Lag bolts holding lvl beam on pergola

[lubos1984]

Have a situation where 2 ply lvl beam is bolted to columns the side of the columns instead of bearing on the top. Bolts are snuggly fastened together. Any potential issues having it done this way ?

 

[JAE]

You can do it that way - just need to make sure the bolt capacity per your local code standards can take the required loading from the deck (dead, live, snow, etc.)


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[lubos1984]

Thanks. I thought so to. My only concern was if there was a slight moment created from the eccentricity between the loading on the LVL beam and the column since the LVL is not bearing directly down on the column. I would assume this would be fairly negligible given the short distance.

 

[JAE]

You can, and should, include that eccentricity in your calculations.

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[hokie66]

Looks like a terrible detail to me. But those aren't lag bolts, as your picture shows rounded heads which could not be tightened. Through coach bolts, I presume. One issue with that type connection is that wood shrinks a lot in the cross grain direction, so the bolts will loosen with time. Are you sure there are not split rings or shear plates between the beam and post?

 

[lubos1984]

Yes they are coach bolts. They are threaded all the way through (see attached pic). I didn’t see any rings or plates. Looks like the bolts just go through the 2 ply lvls and post. From a shear and bending there is no issue with the connection detail but you raise an interesting point regarding shrinkage. Perhaps adding a hanger between beam and post for additional reinforcement? Otherwise could ask for rework and have beam bear directly on post or maybe have one lvl on each side bolted through post ?

 

[hokie66]

One each side would be better. Providing a bearing notch for each is much better still. All depends on the amount of load the connection has to take.

 

[Ron]

The LVL's have been used in another application before, considering the other holes that were drilled and not used and the clean area showing previous application. How were they used and what was their stress level before?


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[lubos1984]

Didn't ask. They didn't appear to be structurally compromised and under the current application they are more then sufficient.

 

[KootK]

1) Interestingly DC6 for decks prohibits this kind of connection. I've always wondered if that prohibition only applied to non-engineered solutions though. Certainly, I've seen plenty of examples of similar connection in other engineer's drawing in the past.

2) If the numbers work on the bolts, I'd think this would be ok. Shrinkage ought not be a problem for engineered lumber. Is this pressure treated PSL? If it's LVL, it's probably not treated which might present a problem in an outdoor application.

3) Assuming that's a 6x6 post, your load eccentricity on the column would be about 4.5". It's probably alright for smaller loads but, at the same time, it's easy to check and I'd be inclined to check it.

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[hokie66]

The LVL might not shrink, but the post will. Looks like it already has a big split.

 

[KootK]

You're not blaming the split on shrinkage restraint induced by the connection are you?

- Looks like run of the mill checking to me which is, of course, another shrinkage induced phenomenon.

- With respect to the post, the bolt layout is really optimal for not inducing shrinkage restraint across the member.

- If the connection is responsible at all, I'd think that it would be by way of accidental joint fixity attempting to behave as a moment connection. That's not my feel for the situation though.

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[hokie66]

No, that was not my point. I wasn't addressing cracking due to restraint, but rather just that shrinkage will result in loose bolts.

 

[T_Bat]

I'm with KootK, LVL's are not good when exposed to moisture. Long term, that could be a bigger issue than the connection to the post.

 

[boo1]

odd screws in the hurricane clips?

 

[phamENG]

I'd say this is no good. I think everyone's touched on my reasons, but to reiterate:

1) As KootK pointed out, LVLs should NOT be used outside. I like to think of them as really thick plywood - have you ever seen plywood after it gets wet a few times? Even exterior rated adhesives is susceptible to long term wetting (or even short term along the edges where the moisture can work in between the plies).

2) Temperature and moisture variations combined with variable wind loading will loosen the connection over time. If you let the beam into the post, no big deal - just tighten them periodically if you notice it. Like this, the failure is more likely to be sudden and catastrophic. Letting it in may not be a requirement for engineered connections, but from a judgement standpoint I don't detail exterior connections without bearing unless it's absolutely unavoidable. In those cases I try to develop some additional redundancy. Unless I'm mistaken, the DCA6 was written in response to a demand to reduce residential deck collapses and the associated injuries. While other engineering options may be available, these are "best practices" to help ensure a resilient structure and I'm hesitant to provide a "less" resilient design.