Concrete columns to steel beams connection 5

[Gus14]

I am doing a new steel residential 3-story building, but the client wants the columns to be concrete
( This is because of his unshakeable belief that concrete columns are safer )

Are there any references or tips to design the connection between the concrete columns and steel beams?

The building is new and the columns will be cast on-site to support the steel framing.

 

[dik]

Generally a plate embedded in the column secured with Nelson studs, and the beam welded to it, or threaded anchor rods embedded in the column to bolt the beam to... the beam either being bolted on top of the column or to the face of the column... also done with embedded plates, too. Bearing connections are nice if you can do them.

I should have added that concrete columns aren't necessarily safer than steel. Properly designed, both are safe... steel usually has a lot more ductility, including the connections where failures often occur. Mixing the two types of construction is costly and it is likely a lot less costly going to steel. Concrete columns take up more floor space which can be detrimental. If your floor to floor height is more than 10' or 12', concrete columns get a little larger, not as slender as steel. Often main floor heights are 15' high or more. You can send him a print of this reply.

So strange to see the singularity approaching while the entire planet is rapidly turning into a hellscape. -John Coates

-Dik

 

[Gus14]

Thank you dik for replying, I am starting to discover the confusing design world of embedded steel plates with cast in place anchor rods.

I should have added that concrete columns aren't necessarily safer than steel.

I know, this client is his own worst enemy.

Locally I am limited Hilti products and their software doesn't include embedded plates so I am in a bit of a dark place.

What do you think of embedding the entire steel beam section into the column ? feels scary

 

[Tomfh]

I agree with cast in plates. These sort of things, customised to suit the column dimensions:

https://granodirect.com.au/precast-tilt-up/panel-brackets/cast-in-plates

If you're bolting a beam to it you can shop weld a cleat plate (or connection of your choosing) to the cast in plate.

A lot depends on the desired appearance. Another way is to cast in some conduit and simply bolt though the column with threaded rod. That ain't going anywhere.

 

[kipfoot]

This suggestion is only slightly in jest: Use steel encased in concrete. The columns will look and feel like concrete columns, but the connections will be steel to steel.

 

[Agent666]

SCI p416 is fairly useful but based on Eurocodes, so as such some people would baulk at the notion of the top bars developing round the bend (myself included).

If you're American based just follow ACI chapter 17 and check all the various limit states that apply to your configuration. Use p416 as guidance to inform your design method.

https://engineervsheep.com

 

[dik]

Not only Hilti, which I spec a lot of... but, you should be looking at Nelson headed studs... You should not be limited to Hilti... headed studs are can be far less costly. There are some excellent texts put out by concrete product suppliers on the design of headed studs. Check

https://www.pci.org/DesignersNotebook

Designer's Notebook #32

So strange to see the singularity approaching while the entire planet is rapidly turning into a hellscape. -John Coates

-Dik

 

[dik]

Getting A325 threaded rod can be a real b*tch in some locales... The humour was that I often get drawings to review where they are using A325 for anchor rods.

So strange to see the singularity approaching while the entire planet is rapidly turning into a hellscape. -John Coates

-Dik

 

[dik]

thanks tom... I didn't realise that you could buy pre-fabbed plates with headed studs, or welded rebar... I guess you could send them a loading requirement and they would supply 'what was needed'.

So strange to see the singularity approaching while the entire planet is rapidly turning into a hellscape. -John Coates

-Dik

 

[dik]

Agent... glancing at your referenced publication, it appears to be excellent. Thanks...

So strange to see the singularity approaching while the entire planet is rapidly turning into a hellscape. -John Coates

-Dik

 

[hokie66]

Another option would be to precast the columns. After all, steel columns would be shop fabricated, so concrete columns can as well, with the appropriate connection components cast in. Three storey concrete columns are manageable, with adequate craneage. I have used three storey precast columns in a concrete building. With steel horizontal framing, the detailing should be simple.

 

[dik]

good idea Hokie, and with better quality control to set the weld plates into the concrete.

So strange to see the singularity approaching while the entire planet is rapidly turning into a hellscape. -John Coates

-Dik

 

[Gus14]

Thank you, everyone, for replying, This is very helpful.
My columns are 20 cm x 60 cm, with most of the factored reactions around 100 KN. So I am having an overwhelming breakout and pullout failure when the beams frame into the 20 cm side. Considering I am pretty much new to this subject do you think this failure is reasonable? Do you think there is an alternative to increasing the column dimensions?

 

[dik]

They could be 20x20 in steel. Not into concrete these days, but I seem to recall min col dimension was 25cm? This was changed in the ACI in 1971... shows my age...

So strange to see the singularity approaching while the entire planet is rapidly turning into a hellscape. -John Coates

-Dik

 

[Gus14]

They could be 20x20 in steel.

Yeah, I am becoming more inclined to Concrete encased columns. Otherwise, I will have to make the columns at least 30x30 cm.

I seem to recall min col dimension was 25cm

I do check stability. It's pretty common here for columns to be only 20 cm wide.

Sidenote, I found a software called DEWALT DESIGN ASSIST. It's far better than any other software and it's free. It does detailed reports too.

 

[dik]

Rather than concrete, can you use gypsum wallboard?... You can even paint it pink if the owner wants... Other than fireresistance, there's little to be gained by encasing it.

If damage due to traffic is a possiblity the use 'elephant feet'; 8" concrete columns will not fare any better. Sorry... forgot it was residential...

So strange to see the singularity approaching while the entire planet is rapidly turning into a hellscape. -John Coates

-Dik

 

[dik]

Didn't know that... not current in concrete (I still don't think I'd use an 8" concrete column... bit of a chikensh*t):

So strange to see the singularity approaching while the entire planet is rapidly turning into a hellscape. -John Coates

-Dik