Beam-to-Solid-Bar-Slip

cqf_2232
Posts: 64
Joined: Fri Dec 10, 2021 1:00 am

Re: Beam-to-Solid-Bar-Slip

Post by cqf_2232 » Tue Aug 02, 2022 9:34 am

Hello, I set pdf_c and pdf_t to 0.6 according to your method, and found that the descending section of the curve does not fit well with the test curve. The descending segment is like a straight line back to the origin and there is no plateau segment, and the resulting curve of pdf_c=0.7~0.9 is not ideal. Is this the reason for DamageTC3D?
After the new version was released, I used "Embed with slip" to simulate slip, and found that the descending part of the hysteresis curve had obvious pinching phenomenon. I tried to adjust the damage parameters, same as the previous question, what is the reason for this?
Attachments
pdf_c 0.6.png
pdf_c 0.6.png (299.68 KiB) Viewed 394 times
embed with slip.png
embed with slip.png (87.95 KiB) Viewed 394 times

STKO Team
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Joined: Tue Oct 29, 2019 8:45 am

Re: Beam-to-Solid-Bar-Slip

Post by STKO Team » Wed Aug 03, 2022 8:41 am

In the real test the unloading-reloading curve has a variable Stiffness, it starts unloading with an almost Elastic Stiffness, then it gradually changes its slope.
This is very difficult to simulate with 3D constitutive model, where instead the unloading-reloading stiffness is constant.
That's why we use a value like 0.6, which is a good compromise.

cqf_2232
Posts: 64
Joined: Fri Dec 10, 2021 1:00 am

Re: Beam-to-Solid-Bar-Slip

Post by cqf_2232 » Tue Aug 23, 2022 2:27 am

Hello, by adjusting pdf_t=0.3, I found that the reload stiffness of the hysteresis curve is consistent with the test, but the unloading stiffness is still lower than the test curve. After that, I wanted to adjust pdf_c=0.95 to increase its unloading stiffness, but found that the curve dropped in advance. Why is this happening?
Attachments
Hysteresis.png
Hysteresis.png (404.52 KiB) Viewed 258 times

STKO Team
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Re: Beam-to-Solid-Bar-Slip

Post by STKO Team » Tue Aug 23, 2022 12:35 pm

It's because it is a 2-surface damage model. If the pdf_t and pdf_c values are very different from each other, the direction of the failure may change. I suggest you to keep those value close to each other.
In the future we are going to implement a new model with a better description of the hysteretic cycles

cqf_2232
Posts: 64
Joined: Fri Dec 10, 2021 1:00 am

Re: Beam-to-Solid-Bar-Slip

Post by cqf_2232 » Thu Sep 08, 2022 7:23 am

Hello,The area above the plastic hinge region of the pier model was corroded. I reduced the yield strength of the rebar in the corroded area, and found that the load of the pier model during the unloading process had not been reduced to 0, and the phenomenon of pinching occurred in advance. What is the reason?
Attachments
analysis.png
analysis.png (143.8 KiB) Viewed 133 times

STKO Team
Posts: 1346
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Re: Beam-to-Solid-Bar-Slip

Post by STKO Team » Thu Sep 08, 2022 5:19 pm

It's hard to tell. Probably you should reduce the area of the rebar (not the yield strength).

cqf_2232
Posts: 64
Joined: Fri Dec 10, 2021 1:00 am

Re: Beam-to-Solid-Bar-Slip

Post by cqf_2232 » Fri Sep 09, 2022 7:35 am

In fact, I have reduced the cross-sectional area and yield strength of the rebar. I found that the reduction of the yield strength of the rebar to a certain extent will affect the pinching of the unloading curve. It is found that the core concrete of the corroded pier is not seriously damaged by comparing the damage diagrams of the non corroded and corroded piers. Is the shrinkage of hysteresis curve in advance related to less damage of core concrete?
Attachments
Snipaste_2022-09-09.png
Snipaste_2022-09-09.png (109.37 KiB) Viewed 113 times

STKO Team
Posts: 1346
Joined: Tue Oct 29, 2019 8:45 am

Re: Beam-to-Solid-Bar-Slip

Post by STKO Team » Fri Sep 09, 2022 8:58 am

It might be related to the different damage patterns in concrete. But I don't understand why it is so different. Try to look at the deformed shape to better understand how it is failing.

However. I also see some differences in the mesh distortion in your pictures... it seems that the non-corroded column has elements that are more distorted than the other model.

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