Cervenka Consulting Forums — FRP model

Re: FRP model

null@example.com (dpryl) — Tue, 27 Apr 2010 07:59:12 +0000

You can define any bilinear w/hardening material using a multilinear law - in that case, the only difference is if you wish to directly define the stress-strain relation points, or if you prefer to give the elastic modulus, yield stress, hardening modulus, and limit strain.
Of course, the opposite is not possible - not all multilinear laws are bilin.w/hardening.

To define a new bond material, go to Materials - Add - Bond for Reinforcement.

Re: FRP model

null@example.com (irene) — Tue, 27 Apr 2010 02:52:20 +0000

dpryl wrote:

Dear Irene,
1. yes, you can use this modelling in ATENA 2D.
It depends if you have the material data for the fibres or for the combined material od the CFRP band (fibres+epoxy) - if you have the values for the fibres, and know the number of fibres per cm, you can enter using the "dimater + number of bars" calculator. Otherwise, just enter the cross section area. Please pay attention not to enter the total cross section area (glue+fibres) with the fibre material (or vice versa).
2. above all, you need to define the stress - strain response of the material. For CF, you need to select the bilinear with hardening or multilinear type
(the other options do not feature any limit strain). Then, set the values according to the test or manufacturer data.
For bond, you define a material "Bond for Reinforcement" and the assign it in the properties of the discrete reinforcement bar.

Dear Sir,
First of all thank you for your replies.
By referring to point 2, if i am to use bilinear with hardening or multinear, any difference in term of results between the two ?
Any examples available in the tutorial with the usage of CFRP? If there isn't any, it would be grateful if Sir can show us some examples on CFRP as I see quite many people in this forum are doubt with questions related to FRP/wrapping etc.

As for the "Bond of Reinforcement" i have read through the atena 2d user manual at section 4.4.3.6. But I am having problem from where do i start to get to the "bond for reinforcement box" as shown in fig-4-14 in the manual. Any examples in the tutorial?

Re: FRP model

null@example.com (dpryl) — Mon, 26 Apr 2010 11:29:06 +0000

Dear Irene,

1. yes, you can use this modelling in ATENA 2D.

It depends if you have the material data for the fibres or for the combined material od the CFRP band (fibres+epoxy) - if you have the values for the fibres, and know the number of fibres per cm, you can enter using the "dimater + number of bars" calculator. Otherwise, just enter the cross section area. Please pay attention not to enter the total cross section area (glue+fibres) with the fibre material (or vice versa).

2. above all, you need to define the stress - strain response of the material. For CF, you need to select the bilinear with hardening or multilinear type
(the other options do not feature any limit strain). Then, set the values according to the test or manufacturer data.

For bond, you define a material "Bond for Reinforcement" and the assign it in the properties of the discrete reinforcement bar.

Re: FRP model

null@example.com (irene) — Mon, 26 Apr 2010 03:59:18 +0000

JanCervenka wrote:

Hello,
FRP strengthening can be modelled by ATENA. There are several methods how to do it.
(1) You can use the reinforcement option. You have the possibility to define an arbitratry stress-strain relationship that corresponds to your FRP material. Also in this case, it is possible to define some bond properties between FRP and concrete.
(2) Second option is to model the FRP strengthening by a thin layer or thin shell elements, where again fibres can be modelled
as special reinforcing layers inside an epoxy material or whatever is used.
If you need a more specific answer we would need to know more details about your structure. You contact us directly
at cervenka at cervenka.cz.
With best regards
Jan Cervenka

Hello sir.

Im using ATENA 2D demo version. I am modeling rc beams using CFRP plates. I am using method NO.1 as u mentioned; CFRP as reinforcement option. Is the explanation in (1) above applies to ATENA 2D? Since CFRP is also under reinforcement group. Similar key-in as for steel reinforcement. May I know which part differentiate the steel and the CFRP while inputing the values? E.g: steel we know the no. of bars and cross section. However, CFRP is a plate. My question is how a straight line representing CFRP and how to define the cross section area for it? Can I just input the actual cross section area of the CFRP plates? I ignored the bar dia. and the no. of bars. Is this the correct way of doing it?

2. Since CFRP is defined as reinforcement, In Material >Add> Reinforcement>Next>Basic>Linear> Miscellaneous>
Under Miscellaneous, to differentiate between steel reinforcement and cfrp, the only input that we can change is in "Specific material weight ratio" and "Coefficient of Thermal Expansion ALPHA"? Any other steps which I miss to define CFRP? Such as the bond between CFRP and concrete?

TQ very much.

Re: FRP model

null@example.com (dpryl) — Fri, 20 Nov 2009 08:24:31 +0000

In 3D, we recommend using smeared reinforcement layer(s) in shell elements, see How to model carbon or glass fibre wrap (CFRP, GFRP) strengthening in ATENA? at http://www.cervenka.cz/faq

In 2D, the depth is averaged-out anyway, which means only the total crossection area of the reinforcement important, and it makes no difference if it is defined as a single bar or 10 bars with 1/10 the total area or if it could be put in as a [full depth] layer of the corresponding thickness.

Re: FRP model

null@example.com (donaldc) — Thu, 19 Nov 2009 10:55:08 +0000

Thanks for the feedback. If I were to do it in 3D, what would be the best material type to use?

I notice you refer to "reinforcement bars." However, the FRP reinforcement that I am trying to model is layers of FRP bonded to the base of the concrete beam that are the full width of the beam, and thus they are not "bars", but more like "plates." Is it still ok, then, to use the reinforcement material?

If this is true, then can you brifely explain why the cross section is irrelevant?

Thanks for your time!

Re: FRP model

null@example.com (dpryl) — Wed, 18 Nov 2009 09:44:27 +0000

Dear donaldc, in 2D, the crossection shape of reinforcement bars is completely irrelevant (except for the automatically offered perimeter length when a bond model is applied).

Interface material can only be assigned to contacts (GAP elements). This may only be of use if you model the FRP+glue layer as a separate macroelement and wish to capture delamination (separation of the FRP layer from the concrete). This modelling would mean more work and much more elements compared to the reinforcement bar approach. Therefore, I recommend to use the discrete bars for the FRP strengthening in ATENA 2D.

Re: FRP model

null@example.com (donaldc) — Tue, 17 Nov 2009 13:40:22 +0000

I'm also trying to model FRP in Atena (2d), but I am unsure as to what type of material to model the FRP as. As Biscaia said, I'm reluctant to model the material as "reinforcement" as it has a rectangular cross section. I've looked at the "Interface" material type, however this includes such parameters as Normal and tangential stiffness, as well as cohesion which aren't relevant.

Any help would be appreciated...?

Re: FRP model

null@example.com (labanlie) — Wed, 12 Aug 2009 05:11:21 +0000

dear HB and Mr. Cervenka
Thank you so much for your suggestions. I've tried it and it worked. I'm going to analyze it right now. I hope I can learn more from you if you don't mind. Thanks again.

Nico

Re: FRP model

null@example.com (Biscaia) — Wed, 05 Aug 2009 11:59:05 +0000

Yes you can Iabanlie.
I'm modelling the interface between GFRP and concrete and I allready used the two suggestions proposed by Mr. Cervenka.
The first option it is not a very good one if the section of the reinforcement isnÂ´t circular. If you donÂ´t want to consider a perfect connection between the two elements you can define a bond-slip law.
In another hand, I think that the second option is better if you are modelling a non circular section and, again, if you donÂ´t want to consider a perfect connection, here you must define the properties of the interface elements based on Mohr-Coulumb rupture law. Here, the definition of this criteria may be more dificult... but if you tell me more about your model I may suggest you some values... well, you allways may suppose perfect connection...

Hope beeing helpfull,
HB

Re: FRP model

null@example.com (JanCervenka) — Thu, 30 Jul 2009 08:52:28 +0000

Hello,

FRP strengthening can be modelled by ATENA. There are several methods how to do it.

(1) You can use the reinforcement option. You have the possibility to define an arbitratry stress-strain relationship that corresponds to your FRP material. Also in this case, it is possible to define some bond properties between FRP and concrete.

(2) Second option is to model the FRP strengthening by a thin layer or thin shell elements, where again fibres can be modelled
as special reinforcing layers inside an epoxy material or whatever is used.

If you need a more specific answer we would need to know more details about your structure. You contact us directly
at cervenka at cervenka.cz.

With best regards

Jan Cervenka

FRP model

null@example.com (labanlie) — Thu, 30 Jul 2009 06:46:39 +0000

Hi, I would like to know if we can make a model for FRP concrete with ATENA. Especially for axisymmetric model. How do we make a model like it? thanks.