I may be biased, but I think the spreadsheet at:
http://newtonexcelbach.wordpress.com/2008/03/25/se...
is pretty good.

Please let me know if you have any questions or suggestions for improvement.

Doug Jenkins
Interactive Design Services
http://newtonexcelbach.wordpress.com/

I wrote my own - took like three minutes??

Thanks, trying it right now. It is possible to combine basic shapes to create some more complex sections? I am working with repairs to aircraft fuselage stringers, so my starting point is a top hat section with flanged edges, to which I am attaching c-section extrusions either side, then maybe a L-extrusion in the corners etc etc. Get the idea? All of the sections I am creating can be broken down into rectangle.

For complex shapes you have to define the shape with coordinates (on the Coords sheet) at the moment. I'm thinking about adding routines to allow simple shapes to be combined, but other things have priority at the moment. It's open source, so maybe MiketheEngineer might like to spend a couple of minutes doing it for us. :)

Doug Jenkins
Interactive Design Services
http://newtonexcelbach.wordpress.com/

Great site...

Dik

HP used to have one in their Structural X package for the 41C and CX.

Mike McCann
MMC Engineering
http://mmcengineering.tripod.com

IDS -

I was thinking more on the lines of I-beams and hollow sections.. What your are talking about is bit more complex.. Archon at $40.00 has a rather decent program for doing these things.... Not easy BUT cheap!! www.archoneng.com.

Mike - it's not really the cost, I just enjoy doing these things myself. I think I'll have a go at adding the feature to combine shapes to my spreadsheet when I have some spare time. Not a 3 minute job, but not a huge amount of work either.

Doug Jenkins
Interactive Design Services
http://newtonexcelbach.wordpress.com/

IDS. If you do add this feature, be sure to allow for different weighting factors (such as modular ratios) to be applied to the different component shapes.

Quote:

IDS. If you do add this feature, be sure to allow for different weighting factors (such as modular ratios) to be applied to the different component shapes.

Not sure how I'd handle that automatically. Wouldn't it be better to leave it to the user to adjust the shapes according to their own requirements?

Doug Jenkins
Interactive Design Services
http://newtonexcelbach.wordpress.com/

I was thinking of a standard shape made of one material being embedded in a shape of a different material. A sort of (linear) generalisation of reinforced concrete.

I'll give it some thought. If anyone has any comments on how this is handled in different software, I'd be interested.

Doug Jenkins
Interactive Design Services
http://newtonexcelbach.wordpress.com/

Such calculations may be very complex for application in excel. The sectional properties of polygonal sections can be calculated using the Green's theorem. You may try using another program or use a more advanced programming environment for such tasks, for example C# etc.
Regards.

Analysis and Design of arbitrary cross sections
Reinforcement design to all major codes
Moment Curvature analysis
http://www.engissol.com/cross-section-analysis-des...

Quote:

Such calculations may be very complex for application in excel.

Not really, this is well within the capabilities availbale within Excel. The only difficulty was applying a correct algorithm, but having thought about it that's not too difficult either. The only remaining problem is finding some spare time to actually do it.

Doug Jenkins
Interactive Design Services
http://newtonexcelbach.wordpress.com/

draw it in Autocad or other software and ask it for section properties? That's what I do...

There are a lot of section databases out there with section data, some in excel... and it's easy to use VLOOKUP to access the data.

Dik

The question was answered admirably by IDS. I've had his spreadsheet stored in a handy location for the last 4 years and consulted it often.

It includes both look-up to get the equations for typical shapes (see DefShapes tab) as well as ability to analyse non-typical user-defined shapes.

=====================================
(2B)+(2B)' ?

Thanks Pete. I think I might make an update my next project, with:

• Function to combine shapes into a compound shape
• Provision for input of modular ratios
• Allow shapes within another shape to be specified as either additive or displacing
• Plotting function for compound shapes
• Not sure about torsion constants. Quite difficult to do properly I think

Doug Jenkins
Interactive Design Services
http://newtonexcelbach.wordpress.com/

In the AISC Steel Tools site www.steeltools.org under Alex Tomanovich's excellent list of spreadsheets is SECTPROP.xlsx which is similar to his useful app for the HP48G and HP50G.

His HP48G app does section properties of known shapes or outlines of described shapes.

Jim H

It took a bit more than 3 minutes, but an updated section properties spreadsheet, which will work with groups of any number of shapes, can be found at the link below. Shapes can be offset and rotated, and given an "elastic modulus", using either actual or relative values.

http://newtonexcelbach.wordpress.com/2013/04/12/se...

Doug Jenkins
Interactive Design Services
http://newtonexcelbach.wordpress.com/

you probably could've done it in 1 minute, if you invented a near-light-speed rocket first, and did your work onboard ...

there's a thought (for a friday afternoon) ... if time dilates, you'd think slower ... wouldn't you ? you're aging slower, an experienced second is 1 minute to someone outside the rocket ship ... so i got to ... if you're aging slower, your metabolism is slower, you eat, breathe (or poop) slower, you'd think and work slower (you'd accomplish 1 second's work in 1 experienced second).

Quando Omni Flunkus Moritati

I agree with (and use) AutoCAD to calculate basic section properties. Create a closed polyline shape and use the 'region' command to define the shape and then the 'massprop' command to calculate the the principle inertias or those about the X and Y axis as positioned in model space.

Every once in a blue moon, I have a 'hollow' shape where the hole and the section do not have the same center of mass. It would be cool if AutoCAD could perform the parallel axis calculations. I am sure somebody who knows LISP has already created the routine...

I don't have AutoCAD, but if you define the hollow shape with a single polyline, as described below, it should give you the correct properties:

- Define the exterior shape with a pline, working clockwise.
- Extend the pline to any point on the interior void.
- Define the void shape, working anti-clockwise.
- Extend the pline back to the starting point on the outer shape.

As long as the two lines connecting the inner and outer shapes are exactly co-incident, and the shapes are defined in opposite directions, the result should give the correct section properties.

Probably a good idea to check the results with a spreadsheet though :)

Doug Jenkins
Interactive Design Services
http://newtonexcelbach.wordpress.com/

Said another way, convert your hollow shape to a non-hollow shape by cutting a vanishingly narrow channel from the outer perimeter to the inner perimieter. Good idea.

=====================================
(2B)+(2B)' ?

Nice way of putting it pete.

Makes it obvious why you should go around the void in the opposite direction to the outer shape.

I meant to add that the same method works with any computation based on coordinates, either CAD or spreadsheet based.

Doug Jenkins
Interactive Design Services
http://newtonexcelbach.wordpress.com/

I use acad as well. It works great! I draw the shape and then use the region command. PLines are not required.
Acad can also find properties of complicated shapes. To remove a hole: region both shapes, them pick modify, solid editing, subtract.
I will hatch the new region to verify I have created the correct cross section.