Composite Steel column

[Gus14]

I have a two story building as the provided sketch. The ground floor will be completely open car park (no wind pressure) with only a stair case.
I can have vertical bracing along the 17 meters direction. In the short direction I am limited to using moment frames.

The problem is that I have a 2.5 meter cantilever near the end of the building thus I will adjust my columns axis as in the sketch for the cantilever connection.
This increases the building drift under wind load. So I am thinking of making these two composite columns for the ground floor to reduce drift, in the first floor I will continue with just the steel section.

What do you think ?

 

[HTURKAK]

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

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.

 

[JAE]

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.

 

[KootK]

What do you think ?

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.

 

[Gus14]

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.

 

[Gus14]

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

 

[dik]

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.

 

[Gus14]

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.

 

[dik]

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