Metal Building Foundation Repair

[j19]

I'm looking for some ideas on how to "repair" a new foundation for a metal building. The building is wide with a low eave height so the kickout forces exceed what can be resisted by hairpins so I designed tie-rods that run from footing to footing. The footings are spread footings with about a 5' high pedestal and the top of the slab is about 4' above the surrounding ground. The contractor "knew" the tie-rods were overkill so he put some rebar, that was 1/3 the area of the tie-rods that were shown on the drawings, in the thickened area of the slab and he tied the ends of the rebar to the anchor bolts with, you guessed it, tie wire. He did add #4 hairpins because they were being used at the endwall posts and he had some left over. Note: These are assumptions because he only poured half the slab so I was looking at the unpoured area. He thinks he's ready to make the second pour and that's the reason for my assumptions.

So, I consider his rebar to be completely ineffective and I'm looking for some options before I meet with the owner, who is aware there is a problem.
1) My first idea is to saw cut the 4" slab at the thickened area all the way to the edge of the slab and jack hammer or whatever it takes to remove the concrete and do the tie-rods right.
2) My second idea is to add a pipe column at approx. midspan beneath the metal building frame to reduce the kickout and see if maybe the #4 hairpins will work. The owner is going to have to make a lot of concessions for this to be a valid option.
3) Third idea is to pour some kind of stem wall outside of the building that would help the footing resist the overturning. There's a lot of details that would have to be worked out with this idea, like how to anchor the stemwall to the footing and column pier. Also, the horizontal load is being applied at the bottom of the column base plate so how can that force be spread out so that I'm not depending on the anchor bolts bearing against the concrete?

I'm looking for any other suggestions or things I need to consider for any of the options that I mentioned. Thanks for any help you can provide.

 

[dik]

I've often used plates with anchor rod holes and rebar welded to the plates to take care of the horizontal thrust.

Dik

 

[Ingenuity]

Active or passive PT bar soil anchors each side of frame column?

Very dependent on soil conditions and local availability of expertise. I would expect the $ to be on the high end of any budget.

 

[PEinc]

This type of wall anchor may be the easiest to install with the least amount of disturbance. I haven't used them in a long time, but they could be the easiest, most economical solution.

http://griptite.com/wall-anchor-system

You drill a vertical hole, about 12 to 14 inch in diameter, down through the floor slab. Then, drill a rod horizontally through the wall over and into to the vertical hole. Place the bearing plate on the rod in the vertical hole and backfill the hole with concrete. Then install the bearing plate against the wall and tighten. Essentially, you are installing a tie rod and deadman system to laterally support the wall. Spacing will be determined by the thrust load to be resisted and the allowable capacity of the tie rod and vertical deadman. As with any deadman system, the deadman needs to be back far enough that its passive zone does not overlap the active zone behind the wall.

http://www.PeirceEngineering.com

 

[JStructsteel]

I would put it back on the contractor, make him or her hire an engineer to design the "fix" so you can review and present to the owner.

As an owner, I would not want a new concrete slab with a trench cut and re-poured.

As the engineer, I would not spend my time to fix another persons mistake. If your drawings were clear and he ignored them, put it on him or her.

I like the idea of soil nails on the exterior.

 

[j19]

Update: I met with the owner on Monday and gave him "the talk". I explained to him the importance of the tie-rods, why they are needed and discussed some repair options etc. etc. (I wrote a thorough recap for my files.) He seemed very receptive to my concerns, although he did ask a couple of times if I really thought there would ever be a problem which I explained to him that I did. I also told him that I would have no problem if he wanted to hire another engineer to review the design to confirm my concerns and proposed repairs, or if he wanted to hire an engineer to do a full investigation and come up with his/her own solutions. I also offered to disassociate myself from the project by sending him and the building official a letter stating that I was doing this, that the foundation had not been constructed in accordance with the foundation plans, and that I recommend remediation take place in order for the foundation to perform successfully. All well and good until I drove by the jobsite yesterday (Tuesday) afternoon and saw that the other half of the slab has been poured. Sigh.

Before I start the process of disassociating myself from the project I am going to call the owner and have him verbally tell me that's what he wants me to do. Assuming that's his decision then I will begin taking the necessary steps. There's a good post from SLTA back in 2014 that discusses steps involved in doing this but I'll start a new post to see if anyone else has been through this and exactly what steps I need to take to cover myself.

 

[JStructsteel]

If your design is sound, and correct, write the letter, and move on. This is why we have building departments, its their baby then.

 

[Once20036]

I`ve been frustrated with a contractor recently who has not followed the drawings, and with the inspector who didn't red flag any of the deviations, and with the owner who assumes these issues will go away on their own. I don't expect it to hit the level of walking away, however, the job isn't done yet.
Anyway, I was interested in the SLTA post referenced above, and went and found it.
I think this is the one, for anyone else interested.

http://www.eng-tips.com/viewthread.cfm?qid=372242