!!! FEA ST1: STABILITY OF A STATICALLY UNDETERMINED BEAM
! created by Tamas Poloskei, 2017. March 01.
!! [N],[Nmm],[N/mm^2=MPa],[N/mm] 

/RGB,INDEX,100,100,100,0
/RGB,INDEX,0,0,0,15 
/VIEW,1,1,1,1   
/ANG,1  
/REP,FAST 

!! Define constant parameters
ELAST=2E5
NU=0.3
F=1E3
A=20
L=500

!! SETUP: element types, materials, sections
KEYW,PR_STRUC,1  ! Preferences / Structural
/PREP7
ET,1,BEAM188

! Define the rectangular crossection
SECTYPE,1,BEAM,RECT 
SECOFFSET,CENT 
SECDATA,2*A,A

MPTEMP,1,0  
MPDATA,EX,1,,ELAST  
MPDATA,PRXY,1,,NU  

! Create the keypoints
K,1,0,0,0
K,2,L,0,0
K,3,3*L,0,0

! Creating the lines
L, 1, 2
L, 2, 3

! Meshing the lines
LESIZE,1,,,5
LESIZE,2,,,10
LMESH,ALL
! Applying the geometric constraints
DK,1,ALL,0
DK,2,UY,0
DK,2,UZ,0
DK,3,UY,0
DK,3,UZ,0
FK,3,FX,-F
FINISH

! Calculate prestress effect
/SOL
PSTRES,1
/STATUS,SOLU
SOLVE   
FINISH

! Eigen buckling analysis
/SOL
ANTYPE,1
! Extract eight modes
BUCOPT,LANB,8,0,0,CENTER
MXPAND,8,0,0,0,0.001,   
/STATUS,SOLU
SOLVE

! Post processing
/POST1
SET,FIRST   

! printing the eigenshapes
*DO, III, 1, 8,1
 PLNSOL, U,SUM, 1,1.0
 /IMAGE,SAVE,strcat(chrval(III),'_eigen_shape'),bmp
 SET,NEXT
*ENDDO