Second moment of area

shanered

Hi guys'n'gals,

I'm looking to create a program that will select a circular and rectangle hollow beam when breadth, depth and diameter is data input into the program and calculate the second moment of area.
I want to keep this program as simple as possible.

I know that the formula for the two are:

(bd^3)/12
((3.14*d)^4)/64

The question's I have are:

1. Is the thickness of hollow beam an aspect of this design?

2. Also follow from the thickness question and depending on the answer, what types of beams could I use depending on the bd of the rectangle/diameter of the circle section? Or is there even set beam types that could be calculated on this data alone?

You help would be greatly appreiciated, and please keep answers as simple as possible where you can.
Thanks in advance!

breadmonkey

1. The second moment of area is dependent on the thickness.

2. What do you mean when you say "what types of beams could I use"? Are you aware that there are tables with all available standard rectangular and circular hollow sections and their mechanical properties?

See here: http://www.tatasteelconstruction.com/en/design_guidance/the_blue_book/

shanered

Needed data entry and example inputs:

Circle:
Outer Diameter (D) = 5
Inner Diameter (d) = 4
Formula is as follows:
"(pi"(D^4-d^3))/64

eg. (3.14(5^4-4^3))/64 = 27.5380231

Rectangle:

Outer Breath (B) =6
Inner Breath (b) =5
Outer Depth (D) = 4
Inner Depth (d) =3
The formula is as follows:
(BD^3-bd^3)/12

eg. ((6*5^3)-(5*3^3))/12 = 51.25

Also the units should be done in meters (m) and the second moment of area answer should be given as:
I=27.5380....
I=51.25...

shanered

I understand that I was using the wrong formula for hollow beams, I've corrected them above.
Are my calculations correct above?
I understand that there is tables but the question I have is from the data above would I be able to select beams from just that data?

breadmonkey

I'm not really sure what you mean. Could you explain what you are trying to do overall?

shanered

Im to make a VBA program that accepts inputs such as depth/breath/diameter and selects a circular/rectangle hollow beam based on those inputs, it the program must also calculate the second moment of area, and if possible, select a beam.

shanered

Its grand, sure! Got it all sorted!