Glulam tension connection

[gwynn]

I am looking for information on high capacity tension connections for glulam. I know there was some work done with embedded and epoxied rods/rebar for moment connections, which could be applicable here, but as far I can see it has either been abandoned or is proprietary as it is not codified.

This is a feasibility study at this point. Glulam is the preferred material, but connecting for tension loads in the range of 50kips to 100kips looks prohibitive with standard connection details.

 

[msquared48]

Why?

Mike McCann
MMC Engineering

 

[gwynn]

Why to which portion of my post?

 

[MikeHalloran]

Go to an IKEA showroom. Look closely at the wood parts.

There ain't a single piece of natural wood so large that it wouldn't fit in your pocket, anywhere. All those little pieces of birch are joined into longer pieces with adhesive bonded finger joints (you can buy the router bit), and the longer composite "sticks" are adhesively bonded into boards, or whatever. Sort of like a Glulam.

ISTR a photo of a 400 ft long 2x4, assembled with adhesive and finger joints, when finger joints first came out. Subject to bending, it broke, but not at a finger joint.

Joining Glulam to metal is a different challenge.



Mike Halloran
Pembroke Pines, FL, USA

 

[msquared48]

The last sentence... I do not see se tension loa as too large for glulams.

Mike McCann
MMC Engineering

 

[gwynn]

MS: I don't see the tension as too large for the glulam, I see the standard connection details as too labour intensive compared to a steel alternative.

Mike: I am joining glulam to steel, so yes it is a bit more challenging.

 

[dhengr]

Gwynn:
We’ll just keep guessing at what you are really trying to do for another week or two, in the mean time you might want to call it a ‘secret feasibility study.’ Then you can give us another clue, and we’ll be off and runnin for another week or so. I say why not, to that other part of your post.

 

[Triangled]

Can you provide some kind of a sketch showing the Glulam and the directions of the loads?

 

[gwynn]

I'll provide a sketch tomorrow as I am going to bed now.

The basics are that I have a horizontal glulam beam-column framing into the side of a steel beam. The glulam has reasonably high shear loads and may be in either compression or tension. The axial loads in the glulam are as given above (50-100kips in either direction). Essentially, think of a purlin framing into the side of a steel beam with some large axial forces thrown in.

 

[msquared48]

OK. And waiting for the sketch...

Just wondering with those forces, if the connection would be that difficult or costly to design and construct, why you are not using a steel beam. Is the glulam an insulator of sorts?

Mike McCann
MMC Engineering

 

[BAretired]

Steel plates with glulam rivets can carry some pretty hefty forces.

BA

 

[dhengr]

Gwynn:
Can the steel beam take a 100k concentrated lateral load? I agree with BA that Timber Rivets and side plates might be a solution. Butt the GlueLam to the stl. bm. or a base pl. on the bm. for compression and then design the side pls. for the tension, so the rivets aren’t worked full strength in both directions.

 

[msquared48]

No sketch. I guess the tension got too much for the OP?

Mike McCann
MMC Engineering

 

[Triangled]

 

[gwynn]

Realised that I can't post here from work, hence the lack of reply or sketch.

In any case, the purlin is also acting as a collector in a large roof which causes the high axial loads. This is at the location where it frames into a braced bay, so the 100kip load goes through into the bracing and does not cause significant weak axis bending in the girder.

Glulam is preferred as the environment is highly corrosive to steel (rough guideline given was only use stocky sections and nothing thinner than 1" to allow for inspections to spot any corrosion issues prior to significant loss of section). We're still investigating steel options, but the cost of glulam connection design and installation looks to be similar to the steel coating costs at this point.

I spoke with a couple (or I guess the couple) of local glulam manufacturers and the concensus was to use Bertsche BVD connections for the axial loads.