*HEADING
 : CPS4 MODEL CHANGE VERIFICATION; FREQUENCY ANALYSIS
*RESTART,WRITE
*NODE
 1, 0.
10,10.
41,0.,1.
50,10.,1.
*NGEN,NSET=BOT
 1,10,1
*NGEN,NSET=TOP
41,50,1
*NFILL,NSET=NALL
BOT,TOP,4,10
*ELEMENT,TYPE=CPS4
1,1,2,12,11
*ELGEN,ELSET=EALL
1,9,1,1,4,10,10
*ELSET,ELSET=REMOVE,GEN
4,34,10
5,35,10
6,36,10
*SOLID SECTION,MATERIAL=RUBBER,ELSET=EALL
1.,
*MATERIAL,NAME=RUBBER
*HYPERELASTIC, N=1
56.00E4, 14.00E4, 1.43E-7
*DENSITY
2.E-4, 
*NSET, NSET=XMOVE,GEN
10,50,10
*NSET, NSET=FIX,GEN
1,41,10
*BOUNDARY
FIX, 1, 2
**
** Step 1: Establish a nonlinear base state for freq. extraction
*STEP,NLGEOM
*STATIC
*NODE PRINT,FREQ=0
*EL PRINT,FREQ=0
*NODE FILE, FREQ=99
U,RF
*ENDSTEP
**
** Step 2: Extract freq. of original beam
*STEP,NLGEOM
*FREQUENCY, eigensolver=lanczos, SIM=NO
5, , 
*MODAL FILE
*END STEP
**
** Step 3: Remove middle elements holding beam in place
*STEP,NLGEOM
*STATIC
*BOUNDARY
XMOVE,1,2
*MODEL CHANGE,REMOVE,TYPE=ELEMENT
REMOVE,
*ENDSTEP
**
** Step 4: Shorten beam
*STEP,NLGEOM
*STATIC
*BOUNDARY
XMOVE,1,1,-0.5
*ENDSTEP
**
** Step 5: Add elements strain-free
*STEP,NLGEOM
*STATIC
*MODEL CHANGE,ADD,TYPE=ELEMENT
REMOVE,
*ENDSTEP
**
** Step 6: Extract frequencies of shortened beam
*STEP,NLGEOM
*FREQUENCY, eigensolver=lanczos, SIM=NO
5, , 
*BOUNDARY,OP=NEW
FIX,1,2
*MODAL FILE
*END STEP