Column seated on edge of foundation stemwall by mistake

[chrislaope]

Hi, Gentlemen:

Here is the scenario:

Company "A" sold a structural product to Client "B". Client "B" hired an Eng. firm "C" to design the foundation for this structural product, somehow for some reason, Eng. firm "C" made some mistakes in dimension measurement that the column is now seated on the outer edge of the foundation stemwall while it should be seated on the center of the stemwall. After they found this mistake, they added a hairpin to balance the outward horizontal load as a retrofit, and the engineer of Client "B" OK'ed with this retrofit.

The unfactored vertical load of this column on the foundation is 180 kips, as is shown in attached diagram.

Now I have 2 questions:

1. How do you calculate the vertical load capacity of the foundation stemwall as now the load is very close to the outer edge of the stemwall (edge distance is only 3.75")? Will you guys validate it as appropriate?

2. This second question is a legal question: As now the structural design engineer in company "A" was also informed this issue, and suppose in future the structural product failed due to this foundation issue, will the structural design engineer in company "A" also blamed to take some liability because he ignored it and did not take any action to prevent this foundation to be put in use?

Thank you very much for your inputs.

 

[EngineeringAdam]

I personally don't think the column base offset is too big of an issue. If you want to be conservative you could check a section of the foundation using concrete column design with and eccentric load. I tend to think that because you have a continuous foundation any buckling that is encouraged by eccentric loads is lessened. In cases like these I have checked the base plate design, concrete bearing, foundation stem as a concrete column assuming a certain length of foundation to define my column dimensions, and finally soil bearing pressure.

If it does fail and there is a lawsuit, you can be sure that anyone involved on the project (not just the foundation issue) is fair game - those covered by insurance, even if not involved with this specific issue, can be forced to give insurance payouts. Insurance companies prefer to payout a settlement quickly instead of hassle with defending the innocent. (costs less).

 

[Ahmmed123]

1) since the load is not at the center of the column then you will have an eccentric load. the eccentricity e = 20/2-3.75= 6.25". ( you will basically have a load and a moment at the center). then I would check for capacity, slenderness, sway and non-sway, and Buckling;....... based on this eccentric load !

2) I as far as I understand from this question, neither B or C will blamed A. but if the foundation failed then A,B and C will be blamed !!!

 

[JAE]

Will you guys validate it as appropriate?

No one on this site can validate a design(whatever that means).

Just giving you pointers/tips and feedback.

 

[shobroco]

The load and the size of the foundation don't seem to be too well matched anyway. Ignore everything except the symetric section about your baseplate & you get a 7 1/2" thick wall on a wide (no dimension) strip footing; I'd be surprised if it's close to its capacity.

 

[hokie66]

You gave a vertical load (downward). Is this column also subject to lateral loading? Uplift?

 

[BAretired]

I would be concerned about the lack of confinement steel preventing a shear failure between the block of concrete below the base plate and the remainder of the stem wall.

If the drawing is to scale, the base plate is approximately 7.5" x 10", so the average bearing pressure is 2.4 ksi which is a bit high (by the Canadian code), particularly when the edge of plate is flush with the edge of concrete.

BA

 

[chrislaope]

Thanks for everybody's input.

BA's concern is also one of my concern, also based on ACI-318, the bearing capacity of base plate seated at edge is only half of that when base plate is seated at center. To avoid possible trouble I am not going to post more information on this, but have last question to ask and would like to get oppinion from you guys:

Current situation is PEs in Eng firm "C" and client "B" approved this foundation. Company "A" do not feel comfortable about this foundation but it seems like non of Company "A"s business and Company "A" do not want to stick nose into other's business. In this circumtance, what is the most appropriate attitude that Company "A" should take to prevent possible (in case) future legal trouble?

Thank you very much.

 

[msquared48]

Put it in writing to the other two companies and the owner.

Mike McCann
MMC Engineering

http://mmcengineering.tripod.com

 

[msquared48]

The thing that struck me is the apparent (as in not deleneated) small size of the baseplate for the load - I would have expected a plate in the order of 14" X 10" or so - which would have fit nicely on top of the wall, but not now.


Mike McCann
MMC Engineering

http://mmcengineering.tripod.com

 

[ztengguy]

Absolutely inform them of your concerns, but politely without saying you did calculations, more just engineering judgment from experience. Also might want to copy building department with the letter.

If you know about it, you can be sued, even if innocent.

 

[Teguci]

You have an ethical and legal obligation to protect the public. Do you know that there is a problem? Probably not. But you, in my opinion, are required to pursue confirmation regarding your doubts.
Step 1 - what potential failures do you envision with this problem (concrete bearing failure, foundation overturning...)?
Step 2 - Ask engineer B how engineer C verified that these failures will not occur?
Step 3 - Determine if you are satisfied with the answers. Otherwise return to step 1 with clarification.
Step 4 - Let us know how it went.

 

[BAretired]

If you have concerns about the detail used, I agree that you have an obligation to bring the matter to the attention of the other engineers. This would give them a chance to review the situation and take remedial action if they agree.

If they do not agree, you must put your concerns in writing, first to the other engineers and secondly, in the absence of appropriate remedial action, to the authority having jurisdiction. That is all you can do. It is not fun, but it is necessary to protect you and your company.

BA