Dear Sir,
I am modelling the shear behavior of beams reinforced GFRP without stirrups in ATENA 2D. The published data adapted from several reseachers. I see that in generally, post-cracking stiffness of beams falls below this from data. In addition, deflection at mid-span is always much higher than that obtained from data (double value!). So, how to deal with this problem? and are there parameters to adjust it?     
Thank you so much!