Bracing Connection at base
Bracing Connection at base
(OP)
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.
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.






RE: Bracing Connection at base
RE: Bracing Connection at base
1) Column orientation.
2) Brace orientation.
3) Concentricity of connection or lack thereof.
4) Approximate angles involved?
One of the options shown below might suit. If the loads are light, as I would expect, it may be cheaper to use web plates on their own rather than cope the flanges.
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.
RE: Bracing Connection at base
Either column orientation, after I get a detail I can engineer it by DG29 design of vertical bracing.
Jed, I will try that scenario... Just never used it before... I'll calculate and see if it works.
**it looks like all the column bracings at base that I found are somehow bearing on the base plate of the column.
RE: Bracing Connection at base
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.
RE: Bracing Connection at base
I also agree with Jed; double-angles are much easier. If you need higher strength then I'd look at HSS braces slotted onto the gusset. I feel that field-welded HSS braces are easier to connect than bolted W-section braces and typically result in lower steel weights for the brace.
Professional Engineer (ME, NH, MA) Structural Engineer (IL)
American Concrete Industries
www.americanconcrete.com
RE: Bracing Connection at base
RE: Bracing Connection at base
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.
RE: Bracing Connection at base
RE: Bracing Connection at base
RE: Bracing Connection at base
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.
RE: Bracing Connection at base
RE: Bracing Connection at base
RE: Bracing Connection at base
RE: Bracing Connection at base
Hey, that was my idea. :P (kidding!) Glad you think it makes sense to you as well.
Obviously I can't change your bosses mind but my previous boss/mentor had similar reservations about HSS sections in industrial settings. After doing a lot of work with steel corrosion in these settings I found that other than surface rusting issues, most of the major corrosion issues were leaks; direct steam/condensate exposure (such as condensate traps), direct exposure to process chemicals, and areas where water could pond against the steel. Overall, if left with no maintenance or in a bad environment, no coating will hold up. Here's a picture of a typical mill column/brace:
It was quite typical to find rust on almost every surface of a column/beam with no coating left. However, a lot of steel had very little section loss. The real corrosion issues were caused by poor setup of the process. In the picture there was a process drain that they let flow on the floor around the column and splash up onto the brace (note the missing column web). Also, note how the brace is a wide-flange turned flat. Terrible idea, every time I saw this the web was rotted out at the bottom end where condensation collected (avoid flat/enclosed surfaces where anything can pond).
Long story short; I don't believe the lack of a coating on the interior of a HSS is going to significantly impact your corrosion resistance. However, if you do expect direct exposure to water/steam/chemicals then either hot dip galvanized or stainless steel will probably be what is required regardless of your section shape. But, if you do go to a high-end corrosion resistance material/coating then you should use an HSS anyway for least weight (stainless HSSs are quite common in paper machine frames). It's also worth noting that I don't recall any time I saw a carbon steel HSS used that it seemed to perform any worse than a wide-flange. I think most people in the industry just shared that mentality of HSS = hidden corrosion.
It's entirely worth noting that I would not put end plates and seal up the HSS. Any condensation left inside would undoubtedly pool on the bottom and corrode it. Leave it open; better, cheaper, plus easier to inspect.
Professional Engineer (ME, NH, MA) Structural Engineer (IL)
American Concrete Industries
www.americanconcrete.com
RE: Bracing Connection at base
I got some funny ones. This is still in operation lol
RE: Bracing Connection at base
Oh, and I did manage to find a picture of the infamous industrial HSS. Don't get too close, it could collapse at any minute! This column was splattered with pulp at the top but the wide flange column right next to it looked slightly worse.
Professional Engineer (ME, NH, MA) Structural Engineer (IL)
American Concrete Industries
www.americanconcrete.com
RE: Bracing Connection at base
RE: Bracing Connection at base
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.
RE: Bracing Connection at base
RE: Bracing Connection at base
hokie66, perhaps you are right idk
RE: Bracing Connection at base
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.
RE: Bracing Connection at base
RE: Bracing Connection at base
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RE: Bracing Connection at base
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.
RE: Bracing Connection at base
RE: Bracing Connection at base
mandateshighly recommends the 2t setback for seismic.Check out Eng-Tips Forum's Policies here:
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RE: Bracing Connection at base
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.
RE: Bracing Connection at base
Here's the commentary from AISC's Seismic Design Manual:
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RE: Bracing Connection at base
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.