Calculations in Content Center for steel shapes

[Anonymous]

I am looking at the Content Center data. In this specific case, ANSI AISC Rectangular flat bar steel.

The calculations for Section Modulus seem to be the same for both parameters Wx and Wy.

The calculation for Wx shows in the column properties as: (({G_W} * {G_H} * {G_W}) / 6)

The calculation for Wy shows in the column properties as: (({G_W} * {G_W} * {G_H}) / 6)

These calculations show in the Expression Column as red text. I can modify them but I have no option to OK the dialog box.

The Moment of inertia calculations that are later in the family table use these sections as part of their calculations.

Am I wrong here in my belief that the Section Modulus calculations are wrong and therefore the Moment of Inertia are wrong also?

As an extension of this question, does the Stress Analysis in 2010 use these calculations? Are these numbers used anywhere?

Thanks,
Randy Mabery
Autodesk Inventor Professional 2009 SP2
Autodesk Productstream 2009
Dell Precision T3400 2.4GHz
2GB Ram
NVIDIA Quadro FX 570

[Anonymous]

> As an extension of this question, does the Stress Analysis in 2010 use these calculations? Are these numbers used anywhere?
I recall reading somewhere that yes, these are the numbers used in stress analysis. The whole family table setup is a confusing mess of columns. I'm pretty sure I have asked before on this forum if there is any documentation on what these columns mean and where they are used but there were no replies.

[bobbyzhou]

If you want to edit this column expression, you need to create a R/W library and copy this family to the R/W library, then you can do the edits. Why is it Red? Because this expression is a little complicated, Inventor 2009 don't caculate it well. In 2010, this problems seems to be already resolved.

[Anonymous]

Thanks for the response, but this is already in a read/write library. For some other reason, I cannot modify these specific columns.

My concern is that if the analysis uses these numbers, then I cannot trust what is coming out of the analysis.

Randy

[bobbyzhou]

It is odd to me. If it is read-write library, we should have the permisson to edit the column expression. Did you see any error message? Or could you please attach any screenshots here?

Bobby Zhou

[Anonymous]

It is definitely in a read/write library because I've added other columns.

I've attached a screengrab showing the column properties window. You can see how the column expression font is red. Also, the OK button at the bottom is not available.

Thanks,
Randy Mabery
Autodesk Inventor Professional 2009 SP2
Autodesk Productstream 2009
Dell Precision T3400 2.4GHz
2GB Ram
NVIDIA Quadro FX 570

[pauldoubet]

Is the R/W file still linked to the parent file?

Paul

[Anonymous]

Yes, the family is still linked to the parent. All my families in the read/write library are linked to their parent.

You got me thinking though...I looked at some of the other categories, take rectangular tube for example. It doesn't show any expression in the Inertia column.

The family in particular that has the errors in the section modulus columns is the rectangular bar.

Does anyone else's rectangular bar look this way?

Thanks,
Randy

[pauldoubet]

That is probably why you can't correct that column. I have added square and rectangular tubes before and I did not leave the families linked to the original file and I was able to edit those columns if I remember correctly. I do not recall if I even looked at the rectangular bars. I reworked all of the basic steel shapes except beams and channels so that they were in the correct order for size and common material i.e., HR Strip, HR Bar, Sq Struct Tube, Sq Mech Tube, Rect Struct Tube, Rect Mech Tube,etc.

Paul

[bobbyzhou]

Yes. This is the original state. You should do some edits, like change the Column Caption, Unit or expression. In Inv 2009, the expression can't be evaluated well, so it was shown with Red color. You can try to modify the expression as you like. BTW, whether your families are linked to theire parent, if only they're writable, the family including the column can'be edited.

[Anonymous]

I am confused by your response that "whether your families are linked to theire parent, if only they're writable, the family including the column can'be edited". What does that mean?

I cannot change the expression. This is part of my original problem.

Why is the inertia equations also shown in red for this particular family but not shown at all in other families?

Thanks,
Randy

[dan_inv09]

Is the equation red or the column red? In iParts columns with excel formulas cannot be edited with the internal iPart editor. Maybe you need to edit the parent?
[I don't mess with the content center, I'm used to where my old iParts are and don't want to confuse the issue (plus it seems like most people have at least some trouble with CC editing).]

[Anonymous]

For the Flat Bar family, the equation is red and the columns are black.

For other families such as Rect Tube, it doesn't show an equation at all and the column is black.

I guess I could recreate the entire family but I'm still not sure if the values that are in here are used by the stress analysis.

Thanks,
Randy

[Anonymous]

I submitted this to Autodesk yesterday and have been talking with a Product Support Specialist.

According to him, the FEA in 2010 does not use these values. It's calculations are independent of what is in Inventor.

I still do not have clarification on why the section modulus calculations are incorrect in the family table. I am currently trying to figure out how I can delete the data. Since it's wrong and the FEA doesn't use it, I'd rather it not be there at all.

Thanks,
Randy

[salariua]

Couple of years later I am having the same problem. The table for  "ISO 1035/3 - 1980 Hot-rolled steel bars - Part 3: flat bars"  is wrong.

Section modulus Wx formula is wrong and it can't be edited because Height G_H, Width G_W are of type "String" and it's expecting values of type "Real" units "mm".

The solution I've come up with was to make another column G_W_N (Width new) and G_H_N (Height new) with exact same values as the original G_W and G_H , BUT made the columns of type "Real" unit "mm".

You then change the formula in the Section Modulus Wx pointing at the new columns and change it to units "mm^3".