Double every third joist....
Double every third joist....
(OP)
I recently came across a plan where the architect calls for every third floor joist to be doubled. I don't understand why.
Anyone have an idea?
Thanks.
Anyone have an idea?
Thanks.






RE: Double every third joist....
RE: Double every third joist....
RE: Double every third joist....
It's used to increase the load carrying capacity x 4/3 for joist structures. The rational, I understand, is that it's part of an assembly where members are increased in strength by 'load sharing' due to the proximity of the framing members... If the added members fall within that spacing, by definition, it also qualifies as load sharing. It becomes part of the load sharing system.
Dik
RE: Double every third joist....
RE: Double every third joist....
I would typically double at every other joist, and have in the past, but not every third joist.
Mike McCann, PE, SE (WA)
RE: Double every third joist....
RE: Double every third joist....
RE: Double every third joist....
Same concept as when you have a metal stud wall and you add studs around windows or other openings but don't change the mid-wall studs....deflections are not compatible and serviceability issues result, particularly with rigid facades like stucco.
RE: Double every third joist....
BA
RE: Double every third joist....
RE: Double every third joist....
RE: Double every third joist....
You essentially have double the stiffness locally in that region. So, the mode shapes will be a little different and can't carry through the structure so easily.