*HEADING
Increase tensile load on the piping system 
and determine lowest frequency.
*RESTART, READ
**
** Step 3 - General step
**
*STEP, NLGEOM, INC=20
Apply 8MN axial tensile load
*STATIC
0.1, 1.
*CLOAD
RIGHT, 1, 8.0E6
*RESTART, WRITE, FREQUENCY=10
*OUTPUT, FIELD, FREQUENCY=10, VARIABLE=PRESELECT
*OUTPUT, HISTORY
*ELEMENT OUTPUT, ELSET=ELEMENT25
S, SINV
*NODE PRINT, FREQUENCY=0
*EL PRINT, FREQUENCY=0
**********************************
** OUTPUT FOR ABAQUS QA PURPOSES
**********************************
*END STEP
**
** Step 4 - Linear perturbation step
**
*STEP, PERTURBATION, NLGEOM
Extract modes and frequencies
*FREQUENCY, EIGENSOLVER=SUBSPACE
7,
*RESTART, WRITE
*OUTPUT, FIELD, VARIABLE=PRESELECT
*NODE PRINT, FREQUENCY=0
*EL PRINT, FREQUENCY=0
**********************************
** OUTPUT FOR ABAQUS QA PURPOSES
**********************************
*MODAL FILE
*END STEP