Column Bearing Capacity of an Existing Concrete Wall

I think you're going to have to hire a structural engineer to take a core sample of the concrete and test it in order to show that it's capable of handling the load.

GA

What kramarat said, plus, it is a load bearing wall, not a column. The reinforcing sounds, umm, peculiar, how do you know what it is. You need a structural engineer to check it against the ACI code requirements. Dammit, you need to hire a structural engineer, period.

Kramarat is correct.

No matter how much the theory confirms the capability of the wall, confirmation with an appropriate series of test cores will provide factual data that can then be used.

107 year old concrete will have significant (and potentially invisible) deviation from modern and recently poured structures.

Carbonation would mean that a portion of the surface thickness cannot be considered to be structural, manufacturing controls on the cement (powder) and then the concrete mix for that time period would also be different than modern conditions.

Have you looked at the interlock for the base of the wall, and the foundations? The wall design may have been fit for its intended purpose, but the additional loading may compromise some other feature of the design.

Finally, the wall may have been designed and constructed of a grade of concrete that is not capable of supporting your load indefinately. Different mixes for different purposes.

On the job actual engineering/scientific data is a must in this circumstance.

The next potential problem I see coming down the pike, is that you may not be able to find a structural engineer that's willing to drill core samples with 18,000 lbs sitting on top of those 107 year old walls. I sure would be nervous.

You're probably already thinking this, but it would have been a good idea to have those walls tested beforehand. Especially if the feds are involved in any way. They have a knack for making your life miserable.

I manage the downtown parking and parking structures in my city. The Feds are tenants in one of these structures. They wanted an existing fence extended 9 feet to accommodate two more secure parking spaces for govt. vehicles.

It took over a year for the $1,800.00 USD project to be completed and approved.

The actual labor to modify the fence took two guys about 4 hours to complete.

Go figure.

Yeah, the project was $1800, but I wouldn't be surprised if a years worth of bureaucratic paper pushing by salaried govt employees was a lot more than that.

Inspectors like to be considered very important people. Hopefully the OP hasn't walked himself into a nightmare. The feds have no problem telling people to take everything apart and start over if it's not right.

I wouldn't have any heartburn coring the wall, but I would need a good re-bar finder. At 18' high, I'm dubious. The code now requires two layers of rebar in 10" or thicker walls, except basements.

I was a bit taken aback that an oil filled transformer was not over a stone filled concrete vault. There are a few manhours needed for a field trip, to write a spec for the coring, research the old codes so as to justify if it won't meet today's code, perform the calculations and write a report.

I was taken aback that this wasn't addressed before putting the transformer up there.

I did a little googling on concrete life expectancy and it doesn't look good. Another problem, considering that this sounds like a long term arrangement, is that a structural engineering firm, not only has to determine whether it's sound now, but will it be fine for another 30-50 years.

You don't say who built the wall originally. If the US government built it (bunker) there will be info on it somewhere. I have seen some of these units in the past that were over built by todays standards, even with the current operation mode of government inspectors.

Some years ago I had an interesting conversation with a gentlemen that was involved in many of the (before TVA was TVA) TVA's dam designs. The engineering involved was quite impressive. He still had many of the drawings and calculation for these units and shared some of that with me. I might say they were very thrall in their approach.

So if your lucky to have one of the old government build projects. you might be ok with the wall as is. But, in reading your write up I doubt it. Your choice to use an existing structure is commendable in todays reuse and save environment, but in this case maybe not so good.

Dear William:

As a Structural Engineer I have my doubts that the existing concrete walls will be structurally adequate to safely support the design reactions that you seek, There's just too many unknowns regarding the existing concrete, especially due to it's age. I wouldn't rely on the wall to act in a column fashion. Additionally, steel rebar of that period generally was smooth bar (no deformations) with a low yield stress.

This is my suggestion to you: I'd play it safe and provide 4 new structural steel columns to support the ends of existing I-beams. These new columns can be snuggled to the inside face of your existing 18-foot high concrete walls. Generally. I would secure the new columns to the inside face of the concrete walls with two epoxy encapsulated Hilti anchors (or equivalent) spaced at 48-inches o.c. vertically. Additionally, I'd provide secondary X-bracing between the two columns that adjacent to one another.

No mention what the existing floor below is (at the base of the bunker). If it's an existing concrete slab of significant thickness placed atop bedrock you may be able to re-use it in order to support the 4 new steel columns. Perform several Windsor penetration tests in each column location to determine the in-situ concrete compressive strength and design your column baseplates accordingly with a fair amount of FS (fudge). Or if the slab is inadequate for any reason provide 4 new reinforced concrete individual spread footings & column piers.....design to take column axial load plus eccentricity (due to offset loading).

Any questions please contact me, okay? Good luck!

Signed,

CaptMoosie, PE (NYS)

Civil, Structural, & Environmental Engineer

PS: Love that you guys are rehabbing these old abandoned hydro plants throughout the NE!

I SUGGEST YOU ABANDON THIS STRUCTURE- IT IS GOOD FOR HISTORY..ENGINEERING WISE THERE ARE TOO MANY UNKNOWNS HENCE NOT WORTH DIGGING

DESIGN A NEW PLATFORM

WORRIED!!

Too many unknowns. for instance what is the F'c of the concrete? what is the Fy for the steel used? what are the connections like at the floor and roof (fixed, supported)?

I suspect it is simple supported connections for the I-Beams, how does the wall connect to the floor?

you should to hire a Structural Engineer, or at least an experienced Civil Engineer to conduct an investigation and analysis.

Dear All:

Thank you for your provocative comments! Based upon your collective concerns, I have retained the services of a registered professional structural engineer to exam my structure. Depending upon his analysis and recommendations, I will strengthen the wall as necessary.

Sincerely,

William K. Fay

West Ware, MA

Could you pop back in on this thread and let us know how it went?

Good luck, hope everything goes smoothly.

Absolutely!!! That is only fair!!!!

WKF

Another tack that can be taken as an alternative or supplement to analysis is to do a structural load test and observe performance. American Concrete Institute (ACI) has procedures for structural load tests on reinforced concrete structures. Where I used to work, I used to do this for elderly reinforced concrete structures where design information for analysis was nonexistent and it was desired to use the structure for a different purpose than the original. Loading would be done in 1/4 increments up to the maximum of 125% (or 150%, can't remember which, have to consult the lastest ACI code) of the maximum design load, the load retained for 12 to 24 hours, and then the load removed in decrements the same as the load increments. After each load increment and decrement, the deflection would be measured and visual inspection made for cracking and other distress. The deflection has to be within the minimum and there has to be no visible cracks, distress or damage. For this application it may be necessary to determine if there is any horizontal design load, if there is, then that has to be applied in the load test also. Water makes a good load medium as it is relatively easily applied and removed if need be, also sandbags, concrete blocks, or hydraulic jacks though a loading frame. I have used all these methods. Load tests can be very expensive, but in many cases they are the best way to determine the fitness of an old structure for an intended purpose. Any good engineering materials testing lab working with a PE should be able to work up and do the test.

I didn't see seismic considerations thus far, but with a structural PE on board, that will surely be covered. (After all, we don't want tilt-down wall construction.)

first, u must find the original plans and summit them to an engineer to be approve. the engineer might ever know where the plans are located