Hi,

I'm analysing the bond between ribbed reinforcement and concrete. My model consists in a steel bar (2 cm diameter) embedded in the middle of a concrete slab. In this steal bar it's applied a displacement simulating a pull-out test. I'm using the material CCReinforcementBondMaterial to model the bond law in accordance to the CEB-FIP Model Code 90.

After obtaining the results, I get the Reaction Force in the point of the steel bar where the prescribed deformation is applied, and I get the displacement in the node A (please see picture in the link below).
http://imgur.com/JSJSxxX

I'm able to determine the Average Bond Stress between the steel bar and the concrete slab using the following equation:
BondStress=ReactionForce/(L*pi*D)
where ReactionForce is the Force in the steel bar, L is the length of the connection between the steel bar and the concrete slab and D is the diameter of the steel bar.

I've analised a model with a connection length of 20 cm. Comparing the AverageBondStress/Displacement of this model with the bond law used in the material CCReinforcementBondMaterial (please see picture in the link below) we can see that these do not match.
imgur.com/JmB8nng

Also I've analised a model with a connection length of 30 cm. Comparing the AverageBondStress/Displacement of this model with the other two (please see picture in the link below) we can see that also these do not match.
imgur.com/6wCuVi8

My first question is, why aren't they coincident?

My second question is the following:
Atena 3D gives me the Bond Stress in the nodes of the steel bar. In a Step (it doesn't matter which Step it is), the bond stress in the nodes of the steel bar that are inside the concrete slab and that are nearest to node A (including node A) tend to zero (please see picture in the link below). In this nodes the bond stress should be maximum and not minimum. Why does this happens?
imgur.com/dkZSvEp

Thanks in advance.