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Laminated Timber Beams

Laminated Timber Beams

Laminated Timber Beams

(OP)
Hi All,

I have a question regarding building a built-up timber beam out of 2x12

We have spec'd solid sam members and they cannot get them in time.

The code has tables for 5-ply built-up sections but does anyone see any reason why a 6-ply would be a problem? Need it for capacity.

As an alternate I could try 2 4-ply built-up beams. Make the 4-ply beams with nails per the code, them thru bolt the two built-up beams together to get a new huge beam??

Thoughts?

RE: Laminated Timber Beams

Could you not go with a structural composite lumber beam instead? I don't know if you'd get the composite action you're after if you use a 4 ply nailed beam with 2 plies bolted on.

RE: Laminated Timber Beams

You'd need to look at how the beam was loaded and what the fasteners would need to do to accommodate the load transfer between plies.

6 plys is not out of the question. But it does beg the question, why not engineered lumber like LSL or LVL. It would likely be much easier in the end.

RE: Laminated Timber Beams

(OP)
Good questions!

The application is an exterior rehabilitation of an existing facility and not for a residential building. The existing structure is all old creosote treated large timber products. Not too sure I should be using LVL outside in the elements, but pressure treated DFL should be fine.

The member would be loaded onto by a nail laminated deck which would extend fully over the built-up beams so not asking the nails in the built-up to pull to all the ply's from a face mounted hanger.

RE: Laminated Timber Beams

Then I don't see a 6 ply being an issue, I'd just be overly conservative with the bolting specification.

Stainless steel or hot-dipped galvanized bolts (not sure if HDG bolts even exist).

LVL and LSL do not have approved exterior grades, but there is a Parallam Plus product that is approved for outdoor use.

RE: Laminated Timber Beams

Sounds workable with the top loading. I would also be worried about LVL outdoors. If needed, I believe that parallam can be made outdoor appropriate.

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: Laminated Timber Beams

Everynameistaken:
I should think that what you want to do with the 6-ply treated DFL would be o.k., since it is uniformly top loaded. But, a couple things you might consider: 1.) cover the top with a piece of rubberized peal-n-stick flashing material to keep any water out from btwn. the plys; 2.) maybe consider using some of the newer structural screws from both sides, of the proper length 8" +, otherwise you are going to have a pin cushion of a beam. The screws will likely pull the whole beam together better after some initial build-up nailing. Apply a few more screws out at each bearing end just to help tie thing together.; 3.) have someone clean up the bearing ends so you actually have more than 2-2x’s bearing.

RE: Laminated Timber Beams

(OP)
Thanks guys,

All in line with what I was thinking. A few great ideas like the peel and stick!

Thanks

RE: Laminated Timber Beams

For this application, I would try to use the Simpson engineered wood ply screws. They have handy load tables that makes it easy to select a pattern based on your loading. The PSL Plus are only readily available in the northwest US and in Canada, or so I've been told. When I need engineered lumber for an exterior application, I've been using Power Preserved Glulams. They work great and are actually pretty readily available and relatively inexpensive.

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