Gentlemen,

I am trying to model a uniaxial compression test of a reinforced concrete short column wrapped with a CFRP sheet (not laminate). The column has a circular geometry. At a first attempt, I modelled a RC column and compared with some experimental results. In this particular, the model was very accurate with the experiments. The problem that I have lies on the confinement effect of the RC column due to the CFRP sheet because for higher loads (closer to rupture) concrete behaves differently and seems to improve its strengh. Therefore, I tryed two alternative models: (i) using the macroelement with discrete bar reinforcements which are the CFRP fibres and, in this case, the macroelement used has poor mechanical characteristics; and (ii) same in i) but the CFRP fibres were modeled using the smeared option available in ATENA and the macroelement has also poor mechanical characteristics. In this second case, I also tryed different fibre orientations (0º and 90º) only to understand if there are significant differences. However, with the fibre orientated with the same direction of the applied load (0º) and with the fiber orientated perpendicularly to the applied load (90º) no significant differences were observed which cannot be possible because this does not correspond to the reality. Of course, in any case the numerical results is not similar to the experiment ones.
I also thought that the problem could be other more complicated to solve, i.e. the problem may be in the model used in ATENA (3D nonlinear cementitious 2) that cannot reproduce the confinement effect on the RC structural elements. If so, I will not be able to model RC columns wrapped with CFRP (or other) sheets in ATENA or am I wrong? Right now, I am crossing my fingers hoping that you will say that I am wrong and also I am expecting that you may have a better and wiser suggestion for my RC column models.
Hope that I may hear from you very soon and a special greeting to Dobromil Pryl,
With best regards,
Hugo Biscaia
ATENA Licence: 247