Old warehouse building - steel beam encased in concrete?

[Lefkas]

Hi, a manufacturing company wants to utilize a second-floor space for production (install storage racks, etc.) in an old warehouse building, and I was hired to analyze the existing floor framing and provide them with the floor's capacity. The floor framing consists of a 2.5-inch wooden deck supported on 7” x 12” wooden joists that frame into 11.5” x 21” deep concrete beams. The wood joists appear to be bearing on a 1/2" steel bent plate that is encased in the concrete. Further, in one location, the concrete beam has experienced some spalling at the connection to the column, and it is apparent that it is supported on a steel bracket with bolts (i.e., steel seated connection).

I'm almost positive there is a steel beam embedded in the concrete, but I wouldn't even know what type of steel member to assume. Further, I'm not sure what purpose the concrete would serve if there is a steel beam. Has anyone seen this type of construction before?

 

[Lefkas]

Not sure if I've uploaded the pictures correctly, so I am posting the links below.

https://files.engineering.com/getfi...5-cc53-44e5-a519-f308fb0c8482&file=overal.JPG

https://files.engineering.com/getfi...82-4dd9-b773-e188841cd875&file=bent_plate.JPG

 

[BAretired]

Is that a timber column?

BA

 

[BAretired]

I'm almost positive there is a steel beam embedded in the concrete, but I wouldn't even know what type of steel member to assume. Further, I'm not sure what purpose the concrete would serve if there is a steel beam. Has anyone seen this type of construction before?

If there are no drawings available, it seems to me you will have to chip away enough concrete to determine if the beams are reinforced and perhaps enough to measure the size of the steel beam inside, if there is one. It is possible that the concrete was intended only as fireproofing for the steel beam.

BA

 

[rowingengineer]

Ground penetrating radar, cover meter are your friends. Non destructive will get you fairly informed before any demo

 

[hokie66]

Why do you think there is a bent plate under the joists? If there is a steel beam in there, wouldn't that be the top flange of the beam?

That bracket/collar is intriguing, as there don't seem to be any fasteners.

Looks like the column continues up. What does it support above?

 

[LittleInch]

How far do those joists go into the "concrete" beam?

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[Brad805]

If you have no drawings it looks to me you have a lot of field investigating to figure out the reinforcing/embed details at each beam. Did you stick a ruler or tape into the space at the beam to determine the bearing length of the wood beams? I see a lot of gaps, so I would think one can find that quite easily.

 

[Canuck65]

You can often figure out if there is a steel beam encased in concrete using a hammer. Generally a concrete beam will sound and feel solid (unless it is delaminated), however, very often the concrete on concrete encased steel beams will not be bonded well and sound very hollow over large areas. The concrete is typically there for fireproofing the steel beam, not additional capacity. A covermeter will also be useful in determining whether there is discrete rebar that you can find with the meter, or is it a fuzzy mess where the meter identifies steel everywhere. Past experience with a covermeter is valuable at the investigation stage.

Only way to obtain the structural properties of an encased steel beam is to jackhammer the concrete off a section and measure (or original drawings).

I would also recommend to calculate the capacity of the wood joists, which is very easy to do. It is likely that they were optimized for the floor loading at the time of initial construction. This should give you an idea of what the original design live load was intended to be. All part of the investigation.

 

[LittleInch]

You could esily be right and there is a wide flange beam hidden by all that concrete, or it could be a single plate bearing on the wooden beam.

Or that column could go all the way up and the concrete thing actually rests on some bearing surface on the metal bracket.

Time for an access platform and a kango....

Or just tell the company you're not sure how the current floor is even held up, never mind adding more load so even if you spend another x weeks doing investigation you have no idea what is there and no way to provide a capacity, so maybe best to just design it like the beam wasn't there??

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[Lefkas]

Thanks, everyone! I hope I answered your questions below. I will upload some more pictures as well.


@BAretired that is a timber column. Also, there are concrete columns at other locations.

@rowingengineer I hired a company that did GPR, and we got a continuous response about 2" from the bottom (suggesting that there might be a metal plate, like a flange?), and when we scanned the sides, we got a continuous response at 4.5" to 5" from both sides (steel web?).


@hokie66, there is one location where the gap between the concrete and the bearing plate for the wood joist is large enough that I can see the bearing plate has a radius. However, I don't think it's the top flange of a beam because there are several locations where this bearing plate protrudes 1" out of the sides of the "concrete" beam. This is why I think it's a bent plate.
At one column location, bracket fasteners are apparent, suggesting that it is a seated connection for a steel beam?
The columns continue up and support the roof.

@LittleInch the joists go in about 4" into the concrete.

@Brad805 yes, the wood joists go into the concrete about 4", and I feel like I'm hitting some sort of plate (web plate?) when I stick a metal object far enough.

@Canuck65 I will try the hammer idea. Thanks! The wood joists give me a capacity of about 150 psf. This suggests that the floor may have been designed for light manufacturing (125 psf), which would make sense since it is an old factory/warehouse.

 

[Lefkas]

Here are some more photos.

https://files.engineering.com/getfi...-a5cf-5e53ce8a6053&file=seated_connection.JPG

https://files.engineering.com/getfi...9b-4f96-9362-6fd2473f1f9d&file=bent_plate.JPG

https://files.engineering.com/getfi...fd595bc10a6&file=wood_joist_bearing_plate.JPG

https://files.engineering.com/getfi...7d1a990d57&file=wood_joist_bearing_plate2.JPG

https://files.engineering.com/getfi...-fb5a-4bc5-ac2d-3481220d9050&file=general.JPG

 

[Lefkas]

@Canuck65, further to my response, the wood deck is 2.5" thick which gives me a considerable capacity. I'm pretty sure this floor was designed for light manufacturing. However, I can't certify that "concrete" beam, and I'm having trouble even coming up with a conservative assumption for what it might be.

 

[hokie66]

From the photos you have presented, I think it is almost certain that there is no concrete beam. The concrete is cover around steel or iron beams. That is probably also the case with the columns.

 

[Lefkas]

@hokie66 yup, I'm sure that's the case. Although I'm not sure why they would use a concrete cover. The rest of the floor framing is wood, so fire proofing the beams doesn't make much sense to me.

 

[BAretired]

From the photos you have presented, I think it is almost certain that there is no concrete beam. The concrete is cover around steel or iron beams. That is probably also the case with the columns.

If the beam is steel or iron, you may be able to get properties from SlideRuleEra's file. In the case of the columns, they are timber.

BA

 

[BAretired]

@hokie66 yup, I'm sure that's the case. Although I'm not sure why they would use a concrete cover. The rest of the floor framing is wood, so fire proofing the beams doesn't make much sense to me.

Heavy timber gets a better fire rating than steel, its combustibility notwithstanding.

BA