*HEADING
 RING BUCKLING ANALYSIS, CPS6 equivalent of 4 X 20 MESH  
*RESTART,WRITE
*PREPRINT,ECHO=YES,HISTORY=NO,MODEL=NO
*NODE
1,99.5,,
801,100.5
 41,70.35712473,70.35712473
841,71.06423151,71.06423151
*NGEN,NSET=SYM
1,801,100
*NGEN,NSET=VARY
41,841,100
*NGEN,NSET=INNER,LINE=C
1,41,1
*NGEN,NSET=OUTER,LINE=C
801,841,1
*NFILL,NSET=ALL
INNER,OUTER,8,100
*ELEMENT,TYPE=CPS6
1,1,201,203,101,202,102
2,1,203,3,102, 103,2
*ELGEN,ELSET=EALL
1,4,200,2,20,2,100
2,4,200,2,20,2,100
*ELSET,GENERATE,ELSET=LOAD
7,1907,100
*MATERIAL ,NAME=A1
*ELASTIC
30.0E6,0.0
*SOLID SECTION,MATERIAL=A1,ELSET=EALL
1.0, 
*TRANSFORM, NSET=VARY
1,1,0,-1,1,0.
*BOUNDARY
SYM,2
VARY,2
*STEP
*BUCKLE
1,
*BOUNDARY,LOAD CASE=2, OP=NEW
SYM,2
VARY,1
*DLOAD
LOAD,P2,1.0
*NODE PRINT ,SUMMARY=NO
U,RF
*MODAL PRINT
*MODAL FILE
*OUTPUT,HISTORY,FREQUENCY=1
*MODAL OUTPUT
*END STEP