Hysteretic + Initial Stress Material

[newuserinopensees]

Hi All,

I am relatively new in OpenSees, hope I can get some help.

I am analyzing a PC member and after I try to run several cases I found out I can use Steel02 with initial stress is specified. I also found if I combine steel02 (without specifying the initial stress) and InitStressMaterial, the program will give the same result (sometimes it even easier to get the convergence in non-linear part).

Now, I need to modify the material properties to calibrate with my test result and I think uniaxial hysteretic material can do. Thus, I combine uniaxial hysteretic material and InitStressMaterial, for example:

uniaxialMaterial Hysteretic 80 1380 0.0069 1567 0.026 1480 0.10 -1380.0 -0.0069 -1567 -0.026 -1480 -0.10 1 1 0 0 0
uniaxialMaterial InitStressMaterial 88 80 1100

and when I run, I got a error message:
"WARNING: InitStressMaterial - could not find initStrain to within tol for material: 88 wanted sigInit: 1100 using tStress: 1480"


And if I try to change the material as:

uniaxialMaterial Hysteretic 80 1380 0.0069 1567 0.026 1100 0.10 -1380.0 -0.0069 -1567 -0.026 -1480 -0.10 1 1 0 0 0
uniaxialMaterial InitStressMaterial 88 80 1100

there is no warning but the result is not correct because if I pull out the stress strain curve of the material, it will give very large strain.

I hope to get some advice. Thank you in advance for the input and comment.

[taoli]

Hi,
I met the same problem when defining a InitStressMaterial based on a Hysteretic, always got this warning. I understand after iteration the difference between sigInit and tStress is larger than the tolerance.

Do you know how to fix this?

Thank you.