Cervenka Consulting Forums — Defining interface bond.model

Re: Defining interface bond.model

2019-11-13T08:30:50Z

Ahmed,

I strictly advice you not to model epoxy as a separate macroelement. Just model FRP wrap directly on the surface of concrete and define bond law.

Bond strength can be calculated acc to MC2010, my calculation is available by the link: https://drive.google.com/open?id=1Iekkl … hiR3SzXYAD

Regarding bond law. Actually, I took standard law for regular bars substituting ultimate strength of bar bond by the ultimate strength from calculation above. However, it is not very good I think. Maybe you can find better law in ACI 447 which I uploaded by the link as well.

Re: Defining interface bond.model

2019-11-12T18:44:39Z

Hi pavlo

Thanks for u reply, I’ll read the ACI guide and if poosible provide me with the calculations because I already define the fibers as a discrete bars with the area and change the bond model from perfect to another one and also define the epoxy as a standard macro element, but when I make the run there is error. So I’m waiting your reply asap please.

Thanks

Re: Defining interface bond.model

2019-11-12T15:49:34Z

Hi Ahmed,
I don't recommend using Gap for your case. Just define sectional area in area and length of contact across the FRP wrap length.
Regarding the strength... it is quite complicated topic to reply in a message. When I faced the same problem I used formulas from ModelCode2010. Also I would recommend to review ACI 447 for FRP modeling. There are many references to Atena as well.
I will send you my calculations of bond strength for FRP as per MC2010

Re: Defining interface bond.model

2019-11-12T14:53:47Z

Dear ahmed, without seeing what you are modelling, it does not make much sense to guess + base any recommendations on possibly wrong assumptions. I suggest to follow Point 3, i.e.:

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If you seek help with your particular modelling, please follow Troubleshooting, 2.1.1 to send us your model along with information about what you are modelling (sketches/photos + explanation). Do not forget to include the information you have about the materials.
***

Regards.

Re: Defining interface bond.model

2019-11-11T18:59:22Z

Dear dpryl

Thanks for u reply, however I want to verify I do the correct steps,

1- defining the Fibers as a discrete bars with the bond-slip law that suits that composite using Bond for reinforcement.

2- defining epoxy as a macrolement with thickness 1.5mm for one of carbon fiber.

For modelling my strengthened beam, these steps enough or I need to create the interface using GAP method or GAP method used with shell/plate part?????

Please help me to be sure cause I read troubleshooting and that What I concluded from it.

Thanks

Re: Defining interface bond.model

2019-11-11T11:32:56Z

Dear ahmed,
1. if your bar is not pf circular cross-section, define the cross-sectional area directly, without using the Calculator option (which only supports circular bars).

2. It sounds you are mixing the ways of modelling from Troubleshooting, 2.2.2 How to model carbon or glass fibre wrap (CFRP, GFRP) strengthening in ATENA?

For general introduction in using Interface elements, please see ATENA Troubleshooting, 2.2.14 I have problems when using the Interface (GAP) material on contacts and ATENA-GiD User's, 5.3.6 Interface Material.

3. If you seek help with your particular modelling, please follow Troubleshooting, 2.1.1 to send us your model along with information about what you are modelling (sketches/photos + explanation). Do not forget to include the information you have about the materials.

Regards.

Defining interface bond.model

2019-11-11T06:23:19Z

I’m using frp as external reinforcement for RC beam. According thé troubleshoot, I defined fibers as a discrete bars, but my first question:

1- The part of diameter bar: I can’t define cause the section of fiber not circle (about 5 mm width and 0.13 mm thick), so what the value in that case???

2- i already did the bond law slip that suits the frp materials and when I defined the cfrp discrete bars I changed the bond from perfect connection to the bond model that I did. However, the step for defining 3D interface between epoxy and concrete, the value of tensile strength??? This for epoxy or concrete????? Also cohesion and friction , the value of these points, for which of them????

I’m looking forward u reply

Thanks