Formula for "J" in AISC manual
Formula for "J" in AISC manual
(OP)
Does anyone know what formula is used to calculate the value of "J" that is listed in the structural tubing tables in the AISC manual of steel construction?
Thanks in advance for the help.
Thanks in advance for the help.
Tony Billeaud
Mechanical Engineer
Franks Casing Crew





RE: Formula for "J" in AISC manual
tg
RE: Formula for "J" in AISC manual
Thanks,
Tony Billeaud
Mechanical Engineer
Franks Casing Crew
RE: Formula for "J" in AISC manual
RE: Formula for "J" in AISC manual
for a rectangular tube,
J = 2*t*b^2*d^2 / (b + d)
where b and d are measured to the mid-thickness,
i.e. for 4 x 2 x 1/4 tube,
d = 4-0.25 = 3.75
b = 2-0.25 = 1.75
t = 0.25
I have obtained this from Blodgett - Design of Welded Structures, section 2.10, Table 2.
Blodgett call it R ( torsional resistance ), we call it J (torsional constant) in Canada. This should be what you're looking for.
tg
RE: Formula for "J" in AISC manual
For a TS 8 x 6 x 1/4 (4*(7.875*5.875)^2/(2(7.75+5.75))*.25= 79.3 in^4
The difference between the AISC number (74.9)and my number is probably because of the corner radii. I got this from Steel Structures by Gaylord and Gaylord page 234.
RE: Formula for "J" in AISC manual
Tony Billeaud
Mechanical Engineer
Franks Casing Crew
RE: Formula for "J" in AISC manual
Give him the star.
RE: Formula for "J" in AISC manual
Thanks
Andrew299
RE: Formula for "J" in AISC manual
http://www.efunda.com/math/areas/SquareTbeam.cfm
RE: Formula for "J" in AISC manual
The T section mentioned above probably qualifies as being both open and thin. The rectangular hollow section mentioned further above does not qualify because it is closed rather than open. A non-hollow rectangular section would probably not qualify because it would not be thin enough.
HTH
RE: Formula for "J" in AISC manual
Look in the site below, under Beams -> Cross sections -> I beams -> Cut : by clicking onto 'Formulas' you'll see a more to the point formula than the general (correct) one given by Denial.
And please start a new thread for a new question.
prex
http://www.xcalcs.com
Online tools for structural design