LVL sistered to properly sized Flitch Beam

[Pete S]

A contractor was required to install a flush triple 1-3/4 x 9-1/4 LVL with a double 3/8" flitch plate. The member was manufactured as prescribed, however upon installation the contractor elected to sister an additional 1-3/4 x 9-1/4 LVL to the member. The sistered LVL was not thru bolted to the existing member but rather face nailed 3 rows at 12" o.c.. Without requiring the contractor to drill and thru bolt the entire modified beam, I'm having trouble assessing whether the face loads on the sistered beam are properly being transferred to the engineered member. This may be trivial and I may simply be overthinking, but I'm not necessarily sure how to approach this case. The connection can simply be fortified with lags but will the offset centroid cause any adverse performance within the beam? First post. Thank you in advance!

 

[Eng16080]

I have a few questions:
[ol 1]
[li]Why did the builder add the extra LVL? I assume they did it for some reason. Whether or not they had a good reason, they're in the wrong for not notifying you first (typical), but it would be good to know what they were thinking.[/li]
[li]Is the beam supporting flush framed joists/beams along both sides, or just one?[/li]
[li]How are the ends of the beam supported?[/li]
[li]What diameter nails and length is used for the face nailing?[/li]
[li]If the intended beam (the 3 plies plus 2 plates) is thru bolted, I'm curious how the extra piece was installed without interfering with the thru bolts. Are the bolt heads countersunk?[/li]
[/ol]

My initial reaction is that I'm rather annoyed on your behalf. I hate it when builders do stuff like this.

 

[Pete S]

1. So it looks to me like the builder cut all his joist to the length he needed to meet up with a 4 ply member and didnt realize the design then transitioned to a 3 ply double flitch. Once he noticed all of his TJIs were now undercut so they made up the difference by adding a ply. I came to the job once the condition was identified, not the original designer.
2. flush on both sides of the beam with the correct hangers
3. the beam is posted on both ends with the additional ply fully supported as well.
4. the nails appear to be common 10d, most likely 3" length.
5. looking at other beams in the house it appears to be carriage bolts w/ countersunk hex nut opposite. the additional beam is mated up to the head of the carriage bolt w/ the hex nut exposed.

Thank you very much for the prompt response. It's really appreciated!

 

[Eng16080]

Looking at manufacturer literature for built-up LVL beam fastening, I don't see any details which would allow the use of nails attaching a single piece of a 4-ply LVL to only the adjacent piece. The typical detail shows either thru bolts or heavy duty wood screws which are attached to three or all four pieces.

While I don't think a face nailed connection like this would necessarily fail, I do think there could be some long term deformation between the outermost ply and the other pieces including the outer ply potentially pulling away from the others. At a minimum, if I were forced to use this detail, I would instead use wood screws and not nails with the screws designed per NDS to support the required loads.

If this were my job, I'd recommend providing new thru bolts with nuts and washers at both the head and nut ends (not carriage bolts). I would design the connection as though the existing carriage bolts didn't exist. The builder will need to drill new holes through the LVLs and steel plates which will likely be a huge pain, but I'm sure there's a way (maybe a mag drill). I would explain to the client that this is the preferred solution, and that while a face nailed connection could potentially work, there would be a risk of long term deformation which they might find unacceptable.

 

[XR250]

Honestly, I probably would not worry about it assuming all the plies are supported at the ends and the nailed connection can resist the shear (might want to supplement with structural screws as you mentioned). The flush framing will likely prevent torsional rotation due to the unbalanced stiffness.

 

[jayrod12]

I don't see why you couldn't check the connection between the single ply and the remaining beam to transfer 1/2 of the load to the rest of the beam. I personally wouldn't be thinking this is too large of an issue, maybe there needs to be additional fasteners provided, because it's unlikely that 3 rows of nails @ 12" are going to cut it. But maybe they will. Additional fasteners would be a simple install. Additional bolts would be a nightmare that I would avoid at all costs.

 

[Eng16080]

To follow-up, I agree with the responses above by XR250 and jayrod12. My earlier recommendation is perhaps going slightly overboard. Considering that the original 3-ply plus double steel plate beam is already adequate without the additional piece, it's probably unnecessary to connect the extra piece in the manner I described above (with thru bolts). I would still want to use wood screws rather than nails though to connect the extra ply, and I doubt the existing nails are adequate anyway.

 

[DoubleStud]

The bolting you are doing is to make sure the beams and the steel plates work together. If they add another member, it is not a problem, however you have to make sure the nailing can handle the load from the joists. Pretty easy check. Just check the 3 nails can handle the plf from the joists on one side of the beam. Technically speaking you are supposed to check this for every multi-ply beam because the hangers are hanging only from the outside ply. A lot of times this gets missed and they are always nailed together the same way (missed by the engineer or by the framer). But technically speaking there is also some capacity from plywood going over the beam that is being ignored.