Excavation Near Unknown PreEngineered Building Foundation

[RichRook]

I'm designing some foundations for equipment supports in a 1970's era pre engineered building. Typical tapered beams and columns. I'm going to have to take out a width of the slab about 10' wide x 22' long running parallel to the bent. The edge of the excavation would be about 6' off the column (measured parallel to the bent) and 1 or 2' off the column (perpendicular to the bent)

The foundation construction is not known. If I'm lucky there is a tie beam and I can avoid it by staying a couple feet off the column line. But in reality I'd expect a hairpin and want to plan for it. Any thoughts on what a reasonable shoring method might look like? Would something as simple as steel straps anchored to the concrete on either side of the excavation and tied into the column with some turnbuckles have potential? I don't see how this would be much less effective than the hairpin. I could even just run the plate column to column if necessary (a rod wouldn't work due to traffic in an aisle).

Afterwards, use mechanical couplings to replace the cut-out hairpin.

Thoughts?

Thanks in advance for the input.

Rich

 

[msquared48]

What is the overall size of the building and bay spacings of the mainframes?

You may be able to afterset bolt and metal strap to the slab, but you should get a hold on the size of the kick from the mainframe before you calc the temporary connection. If it has hairpins, #5 or smaller, then the kick is probably 7K or less.

Mike McCann
MMC Engineering

 

[RichRook]

The Bent span is on the order of 60 ft (I'm on the wrong computer for the exact answer) and bents are 26' c/c. I'll have to work out an estimate of the thrust. I'm waiting for the soil tests to finish the design.

Thanks
Rich K

 

[msquared48]

Something of that order, probably with 16 to 18 foot eaves too, will mostlikely have a tie beam at the mainframes, not hairpins.

Mike McCann
MMC Engineering