Learning Forum

[king79]

Hi,

I modelled a solid cylinder surrounded by soil and would like to apply a bending moment at the top and check the nodal rotations. Can this be achieved in Ls-Prepost?

I am trying to capture the response of a pile foundation subjected bending moment. This analysis has been performed in Abaqus FEA using rigid body constraint but not sure if a similar approach can be achieved in Ls-Prepost. Please can you offer any assistance.

Thank you

[Ram Gopisetti]

you can apply moment via boundry_precribed_motion and setting the DOF=respective to axis.VAD =2 and define the rate of twist(angle) as curve.
bending moment is the output of an beam type via DISBOUT.
Cheers, Ram

[king79]

thanks for the feedback. I also want to extract the rotation at the the top of the pile. Is there a way to do so in Ls-prepost. Results for translations are available but no output for rotation.

[Ram Gopisetti]

perhaps an NDV fringe might help in this case, and you can also use vector plot to visualize the rotation as displacement criteria.
Cheers, Ram

[Andreas Koutras]

of course nodal rotations cannot be applied to solid elements because solid elements do not have rotational DOFs. Your approach in Abaqus was correct. You can do the same in LS-DYNA by using *CONTSTRAINED_NODAL_RIGID_BODY to impose a rigid body constraint to the nodes at the top face of the pile. Then you can apply moment or rotation to the CNRB through *LOAD_RIGID_BODY or *BOUNDARY_PRESCRIBED_MOTION_RIGID respectively. The rotation at a node at the top of the pile can be extracted through *DATABASE_NODOUT.

[king79]

Hi I tried the suggestion and ran the analysis, but I got an error message indicating that LOAD_RIGID_BODY requires at MAT_rigid part. When I assigned a Mat_rigid material to the pile then ran the analysis, I got an error message indicating that Mat_rigid and LOAD_RIGID_BODY cannot be used together.

[king79]

Actually, the error message was related to Constrained_Nodal_Rigid_Boday and Load_Rigid_Body not permitted in the same analysis. Not sure why.

[Andreas Koutras]

*LOAD_RIGID_BODY can be applied to a *CNRB. I suggest you try it in a new test model.
Best regards

[king79]

How do I apply a *LOAD_RIGID_BODY to *CNRB when the part ID does not show up in the drop-down menu?

[Andreas Koutras]

That's a known issue of LSPP. Please enter the *CNRB part id manually, thanks.

[king79]

I followed the suggestion and still get an error message:

[Andreas Koutras]

Try the following example.

$# LS-DYNA Keyword file created by LS-PrePost(R) V4.9 (Beta) - 20Sep2021
$# Created on Sep-22-2021 (03:12:47)
*KEYWORD
*TITLE
$#title
LS-DYNA keyword deck by LS-PrePost
*CONTROL_TERMINATION
$#endtimendcycdtminendengendmasnosol
0.099900.00.01.000000E80
*DATABASE_BNDOUT
$#dtbinarylcurioopt
1.00000E-4001
*DATABASE_SECFORC
$#dtbinarylcurioopt
1.00000E-4001
*DATABASE_BINARY_D3PLOT
$#dtlcdtbeamnpltcpsetid
1.00000E-40000
$#iooptratecutoffwindowtypepset
000
*DATABASE_EXTENT_BINARY
$#neiphneipsmaxintstrflgsigflgepsflgrltflgengflg
00301111
$#cmpflgieverpbeamipdcompshgestsszn3thdtialemat
00011121
$# nintsldpkp_sensclphydromssclthermintoutnodout
001.0000
$#dtdtrespltneipbquadsldcubslddeleres
00000
*DATABASE_CROSS_SECTION_PLANE_ID
$#csidtitle
1
$#psidxctyctzctxchychzchradius
1-10.0-10.025.0-10.0-10.030.00.0
$#xhevyhevzhevlenllenmiditype
30.0-10.025.040.040.012
*SET_PART_LIST
$#sidda1da2da3da4solver
10.00.00.00.0MECH
$#pid1pid2pid3pid4pid5pid6pid7pid8
10000000
*BOUNDARY_SPC_SET
$#nsidciddofxdofydofzdofrxdofrydofrz
10001000
*SET_NODE_LIST_TITLE
Base
$#sidda1da2da3da4solver
10.00.00.00.0MECH
$#nid1nid2nid3nid4nid5nid6nid7nid8
123410111920
270000000
*LOAD_RIGID_BODY
$#piddoflcidsfcidm1m2m3
25110000.00000
*PART
$#title

$#pidsecidmideosidhgidgravadpopttmid
11100000
*SECTION_SOLID
$#secidelformaetunusedunusedunusedcohoffgaskeit
1100.00.0
*MAT_ELASTIC_TITLE
Steel ton, mm, sec
$#midroeprdadbnot used
17.80000E-9210000.00.30.00.00.0
*DEFINE_COORDINATE_NODES
$#cidn1n2n3flagdir
13334361X
*DEFINE_CURVE
$#lcidsidrsfasfooffaoffodattyplcint
101.01.00.00.000
$#a1o1
0.00.0
0.110.0
*SET_NODE_LIST_TITLE
Top
$#sidda1da2da3da4solver
20.00.00.00.0MECH
$#nid1nid2nid3nid4nid5nid6nid7nid8
101102103104110111119120
1270000000
*CONSTRAINED_NODAL_RIGID_BODY
$#pidcidnsidpnodeiprtdrflagrrflag
2020000
*ELEMENT_SOLID
$#eidpidn1n2n3n4n5n6n7n8
1112345678
21210113614157
31431920872324
4131127197153123
513334353637383940
613442433538464739
713635515240395556
813543595139476355
91567833343536
10161415734424335
11187232436355152
121715312335435951
13137383940101102103104
14138464739102110111103
15140395556104103119120
16139476355103111127119
*NODE
$#nidxyztcrc
10.00.00.000
210.00.00.000
310.010.00.000
40.010.00.000
50.00.010.000
610.00.010.000
710.010.010.000
80.010.010.000
1020.00.00.000
1120.010.00.000
1420.00.010.000
1520.010.010.000
1910.020.00.000
200.020.00.000
2310.020.010.000
240.020.010.000
2720.020.00.000
3120.020.010.000
330.00.020.000
3410.00.020.000
3510.010.020.000
360.010.020.000
370.00.030.000
3810.00.030.000
3910.010.030.000
400.010.030.000
4220.00.020.000
4320.010.020.000
4620.00.030.000
4720.010.030.000
5110.020.020.000
520.020.020.000
5510.020.030.000
560.020.030.000
5920.020.020.000
6320.020.030.000
1010.00.040.000
10210.00.040.000
10310.010.040.000
1040.010.040.000
11020.00.040.000
11120.010.040.000
11910.020.040.000
1200.020.040.000
12720.020.040.000
*END

[king79]

Is there a link to the file for this example on your website? If not, can you explain how to input the command script in Ls-Prepost? Thanks