Topic: Confinement

So I modeled FRP as discrete reinforcement bars spaced at 2.5cm, FRP was used for confinement purposes in the experiment. my question is does ATENA take into account the increase in bond strength of bars and the increase in concrete compressive strength in the confined region ?

Re: Confinement

Dear Njoukhadar9,
regarding the confinement in concrete: yes, please see ATENA Troubleshooting, 2.2.7 How to include confinement in the analysis? for more information.

Regarding the bond: in the current version, the bond law can not take lateral stresses into account, i.e., you have to choose the Confined or Unconfined option when generating the function for the bond law.

If the friction contribution for bonding the FRP is expected to be important (and differ during the analysis or/and along the connection surface), you may wish to consider some of the more advanced options for representing the strengthening from Troubleshooting, 2.2.2 How to model carbon or glass fibre wrap (CFRP, GFRP) strengthening in ATENA?

Regards.

Re: Confinement

I see, Thanks for your prompt reply.

So If I want to set a larger bond strength to a certain segment of the bar (Not along the whole length) how can I do so?
Thanks again for your help.

Re: Confinement

Dear njoukhadar9,
there is currently no direct way to do this. However, as already discussed, if you expect this to be critical, you can use a more advanced (=more complicated) way of representing the strengthening, connecting to the concrete through an Interface (with Contact elements).

Regards.

Re: Confinement

I am interested in this advanced technique in order to increase bond. I'm trying to use the interface (contact element) but it only allows me to apply it to a surface between two concrete macro elements and not between a reinforcement bar and concrete.
Could you please explain further on how to model that?
Thank you.

Re: Confinement

Dear njoukhadar9,
1. in 3-dimensional models, the Interface material only makes sense to be assigned to Contact Volumes (in 2-d models, Contact Surfaces). For more information, see the ATENA-GiD User's Manual, 5.3.6 Interface Material.

2. Please also see again Troubleshooting, 2.2.2 How to model carbon or glass fibre wrap (CFRP, GFRP) strengthening in ATENA? for options allowing to employ Interface elements between the concrete and the strengthening - I specifically mean the approach with Shell elements (embedding your bars).
I also suggest to look at the examples described in the ATENA Science Strengthening Tutorial (both the document and the models are included in ATENA installation, and the PDF is also available for separate download from our web).

Regards.

7 (edited by njoukhadar9 2019-01-17 20:23:58)

Re: Confinement

Hello,
I'm sorry I don't think I made my question clear.
I would like to increase the bond strength of rebars (steel) embedded in concrete. I would like to have two different bond models along the bar.
Is there a way to fix certain nodes of the reinforcement with that of the surrounding concrete to enable perfect connection? (only to a segment of the bar and not the whole length).
Since the software does not support this type of input, is there a way to work around it?
Regards

Re: Confinement

Dear njoukhadar9,
I. if you seek help with your particular model, you can follow Troubleshooting, 2.1.1 to send us your model along with information about what you are modelling (sketches illustrating the geometry, loads and supports, questions to be answered through the analysis, what is the difference between the bond laws, which should act on 2 segments of a single bar, ...).
If you explain us your targets, we can probably help you find a way.

II. Ad blocking bond slip for some nodes: please see the option "no slip at the beginning / end".

III. If you have ribbed bars, you typically do not need any bond law (provided your mesh is fine enough), as the bond damage is reasonably captured by cracking in the concrete (and confinement works in the concrete...).

Regards.