Cross section definition

[arailosotenet_gr]

Hello there,

Firstly, being a newbee I would like to apologize for matters that I ask and have been extensively discussed in this forum by my ignorance.

I am trying to define a thin walled cross-section formed from three TRON sections combined. After creating a dxf and importing it in section definition tool and defining the width, the results I get are fine as shown in the first image.

When I save the section and open it in the section database I get the second image.

My question are?

• Why don't I get values for Vx, Vy and Wx,Wy,Wz,Wply,Wplz?
• Why is that the cross section does not appear as it is, rather than three small triangles, although the properties of the section are correct? If I proceed as it is will I face problems?
• What are the Dimension1,2,3 that are needed when saving the section in the database?Do they play important role in defining the section or are there only for naming it?

Morerover I tried to define the section with 2 TRON sections (MAV in ruserpro.xml) and although I can see the section in the database there are no values for Vx, Vy etc.

Thanks in advance

[Artur.Kosakowski · Accepted solution]

Try to define your section as a solid rather than a thin walled and then calculate its properties in the Section Builder module. Save it to the user database (assign the 'right' section type if you intend to use it in the steel design module). Finally replace Ix value which may be inaccurate with the one calculated for the thin walled section.

If you find your post answered press the Accept as Solution button please. This will help other users to find solutions much faster. Thank you.

[arailosotenet_gr]

Hi there,

I had some successful attempts when analysing the three TRON cross-section as solid but I have results where I don't get values for Ay,Ay,Wy,Wz as shown in the picture for 4 TRON. Moreover, when I re-analyse the first cross section I don't get these values.

Does the discetization need to be dense?

I have attached the dxf file that I used and a picture of the cross section with the calculated results to give you an idea of what I want to do...

[Rafal.Gaweda]

Does the discetization need to be dense?

This section should be calculated as thin walled so for this type of sections mentioned properties are not calculated.

User can not control discretization density in Section Design module.

[arailosotenet_gr]

So if I calculate it as a thin-walled without getting these values will the results in the building analysis would be credible?

The discetization that I ment was when importting the dxf file...

Why is that Artur suggested that I should firstly calculate the section as thin walled note the Ix and then calculate it as solid and replace the Ix value that might be wrong and use the solid one.....?

I am bewildered that some times these values are calculated and others not....

For example in the previous attachment you can see a 4 TRON section. This section has been calculated as I want with these values (Ay,Az etc)....

If I delete the upper and lower circles and leave a 2 TRON section I don't get results...

[Rafal.Gaweda · Accepted solution]

So if I calculate it as a thin-walled without getting these values will the results in the building analysis would be credible?

Check the results of A, Ix Iy Iz. If reasonable use such section.

A, W values might be used in steel design but Robot is not capable to run design for such section so in fact it does not matter if you have them in database or not.

The discetization that I ment was when importting the dxf file...

I ment discretization for calculations.

Why is that Artur suggested that I should firstly calculate the section as thin walled note the Ix and then calculate it as solid and replace the Ix value that might be wrong and use the solid one.....?

Some properties are not calculated in thin walled module. Unfortunatelly these properties for this section are not calculated by solid section module.

[STGT]

Hello,

is there a way in Robot to multply characteristics of tappered cross sections, for example instead Iy to put 100*Iy ?

Another question: why i cant in shell autodesk robot model put rc column of user defined cross section (picture below)?

Thanks.

[Rafacascudo]

for RC beams and columms you have moment of inertia multipliers

Yes you can import custom sections on shell structure type.

Just save it to USER´s database and import it  through "new section"

[STGT]

Can i multiply cross section characteristics of steel tappered sections?

[STGT]

Do you also know how to delete user section family?

Thanks.

[Rafal.Gaweda]

Can i multiply cross section characteristics of steel tappered sections?

No.

[Rafal.Gaweda]

Do you also know how to delete user section family?

From database?

see webinar 8 , slides 40-42

[STGT]

Where I can find that Webinar?

Thanks.

[Rafal.Gaweda]

http://forums.autodesk.com/t5/robot-structural-analysis/robot-structural-analysis-webinars/td-p/5523...

[STGT]

hello,

is there a way to rotate principal system od cross section in cross section definition tab?

thanks

[Rafal.Gaweda]

Only on Arbitrary system tab