Area Moments

Hi all,

Would it be possible to use the "AreaMoments" command from Rhino to Grasshopper?

Or would it be possible to add a component that computes the area moments of a surface/closed curve?

Thanks

BMA

Replies to This Discussion

Permalink Reply by David Rutten on July 5, 2011 at 5:18am

I have these properties for AreaMoments. Which are the ones that you'd need?

David Rutten

david@mcneel.com

Poprad, Slovakia

Permalink Reply by bma on July 5, 2011 at 5:33am

Yes that's what I need!

How can I get this list?

Thanks David

Permalink Reply by David Rutten on July 5, 2011 at 5:59am

That is the list of properties that the Rhino SDK provides. I can make a component that outputs these, but I think outputting them all is a bit of overkill. Do you need the world or the centroid moments? Do you need the error data?

David Rutten

david@mcneel.com

Poprad, Slovakia

Permalink Reply by bma on July 5, 2011 at 7:14am

CentroidCoordinatesMomentsOfInertia and its error data would be perfect!

One more question, is it possible to use these properties in a VB component with the current version of Grasshopper?

Thanks a lot David.

Permalink Reply by David Rutten on July 5, 2011 at 7:39am

Yes, you'll need to compute the AreaMassProperties and then all these properties will be available (see attached).

David Rutten

david@mcneel.com

Poprad, Slovakia

Attachments:

area_moments.ghx, 42 KB

Permalink Reply by bma on July 5, 2011 at 7:48am

Thank you very much, it's exactly what I need!

Permalink Reply by David Rutten on July 5, 2011 at 7:54am

I just added Area and Volume moments components for the next release.

David Rutten

david@mcneel.com

Poprad, Slovakia

Permalink Reply by Dedackelzucht on July 5, 2011 at 7:55am

Hey David,

mh....I do not get it, what are Area and Volume moments?

Best Regards

DeDackel

Permalink Reply by David Rutten on July 5, 2011 at 10:29am

I'm not really clear on this myself, but I think it's to do with how objects behave under rotation. For example imagine you have a metal ball weighing 1 kg. It takes a certain amount of energy to start it spinning around the centre point at one rotation per second. Now imagine a very thin but long cylinder also weighing 1 kg. If you want to get this cylinder to spin at 1 revolution/s then you'll need to add a lot more energy as a lot of the atoms are now travelling much farther through space before a single revolution is complete.

But someone please correct me if I'm wrong.

David Rutten

david@mcneel.com

Poprad, Slovakia

Permalink Reply by David Rutten on July 5, 2011 at 10:30am

ps. And of course it depends around which axis you spin the cylinder. If you spin it around the long axis it will take considerably less energy than the ball, if you spin it around an axis perpendicular to the cylinder center line it will take more energy.

David Rutten

david@mcneel.com

Poprad, Slovakia

Permalink Reply by taz on July 6, 2011 at 2:08pm

Just to add...

The second moment of inertia is a static property used for structural load/deflection calculations.

For structural purposes this property is still usually referred to as "moment of inertia" with the symbol "I" so it can all get a bit confusing... Jon M's section property GeoGym components would all relate to these structural conventions.

S = section modulus

r = radius of gyration

Z = plastic modulus

The axis about which the properties are calc'd (as David mentioned) matters.

Permalink Reply by Hrvoje Petrovic on July 6, 2011 at 3:06pm

Like taz said - it's a kind of holy numbers to structural engineers, you learn how to evaluate them at the first contact at the university and you die with them... Essential numbers for any structural calculation.

Opening loads of new possibilities for structural engineers within GH (thanks David!).