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Re: Autocad Section Property Calculation

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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.

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)