Any ideas for connecting to the side of an existing concrete encased steel beam?

[BSPE90]

So I've got an existing concrete encased steel beam (red in the image). An additional 8" needs to be added to extend the floor to support a non-loading bearing partition wall. One suggestion was to attach an 8" angle (in blue) to the side of the existing concrete. How would one go about making a structurally sound connection to the existing beam? Would a row of adhesive anchors anchored into the concrete be sufficient or does it necessarily have to tie into the steel?

 

[r13]

I don't see good way out of this mess. Suggest the detail below, though I'm not fond of it.

 

[dik]

How heavy a force? can you use Teks to top flange?

Dik

 

[r13]

What is Teks?

 

[r13]

I also would add stiffeners (pair at the anchors) to the angle, and consider add strips of wire mesh (attached to the beam) to hold the concrete/grout in place, if the detail is accepted.

 

[Retrograde]

Epoxy adhesive anchors should be fine.

 

[dik]

http://www.buildex.ca/products/1/teks-metal-fastening-screws

I've used Teks3 and Teks5 for decades... some have good holding capacity.

Dik

 

[WARose]

My answer depends on the rebar details around the steel beam.

But assuming there is such rebar (and is adequate)....some type of adhesive anchor (like Hilti) may be on order.

If not, probably something like cutting through and attaching directly to the beam (like retired13 is talking about) may be the only way.

 

[r13]

dik,

Thanks.

 

[BSPE90]

Thank you all of your responses. Very helpful to get different perspectives. I've taken different aspects and came up with the following. Can someone give me a sanity check that this is a viable solution? It is basically a two angle solution connecting to the existing steel while trying to minimize the amount of disturbance to the existing concrete. I was not comfortable with only anchoring to the concrete.

edit: After another glance, I am guessing grout in lieu of (or in addition to) the spacers that are noted is more appropriate for proper contact of the vertical leg.

 

[RPMG]

I've run into this. The architects won't allow that because the concrete encasement acts as fire protection.

Epoxy anchors may be used, but the concrete is not bonded to the steel. There are some obvious durability and strength issues with that, so that requires some judgement.

Another option is to thru-bolt with intumescent taped bolts. That might be an issue if that detail is to scale.

Other than that, I would look outside the box and consider other options. Possibly building out into the slab region.

 

[BSPE90]

Wouldn't infilling it back with concrete restore that fire protection?

 

[r13]

My concern on your detail will be the difficulty in placing such thin concrete/grout and hope it to stick/stay. Like RPMG suggested, another option is to build out a parallel beam to accommodate the partition wall. However, it still needs to be tied to the existing beam.

 

[BSPE90]

retired13, what if I increase the gap between the vertical leg and the existing beam to say, 1 inch? The bottom gap would then need to be sealed somehow for the grout to be pumped in.

 

[r13]

I would say if the concrete/grout wraps around the flange will have a better chance to survive then place the concrete/grout on top of flange only. It will help a lot if you can weld wire mesh strip to the flange and wrap it around too. The concrete/grout holds better on rough surface due to better bonding.

 

[BAretired]

What is the thickness and height of the partition?
How much does it weigh?
How is it laterally supported at the top?
Does it need to be fire rated?
What about the sliver of floor you are adding?
That will not be fire rated with your proposed detail.

BA

 

[BSPE90]

The guy on site just told me there is about 4" of concrete cover above the flange so if we wanted to pump grout underneath the flange, that wouldn't leave much room to anchor the vertical leg of the angle to the existing concrete, as shown in your first markup.

Another thought I just had is what if I just put a bent plate with a 4" vertical leg on top of the flange like below?

 

[BSPE90]

BAretired,
The partition wall is 6" metal stud with height of maybe 14 ft.
It is laterally supported by the floor above.
Since it was the architect that suggested the angle idea initially, I am assuming it does not have to be fire rated.

 

[CrabbyT]

You could consider breaking out the concrete and connecting steel to steel directly, then replace the concrete that was removed. Try not to damage the existing mesh/studs/whatever they put in there to bond the concrete to the steel (see the AISC Steel Construction Manual from 1963, or see Blodgett's Design of Welded Structures pg. 4.8-3)

Or, you might use post-installed anchors (adhesive or mechanical). Don't forget the tensile component in your tension flange if you have a bending moment at the end of your beam.

Or, you might drill all the way through the concrete and the encased beam (drill all the way from one side to the other) and then make an encased beam sandwich using plates (i.e. plate, encased beam, plate). Secure the plates together with some long bolts or threaded rods. Attach your new beam to one of the plates.

 

[r13]

You are still going to provide angle to support the bent bar, right?