Download section properties spreadsheet from:
Pingback: Evaluate Function « Newton Excel Bach, not (just) an Excel Blog
There is a problem if you use for numbers (,) , not point (.)
This seems to be a problem with the evaluate function. I couldn’t find any solution from a quick search. The only way around this I can think of (other than switching to using the decimal point) is to add some code to substitute “.” for “,” before calling the Evaluate function.
Can you give example how function will looks?
It is for function “eval”.
I cant understand where is the problem.
I want to calculate section properties for circle with radius 1000, but it’s give theta=-38,88
Link to file:
Hi metroxx – it seems that for a radius bigger than about 300 the calculation of Ixyc (which should be zero for a symmetrical shape) suffers from numerical inaccuracies, and this results in a non-zero Ixyc and Theta. Changing the units to make the radius smaller seems to fix the problem.
Did you get the e-mail I sent with a fix for the , decimal point, and did it fix the problem?
Yes, it is, if higher than 300, than mistake. It is not fixable ?
About email, sorry, I was missed your email. I will take a look and answer you to email. Thank you!
OK, now fixed at http://www.interactiveds.com.au/software/Section%20Properties07.zip
I’ll write it up in the next few days.
It’s looks ok right now. About Eval2-comma spreadsheet. When copy modules to the Section Properties then show error (Problem with GetArray function in module mCoords).
What is right now incorrect?
I have increased the relative tolerance value from 1E-14 to 1E-12. That should be big enough to avoid all these incorrect theta values, but still accurate enough for all practical purposes.
I’ll have a look at the eval2-comma function now.
metroxx – the Eval function in the Section Properties spreadsheet is a modified version of the original. It allows an extra parameter range, and it converts angles from radians to degrees.
I have modified it to accept a comma decimal separator here:
It seems to work OK with the decimal set to either , or . but I would be grateful if you could give it a thorough check and let me know if you find any problems.
Right now everything is perfect. Thank you.
I think will good if will be possible to calculate also:
1) Section perimeter (P = sum( sqrt[(yi-yj)²+(xi-xj)²])) – but by this simple way impossible not to take into account interior perimeter of section (For example if it is closed section, Hollow section)
2)Moment resistance (Elastic, Plastic)
3)Torsional moment of inertia (It)
4) Wrapping constant (Iw)
5) Radius of inertia (iy,iz)
6) J – torsional stiffness constant calculated by coordinates. For example you define coordinates and section type (T, L, O, closed etc …)
The section modulus (2) and radius of gyration (5) would be straightforward, and the perimeter would be a bit more tricky, but should not be too difficult, so I’ll look at incorporating those. The rotational moment of inertia (3) should also be straightforward. The torsional stiffness (6) and warping constant (4) are more difficult because they depend on the configuration of the section, and that would be difficult to detremine from coordinates, even with a section type. I will have a look at the calculations on the “defined shapes” sheet though and add to those.
Is it possible to calculate this profile? (Two profiles near each other)
Just add a “web” of zero thickness between the two parts, along the axis of symmetry.
If you select section type 26 (I section 2) on the “Defshapes” sheet you can define the flange sizes, and set the web thickness to zero, then copy that shape to the “coords” sheet.
But If we will talk about more difficult section?
metroxx – as for the other one, you could find the properties for the two sections acting as a single section by connecting them along a horizontal line through the centroid.
I should emphasise that this is only appropriate if the two sections are connected so that they act as a rigid beam; i.e. a plane section through both members remains plane after bending. If they are not connected they will act as two separate beams (and the section properties for the individual members should be just added together). If there is a partial connection (just a plate connecting the separate beams at the ends for instance) the true section properties will be something between the sum of the two sections, and the value for the two sections acting as one.
Yes, I understand.
But I was think, that will be good to use it for example to find properties for welding (To calculate detailed welding connection). As you know, for example by Eurocode you can check welding by simple and by detailed design. If you want to take into account moment action to the weld you need to know welding contour properties and this will not be connected to each other(Moment of inertia etc.)
Pingback: Daily Download 20: Section Properties | Newton Excel Bach, not (just) an Excel Blog
Pingback: Section properties for groups of defined shapes | Newton Excel Bach, not (just) an Excel Blog
I do trust all the ideas you’ve offered to your post. They’re very convincing and
can definitely work. Still, the posts are too brief for novices.
May just you please prolong them a little from next time?
Thanks for the post.
Often time available is a problem, but do feel free to ask further specific questions here, either on the use of the spreadsheets, or the background theory.
First thanks for the spreadsheet. I seems like it will be a very helpfull tool for me. I tried to use this to compute section properties like I, Sx, J and so on. I have a situation where I need to compute a section properties of a shape which consist of bunch of plates and angles. I defined the section but was not able to get reasonable output because some members are not connected technically. I have pasted my input of the co-ordinates below. So, please guide me how to effectively model this section. Element on right and left are not technically connected. I tried to connect them with a really thin plate but the output doesnot seem reasonable.
Robbie – I’ll have a look tomorrow. If you could send a copy of the spreadsheet with your data to dougaj4 at gmail, that would be helpful.
You have defined the right hand section with coordinates listed anti-clockwise, which generates negative values, so the combined values are close to zero. If you list all the points in a clockwise direction it will give the correct results.
Alternatively for area and properties about the X axis you could just double the results for one shape.
Can I download the spreadsheet for channel section? Many thanks.
Just click on the link. It includes channel sections.
Fill in your details below or click an icon to log in:
You are commenting using your WordPress.com account. ( Log Out / Change )
You are commenting using your Twitter account. ( Log Out / Change )
You are commenting using your Facebook account. ( Log Out / Change )
You are commenting using your Google+ account. ( Log Out / Change )
Connecting to %s
Notify me of new comments via email.
Notify me of new posts via email.