Design by rule of thumb 20

[HvZ]

Hi all,

I am collecting all "rules of thumb" examples in engineering used to either design or give a design a quick sanity check. Could you please e-mail any that you use or know of to me. If you know the origin or explanation (maths) behind it, I would appreaciate it.

I think it is very interesting and have to date not yet found a database of these "quick short cuts", which is the result of years of experince in engineering.

 

[bmike]

For a complete canon of rules-of-thumb (not just engineering, but applicable to almost all areas)get Tom Parker's books: Rules of Thumb, Rules of Thumb 2, and Never Trust a Calm Dog - More Rules of Thumb."

Don't have a copy close at hand, but they are categorized by subject, may for engioneering and building.

A favourite is for parachuting: Open your chute when cars look as big as ants; if you wait until ants look as big as cars, you've waited too long.

 

[NigelB]

Here's a rule of thumb for wood framing:
The shear capacity of wood is 1 kip per foot.

That is:
one 2x12 will carry about 1000 pounds,
one 2x6 will carry about 500 pounds,
etc.
Nigel

 

[unclesyd]

When your design is up for review “Don’t lead with your Lips”

A fool proof design will only fool the designer.

 

[jheidt2543]

NigelB,

Is that 1 kip/bf (one kip per board foot)?

 

[lapstruct]

"when in doubt, make it stout"...sorry PEinc if it costs a little more, but IMHO, the structural engineer is NOT the person to penny pinch with! Obviously opinions vary.....

when a PM/Owner/Contractor comes to you and says "can't you just....." he is typically trying to oversimplify a situation that he knows just enough about to be dangerous.