Double angle section

[rubenpezu]

Hello,

I am calculating a double-angle sections for a bracing member in a steel lattice tower. My doubt is when I calculate de distance (a) between connections. Acording the formula in AISC Section E6.2 I have read that the distance is equal to effective length divided by the number of spaces (a=L/nº spaces) but when I see an example I always see this kind of formula a=L*(12)/nº spaces. What is 12? American standard is not common for mi.
I have found the example that I attached.

Thanks

 

[rubenpezu]

I just discover that 12 is the equivalence between feet and inches, 1ft=12in

 

[transmissiontowers]

Yes, we Americans are stuck with feet and inches so the 12 factor is to convert feet to inches in the formula. All properties for angles are in inches but we sometimes measure lengths in feet so for the units to work out for L/r the length must be converted to inches.

I am still puzzled by concrete where you take the square root of the compressive strength that is in pounds per square inch and add some factors to get development length. The square root of PSI does not work out for the units.

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I have been called "A storehouse of worthless information" many times.

 

[rubenpezu]

Thanks for the clarification!