autocadd massprop command question

4Boomers · Mar 9, 2016

Hello All,
I am trying to obtain the moment of inertia of built up steel members by drawing the sections in AutoCadd and using the massprop command. When I check AutoCadd's results with hand calcs, it appears that AutoCadd is computing the section properties about at the lower left hand point of the section.

Is there a way to have AutoCAD compute the section properties about the centroid of the composite section?

Any ideas would be appreciated!

CarlB · Mar 9, 2016

AutoCAD MASSPROP appears to calculate the properties about the x and y axes (0,0 coordinates).
Move the object and you'll get different results.

MASSPROP also reports moments about the centroid, isn't that what you want?

IFRs · Mar 9, 2016

Try this: run massprop, then move the object from the calculated and centroid location to 0,0, then run mass prop again. You will see what it does calculates clearly by comparing the massprop outputs.

Sparweb · Mar 10, 2016

If you want to leave the cross-sections where they are, instead you can place a POINT at the coordinates of the centroid, then set the origin at that point (UCS, Origin, click the point).
Then run MASSPROP again. The centroid should be found at 0,0 and the Ix / Iy will be around the centroidal axes.

STF

4Boomers · Mar 10, 2016

Thank you for the solution!

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autocadd massprop command question

4Boomers

Structural

CarlB

Civil/Environmental

IFRs

Petroleum

Sparweb

Aerospace

4Boomers

Structural

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