Shear failure in CDP model

[Vimukthi]

Hi all,

I'm fairly new to the Abaqus program so go easy on me. The issue is, I'm getting the same failure load in a simply supported beam (4 point bending) even if I reduce the spacing of stirrups. From stress contours I can observe that any steel rebars are not yielding indicating there's no flexural failure. And compressive failure at top is also not observable from stress contours. This was expected since the r/f was designed to avoid flexural failures. Without stirrups I'm getting the expected results according to Euro code. But with stirrups something goes wrong. Also stress contours of stirrups are not exceeding yield stress. I have attached some relevant diagrams for reference. Also note that strength of both stirrups and rebars is 500 N/mm2 and concrete is grade 25.

Thanks.

 

[FEA way]

The problem may be caused by ill-defined interactions (embedded constraint, contact) or too coarse mesh. Take a closer look at these parts of the model definition.

 

[Vimukthi]

Tried with a finer mesh but still the same results.