• Registered: 2015-05-19
  • Posts: 15

Topic: Experimental stiffness vs ATENA Ec

Dear Sir,

I am modeling the shear failure of a prestressed concrete girder using ATENA 3D. I know the secant stiffness of the concrete through performing modulus tests; however, I had not used the stiffness values in my material model. Instead, I used the Ec values suggested by ATENA.

I only specified the compressive strength and used the automatically generated stiffness. Because the stiffness of the experimental results seems to be lower than that produced by ATENA, I would like to use the experimentally determined stiffness in my material model.

I believe the Ec value that is asked for, in the 3DVariableNonLinearCementirious material is not the secant stiffness in a uniaxial stress-strain relationship. Is the Ec that the user has to input for the "biaxial stress-strain relationship by KUPFER"?

Ec=f'ef/ec? or Ec=sigma,c/e,eq?

I would appreciate your help.

Thanks,

Roya

Quote Post 1

  • dpryl
  • CC software developer
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  • Registered: 2007-07-13
  • Posts: 1,107

Re: Experimental stiffness vs ATENA Ec

Dear Roya,
the elastic modulus to be entered in the material definition is the initial modulus (=of the undamaged material) under uniaxial loading (tensile or compressive should give the same E near 0).

If you have a stiffness difference between your analysis and the measurement, please follow ATENA Troubleshooting, 2.2.18 My analysis results do not match the experiment/expectations. How can I improve my model?

The important question is if the stiffness differs from the very beginning (-> check the boundary conditions and the elastic modulus) or later (check the nonlinear parameters).

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Quote Post 2