• Qas
  • New member
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  • Registered: 2016-11-27
  • Posts: 1

Topic: Reduction for the Compressive strength for plain concrete

Dear All
I appreciate all the valuable advices that you offer here.
Kindly, I have axial symmetry problem for plain concrete under tensile loading conditions and the result I have ( after using all the available suggestion on the Troubleshooting file) still have difference from experimental in terms of initial stiffness and maximum load.
I have some remedies but looking for your opinion:
1-When I reduced the reduction for compressive strength due to crack from 0.8 to be 0.4 the maximum load tends to be as close to experimental results that I have.( the element I used 3D Nonlinear Cementitious 2 .... I don't have any reinforcement).Is that correct?
2- Also I tried to include shrinkage effect by reducing the tensile strength between 0.1-0.3 and it works for maximum load. Again, Is that correct? ( reducing tensile strength)
3- Finally, What values would you suggest( for 2D or Axial symmetry  and plain concrete) for the following factors, please:
                      a-Plastic strain at strength.
                      b-Crack shear stiffness factor.
                     c-Direction of the Plastic flow.
and if you have any suggestion would be appreciated. Looking for your answers.
Best Regards
Qas

Quote Post 1

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

Re: Reduction for the Compressive strength for plain concrete

Dear Qas, without seeing your model and at least a sketch of the experiment, I can only guess - see also Troubleshooting, 2.1.1. Please also send a graph comparing the measured and calculated Load-Displacement curve.
Moreover, it is not clear what information you have about the material?

Ad 1.: Your observation suggests compression (or shear) have significant influence. This might be happening in the experimental setup, however, speaking about direct tension,  I suppose a problem in representing the boundary conditions (or maybe a somewhat problematic or unusual tensile test setup).

Ad 2.: As you speak about plain = unreinforced concrete, I see no reason for modelling shrinkage as there are no bars acting against the volume change.

Ad 3.: If unsymmetric localization is responsible for the difference, you should model the whole specimen.

Sorry, without seeing your model and having some information about the real setup (see above), I can not recommend any parameter changes. I assume you have already read Troubleshooting, 2.2.18 My analysis results do not match the experiment/expectations. How can I improve my model?

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Quote Post 2