4.5.3. rigidDiaphragm command

rigidDiaphragm(perpDirn, rNodeTag, *cNodeTags)

Create a multi-point constraint between nodes. These objects will constrain certain degrees-of-freedom at the listed secondary nodes to move as if in a rigid plane with the primary (retained) node. To enforce this constraint, Transformation constraint handler is recommended.

perpDirn (int)	direction perpendicular to the rigid plane (i.e. direction 3 corresponds to the 1-2 plane)
rNodeTag (int)	integer tag identifying the retained (primary) node
cNodeTags (list (int))	integar tags identifying the constrained (secondary) nodes