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equal displacement occurs along the translational DOF specified. No coupling occurs between translation and rotation, differentiating an equal constraint from a body constraint. Equal constraints are useful for modeling expansion joints and locations where two elements connect to form a slot-pin connection, as described in the Modeling pinned connections between crossing members tutorial.
To fully connect meshes which do not share common joint locations, body constraints should be used, rather than equal constraints. Otherwise, the constraint may restrain the system against certain types of behavior, thus stiffening the model, and generating unrealistic moment values. This will affect analysis and may lead to the reporting of a lack of equilibrium among constraint forces.
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TO DO: Migrate Body vs. equal constraint Test problem 1 from migration1d to Constraint test problems. Question 1: Why do equal constraints affect analysis when body constraints should be applied? Extended Question 1: The CSI 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 1: Please refer to the |