*HEADING
FLEXURAL BUCKLING (EULER COLUMN):B31OS, *BEAM SECTION,SECT=I 
*RESTART,WRITE,FREQUENCY=999
*NODE
 1,0.0,0.0,0.0
 21,12.0,0.0,0.0
*NGEN,NSET=ALL
 1,21
*ELEMENT,TYPE=B31OS
 1,1,2
*ELGEN,ELSET=BEAM
 1,20,1,1
*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
*ELSET,ELSET=PRINT
10, 
*BOUNDARY
 21,1,6
 ALL,4,,0.
*STEP
*BUCKLE
 10,
*CLOAD
 1,1,100.
*NODE FILE, LAST MODE=4
U, RF
*EL FILE, ELSET=PRINT, LAST MODE=4
ENER,
ELEN,
*END STEP