TJI Bridging or Blocking
TJI Bridging or Blocking
(OP)
Does anybody use blocking are bridging at mid-span (or other) for TJI roof or floor systems?
I've been told for many years that the typical TJI system does not require bridging or blocking because of their "structural integrity" or similar expression.
Unless you specify the 360 or 560 series TJI joists, and the span is not excessive (open to debate or discussion), the "slenderness ratio" for the 110, 210 or 230 series is not much better than any other slender element joist.
I have a project where I WILL be providing solid blocking where RTU's are bearing on LVL's that are amongst the TJI's, BUT... I would also like to specify bridging or blocking for the rest of the system, but, that tends to go against the current trend.
Comments? Thank you!
I've been told for many years that the typical TJI system does not require bridging or blocking because of their "structural integrity" or similar expression.
Unless you specify the 360 or 560 series TJI joists, and the span is not excessive (open to debate or discussion), the "slenderness ratio" for the 110, 210 or 230 series is not much better than any other slender element joist.
I have a project where I WILL be providing solid blocking where RTU's are bearing on LVL's that are amongst the TJI's, BUT... I would also like to specify bridging or blocking for the rest of the system, but, that tends to go against the current trend.
Comments? Thank you!






RE: TJI Bridging or Blocking
If, you needed it for diaphragm action, then that's on you to specify. Otherwise it'd be up to them.
On the random topic of TJI diaphragms, see the attached.
RE: TJI Bridging or Blocking
RE: TJI Bridging or Blocking
Don’t the manuf’ers. actually make, or can’t you make up blocking from an extra TJ member or two? Then, you still need web to web blocking (2x3 or 2x4, short of the chord to chord vert. dimension) to fix the blocking pieces to the joist web. It seems to me I’ve seen that done. Why wouldn’t a piece of plywd. diaphragm material work just as well? Put the 2x3 web blocks on opposite sides, during your pre-fab., so you can just rotate the blocking in btwn. the TJ’s on installation. Probably, screws would work better than nails because these fasteners must work in tension to be affective. Think about penetration and pull-through on the OSB webs. The TJI people pitch the fact that their product doesn’t need the same amount of blocking/bridging as solid sawn, so that’s some labor savings for their system. Then, they’ll also blame some floor squeaking on any blocking, and you can fight about that. They don’t like you using X-bridging becuase there is no good way to fix it at its ends, and it ends up imparting a tension component (unzipping force) on the glue joint btwn. the web and the bot. chord member. That’s still a no-no. Why isn’t the LVL (or some such) a curb, for the RTU’s, above the roof? That would certainly help distribute the concentrated loads to adjacent joist. And, that’s basically what blocking or bridging is intended to do.
RE: TJI Bridging or Blocking
RE: TJI Bridging or Blocking
I think that this is an important observation. As others have noted, there are a number of reasons for blocking and most of them are related to serviceability issues which could, potentially, be set aside if the product performs well. There is one use for blocking that is more critical however: in roofs with uplift, the blocking provides lateral torsional buckling resistance when the bottom flange goes into compression. The slenderness that you mentioned will kill 'ya there.
I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.
RE: TJI Bridging or Blocking
KootK...I have specified blocking in roof systems with i-joist before for that reason. But afterwards questioned my logic because gyp board was attached to the bottom side. I believe that provides enough connection to consider the bottom flange fully raced in an uplift condition. I you had a drop ceiling it certainly would be different.
RE: TJI Bridging or Blocking
thread507-420136: Boise Cascade - Ijoist - Question
RE: TJI Bridging or Blocking
I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.