Return to index: [Subject] [Thread] [Date] [Author]

RE: Autocad Section Property Calculation

[Subject Prev][Subject Next][Thread Prev][Thread Next]
Use the massprop command once to get the centroid and then move the object by that amount to the origin. THen use massprop again.
-----Original Message-----
From: vicpeng [mailto:vicpeng(--nospam--at)vtcg.com]
Sent: Wednesday, May 31, 2000 7:09 AM
To: seaint(--nospam--at)seaint.org
Subject: Re: Autocad Section Property Calculation

Ahh  yes.  Thanks.  That makes the example I have make sense.  But how do I get the real centroid of the section, i.e. where is 0,0 with respect to the section?

Thor A Tandy P.Eng
Victoria BC
Canada
e-mail: vicpeng(--nospam--at)vtcg.com
----- Original Message -----
Sent: Wednesday, May 31, 2000 6:16 AM
Subject: Re: Autocad Section Property Calculation

Make sure the object centroid is at 0,0.  Autocad calculates all
properties about that point.  If you have a 2x4 at 10' from the origin,
you will get a very large inertia.  Then other option is to use the
parallel axis theorem and subtract out the ad^2 term by hand to account
for the displacement.

Enjoy,
Jake Watson, E.I.T.
Salt Lake City, UT

> vicpeng wrote:
>
> I have a feeling that this might have been posted before.
>
> In AutoCAD under "massprop" the section properties such as area,
> perimeter, centroid, Moment of Inertia etc are calculated.
>
> I did a check on a complex section by hand and I found that AutoCAD
> produces a different answer from mine for the Moment of Inertia.  The
> other values appear correct but not "I".
>
> Does anyone know if I did something wrong or what AutoCAD is doing?
> This is not my software so the licensee may have set up something in
> the program??
>
> Thor A Tandy P.Eng
> Victoria BC
> Canada
> e-mail: vicpeng(--nospam--at)vtcg.com