*node
1001,0,0
1002,1,0
1004,3,0
********************
*element,type=b21,elset=one
2001,1001,1002
2002,1002,1004
*BEAM SECTION,elset=one,sect=rect,material=elas
1.0,1.0
0,0,-1
*MATERIAL,name=elas
*elastic
1.e8,
*density
1.e1
************************
*STEP
*substructure generate, type=z1, overwrite, 
recovery matrix=yes, mass matrix=yes,libr=libbeam2d
*RETAINED NODAL DOFS
1001,
*substructure matrix output, stiffness=yes, 
mass=yes, recovery=yes, file=LibMatBeam2D,sload=yes
*END STEP