Built-up Beam Repair 1

[flashyyc]

Hi All,

I am looking at a possible repair of a built-up beam. Upon inspection by the city, it was noted that some of the splice locations weren't code compliant and recommended to either tear the whole thing down and start over or ask some structural engineering guidance. That is where I come in.

Some notes:
1. Built-up beam consists of (3)-2x8.
2. Beam pieces are glued together in between.
3. Beam was assembled on the ground and hoisted up over the (4)-wood posts as one single piece.
4. Beams are continuous over the supports.
5. Wood posts are 6x6.
6. Built-up pieces fastened together top and bottom @ 8" oc (quite conservative).
7. Homeowner was wise enough to at least build the beam so that there aren't more than 1 splice locations at any single span.

The homeowner has stressed that he prefers a structural solution that does not involve removing joist hangers as that amounts to a lot of work and ruins the deck altogether. I've come up with a few solutions:
1. A new built-up header consisting of (3)-2x8's installed underneath the existing beam and fixed in place with clip angles with fasteners. Probably some knee-bracing at both ends if the clip angle connection is inadequate. Plus a few vertical metal straps between the existing and new header. My concern with this strategy is that the two beams may in time shrink/expand both in different amounts and different directions which may result in serviceability problems.

2. A steel plate fastened to the bottom and supported with clip angles at the ends. A few vertical straps to the existing beam. Probably a knee bracing too. This is really just to compensate the loss of shear/bending strength at critical splice locations.

3. Similar to item #1 but instead of wood, an HSS header.

I would appreciate any comments or better yet, any other solutions along these lines.

 

[phamENG]

I would run screaming from this project - or at least give the homeowner some advice and let him say no thank you.

Your concerns about number 1 are valid. Number 2 and 3 will have connection issues at the posts. Best thing I can think of is to use a small wide flange with flush end plates. Use structural screws from under the top flange into the beam above. Lag/screw the end plates to the posts. And then through bolt some large blocks (shaped so they look nice) for a bearing connection. Hot dip galvanize the thing after the end plates are on.

Other concerns - once you do this, you own the whole deck. Somebody leans on that railing with a super shoddy base connection and breaks their neck? You. Was the ledger installed and flashed properly? Hope so, because if the wall rots out and the deck collapses, also you. Does the deck have adequate lateral bracing? The list goes on and on. Decks account for the most frequent occurrence of injuries and deaths than the failure of any other kind of structure...I take them pretty seriously.

 

[jayrod12]

Can you provide a sketch in plan view showing the actual splice locations for each ply and the post locations? You may be able to do some analysis gymnastics to get it to calc out. Often I've had some luck in that method. Barring being able to just make it calculate out in it's current setup, removal and replacement is honestly the quickest besides maybe adding a new beam with face mount hangers to the posts below each deficient beam.

 

[flashyyc]

Thanks for the insight on liability, phamENG. Quite honestly, I have not fully committed to this project, so there are still options for me to talk to the owner and consider other options.

 

[flashyyc]

jayrod12 , I do not have a plan drawing at the moment but I have something better (or so I hope). The elevation view below shows the splice locations. The inset drawing shows which plies are cut at those locations.

 

[phamENG]

Sorry - didn't mean to come across as a liability lesson. My point was more along the lines of considering the whole structure. There are a some things about that picture that scream inadequate design and construction, and so I would tread carefully. I'm not sure you can ruin that deck - it's got plenty of problems already and requiring replacement of the beam would fix the two biggest ones I see (guardrail post connections and beam to column lack of connections, unless there's a drift pin?).

 

[flashyyc]

There is a beam-post connection, but it's not your standard Simpson connector. The owner is using clip angles as shown in the pic below. The rails are attached to the beam which I believe are carriage bolts.

 

[jayrod12]

The ply#2 splice and ply#3 splice near mid-span are the only ones that concern me. I'd bet the rest of the locations, a 2 ply beam would work just fine.

All of the other concerns raised by Pham are applicable.

It is potentially possible the beam is good as only a 2 ply even. A 2 ply 2x8 is pretty robust over only 8 feet for standard residential loading.

But also as Pham indicated, would be tough to limit your liability to only the beam splices.

 

[phamENG]

Right...I stand by my comments.

That 'connection' of the beam to the post imparts no real lateral stability. I see you're in Canada - not sure about up there, but south of the border that would not meet the basic requirements of the NDS, the IRC, or any other building code I'm aware of. The fact that the joists frame into the side help, but most of the joist hangers don't have great tension capacities (if any). Add to that a wet use factor and the contribution is questionable at high loads or after a few years of weathering.

The guardrail posts are notched and bolted to a beam with marginal lateral stability/torsional resistance at its connections. So the bolts may never fail, but does the post work as a 2x4 on the flat in bending? How does the beam do in torsion? How well does that connection hold up? It's not exactly this connection, but similar ones were tested at Virginia Tech a while back. Tested Guardrail Post Connections for Residential Decks

 

[XR250]

You could add (2)2x8 below the existing beam fastened to the post with HUC28-2 concealed hangers.

 

[flashyyc]

Thanks for the comments thus far everyone. They have been very helpful. phamEng, really appreciate the document you sent and I agree with your comment on the decreased cross-section of the railing. That definitely deserves at least some closer look and review.

XR250, I don't think it would be possible to install the new header as you've suggested once the concealed hangers have already been installed as the existing beam would block the new header from getting in place. Or perhaps, you're seeing something I don't?

 

[XR250]

Ugh, yeah, I guess you are right. Maybe regular hangers would have enough nail edge distance? Could also maybe do a single member beam below - in which case a regular hanger should def. work.