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#1 2019-03-31 05:02:22

nirmaljoshi
Member
From: Japan
Registered: 2018-10-12
Posts: 152

sudden drops in Mazar model

Hi,
While calculating force displacement curve for a beam, I get sudden drop near the peak values (check the image file attached). Why is it so? I expected smooth transitions. I tried changing the increment but its not working. What am I doing wrong? Is there any alternative method for the analysis?

The parameters for mazar model seems fine.

Last edited by nirmaljoshi (2019-03-31 05:02:55)


Attachments:
mazardrop.zip, Size: 11.58 KiB, Downloads: 68

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#2 2019-04-01 17:50:50

jlf
Member
Registered: 2007-11-22
Posts: 239

Re: sudden drops in Mazar model

Hi,

You use DKT in your model. I am not sure it's a good choice. DKT is for 3D dimensions study.
You use also 2D_BARRE

==> Perhaps in your case it's D_PLAN or C_PLAN

model = AFFE_MODELE(
   AFFE=(
      _F(GROUP_MA=('Group_concrete', ), MODELISATION=('C_PLAN' or 'D_PLAN', ), PHENOMENE='MECANIQUE'),
      _F(GROUP_MA=('Group_rebar', ), MODELISATION=('2D_BARRE', ), PHENOMENE='MECANIQUE'),),
MAILLAGE=mesh)


JLF

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#3 2019-04-02 04:20:21

nirmaljoshi
Member
From: Japan
Registered: 2018-10-12
Posts: 152

Re: sudden drops in Mazar model

CPLAN or DPLAN has no option to specify thickness ,so i used DKT.

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#4 2019-04-02 06:25:58

jlf
Member
Registered: 2007-11-22
Posts: 239

Re: sudden drops in Mazar model

Hi,

C_PLAN or D_PLAN as a [1]unit thickness.
If you use DKT, your problem in not 2D but 3D. You can't use 2D_BARRE for 3D problems. 

Take a look on C_PLAN or D_PLAN approach.

JLF

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#5 2019-04-02 09:24:15

nirmaljoshi
Member
From: Japan
Registered: 2018-10-12
Posts: 152

Re: sudden drops in Mazar model

Thank you for your comments. In your opinion, what elements should i use?
I have already done full 3d model, but it takes a lot of computation time, hence I am downgrading to 2D model.

I need to simulate the beam with given thickness and steels.

Last edited by nirmaljoshi (2019-04-02 09:24:32)

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#6 2019-04-02 12:43:04

jlf
Member
Registered: 2007-11-22
Posts: 239

Re: sudden drops in Mazar model

Hi,

The only modification is in AFFE_MODELE replace DKT by  C_PLAN.
Code_Aster know you are in 2D (mesh in plane XY, z=0) and affect the goods elements : QUA4, TR3, QUA8, TRI6, ...

The thickness is [1] unit. For concrete is fine, for steel you must give the section by [1]unit.

For example for steel :  your unit is [m]
If you have 5*(rebar diam= 20mm) for 1m thickness. You give Section=5*[Pi*(20E-3)^2/4] for your steel.

To be sure of your data, make a test with elastic behavior for steel and concrete. It's easy to compute the homogeneous inertial for a beam of 1m thickness, the neutral position and the elastic displacement.

JLF

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