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Convergence issue and wrong results with BEAM 188 and BEAM44
 
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xi.chen
User


Joined: 07 May 2013
Posts: 8

PostPosted: Tue Jan 24, 2017 4:17 pm  Reply with quote

Dear All:

I’m trying to model a power pole. The pole itself is modeled with beam element and the cable forces, wind forces and dead load are all applied as point loads on nodes of the pole. The cable forces are lateral loads with large magnitude.
It is a very simple model. It shouldn’t have any problem since I had some experience with ANSYS for some time.

I made two models, one with the BEAM188 element and one with BEAM44 elements. Both works fine if the geometric nonlinearity option is off. The problem is once I turn on the geometric nonlinearity option, the model doesn’t work anymore. The beam 44 element model simply cannot get a converged result. The BEAM188 element seems to work fine, all the deflection, moments are roughly correct. However, the axial forces are all messed up. The pole should only be in compression, due to the fact there is no uplifting force but only dead loads. The axial force diagram should be monotonically increasing. But in the segments where the cable load (lateral load) is applied, there is tension in the pole. This doesn't make any sense and makes me doubt my model.
I know my pole has large deflection which will cause large geometric nonlinearity. It may be an issue in convergence, but I used another commercial software to model the same pole. There is no issue at all. The axial force is monotonically increasing.

I have attached my model to this question, would someone please run it and have a look at the result. It is a fairly easy model and doesn’t have any virus. You can see from the commands.
Why my beam44 model doesn’t work and why my beam 188 model have tension in the pole. Is there something wrong with the usage of my elements?
Thank you.



!!!!!!!!!!!!!!!!!!!!!!BEAM 188 Model
FINISH
/Clear
/FILNAM,poleBEAM188
/TITLE,poleBEAM188
/PREP7

et,1,link180
et,2,link10
et,3,beam188
keyopt,3,1,0


mp,ex,4,7722e6 !Western Red Cedar
MP,prxy,4,0.2
mp,dens,4,800.9
MPTEMP,,,,,,,, !
MPTEMP,1,0
MPDATA,ALPX,4,,3E-6


!!!!!!!!!!!!!!!!!!!!!!!!!!! Define Sections
SECTYPE, 1, BEAM, CSOLID, Pole1, 0
SECOFFSET, CENT
SECDATA,0.160412267,10,5,

SECTYPE, 2, BEAM, CSOLID, Pole1, 0
SECOFFSET, CENT
SECDATA,0.157802126,10,5,

SECTYPE, 3, BEAM, CSOLID, Pole1, 0
SECOFFSET, CENT
SECDATA,0.155207901,10,5,

SECTYPE, 4, BEAM, CSOLID, Pole1, 0
SECOFFSET, CENT
SECDATA,0.152597759,10,5,

SECTYPE, 5, BEAM, CSOLID, Pole1, 0
SECOFFSET, CENT
SECDATA,0.149287337,10,5,

SECTYPE, 6, BEAM, CSOLID, Pole1, 0
SECOFFSET, CENT
SECDATA,0.145976914,10,5,

SECTYPE, 7, BEAM, CSOLID, Pole1, 0
SECOFFSET, CENT
SECDATA,0.142650575,10,5,

SECTYPE, 8, BEAM, CSOLID, Pole1, 0
SECOFFSET, CENT
SECDATA,0.139340153,10,5,

SECTYPE, 9, BEAM, CSOLID, Pole1, 0
SECOFFSET, CENT
SECDATA,0.13602973,10,5,

SECTYPE, 10, BEAM, CSOLID, Pole1, 0
SECOFFSET, CENT
SECDATA,0.132719307,10,5,

SECTYPE, 11, BEAM, CSOLID, Pole1, 0
SECOFFSET, CENT
SECDATA,0.129392969,10,5,

SECTYPE, 12, BEAM, CSOLID, Pole1, 0
SECOFFSET, CENT
SECDATA,0.126082546,10,5,

SECTYPE, 13, BEAM, CSOLID, Pole1, 0
SECOFFSET, CENT
SECDATA,0.122772123,10,5,

SECTYPE, 14, BEAM, CSOLID, Pole1, 0
SECOFFSET, CENT
SECDATA,0.119445785,10,5,

SECTYPE, 15, BEAM, CSOLID, Pole1, 0
SECOFFSET, CENT
SECDATA,0.116135362,10,5,

SECTYPE, 16, BEAM, CSOLID, Pole1, 0
SECOFFSET, CENT
SECDATA,0.112824939,10,5,

SECTYPE, 17, BEAM, CSOLID, Pole1, 0
SECOFFSET, CENT
SECDATA,0.109498601,10,5,

SECTYPE, 18, BEAM, CSOLID, Pole1, 0
SECOFFSET, CENT
SECDATA,0.106188178,10,5,

SECTYPE, 19, BEAM, CSOLID, Pole1, 0
SECOFFSET, CENT
SECDATA,0.102877755,10,5,

SECTYPE, 20, BEAM, CSOLID, Pole1, 0
SECOFFSET, CENT
SECDATA,0.099567332,10,5,

SECTYPE, 21, BEAM, CSOLID, Pole1, 0
SECOFFSET, CENT
SECDATA,0.096272825,10,5,

SECTYPE, 22, BEAM, CSOLID, Pole1, 0
SECOFFSET, CENT
SECDATA,0.092978318,10,5,


!!!!!!!!!!!!!!!!!!!!!! Pole Nodes
n, 1,60,-1.676, 60
n, 2,60,-1.176, 60
n, 3,60,-0.784, 60
n, 4,60,-0.392, 60
n, 5,60,0 , 60
n, 6,60,0.5 , 60
n, 7,60,1 , 60
n, 8,60,1.5 , 60
n, 9,60,2 , 60
n,10,60,2.5 , 60
n,11,60,3 , 60
n,12,60,3.5 , 60
n,13,60,4 , 60
n,14,60,4.5 , 60
n,15,60,5 , 60
n,16,60,5.5 , 60
n,17,60,6 , 60
n,18,60,6.5 , 60
n,19,60,7 , 60
n,20,60,7.5 , 60
n,21,60,7.997 , 60
n,22,60,8.494 , 60
n,23,60,8.992 , 60


!!!!!!!!!!!!!!!!!!!!! Pole Elements
type,3
mat,4
Real,4
*do,i,1,22,1
SECNUM, i
e,i,i+1
*enddo

!!!!!!!!!!!!!! Gravity Load

F,1 ,FY,0
F,2 ,FY,-486
F,3 ,FY,-367
F,4 ,FY,-356
F,5 ,FY,-344
F,6 ,FY,-461
F,7 ,FY,-442
F,8 ,FY,-423
F,9 ,FY,-405
F,10,FY,-387
F,11,FY,-369
F,12,FY,-352
F,13,FY,-335
F,14,FY,-319
F,15,FY,-303
F,16,FY,-287
F,17,FY,-557
F,18,FY,-258
F,19,FY,-467
F,20,FY,-229
F,21,FY,-215
F,22,FY,-202
F,23,FY,-189

!!!!!!!!!!!!!!!!! out-of-plane Wind load
F,1 ,FZ,0
F,2 ,FZ,0
F,3 ,FZ,0
F,4 ,FZ,0
F,5 ,FZ,-20.00
F,6 ,FZ,-20.00-20.00
F,7 ,FZ,-19.00-19.00
F,8 ,FZ,-19.00-19.00
F,9 ,FZ,-18.00-18.00
F,10,FZ,-18.00-18.00
F,11,FZ,-17.00-18.00
F,12,FZ,-17.00-17.00
F,13,FZ,-17.00-17.00
F,14,FZ,-16.00-16.00
F,15,FZ,-16.00-16.00
F,16,FZ,-15.00-15.00
F,17,FZ,-15.00-89.00
F,18,FZ,-14.00-14.00
F,19,FZ,-14.00-75.00
F,20,FZ,-13.00-14.00
F,21,FZ,-13.00-13.00
F,22,FZ,-13.00-13.00
F,23,FZ,-12.00


!!!!!!!!!!!!!!!!! in-plane Wind load and cable load.
F,1 ,FX,0
F,2 ,FX,0
F,3 ,FX,0
F,4 ,FX,0
F,5 ,FX,35.00
F,6 ,FX,34.00+34.00
F,7 ,FX,33.00+33.00
F,8 ,FX,32.00+33.00
F,9 ,FX,32.00+32.00
F,10,FX,31.00+31.00
F,11,FX,30.00+30.00
F,12,FX,29.00+30.00
F,13,FX,29.00+29.00
F,14,FX,28.00+28.00
F,15,FX,27.00+27.00
F,16,FX,26.00+27.00
F,17,FX,26.00+6148.00 !!!!!!! very large cable load
F,18,FX,25.00+25.00
F,19,FX,24.00+7913.00 !!!!!!! very large cable load
F,20,FX,23.00+24.00
F,21,FX,23.00+23.00
F,22,FX,22.00+22.00
F,23,FX,21.00



!!!!!!!!!!!!!!!!!!!!!! boundary conditions, 5 nodes are below earth surfeces.
d,5,ux
d,5,uz

d,4,ux
d,4,uz

d,3,ux
d,3,uz

d,2,ux
d,2,uz

d,1,uz
d,1,ux
d,1,uy




/solu
antype,0

outres,all,all
nlgeom,on
nropt,full,,on
SOLCONTROL, on
sstif,on
kbc,0
allsel,all

time,10,,,
NSUBST, 25,
DELTIM, 1, 1, 1
allsel,all
solve

finish


/post1
ETABLE,FN1,SMISC, 1 !!!!! axial forces
ETABLE,FN2,SMISC, 14 !!!!! axial forces
ETABLE,MZ1,SMISC, 2 !!!!! Z-moments
ETABLE,MZ2,SMISC, 15 !!!!! Z-moments
ETABLE,MX1,SMISC, 3 !!!!! X-moments
ETABLE,MX2,SMISC, 16 !!!!! X-moments




!!!!!!!!!!!!!!!!!!!!! BEAM 44 model
FINISH
/Clear
/FILNAM,poleBEAM44
/TITLE,poleBEAM44
/PREP7

et,1,link180
et,2,link10
et,3,beam44


mp,ex,4,7722e6 !Western Red Cedar
MP,prxy,4,0.2
mp,dens,4,800.9
MPTEMP,,,,,,,, !
MPTEMP,1,0
MPDATA,ALPX,4,,3E-6


!!!!!!!!!!!!!!!!!!!!!!!!!!! Define Sections
R, 1, 0.080840, 5.20044E-04, 5.20044E-04, 0.160412, 0.160412, 1.04009E-03,
R, 2, 0.078230, 4.87014E-04, 4.87014E-04, 0.157802, 0.157802, 9.74028E-04,
R, 3, 0.075679, 4.55769E-04, 4.55769E-04, 0.155208, 0.155208, 9.11539E-04,
R, 4, 0.073155, 4.25875E-04, 4.25875E-04, 0.152598, 0.152598, 8.51751E-04,
R, 5, 0.070016, 3.90105E-04, 3.90105E-04, 0.149287, 0.149287, 7.80210E-04,
R, 6, 0.066945, 3.56637E-04, 3.56637E-04, 0.145977, 0.145977, 7.13274E-04,
R, 7, 0.063929, 3.25225E-04, 3.25225E-04, 0.142651, 0.142651, 6.50450E-04,
R, 8, 0.060996, 2.96070E-04, 2.96070E-04, 0.139340, 0.139340, 5.92141E-04,
R, 9, 0.058132, 2.68921E-04, 2.68921E-04, 0.136030, 0.136030, 5.37843E-04,
R,10, 0.055337, 2.43684E-04, 2.43684E-04, 0.132719, 0.132719, 4.87367E-04,
R,11, 0.052598, 2.20157E-04, 2.20157E-04, 0.129393, 0.129393, 4.40314E-04,
R,12, 0.049941, 1.98477E-04, 1.98477E-04, 0.126083, 0.126083, 3.96954E-04,
R,13, 0.047353, 1.78439E-04, 1.78439E-04, 0.122772, 0.122772, 3.56877E-04,
R,14, 0.044822, 1.59872E-04, 1.59872E-04, 0.119446, 0.119446, 3.19745E-04,
R,15, 0.042372, 1.42872E-04, 1.42872E-04, 0.116135, 0.116135, 2.85744E-04,
R,16, 0.039991, 1.27265E-04, 1.27265E-04, 0.112825, 0.112825, 2.54531E-04,
R,17, 0.037668, 1.12908E-04, 1.12908E-04, 0.109499, 0.109499, 2.25816E-04,
R,18, 0.035424, 9.98607E-05, 9.98607E-05, 0.106188, 0.106188, 1.99721E-04,
R,19, 0.033250, 8.79783E-05, 8.79783E-05, 0.102878, 0.102878, 1.75957E-04,
R,20, 0.031145, 7.71893E-05, 7.71893E-05, 0.099567, 0.099567, 1.54379E-04,
R,21, 0.029118, 6.74691E-05, 6.74691E-05, 0.096273, 0.096273, 1.34938E-04,
R,22, 0.027159, 5.86971E-05, 5.86971E-05, 0.092978, 0.092978, 1.17394E-04,

!!!!!!!!!!!!!!!!!!!!!! Pole Nodes
n, 1,60,-1.676, 60
n, 2,60,-1.176, 60
n, 3,60,-0.784, 60
n, 4,60,-0.392, 60
n, 5,60,0 , 60
n, 6,60,0.5 , 60
n, 7,60,1 , 60
n, 8,60,1.5 , 60
n, 9,60,2 , 60
n,10,60,2.5 , 60
n,11,60,3 , 60
n,12,60,3.5 , 60
n,13,60,4 , 60
n,14,60,4.5 , 60
n,15,60,5 , 60
n,16,60,5.5 , 60
n,17,60,6 , 60
n,18,60,6.5 , 60
n,19,60,7 , 60
n,20,60,7.5 , 60
n,21,60,7.997 , 60
n,22,60,8.494 , 60
n,23,60,8.992 , 60


!!!!!!!!!!!!!!!!!!!!! Pole Elements
type,3
mat,4
*do,i,1,22,1
REAL, i
e,i,i+1
*enddo

!!!!!!!!!!!!!! Gravity Load

F,1 ,FY,0
F,2 ,FY,-486
F,3 ,FY,-367
F,4 ,FY,-356
F,5 ,FY,-344
F,6 ,FY,-461
F,7 ,FY,-442
F,8 ,FY,-423
F,9 ,FY,-405
F,10,FY,-387
F,11,FY,-369
F,12,FY,-352
F,13,FY,-335
F,14,FY,-319
F,15,FY,-303
F,16,FY,-287
F,17,FY,-557
F,18,FY,-258
F,19,FY,-467
F,20,FY,-229
F,21,FY,-215
F,22,FY,-202
F,23,FY,-189

!!!!!!!!!!!!!!!!! out-of-plane Wind load
F,1 ,FZ,0
F,2 ,FZ,0
F,3 ,FZ,0
F,4 ,FZ,0
F,5 ,FZ,-20.00
F,6 ,FZ,-20.00-20.00
F,7 ,FZ,-19.00-19.00
F,8 ,FZ,-19.00-19.00
F,9 ,FZ,-18.00-18.00
F,10,FZ,-18.00-18.00
F,11,FZ,-17.00-18.00
F,12,FZ,-17.00-17.00
F,13,FZ,-17.00-17.00
F,14,FZ,-16.00-16.00
F,15,FZ,-16.00-16.00
F,16,FZ,-15.00-15.00
F,17,FZ,-15.00-89.00
F,18,FZ,-14.00-14.00
F,19,FZ,-14.00-75.00
F,20,FZ,-13.00-14.00
F,21,FZ,-13.00-13.00
F,22,FZ,-13.00-13.00
F,23,FZ,-12.00


!!!!!!!!!!!!!!!!! in-plane Wind load and cable load.
F,1 ,FX,0
F,2 ,FX,0
F,3 ,FX,0
F,4 ,FX,0
F,5 ,FX,35.00
F,6 ,FX,34.00+34.00
F,7 ,FX,33.00+33.00
F,8 ,FX,32.00+33.00
F,9 ,FX,32.00+32.00
F,10,FX,31.00+31.00
F,11,FX,30.00+30.00
F,12,FX,29.00+30.00
F,13,FX,29.00+29.00
F,14,FX,28.00+28.00
F,15,FX,27.00+27.00
F,16,FX,26.00+27.00
F,17,FX,26.00+6148.00 !!!!!!! very large cable load
F,18,FX,25.00+25.00
F,19,FX,24.00+7913.00 !!!!!!! very large cable load
F,20,FX,23.00+24.00
F,21,FX,23.00+23.00
F,22,FX,22.00+22.00
F,23,FX,21.00



!!!!!!!!!!!!!!!!!!!!!! boundary conditions, 5 nodes are below earth surfeces.
d,5,ux
d,5,uz

d,4,ux
d,4,uz

d,3,ux
d,3,uz

d,2,ux
d,2,uz

d,1,uz
d,1,ux
d,1,uy




/solu
antype,0

outres,all,all
nlgeom,on
nropt,full,,on
SOLCONTROL, on
sstif,on
kbc,0
allsel,all

time,10,,,
NSUBST, 25,
DELTIM, 1, 1, 1
allsel,all
solve

finish


/post1
ETABLE,FN1,SMISC, 1 !!!!! axial forces
ETABLE,FN2,SMISC, 14 !!!!! axial forces
ETABLE,MX1,SMISC, 5 !!!!! X-moments
ETABLE,MX2,SMISC, 11 !!!!! X-moments
ETABLE,MZ1,SMISC, 6 !!!!! Z-moments
ETABLE,MZ2,SMISC, 12 !!!!! Z-moments
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