints|kb:Joint] such that their displacement is equal along each translational DOF specified. There is no coupling between translation and rotation, which differentiates an equal constraint from a [body constraint|kb:Constraint]. Equal constraints are useful for modeling expansion joints and locations where two elements connect to form a hinge, as is described in the [Modeling pinned connections between crossing members|tutorials:Modeling a pin connection between crossing members] tutorial.

Body constraints should be used, rather than equal constraints, to fully connect meshes which do not share common joint locations. Otherwise the constraint may restrain the system against certain types of behavior, stiffening the model and generating moment unrealistic moment values. This will affect analysis and may lead to the report of constraint forces not in equilibrium.

\\

{hidden-content}
h2. Why do equal constraints affect analysis when body constraints should be applied?

*Extended Question:* The {new-tab-link:http://www.csiberkeley.com/}CSI{new-tab-link} [_Analysis Reference Manual_|doc:Analysis Reference Manual] (Equal Constraint >, page 59) states that equal constraints may unrealistically stiffen the structure when applied between meshes which do not share common joints. Is an explanation and an example available?

*Answer:* Please refer to the [Body vs. equal constraint|migration1d:Body vs equal constraint-test problem 1] test problem for response.

{hidden-content}