** SUBSTRUCTURE GENERATION FILE FOR substrframe_b31.inp
*NODE
1, -4., -4.
11, -4., -4., 2.4
*NGEN
1,11   
*ELEMENT,TYPE=B31,ELSET=COLUMN
1,1,2
*ELGEN,ELSET=COLUMN
1,10
*BEAM SECTION,SECTION=RECT,MATERIAL=STEEL,ELSET=COLUMN
0.1 , 0.1
 0, -1.
3,3
*MATERIAL,NAME=STEEL
*ELASTIC
2.1E11 , 0.3
*DENSITY
7200., 
**
**
*STEP
*SUBSTRUCTURE GENERATE,TYPE=Z101,MASS MATRIX=YES,OVERWRITE
*RETAINED NODAL DOFS
1,
11,
*END STEP