Topic: Interface failure test


I'm trying to simulate the interface failure test example provided in the documentation in ATENA 2D, Although I'm using same input conditions and keeping the boundary conditions also same, I'm not getting the correct/expected shear stress at the concrete-concrete interface.

Can you please help me with the following questions?
-Where are the monitoring points located in the analysis for plotting the load-displacement curve?
-What is the load step multiplier for both type of prescribed deformations; compression and lateral force?
-What is the solution method used for the analysis? Newton-Raphson or modified NR and how many iterations?
-What is the thickness of the macroelements and the interface?
-Will there be any difference in the results if instead of using SBETA material I'm using non linear cementitious 2 material properties?

These details are not provided in the manual.
Awaiting response on the above queries.

Re: Interface failure test

Dear arjun.vithalkar,
please see the corresponding example model, included in the analysis and referred in the Example Manual. The typical installation location of this model is

%Public%\Documents\ATENA Examples\Engineering\Example Manual\NGAP\NGAP.cc2


Re: Interface failure test

Thank you for the directions to access the example file. However, I am still facing some problems with the model

-The model dimensions in the ATENA file are 300 * 130 mm whereas, in the manual it is mentioned to be 400 * 130 mm. Hence, this will have an effect on the results as the maximum reaction obtained in the load displacement curve is only 150 kN(model) whereas, it should be around 255 kN(manual) for a 400mm long specimen
-The shear stress at the interface at the end of load step 21, as mentioned in the manual and also theoretically should be 2.53 MPa. However, this is also not the case in the model, when I run the analysis the maximum shear stress at the interface is coming out to be 1.55 MPa, thus, not satisfying the expected value.

Can these ambiguities in the model be explained?

Re: Interface failure test

Dear arjun.vithalkar,
1. the figure in the Example Manual is identical to the NGAP.cc2 model, and I guess the typo in the dimension is related to the 0.1m X coordinate of the left edge.

2. When I run the model, the maximum reaction is 183kN in Step 7.

3. The maximum Interface shear stress in the model is 2.498MPa (in Step 7).

4. There were some small changes in the Interface material model, using a smooth elliptical failure curve instead of bilinear (in ATENA Science, it is possible to switch back to the original behaviour).

5. I am adding your report to the list of issues with the Example manual to be checked / adjusted to reflect program changes when preparing a future ATENA version.


Re: Interface failure test

Dear dpryl,

Thank you again for the explanation. I am getting the exact same results which you mentioned in points 2 and 3.
Although, could you please elaborate on the 4th point which you mentioned about the interface material model?
Do I make any changes to the default settings of the interface material model?

Re: Interface failure test

Dear arjun.vithalkar,
please see ATENA Theory, 2.6 Interface Material Model, especially Fig. 2-37:  Failure surface for interface elements. Basically, the dotted line corresponds to the "old" initial surface.
For additional details, you can also see the explanation of TENSION_ELIPS in the ATENA Input File Format Manual, 3.6.5 Interface Material. Please understand that this option is only supported through the ATENA-GiD user interface of ATENA Science.