*HEADING
 RING BUCKLING ANALYSIS, C3D8I, 4 X 20 MESH
*PREPRINT,ECHO=YES,HISTORY=NO,MODEL=NO
*NODE
*NGEN,NSET=SYM1
*NGEN,NSET=VARY1
*NGEN,NSET=INNER,LINE=C
*NGEN,NSET=OUTER,LINE=C
*NFILL,NSET=ALL1
INNER,OUTER,8,100
*NODE
*NGEN,NSET=SYM2
*NGEN,NSET=VARY2
*NGEN,LINE=C,NSET=INNER2
*NGEN,NSET=OUTER2,LINE=C
*NFILL,NSET=ALL2
INNER2,OUTER2,8,100
*NSET,NSET=SYM
SYM1,SYM2
*NSET,NSET=VARY
VARY1,VARY2
*NSET,NSET=ALL
ALL1,ALL2
*ELEMENT,TYPE=C3D8I
*ELGEN,ELSET=EALL
*ELSET,GENERATE,ELSET=LOAD
*MATERIAL ,NAME=A1
*ELASTIC
30.0E6,0.0
*SOLID SECTION,MATERIAL=A1,ELSET=EALL
1.0,
*TRANSFORM, NSET=VARY
*BOUNDARY
ALL1,3
SYM,2
VARY,2
*STEP
*BUCKLE
1,
*DLOAD
LOAD,P4,1.0
*BOUNDARY,LOAD CASE=2, OP=NEW
ALL1,3
SYM,2
VARY,1
*NODE PRINT ,SUMMARY=NO
U,RF
*MODAL PRINT
*MODAL FILE
*OUTPUT,HISTORY,FREQUENCY=1
*MODAL OUTPUT
*END STEP