Glulam Cross Grain Bending 2

[XR250]

I am trying to avoid cross grain bending in this connection. The column is flagpoled off a large footing. As the hanger cannot technically take tension, the load is coming in thru the floor sheathing. As such, there is weak axis bending in the glulam. Any suggestions? Is there a design value I can use for this or is it strictly prohibited?
I thought about extending my saddle up full-height but I am concerned that it will causes longitudinal cracking in the glulam due to end rotation. Perhaps I could use a slotted top hole to prevent this.

 

[phamENG]

What does this look like in plan? If that is a floor diaphragm, won't that wind load be carried by the diaphragm to side walls/beams and load them longitudinally? You'll still get some cross grain bending in your glulam, but I think it'll be a lot less than you're anticipating now. Run your diaphragm analysis, determine deflection, and then come up with an equivalent week axis load on the top of the glulam that would produce the same deflection in the beam. If it's still higher than you're comfortable with, then extending the saddle could be a good idea. Take a look at the AWC's do's and don'ts of glulam connections. Deep saddles require special detailing to prevent cracking, but you already know that based on your comment.

Maybe some Simpson ties on the bottom of the joists? They have some light duty tension ties for this kind of situation. The LTT19, for example. It would at least help to lower the reaction if the joist can transfer it through the web.

 

[XR250]

Pham,

The entire house is flagpoled on the HSS7's. There are beams that run parallel to the wind direction in all cases so perhaps just use those as the resisting elements (assuming the diaphragm checks out - which it should). I was trying to keep the column and footing sizes reasonable so using all the columns to resist the lateral would be ideal. i considered using the Simpson DTT1Z's at the bottom of the joists but the contractor balked due to it conflicting with his smooth ceiling. I may revisit that. I am not sure I can use those on the side of the I-joist flange as it may split. The LTT19's look promising.

Thanks for your help!

 

[jayrod12]

Provide 2x web blocking on the I-Joist and then fasten the simpson tie to that as close to the bottom flange as possible. Avoids the smooth ceiling.

 

[XR250]

Actually either of the DTT1Z or LTT!9 should work and not mess up the ceiling. I am not sure what the issue was for the contractor.

 

[XR250]

Provide 2x web blocking on the I-Joist and then fasten the simpson tie to that as close to the bottom flange as possible. Avoids the smooth ceiling.

Good idea, thanks

 

[KootK]

I'm going to break rank with my colleagues a bit on this one:

1) With everything flagpoled I don't feel that diaphragm action will help matters enough. No doubt phamENG would have agreed with this if he'd initially known the truth of the lateral system in it's entirety.

2) I actually feel that the lateral ties will make matters worse by stiffening what is already a crap load path.

I thought about extending my saddle up full-height but I am concerned that it will causes longitudinal cracking in the glulam due to end rotation. Perhaps I could use a slotted top hole to prevent this.

I think that you were knocking on the door of infinite correctness with that idea. Not bad for a guy who doesn't fully understand the physics of spoked wheels. See my proposed solution below, on the right. The left is the naughty. If you let your detail swing back and forth in the wind, even with the straps, you'll eventually get glulam cracking right where you showed it, I guarantee it.

 

[phamENG]

KootK for the win on this one.

 

[XR250]

OK, I like that idea. About 50% of the columns have glulams tee into one another so I could use a leg as a nice drag collector.

Thanks to everyone who contributed. It is great to have this forum available.