I'm modeling an over-reinforced concrete beam using CDP for a 4-point bending test in ABAQUS, and I'm encountering some unexpected behavior. As it's an over-reinforced concrete, I expect to see brittle failure, with the concrete crushing at the top mid-portion, followed by a sudden drop in load on the load-displacement curve. However, what I'm observing is quite different.
I've conducted both load-controlled and displacement-controlled tests, and regardless of the approach, I'm seeing compressive stresses (S33, von Mises, and others) at and near the load points and boundary restraints significantly higher than the ultimate compressive strength of the concrete (as can be seen in the attached screenshot). I've even checked the stresses at integration points using the probe value function, and they still show stress levels above the concrete's ultimate compressive strength
I've tried different mesh sizes and element types, but these changes haven't had a substantial impact. Because of this issue, IMO I'm unable to achieve the brittle failure I expected, as the concrete compressive stresses never seem to reach the ultimate compressive strength at the top mid-portion. Instead, I'm getting ductile failure with reinforcement yielding especially the top reinforcement yielding at the location of the load points.
Has anyone encountered a similar problem or have any suggestions on how to address this issue and obtain the desired brittle failure behavior in my simulation?
Any help will be greatly appreciated.
How do you know if the beam is over- reignforced if it exceeds ultimate strength?
Ensure sufficient over reinforced beam to see whether still model is working or not. Some time little higher values may not have any impact. Complete crushing above neutral axis will ensure yielding of steel.
If the top reinforcement is equal to bottom reinforcement then this will act as steel beam and this typical behaviour can be experienced
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