ACTB feature

#1

Hello, I am using the ACTB active bending feature to calculate the stress distribution and deformation of the 22 m length bar with a circular cross-section.
I used both ways suggested in the ASE manual and Teddy examples:

  1. Earlier application of Sofistik in which a straight beam is bent and analyzed with the full nonlinear geometric analysis.
  2. ACTB function.
    I expect the model to act as an Elastica curve (regarding the deformations) but using the ACTB feature ends in the strange shape which is not really desired. (I should say I checked the available Teddy examples provided from Sofistik and the difference was the same!).
    It seems that both simulated bars give “approximately” the same deformed shape but quite difference in the amount of displacements and not having the same curvature along its curvilinear axis.
    Can you help me with solving this problem?
    (As far as I am a new user, the website does not let me uploading attachments!!!)
#2

Hello Tara

I have updated your trust level. Now you should be able to post pictures and files.
Without any further information I can’t analyse your problem.

So you don’t understand, why the deformation differs between the two methods?
Have you tried the function ACTB on a simple system?
For example a similar system as show in the TEDDY example “ase > active_bending > active_bending_overview.dat”?

Best regards
Frederik Höller
Your SOFiSTiK Support Team

#3

Hello Frederik,
Many thanks for the profile update. Yes, I cannot understand the reason for the existing differences in the deformation in the two methods. they should match and actually in my view the result deformation from ACTB is like a bell-shape which is strange.
I have tried the function ACTB in the TEDDY examples, exactly the same one as you addressed, The problem is the same but as far as the bar in that example is 4 meters long, the bell-shaped deformation is smaller and can be ignored.
I attached the codes I used for both methods and I will be grateful if you can help me.
Many thanks for your attention.
Bests,
Tara

Bending-active-13.dat (5.9 KB)
Bending-active-14.dat (8.2 KB)

#4

Dear Frederik,
I am writing this reply as a reminder of my open question on the ACTB function of Sofistik.
Since I am a Ph.D. Student and I want to use Sofistik as the main software for analyzing my thesis which is in the field of Active bending structures, it is very essential for me to check everything and be aware of the mechanisms. I will be grateful if you can help me.
Thanks in advance.
Bests,
Tara

#5

Dear Tara

I have looked at your example project, but I can’t see your described problem. Could you perhaps post a picture of the differences in deformation and attache your desired values.
If you are wondering about the changes in deformation before and after the ASE calculation (with ACTB), you have to know that they are generated because of the command ACTB. This command pushes the beam “automatically into an equilibrium active bending shape” (see ASE manual page 2-77).

image
image740×365 42 KB

(ASE manual page 2-77)

Best regards
Frederik

#6

Dear Frederik,
Many thanks for the reply. I read the mentioned user manual several times. My question is about differences in curvature in these 2 models (Different Final geometry as result.)
By using ACTB, the deformed shape will be bell-shaped which means in the calculation there should be some constrained in ACTB function which is not clear for me.
But, in the other method (Bent bar), the final deformation is more arch shape.
I want to know why these final deformations are not the same.
I have attached the final deformations of the files to this message.
Thanks in advance for the help.
Bended bar.pdf (25.5 KB) ACTB bar.pdf (25.5 KB)

#7

Dear Tara

I think the problem is that you have two different initial situations. The first bar (with ACTB) has a rounded primary shape that is similar to the deformed structure. The original shape of the second bar is completely flat.
As soon as you compare the final deformation vectors of the two structures you realise that they differ not only in value, but also in orientation. You get these different results, because of the different initial situations. In order to create the active bent beam, the two bars have to be deformed in two different ways. The different deformations are shown in the screenshots of your two .pdf.
Another problem you are facing is that the vectors are not drawn in the same scale. As I already mentioned the initial form differs between the two beams, so the exaggerated vectors do look different as well.

If you want to compare the shape of the two beams, you can try to model them within one TEDDY project. Now you should see the deformed beams next to each other. But be careful not to increase the scale of the visualisation.

Best regards
Frederik

#8

Dear Frederik,
Many thanks for your kind reply. But unfortunately, the question remains open. For your first comment, I should mention that the deformation of the initially flat one is according to reality and can be considered as a correct one. The deformation of the ACTB is not right regarding the bell shape that it has. As far as I understand in the ACTB function, we should define the semi-final desired geometry, and the software will consider and calculate it the way that it was flat initially (?). So, the initial states are the same. My question is about the ACTB and its final deformed shape.
Regarding the scale, I changed the scale of ACTB by purpose to show the effect of bell-Shaped as I am talking about. Is it possible to arrange a very short zoom meeting together to discuss this problem, if you don’t mind?
Many thanks…
Tara

#10

Hello Tara

I have calculated the two beams in one project. Now you can see that the deformations are pretty similar.
grafik

Keep in mind that the deformation vectors depend on the undeformed system

Another possible method to verify the results is, to release the supports of the two structures as stated within the ASE manual (page 2.80). Now both beams should relax into the flat initial state.

Best regards
Frederik

#11

Hello Frederik,
Many thanks for the reply and calculations you made.
I calculated the two beams with a different method in one project, and the results were the same as yours, which you attached. You can see in the attachments with the name “flat-actb-bending-active-16”.
But there is no difference between the results when they are separated into two projects or one. The deformation is still different. If you check the deformation in the global Z-direction, you can see the difference, which caused the structure to be deformed as the bell-shaped with ACTB function. (See the attachment ‘flat-actb-bending-active-16-Displacement’).
I tripled the deformation scale; you can see how both structures are not the same. As the arch is in compression, this will have effects that are not negligible. (See the attachment ‘flat-actb-bending-active-16-deformation’).
Many thanks for your consideration.

Bests,
Tara

Attachments:
flat-actb-bending-active-16.pdf (19.1 KB) flat-actb-bending-active-16-Displacement.pdf (16.8 KB) flat-actb-bending-active-16-deformation.pdf (13.2 KB)