Using SSLA to consider Concrete Confinement

SOFiSTiK Teddy
,
1

Hello,
We are working in a concrete shell nonlinear model and our goal is to modify the stress-strain curve of the material to have in consideration the confinement following 3.1.9. EN 1992-1-1.

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(We need to use a concrete material as we need to introduce reinforcement in the model)
To introduce the modified material, we are using the command: SSLA and the output diagram on the AQUA report seams satisfactory:

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However, after numerous attempts with Non-linear ASEs we have come to the conclusion that it only reaches a strain of 3,5 ‰. Regardless of the SSLA we use we have been unable to introduce a working code that allows us to get over that limit.

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We have been investigating the following parameters without any luck:

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I’m attaching the teddy file with the simplified problem on a square plate, to see if you can help us achieve ductility of the concrete, overcome the phantom limit of 3.5%, and be able to apply the stress-strain curve that we described.
Thank you very much in advance :blush:

SSLA_Concrete_Confinement .dat (4.1 KB)

2

Hello,

try typing
CTRL WARN (350 355 1)
in ASE
I am not 100% sure it will work with CONC, but it helps with STEE to reach high strains

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3

Thank you very much, you are so kind :blush:
It worked perfectly!

4

Hi martinez，
I’m also interested in this topic. So I put “CTRL WARN (350 355 1)” in the last two ASE in the " SSLA_Concrete_Confinement .dat" that you provided
But I still get 3.5%.
How to fix it?

Thank you
Sean

5

Hello,
Sorry for the delayed response.
It is true, that on the teddy as it is, if you only add CTRL WARN (350 355 1) on the last two ases, which are the NONL, it doesn´t reach strains above 3.5%.
This is because of the law of the concrete introduced in aqua:
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As you can see it only reaches strain’s above 3.5 for ULTIME DESING (red).
In order to activate this on the ases, you have to change
NSTR KSV ULD KSB ULD

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Then, if you run it like this:

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You’ll get this strains:

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6

Hello,

I changed the teddy code as follows

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But I still got small strains compared to yours

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7

Hello again,
It is true that your stress are lower than mine. If you look closely to the image of the teddy i attached you can see I increased the FACT 5%

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I am sorry, I should had remarked this. I did this so that the result in stress were higher so that the effect was more obvious. As the model is reaching the non convergence zone due to failure, little increases in the load generate very high increases in strain.
Any way, I see that your results are above 3.5% in loadcase 101 so it seams it is working okey.
Hope it helps!

Best regards

1 Like