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RE: Finding Moment of Inertia of Solids in AutoCAD

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To add to all the previous comments...
If you are trying to find the properties for built up sections, align the
edges of your regions, and use the Union command.  If done correctly, you
will notice the common line of the objects will disappear.  This, combined
with the region and subtract commands, will make all the objects into one
coplanar region.  Massprop will then give the properties for the entire
built-up section.

Lucas Jolly
Staff Designer
Lionakis Beaumont Design Group
phone: (916)558-1900
fax: (916)558-1919

-----Original Message-----
From: Gina Gobo [mailto:GoboGT(--nospam--at)]
Sent: Wednesday, December 05, 2001 7:41 PM
To: seaint(--nospam--at)
Subject: Finding Moment of Inertia of Solids in AutoCAD

Does anyone have any experience using AutoCAD to find the section properties
of solids? I understand how to use the "region" and "massprop" command to
find the moment of inertia of a section. However, these commands only take
the outline of an object. I think that you need to make an object a solid in
order to get the section properties of built-up sections with objects like
tubes. When I try to use region and mass prop for these types of sections,
AutoCAD takes the moment of inertia of the section as a solid and does not
take into account hollow sections. 

If anyone can help with this, I'd appreciate it. I cannot seem to figure it


Gina T. Gobo, EIT
Carter & Burgess, Inc
Facilities - Structural Engineering
Seattle, WA
Ph. 425-822-7096
Fax 425-822-7246

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