For retrofitting and strengthening purposes of Rc structure, using FRP is one of the common methods. However, the simulation of interface of concrete and FRP is very critical. I would like to know whether the tie constraints accurate enough to capture the interface behavior of FRP and concrete? or it is necessary to use the cohesive element or the other methods? it would be great if you share your information regarding the damage properties in FRP as well.
Dear All , see to the attached file for Cohesive Interaction and please give me your feedback & discussions.
in addition to Soheil, i can say that:
1. modeling contact: if you use rough contact this will act similar to tie constraint. that is no separation between the matrix and reinforcement
2. modeling contact: if you use contact with some shear stress threshold, fiber will move after the condition met. and of course you can give friction coefficient
3. CZM, VCCT: i think CZM should fit your application, but you need some constants of CZM. any other fracture mechanics approach can also be used
4. you can model interphase as different material and apply a material failure to that region
regards
Modelling interfaces is complex and can be computationally expensive. "Appropriate" models can only be developed if one knows 'exactly' what they need. For example, if only ultimate (peak) loads are required, much simplification can be made in the model; else if unloading characteristics are essential, traction-slip relationship will be required. If you wish to examine the cyclic load characteristics, then much more careful detailing will be necessary. Please read Computers and Structures 144 (2014) 23–39 - you may get an idea of interfaces. This method work well if you are not very keen on large slips. For large slips a surface contact representation as in Engineering Structures, 49, pp. 615-627 would be useful.
Thanks a lot for your answers. Actually, I would like to know the difference in results when using Tie or interaction(rough, penalty,...). If failure load is required, then how much the interface modelling between FRP and concrete( using Tie ,rough, tangential...) can make difference in results. I also would like to know about the fiber reinforced composite damage(Hashin). How can we define the damage parameters.
I have so far used tie between FRP and concrete and regenerated results of some quite good papers. In my idea, tie is enough.
the best way to model interaction between FRP & concrete is Cohesive surface interaction
Ibrahim Metwally, Could you please let us know how to define the parameters, Knn, Kss, Ktt and others,? What equations or models you have used to define the parameters.?
Dear All , see to the attached file for Cohesive Interaction and please give me your feedback & discussions.
hi,Ibrahim.I have read your attached file.It help me understand cohesive element more deeply.
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