*HEADING
 RING BUCKLE EIGENVALUE ESTIMATE ( 5*2 STRI3 )   
*PREPRINT, HISTORY=NO
*NODE
1,,,
2,,1,
10,70.71068,,70.71068
21,70.71068,1.0,70.71068
20,100.,,
31,100.,1.
*NGEN,NSET=ALL,LINE=C
10,20,1,1
21,31,1,2
*TRANSFORM,TYPE=C,NSET=ALL
,,,,1,
*ELEMENT,TYPE=STRI3
1,10,12,21
2,21,12,23
*ELGEN,ELSET=ELMT
1,5,2,2
2,5,2,2
*SHELL SECTION,MATERIAL=A1,ELSET=ELMT
1.,3
*MATERIAL,NAME=A1
*ELASTIC
30.E6, 
*NSET,NSET=ONE
20,31
*NSET,NSET=TWO
10,21
*STEP
*BUCKLE
1, 
*DLOAD
ELMT,P,-1.0
*BOUNDARY
ALL,3,5
ONE,2
ONE,6
TWO,2
TWO,6
*BOUNDARY,LOAD CASE=2, OP=NEW
ALL,3,5
ONE,2
ONE,6
TWO,1
*EL PRINT
S, 
*MODAL FILE
*OUTPUT,HISTORY,FREQUENCY=1
*MODAL OUTPUT
*END STEP