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 7, 2011 at 2:54am

In that case should I rename the output parameters to use standard symbols instead of the ones I came up with. Is there an internationally acknowledged notation for these?

David Rutten

david@mcneel.com

Poprad, Slovakia

Permalink Reply by Hrvoje Petrovic on July 7, 2011 at 3:26am

The letters for the output parameters you have are fine, they are like in taz's scan (American symbols). Over here in Europe the letters are the same. The graphics for the icon - well, once you know which it is, you don't forget it. Rhino has those wavy rectangles and boxes with M and V, so I think it is a matter of getting used on it. Maybe somebody else has a different point of view.

taz, isn't there a bug in the scan for the rectangle? Shouldn't it be I=bxd^3/12? Blame to the AISC...

Permalink Reply by taz on August 1, 2011 at 7:52pm

Just saw this...

The typical rectangular case (with an axis through the centroid) is on the previous page (with 12 in the denominator).

Permalink Reply by Victor Leung on August 1, 2011 at 3:55am

Although I dont use these components myslef, I respect the fact that more and more commands are added to the standard batteries.

David, do you think it is possible to add more description to the text in the right click help. I start to find it confusing for beginners.

Cheers

Victor

Permalink Reply by David Rutten on August 1, 2011 at 4:47am

Hi Victor,

I'm planning to rewrite the entire help system from scratch. I've been planning this for a long time which is why I haven't invested any effort at all in adding topics to the current one. This is a fairly long term project though.

David Rutten

david@mcneel.com

Poprad, Slovakia

Permalink Reply by Victor Leung on August 1, 2011 at 6:02am

I'm more than glad that there is a plan for this.

Permalink Reply by Nick Schiller on August 31, 2011 at 8:19am

Hello all,

I have been using the Area Moments function and have been able to do most of what I am trying to do. I do however have two questions.

In Rhino I am able to to take the area moments of two curves (essentially a sections of a solid with a cutout). The area moments ananlysis gives me the area centroid of the cumulative area as well as the moments of inertia thereof.

In Grasshopper I end up with two areas, two centroids and two sets of inertia moment values. Is there a way to sum this? Please see attached image.

The second question I have regards the output 'S', I am unsure about what exactly these values are?

Let me know if any of this is not clear.

Thanks for you help,

Nick

Permalink Reply by alex on September 20, 2011 at 1:37am

Hello Nick,

This feature would be very nice. Do you hav any progress on the cumulative area and/or volume properties for multiple items?

Regards,

Alex

Permalink Reply by Nick Schiller on September 23, 2011 at 3:11am

Hello Alex,

currently not as I have not had much time to further explore this. I am currently doing this manually. I do however plan on working on this problem later next week and will share any findings here.

There are a few other things I am trying to do in conjunction with this and I will share those problems later.

Kind Regards,

Nick

Permalink Reply by Lucas Epp on September 24, 2011 at 4:48am

You can use the parallel axis theorem to fairly easily work out the cumulative area moments of multiple planar curves.

David - it would be useful for some of us engineers to get these functions exposed.

In particular, it would be useful if Area Moments could take in a user-defined axis system (plane) and calculate the properties about these axes.

One other note - the Volume Moments must output a plane / axis system (not just a centroid point) for the moments to be useful, as for an arbitrarily shaped volume it is not obvious what the principal (centroid) coordinate system of the volume is.

Permalink Reply by Nick Schiller on September 26, 2011 at 2:40am

Hello Luke,

thanks for the tip I will look into it and see if this works for my problem. I have ended up doing this manually in the mean time.

Regarding the other point that you raised (bending axis position). I am actually taking my sections and rotating and projecting them to one of the world planes. Then I use the parallel axis theorem, my defined bending axis and the output from Area Moments 'I' to work our the second moment of area of any section in space with any given bending axis. This works very well and I have validated this with multiple models.

Let me know if you would like more information on this.

Regards,

Nick

Permalink Reply by Toby Shaughnessy on May 3, 2013 at 9:14am

Hi I'm new to Grasshopper so maybe there is an easy way to do this but I have not found an answer anywhere. Often you want only one component of the inertia output. the inertia about the the x-axis only for example, How do I extract just this value for use?

-Toby