Special Connection

[Chengineer4]

I have a two story wood framed building. the second floor cantilevers 4'-0" past the wall below. there are segmented shear walls that occur at the cantilevered portion of the second floor. the shear walls sit on a Glu-lam which is supported by a steel post at both ends. Am i allowed to anchor the holddowns for the shear wall into the glulam? i have Simpson HDU2 holddowns which require a 5/8" diam. anchor and a 18" deep glulam. will i have enough depth to develop the anchor?

 

[jayrod12]

Well yes you can have your shearwalls come down on the glulam. Can your glulam take you anchor load?

I'm sure there is a way to connect the hold down to the glulam (a thru bolt comes to mind with a steel saddle)

I'd probably be tempted to custom fab my hold down as opposed to using a pre-engineered product in this case

 

[Chengineer4]

yes i have the glulam designed to take the anchor loads and i was thinking of using lag screws for the holddown anchors do you think that will be sufficient enough. the thru bolt option might interfere with the beam to post connection.

 

[jayrod12]

If you post a detailed sketch we could probably help in that regard. Depending on the magnitude of the uplift it may be possible to use a lag screw. But I have my doubts personally

 

[Chengineer4]

here is what i have so far the uplift force per anchor is about 2kips so i am using HDU2 holddowns

 

[wannabeSE]

If ASCE 7 is applicable and seismic loads are not negligible, don't forget about the seismic requirements for offset shear walls (Type 4 vertical irregularity) in ASCE 7

 

[jdgengineer]

For 2 kip load I'm sure you can get a lag bolt to work. Check the lag capacity per the NDS. You could also look at strap options or through bolt (but be careful not to countersink as it can composite glulam strength)

 

[jayrod12]

A discussion about lags has been had previously, I'm still not a fan. I would prefer a strap on each face of the shearwalls end post that extended down onto the sides of the glulam. That's a more trustworthy connection to me.

 

[KootK]

A discussion about lags has been had previously, I'm still not a fan.

For OP referrence, I believe that this is that discussion.

@Jayrod: do you feel any better about this one given that it's not a permanent load application?

will i have enough depth to develop the anchor?

What make me nervous here is that you've really got two connections here that will tend to induce perpendicular to grain stress in the glulam between the hold down and the post: 1) the hold down to glulam connection and 2) the glulam to post connection. As others have pointed out, however, the load is pretty small. If the two connections work by the numbers then it works.

If the connection didn't work by the numbers, one option might be to do something like this:

1) Move your boundary stud pack and hold down 1' inboard of the steel post.

2) Thru-bolt your hold down all the way through to the bottom of the glulam.

3) Thru-bolt your post cap plate all the way through to the top of the glulam.

In this way, you've sort of got a "lap" between connections to borrow from concrete terminology.

I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.

 

[jayrod12]

Still no, I'd be inclined to go a different route on the connection, but that's me. Everyone has their own level of comfort, and mine when it pertains to lag screws is extremely low (a lot is due to my own personal experience with pre-drilling lag screws on my own home renovation projects).

 

[molibden]

Do you use self tapping screws in the US? In Europe we use these. No pre-drilling. Screws are long as you like. I would just use the one that fits in you glulam - and it acts as reinforcement against splitting perpendicular to grain as well.

 

[jayrod12]

We do have similar screws to that, manufacturer's include Simpson strong tie and GRK. I may be more open to something like that where I didn't have to worry about some lackey pre-drilling to the correct diameter for standard lag screws.