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Re: Autocad Section Property Calculation

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Jake Watson wrote:

>>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.<<

For shame that a program like AutoCad would have such a half-a**ed 
application!

Tiring of calculating centroids and inertias, I wrote a program for my HP-67 
(the hand held calculator that used tiny magnetic cards) a number of years 
ago that calculated the centroid, centroidal moments and products of inertia 
for composite areas made up of regular geometric shapes that could also be 
combined with standard shapes (rolled steel sections, P/S concrete 
sections, etc.).  You started with an arbitrary set of axes and it would 
calculate the values I stated above.  Optionally, it would also give you the 
values about the arbitrary axes.

The program was submitted to and accepted in HP's library of HP-67/97 
programs.  I don't know if that library still exists, and my HP-67 has died.  
I have started a couple of times to convert the program into a FORTRAN 
program for the computer, but never have completed it.  (When I positively, 
absolutely need the program, I will finish it.)

A. Roger Turk, P.E.(Structural)
Tucson, Arizona