Thanks for that. Yes i have also made a number of attempts to try and resolve this, initially i considered the reinforcement was not connected to the concrete, as i used the new ANSYS method for defineing a line element. However i have attached a shell to the underside of the beam to represent equivalent reinforcement and it still failed at first crack. Similarly i also tried an older method using LINK180 elements linked to the concrete with constraint equations, and even after ensuring their nodes were coincidentit did not work.
I don't have permission to release the wilson study, but i appreciate your help as no one else has been forthcoming. I am trying to avoid moving to SOLID65 as i previously had to abandon the Menetrey-William model when i could not validate the results.

I'm going to look again at the microplane setup and parameters. Do you think i have set it up correctly

Thanks again for your help.