Lag Screw Withdrawal from Top of LVL

[HDStructural]

Hello,

I am designing a garage with an LVL floor beam that supports a 6x6 post going up to the roof. Since it goes up to the roof, there is uplift on this post.

I am looking to anchor this post into the LVL with a concealed connection that won't stick out too much. I am planning to use Simpson Strong Tie's ABU type connection. I am aware this is typically used in concrete.

My question has to do with the design of the 1/2" anchor which would be a lag screw loaded in withdrawal from the top of the LVL. The withdrawal table for lag screws in NDS (Table 12.2A) notes that it is for withdrawal in the side of the member. This connection would be into the top of the member, which is similar to the end for an LVL. Would I just apply the end grain factor for lag screws in withdrawal (0.75) and call it a day?

I'd get my withdrawal values for g=0.50 which is the equivalent specific gravity for microlam LVL's.

Your thoughts are appreciated.

 

[XR250]

The other nice thing about using L/480 or greater (at least for me), I don't bother checking creep as I am covered or even stress as I know it will never control.
Obviously If I had a short span or a large sustained dead load, I would check those and other limit states.
Makes it quicker to do hand calcs. 22.5 WL*4/EI and I'm done.

 

[HDStructural]

Thank for that input phamENG. Since it is carrying the roof, there are many deflection cases.

D: considering all long term effects, L/480
S: short term, L/725
L: short term, L/690
Lr: short term, L/907

It was D + 0.75L + 0.75S that was coming out to around L/240. I realize this isn't a load combination to consider for deflection, but my program was spitting this info out.

D + L comes out to L/283. I'm guessing you would recommend changing some things up to get a better total load deflection ratio.

 

[phamENG]

In this situation, it's less about the ratio and more about the local differences. The beam is parallel to joists, so is the absolute deflection a lot more than those joists? If it is, it will be noticeable. What's going on at the roof? Is there an opportunity for a similar issue? Also, some roof members can be extra sensitive to deflection - like ridge beams. They are usually there because a more robust load path is unavailable, so they will deflect. Nobody wants their gable roof to 'smile'...so once you get beyond 20' or so the absolute deflection number becomes more important than the ratio.

 

[Craig_H]

If this is a multi-ply LVL that you are fastening to, could you not have a knife plate between the plies with dowels through the LVL? Knife gets stabbed into the column above. Not much fabrication apart from cutting a plate and drilling a few holes. That's about as concealed as you can get, no withdrawal or splitting issues. You seem quite close to capacity, but you might be able to tolerate a small router in the inner plies so that the knife plate can fit in without creating a visible gap.

 

[XR250]

I imagine the framers would prefer something much simpler.