Attaching wood nailer to Channel with welded on threaded studs 1

[Ron247]

I have a job where the Architect does not want bolt heads showing on a channel that has a wood nailer to be fastened to it. In order to satisfy the builder, the fabricator proposed welding threaded studs to the channel to attach the wood nailer to. I have no basic problem with this other than working out the "details". While the fabricator is good at his job, I am not so sure about the carpenters who will be doing the rest of the work. I would appreciate any input on notes or requirements to help insure proper attachment of both the studs to the channel and the nailer to the channel. As far as I know right now, the fabricator was going to fillet weld the stud to the channel. The following are some thoughts so far:
[ul]
[li]after installing the nailer, have the holes sealed with a wood epoxy before installing washers and nuts[/li]
[li]size the fasteners for twice the calculated load if adjacent fasteners fail to take their share of the load[/li]
[li]setting a maximum tolerance for studs to not be perpendicular to channel web[/li]
[li]studs cannot be a heat treated material[/li]
[/ul]

 

[XR250]

I imagine they will lay the nailer on there and hit it with a hammer down the length to get imprints of the studs for drilling accuracy.
Perhaps you can detail the bottom of the nailer to be tapered to match the slope of the channel bottom flange (if that meets the Arch's aesthetic). That way the load is carried by the flange and not the bolts and oversize holes become a non-issue.

 

[KootK]

I don't think that you need to sweat this really. Like XR said, they'll likely mark the holes by taking an impression and all will be fine. Or it won't and all the notes in the world probably wont make a difference. If you want to add some margin to this, I'd tighten the stud spacing and/or increase the stud diameter.

What are the stakes here? What attached to the ledger and how? Is the ledger a single 2X? It would feel pretty great to make it a wider piece and shape it for flange bearing like XR suggested.

 

[JAE]

1. Just specify the hole diameter per NDS. Agree with XR250's description of hitting the wood down on the studs to mark the hole locations.
2. Is the nailer taking load perpendicular to the axis of the channel? You didn't say.
3. If it is taking load perpendicular to the channel, the load is eccentric to the channel's shear center so do consider the rotation in the channel that could occur.
4. Wood is "soft" to a degree so with loading, all studs will begin to take the same load as the holes deform a bit.
5. Welding studs to the channel web could result in some slight deformation of the web surface, and possibly some burn issues showing through to the opposite side. Assume its painted?

 

[azcats]

Install of the nailer doesn't seem much different than a ledger on a CMU or concrete wall that carpenters have been doing forever. I wouldn't sweat that either.

Can the fabricator use a threaded stud welder - like nelson studs?

[URL unfurl="true"]https://www.youtube.com/watch?v=gWymKHVABKo[/url]

 

[Ron247]

To answer some questions.
[ul]
[li]The ledger holds floor joists mounted with joist hangers. It is a single 2x8 pressure treated material. [/li]
[li]The channel is painted.[/li]
[li]The load is a shear load predominantly of less than 500 lbs if spaced at 2' oc.[/li]
[li]I think they are going to hit the joist with a hammer to mark them, but I think they will hit it multiple times with it jumping around each time. I have little faith in the carpenter's as compared to the fabricator.[/li]
[li]The joists hold the edge of this porch to the building. The nailer falling down will land on the flange as stated by XR250 but it will not hold the floor to the main building if it pulls loose laterally.[/li]
[li]Fabricator will probably use a stud welder. I was not sure how well those keep a right angle.[/li]
[/ul]

 

[oldestguy]

azcats: Great video!

 

[Earth314159]

This type of detail is done a lot. However, if you are concerned, you can add epoxy into the bolt holes. This ensures a more even loading on the bolts and really stiffens up the connection.

In our code, bolt capacities are a fraction of what they used to be and I don't see any old bolted connections failing. This just tells you that the capacities are conservative.

From an aesthetic perspective, you can also consider using countersunk holes and screws from the back of the channel. Once it is painted out, most people won't notice the screws. This is a bit more expensive sine the holes have to be drilled rather than punched and you need more holes but it is more predictable in terms of the structural behaviour.

 

[Ron247]

Thanks all, I feel a lot more comfortable proceeding with this. Azcats-ditto on the great video comment.

 

[HouseBoy]

I don't know if you have the availability for this (and I recognize that pre-placing the threaded rods will make this more difficult) but.... I like to specify that the "ledger" be bevel cut on the bottom so that it bears tight on the top of the bottom flange. That way the bolts are not doing nearly so much work.
It sounds like you do not have that available to you in this instance but ....FWIW.