Posted by JimM on July 22, 2002 at 05:59:28:
In Reply to: Re: structual stiffness posted by Steve on July 19, 2002 at 08:41:27:
Thanks for the compliments! The M.E. program at Drexel in the 70's, plus working in aerospace has helped.
You mention "directly related to thickness". You may be surprised to hear that the stiffness increases as the CUBE of the thickness! In a rectangular cross-section, a property called "moment of inertia" (symbol used is "I" - think of a measure of stiffness where the type of material hasn't yet been taken into account) equals the width (base) times the thickness (height) cubed divided by 12. Or, I = (bh^3)/12. Because of this, a 2x6 rafter is about four times as strong as a 2x4. Amazing, huh??