Metal Building Foundation Repair
Metal Building Foundation Repair
(OP)
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.
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.






RE: Metal Building Foundation Repair
I design about 6 metal building foundations/year and have been told to avoid tie rods and hairpins at all costs. I have had some chances to scope out the designs of the competition too and I can never get how someone can justify a 4x4 footing under a column with 4' of frost protection and the column on a 4' knee wall, no center column and a 60' clear span. This is probably where your problem originates.
RE: Metal Building Foundation Repair
By "do the tie rods right" do you mean they would cut a trench all the way across the building?
I wonder if they could grind the slab in a groove and use CF in some way. Seems like it would be taught to rationalize the traffic wear on the CF if it is located at the surface. Just "thinking out loud".
Alternatively to excavating and removing concrete from under the column (guess you could shore the frame for temp loads) could you fabricate a steel bracket that could connect the column BP directly to the new tie rods?
RE: Metal Building Foundation Repair
You need to provide us with some load numbers and dimensions so we can make some educated suggestions. First we need to know the width, length and eave heights of your building as well as roof slope and single or double slope roof profile(symmetric or non-symmetric). We also need to bay lengths. Then we will know controlling loads at the column bases.
I am currently working on a 90' wide x 90' long x 17' actual eave height building with a 1/2:12 symmetric roof pitch and 3-30' bays. It has 47 kips gravity load, 8 kip uplift and 45 kip horizontal kickout. Snow load is the controlling load case when combined with the other appropriate load cases. I wanted to add another column at midspan but was overruled by the owner who wants a clearspan building. So I am using tension ties across the building.
If the owner of you building wants a clearspan then a demo and reinstallation of the tension ties seems the most appropriate solution. I won't make any other suggestions until I have more information to go on. Is the concrete contractor, who didn't follow the plans, going to pay for the re-work?
Jim
RE: Metal Building Foundation Repair
RE: Metal Building Foundation Repair
Is CF short for Concrete Floor?
Jim
RE: Metal Building Foundation Repair
Dave
Thaidavid
RE: Metal Building Foundation Repair
CF = Carbon Fiber
RE: Metal Building Foundation Repair
RE: Metal Building Foundation Repair
RE: Metal Building Foundation Repair
The is a gable building, 120' wide, clear span with either 10' or 12' eave heights. The reactions from the MB manufacturer show that under Dead + Collateral + Live Load the kickout is around 40 kips.
By "do the tie-rods right" I did mean to cut through the slab that has been poured, which is about 60' length. There are only two frame lines so that would mean cutting about 120 lf of trench.
This building is an add on to an existing building so I can't raise the slab. By the way, the existing building was built about 10 years ago and the contractor complained about the tie-rods but in the end he did what was called for on the drawings.
As far as buttresses, I was calling these stem walls but buttresses are a better description. This could be done but the forming and tieing into the existing I'm thinking the cost would be much more than cutting the slab.
I am not familiar with the carbon fiber solution that was mentioned. Where can I find some info on this?
RE: Metal Building Foundation Repair
RE: Metal Building Foundation Repair
RE: Metal Building Foundation Repair
But seriously, I would push to have the contractor trench the slab and put in the tie rods if this was on your drawings and part of your design. With regard to shear on the bolts, shear lugs are always a possibility,....for next building.
Sure creates a mess. You'd almost need to cut a decent 18" to 24" wide or more section of slab out each column line in order to have room to be able to dowel back into the slab on the sides. Pretty much looking at a existing slab trench repair detail.
Can't see trying to just remove enough concrete to set a bar in and then patch/cover the bar. Maybe there are some good high strength polymer patching solutions for this possibility by Sika or others.
Hope this helps.
RE: Metal Building Foundation Repair
RE: Metal Building Foundation Repair
1) Another permutation of usable space encroachment and;
2) A re-evaluation of the portal frames.
Like others, my gut feel is that reinstating the SOG tie rods will be the way to go. That could get quite ugly though if it winds up being necessary to demo the piers as well in order to robustly connect the tie rods and the column bases.
For such applications in the US, I believe that the code requires tension tie reinforcement to be continuous or spliced with welds or mechanical couplers. Irrespective of other shortcomings, that alone may render your contractor's DIY alteration 100% code ineffective.
I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.
RE: Metal Building Foundation Repair
Ugly is relative I suppose.
I'm thinking maybe a steel "boot" can be welded to the base plate and bottom of column that would accommodate such a connection.
Some eccentricity to deal with...
RE: Metal Building Foundation Repair
RE: Metal Building Foundation Repair
RE: Metal Building Foundation Repair
That mechanism (eccentric footing at the column) is how I've seen new foundations designed when a stem wall is needed.
RE: Metal Building Foundation Repair
Dik
RE: Metal Building Foundation Repair
Very dependent on soil conditions and local availability of expertise. I would expect the $ to be on the high end of any budget.
RE: Metal Building Foundation Repair
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.
www.PeirceEngineering.com
RE: Metal Building Foundation Repair
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.
RE: Metal Building Foundation Repair
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.
RE: Metal Building Foundation Repair
RE: Metal Building Foundation Repair
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