Hi Fatima,

In TNO Diana  you can model the stirrups as embedded or as discreet. The easiest way is to model them as embedded . After you create the mesh for your 3D beam, create the stirrups as lines and just mesh them as 1D mesh with 1 element. The processor will include the stiffness of the stirrups  to each element that is being crossed by it. and it reverse the process at the end of the analysis.

I hope that it was clear enough. I wiss you luck.

Best regards,

Dan