*Heading
 B21 Elements, Static Analysis
*Node
*Element, type=B21
** Region: (Secn:Picked), (Beam Orientation:Picked)
*Elset, elset=I1, generate
** Section: Secn  Profile: Prof
*Beam Section, elset=I1, Section=RECT,material=Elas
1, 1
0.,0.,-1.
**Nset, nset=Set4
 **1,
**Nset, nset=_Set5, internal, instance=Beam2d-1
** 3,
**
** MATERIALS
**
*Material, name=Elas
*Density
10.,
*Elastic
 1e+08,0.
*step
*frequency,eigen=lanc
6,
*boundary
1,1,6
2,1,6
3,1,6
*node print
u,
*end step
*STEP
*substructure generate, type=z1, overwrite,
recovery matrix=yes, mass matrix=yes,
libr=lib_rbm_beam2d
*RETAINED NODAL DOFS
**,sorted=no
*Retained Eigenmodes
*substructure matrix output, stiffness=yes,
mass=yes, recovery=yes, file=lib_rbm_beam2d
*END STEP