*HEADING
: EIGENVALUE ANALYSIS OF AN UNCONSTRAINED 1-ELEMENT MESH  [PIPE31H]
AN EXTRA NODE IS USED TO DEFINE THE BEAM SECTION ORIENTATION
*NODE,NSET=NALL
1,0.
2,1.,2.,3,
3,1.,2.,2,
*ELEMENT,TYPE=PIPE31H, ELSET=EALL
1,1,2,3
*BEAM SECTION,SECTION=PIPE,MATERIAL=A1, ELSET=EALL
10.,1.
1.0,0
*MATERIAL,NAME=A1
*ELASTIC
30.E6, 
*DENSITY
7.5E-4, 
*STEP
*FREQUENCY, eigensolver=lanczos
12, , ,-1.0E4 
*OUTPUT,HISTORY,FREQUENCY=1
*MODAL OUTPUT
*END STEP