(35s) Moment of Inertia, n rectangular elements

[Jazmond]

Hello all, I'm an engineering student who has been benefiting greatly from the community and wanted to share my life-saving/time-saving program which takes n rectangular elements, their width and heights, and the centroidal distances to the composite centroid, the second area moment of inertia, and the total area.

(I001) LBL I
CLVARS
CLE
XEQ I046
INPUT N
RCL N
STO S
INPUT B
INPUT H
INPUT Y
XEQ I018
DSE S
GOTO I008
XEQ I034
RCL C
RCL T
RTN
RCL B
RCLx H
STO (I)
RCL Y
STO (J)
E+
RCL H
3
y^x
RCLx B
12
/
STO+ T
XEQ I051
RTN
xW ///DD??
STO C
XEQ I046
RCL (J)
RCL- C
x^2
RCLx (I)
STO+ T
XEQ I051
DSE N
GOTO I037
RTN
10
STO I
20
STO J
RTN
1
STO+ I
STO+ J
RTN

This stores the total moment of inertia under T, the area under A, and the centroid under C. The program ends by printing
Y: Centroid
X: Mom. of Inertia

[Nihotte(lma)]

Hi Jazmond,

Thanks for the program

Would you like to provide us with some numerical examples to accompany your program?
In what practical context have you already implemented it?


Laurent

[PedroLeiva]

I will also add, please show a graphic illustration for those not so familiar with physics. Thank you in advance. Pedro

[Johnh]

Hi Jazmond
Nice work. I can appreciate how useful that is. Im a structural engineer and teacher and its useful for the properties of irregular sections. I have some that do similar.

Here's an extended challenge: Can you Include the section modulus (Z) at the top and the bottom of the section?Then you have all the properties needed to work out stresses. To do that, you could keep track of the highest and the lowest points that exist as you process each rectangle. Don't need to store them all, just the max and min. Then you can subtract the centroid level and divide into Into I to get Z top and Z bottom.

cheers
John