Composite Steel column

• Tuesday at 3:21 PM

• #2

HTURKAK

Structural

Jul 22, 2017

3,191

Gus14 said:

.....thus I will adjust my columns axis as in the sketch for the cantilever connection.

Click to expand...

No need to rotate the subject column axis. Regarding the cantilever , you have back span beam .

EDIT: You are using metric units and the following doc. as per Euro codes may give some insight for Beam to column minor axis joints.

 

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• 06-GB_Moment_Connections.pdf

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• Tuesday at 3:26 PM

• #3

JAE

Structural

Jun 27, 2000

15,565

I'm thinking you need to rotate the columns at that cantilever end because it's a two-story building and your column extends up above and you want to use a moment connection through the column to achieve the cantilever, correct?

I'd be inclined to terminate the column (keeping the orientation like the other columns) and let the beam extend over the column with a continuation of column above the beam. Vertical stiffeners would be used through the beam depth to deal with web buckling and beam layover.

 

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• Tuesday at 3:51 PM

• #4

KootK

Structural

Oct 16, 2001

18,554

Gus14 said:

What do you think ?

Click to expand...

I don't love it. Introducing a new technology to the project for only a small number of elements usually winds up being cost prohibitive. And, because it's a moment frame, you really want that composite stiffness through the beam to column joint and not just over the height of the column. And that's a much bigger ask.

As the other guys have mentioned, there may well be other ways to frame the cantilever without turning the columns.

 

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• Tuesday at 3:54 PM

• Thread starter
• #5

Gus14

Civil/Environmental

Mar 21, 2020

194

Thank you HTURKAK and JAE for replying. In steel I am used to doing the basics so this is new to me.

Having moment connection on both sides of a column web is interesting thank you for providing that document. I guess since the column net moment will be almost zero its doable.

Yes JAE your understanding is correct. I find your approach simple to construct, I will also look into the design method for that connection.

 

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• Tuesday at 3:55 PM

• Thread starter
• #6

Gus14

Civil/Environmental

Mar 21, 2020

194

Thank you Kootk for replying, I will look into the other two methods.

 

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• Tuesday at 4:36 PM

• #7

dik

Structural

Apr 13, 2001

26,021

Can you increase the column size rather than go for a composite section? It's generally more cost effective. I occasionally use composite columns for added fire protection.

 

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• Tuesday at 6:56 PM

• Thread starter
• #8

Gus14

Civil/Environmental

Mar 21, 2020

194

Yes I could but its going to become pretty heavy to stay with reasonable drift. The building location is in a very windy coastal area.

 

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• Tuesday at 9:50 PM

• #9

dik

Structural

Apr 13, 2001

26,021

Steel may be less expensive than the conc fill and the effect of the concrete fill may be lacking.

 

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• Wednesday at 6:26 AM

• Thread starter
• #10

Gus14

Civil/Environmental

Mar 21, 2020

194

I will just do the connection suggested by HTURKAK. Its more like making a beam moment splice through the column web. Providing a moment splice at maximum beam moment is not ideal but its okay. The column web will see some moment, will look out for it.

 

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• Wednesday at 2:53 PM

• #11

KootK

Structural

Oct 16, 2001

18,554

The bolted end plate connection will be cost effective but it's not as though there aren't other connection types that would allow you to avoided column web flexure should that become a goal.

An important consideration may be the need for column stiffeners behind the flanges of your moment frame beam which may interfere with a bolted end plate connection.

 

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• Wednesday at 5:31 PM

• Thread starter
• #12

Gus14

Civil/Environmental

Mar 21, 2020

194

Do you mean continuing the beam over the column? Gravity moments are larger than wind moments so it accrued to me if I should be splicing my column rather than my beam. I might leave it to the contractor to choose. Having columns with different lengths might be tricky.

Gravity moments for the ground roof are around 100 Kn.m thick plates and large bolts should be good. I choose a column section so I would not be needing a stiffener for the moment frame.

 

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• Wednesday at 5:33 PM

• #13

KootK

Structural

Oct 16, 2001

18,554

Gus14 said:

Do you mean continuing the beam over the column?

Click to expand...

No. Some kind of flange plate arrangement that passes the cantilever beam flange forces through the column.

 

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• Wednesday at 6:08 PM

• Thread starter
• #14

Gus14

Civil/Environmental

Mar 21, 2020

194

I will have to dig deeper for that.
Moments from the moment frame are not that much less than the gravity moments any way. the plate bearing the beam and the one below the first column will still have to work a lot to transfer the moments to the top of lower column I will also have to dig deeper for that.

 

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• Wednesday at 9:36 PM

• #15

JoshPlumSE

Structural

Aug 15, 2008

10,341

What about a cruciform column. Start with the same size and orientation as the other columns. But, you weld structural tees to the weak directions so that you can have standard moment connections in both directions. No strange technology for the contractor. Most of the strange work would be done in the controlled environment of the steel shop.

FWIW, I don't think composite columns would be bad idea. I just think cruciform columns would be a cleaner solution.

 

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• Thursday at 1:51 PM

• Thread starter
• #16

Gus14

Civil/Environmental

Mar 21, 2020

194

Thank you Josh for replying, using a cruciform would be less critical than the beam moment splice. I will see what the contractor is comfortable with. I also found the connection Kootk was talking about, the flange plate would also double as a stiffner for the moment frame, but I will have to play with the connection a bit to reach zero moment on the web.

 

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