Angular steel cross sections to cross section table

Replies to This Discussion

Permalink Reply by Karamba3D on May 22, 2017 at 12:40pm

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

Permalink Reply by Balazs Kisfali on May 23, 2017 at 2:14am

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]	[mm2]		[mm4]	[mm3]	[mm]		[mm4]	[mm3]	[mm]		[mm4]	[mm3]	[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

Permalink Reply by Karamba3D on May 24, 2017 at 12:33am

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

Permalink Reply by Balazs Kisfali on May 24, 2017 at 1:11am

Hi Clemens,

Thanks for the reply.

Regards, Balazs

Permalink Reply by Balazs Kisfali on May 24, 2017 at 3:24am

Hi Clemens,

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

Permalink Reply by Balazs Kisfali on May 24, 2017 at 3:26am

The file upload was drop due to the size, ...now I re-upload only the CSV, that is smaller than 5MB

Attachments:

• CrossSectionValues_sortedForHeight_Angular_Chinese_v1.0.csv, 2.7 MB

Permalink Reply by Karamba3D on May 24, 2017 at 12:20pm

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

Permalink Reply by Balazs Kisfali on May 24, 2017 at 1:21pm

Hi Clemens,

Now I tried. But actually when I choose the shape, in the dropdown menu there is no shape "T" as such. Actually I could see these shapes only in the big cross section table. See attached.

Regards, 

Balazs

Permalink Reply by Karamba3D on May 29, 2017 at 12:45pm

Hi Balazs,

use an I-profile with zero lower flange width.

Best,

Clemens

Permalink Reply by Balazs Kisfali on May 31, 2017 at 1:56am

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