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Torsional Properties...

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X4vier

X4vier

Civil/Environmental
Joined
Feb 24, 2018
Messages
167
Location
CO
I'm looking for formulas and/or tool for calculating the torsional properties used in Design Guide 9.
Wno
Sw1
Qf
Qw

Thanks.
 
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What type of shape are you dealing with? There are closed form solutions for some shapes, and approximate solutions are needed for other shapes.
 
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Clasical W-shape with Channel on top.
I have found them in SCI Publication 057, but for the individual shapes separately.
Torsion_Wshapes_qcixyb.png

Torsion_Channels_pu4luq.png

Any idea for combined them to calculated the W-shape with Channel on top?

Thanks.
 
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Do you have any section analysis program? I think you want the FEA approximate solution that is readily generated by these tools. There is a python library that can solve it [URL unfurl="true"]https://sectionproperties.readthedocs.io/en/latest/rst/theory.html[/url].

I would not expect much improvement on the torsional section properties by putting a hat channel on a WF, the final section is still an open section and the shear flow for torsion has to squeeze through the beam web.
 
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You do get a moderate improvement DL -- just by nature of extending the half-sine buckling shape of the compression flange wanting to squirt out sideways. Not nearly as much as a closed shape of course, but it's a common solution.
 
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@Lomarandil fair enough. Perhaps Xavier will let us know his results and compare the bare wf to the reinf.
 
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I will do if I find a tool .. [pc2] not phyton yet in my abilities.

Thanks.
 
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Some Other options I have used are (not certain they can all get the torsional properties)
Enercalc Section Designer
Robot Structural Analysis
SAP2000 Section Designer
RISA Section
Dlubal, IESWeb. Most all good structural packages have some ability to model custom sections or at least generate section properties.
 
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I had a look at this type of thing a year or so ago.
I forget what the conclusions I made were, so read all the prior posts in the series I guess. For torsion constant I think I recall coming to the conclusion that adding the two together was correct, for the warping constant I cannot recall...

That python code was for version 1 of sectionproperties, but if you were going to dip your toes into python it should be similar for version 2.

 
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i can confirm SAP2000 only calcs J.
SAP-Properties_cuahtn.png


I'm not ready for phyton now, any other ideas?
 
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IES Shapebuilder will do it and calculates the stresses from an applied load.
 
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What is the orientation of the channel? Can you attach a sketch of what you are trying to analyze? I may have an easy solution for you.
 
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Agent666 said:
For torsion constant I think I recall coming to the conclusion that adding the two together was correct, for the warping constant I cannot recall...
Click to expand...

I believe you are correct in that torsion constants can be added, warping constants depend on the shape. For angles, you can add them but for other composite shapes you can't as far as I am aware. I'd have to test further.
 
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I can confirm IES Shapebuilder makes the work, at least the warping function.
 
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CISC torsional properties handout has formulas for pure torsion and warping torsion constants for channel cap beams. I'm not sure exactly what properties you are looking for and why you would need properties other than those two though.
 
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Composed sections like those used as runway beams of heavy cranes.

W-shape with a channel on top.
Buil-up w shapes with unequal flanges.

Thanks.
 
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For those wanting to use the sectionproperties program without getting into Python programming, an Excel front end is available at:

You will need Python and section properties installed, and also pyxll to connect the python code to Excel. Pyxll is a commercial package but is quite cheap.

Once everything is installed you can use the sectionproperties functions like Excel built-in functions, without any coding.

Doug Jenkins
Interactive Design Services
 
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$29/month isn't cheap.
IES shapebuilder is cheaper than that, it's just a part of the solution.
 
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X4vier said:
$29/month isn't cheap.
IES shapebuilder is cheaper than that, it's just a part of the solution.
Click to expand...

For a general purpose application, it seems reasonably cheap to me, but sure if linking to a section properties app was all you could do with it, it wouldn't be worth it.

Doug Jenkins
Interactive Design Services
 
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Do you use revit? The building suite comes with Robot Structural analysis that has a powerful section analysis tool.
 
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