Glulam Beam Splice Moment Connection

[jerseyshore]

We are working on a splice detail to repair a 50 ft long glulam roof beam. The first 6 ft or so is completed damaged so the intention is to cut that part out and splice in a new matching member with a steel side plate on each side. The existing glulam is 6.5" wide x 32.5" deep.

We've run some calcs and came up with about (12) 3/4" (2 rows of 6) bolts with 4" dia. shear plates required at both the top and bottom of the beam to resist the tension/ compression forces.

If we don't use the shear plates, we would need roughly (14) or (16) bolts in each zone. Might even have to bump up to 1" dia bolts.

We normally try to avoid wood moment connections at all cost, but are stuck with it here. Client obviously wants to minimize the splice cost as best as possible.

My question is, do we stick with the shear plates, even with the added cost, to reduce slip in this connection? Or do they not add any additional advantage here and just go ahead with adding the extra bolts?

 

[ANE91]

There’s a nifty shrinkage equation somewhere in either the FPL handbook or some ASTM or both. I’ll dig it up tomorrow. You might start with 19% MC and anticipate an in-service drop to 9%.

Nvm found it in one of my old Mathcads.


The fact is that your new 6ft segment is not going to be at the same MC as the remaining 44ft. Vertical slots let you deal with that, since the force couple creating your moment is horizontal. Any slop or slip horizontally will be what opens up the joint and kills your rotational rigidity. See below…also not my detail.



You mentioned end damage — if that’s rot, then your existing beam might actually be “wetter” than the one you’re putting in. Pronged moisture probes might give you a rough idea of the MC nearest the surface.

 

[dik]

Never seen those designed or come across them before.

I think I've only ever used them... don't recall ever using lag screws. Look into it; it's a really good approach.