Column blockout at diagonal brace

[bhiggins]

Hi All,

I'm designing a a brace frame steel structure which is supported on concrete straight shaft piers. I am doing a concrete blockout detail and was wondering what is more customary at diagonal braces? Is it acceptable to bury the brace connection in the blockout or should I shift the brace connection out of the blockout and deal with the eccentricities? I'm thinking that if the brace connection is in the blockout then there would be cracking issues, but I'm not sure if the happens in practice. I've attached an elevation of the frame.

Thanks!

 

[jittles]

Common to bury it in the blockout, in my experience.

If this were an SCBF with an assumed hinge in the gusset, I would provide some compressible foam filler material around the gusset hinge region to allow it to buckle as intended by design.

 

[KootK]

Agree. I like the gusset, but not the HSS, going into the blockout. I've not heard of cracking in practice but jittles' isolation concept sounds great. I'd also like to see a grade beam between piles unless you're duping your brace shear straight into the SOG. Otherwise, shear breakout in the piers can be tough to deal with.

 

[KootK]

I just noticed that you appear to be dealing with pretty much the same eccentricity at the top as you would be at the bottom anyhow. Given that, maybe keeping the connection above the SOG wouldn't be so punitive after all.

 

[bhiggins]

I appreciate the quick responses. This frame is governed by wind so we don't need to detail for seismic. I'm just going to bury the gusset and HSS. The building is old and "rustic" so the client wouldn't really care about a little cracking at the slab if it did happen.

I was going back and forth about a grade beam tie. At first I was going to handle the shear breakout with supplemental tie reinforcement at the pier, but it's just better to have a tie in general for shear breakout and to distribute the loads. I've attached a revised detail of the entire frame. I guess what I've drawn is no longer a blockout, its more like filling in a trench.

 

[KootK]

LOVE it. As you would expect.