*HEADING                                                                      
TORSIONAL BUCKLING: B32OS, *BEAM SECTION, SECTION=I  
*RESTART,WRITE
*NODE
 1,0.0,0.0,0.0
 21,12.0,0.0,0.0
*NGEN,NSET=ALL
 1,21
*ELEMENT,TYPE=B32OS
 1,1,2,3
*ELGEN,ELSET=BEAM
 1,10,2,1
*BEAM SECTION,SECTION=I,ELSET=BEAM,MATERIAL=MAT
 0.345,0.69, 0.3,0.3, 0.027,0.027, 0.0145
 0.0,-1.0,0.0
*MATERIAL,NAME=MAT
*ELASTIC
 2.1E11,0.3125
*BOUNDARY
 1,1,4
 21,2,4
*STEP
*BUCKLE
15,
*NODE PRINT
U, 
RF  , 
*NODE FILE,FREQUENCY=1
U,RF  
COORD, 
*CLOAD
 21,1,-10.0              
*EL PRINT,FREQUENCY=0
*MODAL FILE
*END STEP