Steel Column supported by Beam 2

[suzpari]

I have a structural steel column that will be supported directly on a beam flange. I know that this is not an uncommon situation. What do I need to check for? Buckling of the beam web? Required spacing of stiffeners etc? Is there an AISC design guide or similar that shows how to detail that connection? Any guidance would be appreciated.

 

[manstrom]

Turn the page upside down and treat it like a point load instead of a column, it's the same concept.

Check to see if you need a web stiffener

When I am working on a problem, I never think about beauty but when I have finished, if the solution is not beautiful, I know it is wrong.

-R. Buckminster Fuller

 

[XR250]

you also need to check LTB of the beam if it is not braced

 

[KootK]

The usual detail is a base plate with four bolts and a pair of full depth stiffeners on either side of the beam at least as thick as the column flanges. It's usually overkill but then it's not the kind of situation where one wants to mess around.

The design checks are identical to those that you would do for a truss web/chord joint connection. The base plate is really extraneous when it comes to the design of the supporting member unless you choose to omit the stiffeners.

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.

 

[mike20793]

Agree with Koot, put the stiffeners in even if they aren't needed.

 

[manstrom]

Personally, I'll just throw in stiffeners under columns above with doing the calc.

When I am working on a problem, I never think about beauty but when I have finished, if the solution is not beautiful, I know it is wrong.

-R. Buckminster Fuller

 

[SlideRuleEra]

KootK - That is a real good idea.

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[suzpari]

Ok. Thanks all. Really appreciate the ideas. How do you determine how far apart the stiffeners should be? These stiffeners are perpendicular to the beam web, correct?

 

[KootK]

The stiffeners are perpendicular to the beam web and located beneath the flanges / sidewalls of the column. If you post a sketch of your detail, we'll happily review it for you.

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.

 

[suzpari]

Thanks KootK. I have attached a sketch of the detail. I did the checks for the beam web crippling and web yielding. In both cases, stiffeners were not required. But there is one other thing. On one side of the W14x34 beam that supports the column, there is another beam framing into the web. Does that affect the detailing in any way? Can this beam be considered to "stiffen" the supporting W14x34 on that side?

 

[jayrod12]

It will stiffen the web.

If web crippling and yielding is not an issue then technically no stiffeners are required however I tend to just include them at all times.

We generally provide two stiffeners on each side, one under each column flange.

 

[KootK]

You're most welcome suzpari. I'm glad that you uploaded your detail. I was thinking of the more common case where the column is oriented the other way.

An additional check that you'll need to do is web yielding and crippling on the column web. That will likely work but, if it doesn't, see below for another option that could help to address that.

On one side of the W14x34 beam that supports the column, there is another beam framing into the web. Does that affect the detailing in any way? Can this beam be considered to "stiffen" the supporting W14x34 on that side?

It's great that this beam is there. It will help to brace and stabilize the whole assembly where that stability is needed most. In an unstiffened scenario, I'm sure that your common framing connection (double angles etc) would help out with web crippling. It might be tough to quantify however. In a stiffened scenario, you'd need to ensure that the connection allowed for the installation of a stiffener of something quite like it at the beam to girder connection.

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.

 

[suzpari]

Thanks all.

KootK, thanks for the sketches. From a design or construction perspective, does it matter which way the column is oriented? I know that this way, the 'N' for my column base plate is not the same 'N' used for the beam web checks.

Why would orienting the columns this way mean that I have to also check web yielding and crippling of the column web? If it's an issue, I think I can turn the columns the other way.

 

[KootK]

From a design or construction perspective, does it matter which way the column is oriented?

If there's a compelling reason to orient the column web perpendicular to the girder then I wouldn't hesitate to do that. It'll work. If there isn't a compelling reason for that orientation, however, then I would align the column web with the girder for two reasons:

1) That's what's conventionally done in my experience. All else being equal, I trust in the collective wisdom of our profession.

2) If you orient the column web parallel to the beam and use the two pairs of stiffeners that have been mentioned, the entire column cross section (flanges and webs) will bear on stiff supporting elements (beam web and stiffeners). This just feels good to most engineers and obviates the need for any plate yielding and crippling checks in the column.

Why would orienting the columns this way mean that I have to also check web yielding and crippling of the column web?

With the column web parallel to the beam, the uniform compressive stress in the beam can stay uniform as it passes into the beam via direct bearing on the web and stiffeners. With the column web oriented perpendicular to the girder, the compressive stresses will leave the column flanges and flow in a more concentrated fashion through the column web and into the girder web stiffeners. That's what I was getting at with the hatched area in my sketch above.

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.

 

[suzpari]

Great. Thanks so much!