Bracing Connection at base 1

[Leftwow]

I'm having a hard time finding a good detail for a bracing connection at a base. Even AISC DG 29 is not giving me a good detail of this. Is anyone familiar with vertical bracing connections?

Background: We are designing connections for bracing, we do not usually do this. The brace is a W6X15 and the column is an indian section "ISHB 250". We are designing the brace in a chevron format. If anyone could help me with this it would be greatly appreciated.

 

[Leftwow]

Thanks Kootk, Why the extra anchor bolt row though?

hokie66, perhaps you are right idk

 

[KootK]

Just felt right when I sketched it up.

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]

Just felt right when I sketched it up.

Funny how often this dictates the design.

 

[JAE]

I'd still want to do something like this in a seismic area, though:

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[KootK]

I wouldn't use the detail that I proposed in a high seismic application where stable hinging was desired at the ends of the brace. Rather, I'd stick with schemes that continue the out of plane flexural stiffness of the brace down to nearly the gusset yield line. Slotted HSS or wide flange with flange angles etc. Last thing you'd want at the connection would be a chain of potential hinges.

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.

 

[Leftwow]

luckily the job site has very low seismic activity =)

 

[JAE]

The code mandates highly recommends the 2t setback for seismic.

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[KootK]

Is that the case even for low R-value systems JAE? Not that the 2t is difficult to provide. I just thought that it was only necessary where one plans to develop plastic hinging in the braces.

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.

 

[JAE]

I believe it is recommended by AISC (not sure about your Canada codes) to avoid brittle ruptures in the gusset prematurely due to out of plane rotations of the brace during the loading cycles.

Here's the commentary from AISC's Seismic Design Manual:




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[KootK]

Thanks for that JAE. The commentary does specifically reference special concentrically braced frames and plastic hinging which strikes me as consistent with my understanding.

The 2t is a relatively minor adjustment. If these connections need to be able to accommodate cyclic plastic hinging for all R values, however, I'd think that a bigger issue would be the kinds of braces and connections that would be acceptable in general. As I mentioned above, there are some schemes that I would definitely not be willing to use in a system that requires stable plastic hinging. To stick with the 2t requirement and then be laissez-faire with the rest seems philosophically inconsistent.

With steel, the Canadian code is always a weaker version of AISC. Whatever AISC says, that's probably what CISC meant.

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.