Dear Sir,

Now I am trying to modeling a pull-out test, in which the steel bar is prestressed by pretension. From your earlier answers, I find you suggested that using cooling to simulate the prestress due to pretension because initial strain (which is the accurate way) doesn't work for reinforcement. So, my questions are:

1) Is this cooling really equivalent to initial strain? Because for pretension, we know how much is the initial strain e0 after we stretch the steel bar. However, at this time concrete has not been cast. After concrete is cast and its strength is fully developed, we release steel bar. The steel bar will contract and the concrete bond will prevent it, thus prestress is introduced to concrete (now, the strain in steel bar is less than e0 and it is unknown and not uniform along its length). However, when I cool the steel bar, the concrete bond has already existed and it will prevent the steel bar from contracting. If I still force steel bar to cool to e0, the strain in steel bar is uniform along its length and the real prestress is higher than pretension.

2) In Atena 3D, could I use 3d model to model the steel bar, i.e., model bar as a cylinder? If I could, what interface material do you think it is suitable to simulate the concrete bond?

Thanks a lot