How can i find the stress or strain results of 3D concrete?

Hello! In this section we'll talk about the post processing module and the data visualization.
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jiayanghnu
Posts: 10
Joined: Wed Nov 29, 2023 9:56 am

How can i find the stress or strain results of 3D concrete?

Post by jiayanghnu » Fri Apr 19, 2024 1:05 pm

Hi, when i used ASDConcrete materials in my modeling process, how can I query the stress or strain results of 3D concrete in the postprocessor?Is it as shown in the screenshot below?
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kesavapraba
Posts: 301
Joined: Sat Mar 28, 2020 2:25 pm

Re: How can i find the stress or strain results of 3D concrete?

Post by kesavapraba » Fri Apr 19, 2024 6:35 pm

Yes, you can use this option, however, I would suggest you to use without enabling "nodal average" option. Nodal averaged plot shows the smoothed or averaged stress value at the nodes shared by multiple elements. However, this can often appear smooth and not present a true picture of the stress distribution. In contrast, unaveraged stress contour plots may not appear smooth but can provide more information about the stress distribution in the mesh.

For more accurate stress/strain interpretation, you should consider using "Gauss plot" instead of "Surface plot". Because, the Gauss points are the locations where the stress/strain are calculated and interpolated to other points in FE analysis.
:: With best wishes ::
Prabakaran Kesavan

jiayanghnu
Posts: 10
Joined: Wed Nov 29, 2023 9:56 am

Re: How can i find the stress or strain results of 3D concrete?

Post by jiayanghnu » Sun Apr 21, 2024 4:30 pm

kesavapraba wrote:
Fri Apr 19, 2024 6:35 pm
Yes, you can use this option, however, I would suggest you to use without enabling "nodal average" option. Nodal averaged plot shows the smoothed or averaged stress value at the nodes shared by multiple elements. However, this can often appear smooth and not present a true picture of the stress distribution. In contrast, unaveraged stress contour plots may not appear smooth but can provide more information about the stress distribution in the mesh.

For more accurate stress/strain interpretation, you should consider using "Gauss plot" instead of "Surface plot". Because, the Gauss points are the locations where the stress/strain are calculated and interpolated to other points in FE analysis.
Thank for your reply, When i considered using "Gauss plot" and without enabling "nodal average" option, i found the maximum cocnrete stress of the postprocessor exceeded the value previously defined by ASDConcrete(9P) material , can you explain this exphonment?
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postprocessor result.png
postprocessor result.png (391.94 KiB) Viewed 187 times
ASDConcrete9p.png
ASDConcrete9p.png (50.85 KiB) Viewed 187 times

kesavapraba
Posts: 301
Joined: Sat Mar 28, 2020 2:25 pm

Re: How can i find the stress or strain results of 3D concrete?

Post by kesavapraba » Mon Apr 22, 2024 1:39 pm

Hi, Compressive stress at the Gauss point can exceed the uniaxial compressive strength of the concrete under multiaxial stress state (biaxial/triaxial compression). Peak compressive strength input, as seen in your material definition of STKO, comes from the uniaxial compression test. However, under triaxial compression (like, hydrostatic pressure) the strength and ductility of the concrete can significantly increase from the uniaxial response. This is called confinement effect of concrete under triaxial compression or hydrostatic effect. I attach a figure below showing this effect - sigma3 increases due to the other compressive stresses (sigma 1 and sigma2). You might refer to the following article published very earlier on this effect:

Richart, Frank Erwin, Anton Brandtzæg, and Rex Lenoi Brown. "A study of the failure of concrete under combined compressive stresses." University of Illinois. Engineering Experiment Station. Bulletin; no. 185 (1928).
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triaxialeffect.png
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:: With best wishes ::
Prabakaran Kesavan

jiayanghnu
Posts: 10
Joined: Wed Nov 29, 2023 9:56 am

Re: How can i find the stress or strain results of 3D concrete?

Post by jiayanghnu » Tue Apr 23, 2024 2:58 am

kesavapraba wrote:
Mon Apr 22, 2024 1:39 pm
Hi, Compressive stress at the Gauss point can exceed the uniaxial compressive strength of the concrete under multiaxial stress state (biaxial/triaxial compression). Peak compressive strength input, as seen in your material definition of STKO, comes from the uniaxial compression test. However, under triaxial compression (like, hydrostatic pressure) the strength and ductility of the concrete can significantly increase from the uniaxial response. This is called confinement effect of concrete under triaxial compression or hydrostatic effect. I attach a figure below showing this effect - sigma3 increases due to the other compressive stresses (sigma 1 and sigma2). You might refer to the following article published very earlier on this effect:

Richart, Frank Erwin, Anton Brandtzæg, and Rex Lenoi Brown. "A study of the failure of concrete under combined compressive stresses." University of Illinois. Engineering Experiment Station. Bulletin; no. 185 (1928).
Thank you for your answer. I see.

kesavapraba
Posts: 301
Joined: Sat Mar 28, 2020 2:25 pm

Re: How can i find the stress or strain results of 3D concrete?

Post by kesavapraba » Wed Apr 24, 2024 11:13 am

You are welcome
:: With best wishes ::
Prabakaran Kesavan

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