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#1 2010-07-27 09:30:43

Johannes_ACKVA
Member
From: Ingenieurbüro für Mechanik, DE
Registered: 2009-11-04
Posts: 737
Website

fiber reinforced concrete, which material law ?

Bonjour,
I am ask to test Code-Aster for the calculation of a fiber-reinforced concrete beam, having the sigma-epsilon-curve as attached. Moreover, the concrete beam is reinforced with rebars. I have to model it with volume elements (HEX8) (because later geometric details must be added). 3 Tests should be calculated: compression, traction and bending. My question: which is the most suitable material law to define in DEFI_MATERIAU for this problem? Personally, I am unexperienced with concrete, but I know continuum mechanics.

Thank You for an answer, Merci pour un reponse
Regards, Johannes Ackva

______________________________________________________________________
Ingenieurbüro für Mechanik
Dr.-Ing. Johannes Ackva
Markgrafenstr. 21
D 91717 Wassertrüdingen

next Introduction Course  to Salome-Meca : September 21th - 25th, 2010  in Wassertrüdingen


Attachments:
MaterialLaw_Matgesetz_ReinforcedConcrete.jpg, Size: 89.14 KiB, Downloads: 457

Ingenieurbüro für Mechanik
D 91717 Wassertrüdingen / Germany

www.code-aster.de                                                Training & Support for NASTRAN and CODE-ASTER

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#2 2010-07-29 11:17:50

Johannes_ACKVA
Member
From: Ingenieurbüro für Mechanik, DE
Registered: 2009-11-04
Posts: 737
Website

Re: fiber reinforced concrete, which material law ?

Bonjour,
this is a test model, consisting of a 1-HEXA8-element of cubic 1x1x1-shape. A Traction and a Compression calc can be made. Any Load is applied on the top face. The bottom face is fixed (but free to move lateraly, for lateral contraction).

The .comm-file contains 3 material modelisations:
- Simple Drucker-Prager, parameters adapted for traction load-displ-curve  (BetonTra=DEFI_MATERIAU(..DRUCK_PRAGER
- Simple Drucker-Prager, parameters adapted for compress load-displ-curve  (BetonCom=DEFI_MATERIAU(..DRUCK_PRAGER
- Double Drucker-Prager, parameters adapted for complete curve (BetDoubl=DEFI_MATERIAU(..BETON_DOUBLE_DP..

The first 2 mat modelisations work fine.

The third mat modelisation is a problem. The attached archive contains 4 calculations done with it.

4 enforced displacement load cases (LC) are calculated:

1)
DispTrac=AFFE_CHAR_MECA(MODELE=Modele,
                        DDL_IMPO=_F(GROUP_MA='TOPFACE',
                                    DZ=0.000375,),);
results in:     test_3D_drucker_prager__displaced-traction-until-elastic-limit.*

2)
DispComp=AFFE_CHAR_MECA(MODELE=Modele,
                        DDL_IMPO=_F(GROUP_MA='TOPFACE',
                                    DZ=-0.00275,),);
results in:     test_3D_drucker_prager__displaced-compressive-until-elastic-limit.*

3)
DispTrac=AFFE_CHAR_MECA(MODELE=Modele,
                        DDL_IMPO=_F(GROUP_MA='TOPFACE',
                                    DZ=0.0004,),);
results in:     test_3D_drucker_prager__displaced-traction-over-elastic-limit.*

4)
DispComp=AFFE_CHAR_MECA(MODELE=Modele,
                        DDL_IMPO=_F(GROUP_MA='TOPFACE',
                                    DZ=-0.004,),);
results in:     test_3D_drucker_prager__displaced-compressive-over-elastic-limit.*

As result always the load displ curve is considered, given by the fonctions
FDisp=RECU_FONCTION(... and
FTopForc=RECU_FONCTION(....

Result of LC 1)  is OK

Result of LC 2)  is bilinear. What is wrong in the Material definition?

Result of LC 3) : works well until elastic limit, then fails. What is the problem?

Result of LC 4) : until elastic limit as LC 2). Over elastic limit there is no negativ inclination (negative pente)

I regret, the results are only in form of 2 columns of number, not diagrams. But xmgrace does not work in my installation, i use the open-office-spreadsheet program instead.

It would be very nice to get help to adapt the Double Drucker-Prager to the curve attached to my previous post.

mit freundlichen Grüßen,

Johannes Ackva

______________________________________________________________________
Ingenieurbüro für Mechanik
Dr.-Ing. Johannes Ackva
Markgrafenstr. 21
D 91717 Wassertrüdingen

next Introduction Course  to Salome-Meca : September 21th - 25th, 2010  in Wassertrüdingen


Attachments:
Test_3D_DruckerPrager.zip, Size: 99.24 KiB, Downloads: 377

Ingenieurbüro für Mechanik
D 91717 Wassertrüdingen / Germany

www.code-aster.de                                                Training & Support for NASTRAN and CODE-ASTER

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#3 2010-07-29 13:15:29

smp
Member
From: EDF R&D - Clamart
Registered: 2007-11-27
Posts: 2

Re: fiber reinforced concrete, which material law ?

Hi Johannes,

I think one of your problem is due to your mesh size. Because of the regularization of the model, you have a criterion to respect for the mesh size. The formulas are in the doc R. For tension you must have  : lc < (E* Gt) /(ft)^2. With your material parameters, I find 1.77mm !
Could you change your mesh and then see if results are better ?

S.

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#4 2010-08-02 16:57:15

Johannes_ACKVA
Member
From: Ingenieurbüro für Mechanik, DE
Registered: 2009-11-04
Posts: 737
Website

Re: fiber reinforced concrete, which material law ?

Thank You S., for Your hint. I will continue later to work on this Double Drucker-Prager model (DEFI_MATERIAU(..BETON_DOUBLE_DP..), because there rise some difficulties with the more simpel model DEFI_MATERIAU(..DRUCK_PRAGER.. which I will explain in a new thread.

Johannes Ackva

______________________________________________________________________
Ingenieurbüro für Mechanik
Dr.-Ing. Johannes Ackva
Markgrafenstr. 21
D 91717 Wassertrüdingen

*** Next Introduction Course  to Salome-Meca : September 21th - 25th, 2010  in Wassertrüdingen ***


Ingenieurbüro für Mechanik
D 91717 Wassertrüdingen / Germany

www.code-aster.de                                                Training & Support for NASTRAN and CODE-ASTER

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