Hi all,
I'm modeling shear-critical beams on ABAQUS and the load-deflection curves agree well with experiments, plus the stress contours and cracking pattern make sense. There is only one issue: the load doesn't decrease after reaching the peak in some specimens or takes a lot of displacement to decrease.
The failure is mainly governed by the concrete. I'm using the CDP model with Popovics curve for compression and 4 points for tension (close to exponential decline).
Also, I'm using the dilation angle of the concrete of 50°. This value worked the best for my specimens, but I believe it's a bit high. How do we define which value of angle to use? Is there a formula to calculate it?
I'm using the other parameters as the default recommended in the User's Manual and 0.0001 for viscosity.
Something similar happens in flexural-critical specimens, the simulation only fails when the long. reinforcement reaches max. strain, but in the experiment the beams fail earlier. If you can help me with this too, I'd appreciate it.
Thank you very much in advance!
Best,
Sálvio.
If it is displacement controlled, the reactions (loads) observed at the supports should logically decrease when cracking occurs.
Alternatively you can try Riks Analysis in ABAQUS to achieve so.
Hi Usman, it is displacement controlled indeed but the reactions only decrease when the bottom reinforcement ruptures.
Can you tell me more about this Riks Analysis? I don't know anything about it.
Thank you!
I think that there may be something missing in the properties of the concrete so that the damage isn't being fully captured (i.e. after cracking/crushing the total reaction goes down very slowly in most cases, if at all!).
I'm defining the following properties:
CDP model
Plasticity:
- Dilation angle = 35°
- Eccentricity = 0.1
- fb0/fc0 = 1.16
- K = 0.6667
- Viscosity = 0.0001
Compressive behavior:
- Stress-strain points in the Popovics formulation (using inelastic strain)
Tensile behavior:
- Stress-strain points in the Nayal and Rasheed curve (4 points defining a curve close to the exponential tension stiffening). I tried using the fracture energy as well, obtaining similar results.
I am not defining tension/compression damage since I'm doing a monotonic analysis, but I did try defining it once and it made little difference.
If there is something else I need to define, please let me know.
Thank you!
Best,
Sálvio.
hi Sálvio , did you solved that problems? what amplitude you're using for?
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