How to calculate section constants for rectangular tubes?

[Thorvald]

Hi.

I was wondering how to calculate I and W for rectangular and quadratic tubes. I have formulas for massive rectangular and square sections and for circular tubes. I tried to make a formula for a square tube section, based on how the formula for the circular tube looks - but I didn't get the correct result (compared with results from "Sectionananalyzer"). I am calculating som wood box columns, and it would be nice to write the formula - even directly in my Excel calculation sheet, rather than using section analyzer.

 

[Lok]

What is I and W?
People here are from different backgrounds or countries terminology differs :P

 

[Thorvald]

Oh allright, I thought it was international.
I = Moment of Inertia.
W = Moment of resistance (?) - Not sure if that is the correct English word.
i = Radius of inertia.
A = Area (this I can figure out how to calculate, though...)

 

[FredGarvin]

http://www.efunda.com/math/areas/IndexArea.cfm

http://www.engineersedge.com/section_properties_menu.shtml

http://hyperphysics.phy-astr.gsu.edu/hbase/mi.html#mi

The list goes on. Do you have a basic engineering mechanics book available to you? There are ususally pretty good tables in the appendices.

 

[Thorvald]

Thank's for the answer. I was asking because some of these formulas is not written in my book.