Concrete01 and Concrete02

[drowning6]

Dear all,

I am modeling column with fiber section using both Cocnrete01 and Concrete02.
However, when I am doing static monotonic analysis, the elastic stiffenss of column
with these two materials are totally different.

The stiffness of column fiber with concrete02 is two times more than that of column fiber
with concrete01.
But after yielding, columns with these two materials go to the same properties which makes sense.

BTW, I am using same compression curve in Concrete02 and Concrete01.
The only difference is there is no tension part in concrete01.

[fmk]

their initial tangent should be the same under 0 strain .. however what might be happening is that for the Concrete01 materials the elements might be imposing some small tensile strain (even if small order 1e-10) that would be enough to make the material point return a tangent of 0.0.