J-series joist
J-series joist
(OP)
I am looking into a new project in a two story building that was built sometime around 1979. The intention is to use the second floor as storage over an existing bar joist system runing across a span of 35 feet.
The joists' depth is 24" and are 24" o.c. I also got a tag from one of the joists with this legend: 74 2J 3.
Can anyone tell me what this tag means so I can determine the lbs/sf this system can support?.
The joists' depth is 24" and are 24" o.c. I also got a tag from one of the joists with this legend: 74 2J 3.
Can anyone tell me what this tag means so I can determine the lbs/sf this system can support?.






RE: J-series joist
I'd start with the lightest 24" joist and see where that puts you compared to the required capacity.
RE: J-series joist
If you can get very accurate sizes of all the members - go to www.steeljoist.org and they have a "calculator" that will help you - maybe.
Good Luck
RE: J-series joist
RE: J-series joist
RE: J-series joist
Had to do this before as well:
Measure the top and bottom chord angles to determine their size and area (A)
Calculate the distance between the center of gravities between the angles (d)
Calculate the allowable moment (approximate):
30kips * Abottom * d = Allowable Moment (in*kips)
Then back calculate "w"
This should get you really, really close. If you don't have a 60 year joist manual, post the info, and I'll look it up for you.
RE: J-series joist