algorithmic modeling for Rhino
Hi,
Can you suggest a way how to use equal angles as steel cross sections for Karamba? How can I build up the cross sections table?
My main issue is to apply a new axis of buckling, the "u" or "v" axis. These are the weak ones, but in many cases these govern the section design. Please see attached image for further reference.
Telecommunication towers and transmission lines are made mainly by angular steel, due to easy packing and efficient structural behaviour within lattice structures.
Thank you.
Balazs
Tags:
Hi Balazs,
you can use the principal values of the moment of inertia of the cross sections to specify them.
In Karamba the calculation will not be exact in case of loads which produce shear, since currently (version 1.2.2) Karamba assumes that the center of shear and the center of gravity of a cross section coincide.
Best,
Clemens
Hi Clemens,
Thanks for your answer.
Can I add more columns to the CrossSectionTable? It will be read by Karamba?
The following is an extract from the table, but I would like to add "Iv" and "Iu" (referring to the above image)
Area |
effective |
effective |
Second |
Elastic |
Elastic |
Plastic |
Radius |
Second |
Elastic |
Plastic |
Radius |
of |
Vy shear |
Vz shear |
Moment |
Modulus |
Modulus |
Modulus |
of |
Moment |
Modulus |
Modulus |
of |
Section |
Area |
Area |
of Area |
upper |
lower |
Gyration |
of Area |
Gyration |
|||
(strong axis) |
(strong axis) |
(strong axis) |
(strong axis) |
(strong axis) |
(weak axis) |
(weak axis) |
(weak axis) |
(weak axis) |
|||
A |
Ay |
Az |
Iy |
Wy |
Wy |
Wply |
i_y |
Iz |
Wz |
Wplz |
i_z |
cm2 |
cm2 |
cm2 |
cm4 |
cm3 |
cm3 |
cm3 |
cm |
cm4 |
cm3 |
cm3 |
cm |
I have a very similar table which I could import to the Karamba table. But I have i_v or i_u values as well as radius of inertia for instance.
1 |
2 |
3 |
4 |
5 |
6 |
7 |
8 |
9 |
10 |
11 |
12 |
13 |
14 |
15 |
16 |
17 |
18 |
dimensjon |
Masse |
Areal |
akse |
Ix |
Wpx |
ix |
akse |
Iy |
Wpy |
iy |
akse |
Iv |
Wpv |
iv |
Width |
Thickness |
Radius R |
[kg/m] |
[mm^{2}] |
[mm^{4}] |
[mm^{3}] |
[mm] |
[mm^{4}] |
[mm^{3}] |
[mm] |
[mm^{4}] |
[mm^{3}] |
[mm] |
[mm] |
[mm] |
[mm] |
||||
L 20x3 |
0.89 |
113 |
x-x |
4,000 |
290 |
5.9 |
y-y |
4,000 |
290 |
5.9 |
v-v |
1,700 |
200 |
3.9 |
20 |
3 |
4 |
L 20x4 |
1.15 |
146 |
x-x |
5,000 |
360 |
5.8 |
y-y |
5,000 |
360 |
5.8 |
v-v |
2,200 |
240 |
3.8 |
20 |
4 |
4 |
L 25x3 |
1.12 |
143 |
x-x |
8,200 |
460 |
7.6 |
y-y |
8,200 |
460 |
7.6 |
v-v |
3,400 |
330 |
4.9 |
25 |
3 |
4 |
L 25x4 |
1.46 |
186 |
x-x |
10,300 |
590 |
7.4 |
y-y |
10,300 |
590 |
7.4 |
v-v |
4,300 |
400 |
4.8 |
25 |
4 |
4 |
L 30x3 |
1.37 |
175 |
x-x |
14,600 |
680 |
9.1 |
y-y |
14,600 |
680 |
9.1 |
v-v |
6,100 |
510 |
5.9 |
30 |
3 |
5 |
L 30x4 |
1.79 |
228 |
x-x |
18,400 |
870 |
9.0 |
y-y |
18,400 |
870 |
9.0 |
v-v |
7,700 |
620 |
5.8 |
30 |
4 |
5 |
L 36x3 |
1.66 |
211 |
x-x |
25,800 |
990 |
11.1 |
y-y |
25,800 |
990 |
11.1 |
v-v |
10,700 |
760 |
7.1 |
36 |
3 |
5 |
L 36x4 |
2.16 |
276 |
x-x |
32,900 |
1,280 |
10.9 |
y-y |
32,900 |
1,280 |
10.9 |
v-v |
13,700 |
930 |
7.0 |
36 |
4 |
5 |
L 36x5 |
2.65 |
338 |
x-x |
39,500 |
1,560 |
10.8 |
y-y |
39,500 |
1,560 |
10.8 |
v-v |
16,500 |
1,090 |
7.0 |
36 |
5 |
5 |
I have diagonals (bracings) which can buckle in these "non-regular" directions too, and they do. If I could add those values then in the Karamba model I could assign specific buckling scenarios..... I can see another challenge which will be at the ModifyElement component, I will not be able to choose these buckling lengths, in these directions.
Do you think this functionality can be added within short, or should I try to find another way to model these members?
Br, Balazs
Dear Balazs,
if a beam is not supported along its axis, buckling will always occur about the weak axis. Karamba assumes that the local Y- and Z- axes correspond to the principal axes of the cross section. In your case that would be Iv and Iu. So simply use these for Iy and Iz.
For correct local displacements make sure to rotate the cross section (in your case 45°), so that external loads are correctly oriented with respect to the angle.
Best,
Clemens
Hi Clemens,
Thanks for the reply.
Regards, Balazs
I have encountered an error, pls see attached. I checked several times but I cannot find any cross section with the given error. What can be the problem?
1. Cross section without family name encountered.
I also noticed that as shape "L" it cannot be imported (maybe) because I had another error which said "Uknown shape". So now I try to "fix" it with giving shape as "T" which I found the closest to "L" shapes. Or, did I missed something, is it possible to import other shapes than listed in the manual?
I have attached my CSV and Excel files so you might take look.
Thank you
Regards,
Balazs
The file upload was drop due to the size, ...now I re-upload only the CSV, that is smaller than 5MB
Did you try to import a small part of the larger table - e.g. one line? With the 'Generate Cross Section Table' component you could export an arbitrary T-cross section and then compare the output to your table.
Best,
Clemens
Hi Balazs,
use an I-profile with zero lower flange width.
Best,
Clemens
Hi Clemens,
Thanks, just managed with the T profile ;) ...I went back to scratch, as you suggested, create a profile in Karamba, export it to CSV and then I started to build up the DB for my profiles in that particular file.
Something else, maybe useful for others too.
There is a gotcha in Excel to create the semi colon separated values as export, because within Excel options is not possible to do it (or at least I was not able) So it is needed to go to the Control Panel:
1. Control Panel
2. Region, Region and Language Option
3. In Tab Format, click customize this format
4. List separator, change from comma (,) to semicolon (;)
5. Ok, -Finish-
Then the usual things with Excel, save the file as CSV and it will be saved with the ";" separators.
Credit to this guy where I found this:
https://social.technet.microsoft.com/wiki/contents/articles/10305.h...
Regards, Balazs
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