Lags into 2x nailers above and below wideflange beam, capacity question

[Bowsers]

Hello!
I’m back with another wood connection question.
I’m working on a balcony attachment plate. The steel plate is ¼” thick. The original plan was to have it attach to the wood nailers at the top and bottom of the steel wide flange beam using lag bolts. It appears my loads are overstressing the wood(max allowable shear is 517#/bolt, and I’m getting 567 # demand/bolt).
My question is am I using the proper modification factors? I want to use a ½” lag in the middle of a 2x nailer. Are there edge distance reductions that I need to take?
As far as I can see, a ½” diameter bolt needs ¾” edge distance, which is centered on a 2x nailer, so perfect. Once I confirm my connection capacity, I will be able to update the plate size and number of holes.
I have used the AWC wood connection calculator to determine the capacity of the wood.
Thank you.

 

[jayrod12]

I would not do this. No no no. This is a fairly critical application and would not be relying on lag screws into the side of a 2x nailer for permanent tension loads.

Can you get to both the top and bottom of the beam (top is more important in this application anyways)?

If so, I would be using a bent plate, and installing the fasteners through the top of the nailer. Much more reliable connection.

 

[KootK]

1) I don't believe that you can deliver shear to the low bolts without putting the bottom plate into cross grain bending which is ill advised.

2) I'm not sure that the stiffness of the sheathing is substantial enough that you could rely on your moment lever arm being the full beam depth.

3) I like jayrod's solution. At a minimum, at least install some 2x something vertical ribs behind the sheathing that would bear directly on the beam bottom flange.

 

[XR250]

As far as I can see, a ½” diameter bolt needs ¾” edge distance, which is centered on a 2x nailer, so perfect

No, not perfect!!
That is not a great detail. I would look at welding something to the I-beam and making sure it can take the torsion
or bolting a band to the web of the beam.
Installing lags into the skinny edge of a 2x4 is extremely sketchy for the following reasons...
They will never actually be centered.
Unless they pre-drill, the 2x will split.
The lower 2x4 will split anyway as soon as it sees any vertical demand
The lower 2x4 is forced into cross grain bending

 

[Bowsers]

Ahh... OK, slight clarification. The whole plate is 1/4" and sits against the wide flange, so not relying on wood shtg to provide any load transfer.

I hear the concern regarding cross grain bending of the bottom load. The nailer is present as attachment to the soffetting, and I will check the capacity of the nailers attachment to the wide flange to transfer the load.

Using 2x behind the plate, and attaching it to the wide flange sounds like the best solution. Alternatively, (as there will already be field welding), would attaching to a traditional stiffener plate be acceptable?

 

[jayrod12]

A traditional extended plate would be the ideal scenario in my mind, I was trying to avoid site welding, but if it's there regardless, this is the optimal solution. But, the bottom flange should be braced against the inwards kicking motion resulting from the torsion.

 

[msquared48]

You could also infill Between the top and bottom flanges on one side and install thru-bolts as needed. No cross grain bending then. Just have to drill thru the wood and steel.

Mike McCann, PE, SE (WA, HI)

 

[KootK]

The whole plate is 1/4" and sits against the wide flange, so not relying on wood shtg to provide any load transfer.

My bad. You mentioned steel in the beginning and I just failed to read gooder.

What are you supporting here anyhow? Wood joists sitting on that 3x3 ledger thing? Notched? I thought this connection typology fell out of favor with the Carter administration. Or is the 3x3 steel too?

 

[Bowsers]

This connection is to support an apartment balcony (DL = 12psf, LL = 60psf). Loads generated from Risa.

Per the contractor, the siding is 2" thick, and we will have a 1" gap between balcony and apartment. Hence 3" plate length.

 

[XR250]

@Bowsers;

You have indicated previously that you are in a small office where the principal is rarely present.
I would strongly urge you to have him/her carefully review your design before it gets constructed.
One thing I would suggest is to, as much as possible, not using RISA to figure out your loads. A balcony should be easy enough to handle with pen and paper and you would likely get a better feel for things.

 

[Bowsers]

I would strongly urge you to have him/her carefully review your design before it gets constructed.

Agreed - But I would rather have it go through 1-2 rounds of review than more. I've gone from doing a significant amount of concrete and steel to more wood in many recent projects, and I still don't have a strong grasp on wood connections.

 

[dhengr]

Bowsers:
It is generally more instructive and constructive if you can sit with your boss, both looking at the same plans, details, specs. etc. Being able to do quick sketches, he says…, “no this won’t work, here’s why, try this,” etc. You can see when each other are not really understanding the other, etc. Your boss should know what you know, and what you don’t know, so he can give you proper guidance and keep you and the company out of serious trouble. If your boss is any good at what he does, you will learn and retain more by interacting with him, rather than going through this guessing game with us, here at E-Tips. Are there only two of you in the office? What’s with the other senior engineers, and experienced draftsmen, they can give you some guidance when a detail looks really crazy, they should see that? You and the boss should have regular review meeting to watch over your work and progress. This will keep you out of dead end paths and calcs. and make his final review easier, since he’s been involved all along. You also need to use some of your own free time to study the NDS, and a good wood design textbook, to show your willingness to really learn. Dig out some old calcs. and plans on similar projects, and study and follow them. Ask well thought out questions, never the same question twice. Good to the boss with good questions and with several possible solutions, and be able to explain your thinking on each, so he can quickly critique them.