Device to determine steel thickness 2

[ajk1]

The contractor has drilled holes in heavily reinforced round spirally reinforced columns, for setting adhesive anchors and threaded rods, but despite having done a magnetic scan of the columns, still sometimes hits steel at about 100 mm in from the column face. From the original drawings we know that the spirals are 1/2" diameter at 2.5" centres and the vertical bars are 2.25" diameter. If it is a spiral that is being encountered, our structural analysis indicates that it could in some cases be core drilled through without too significantly reducing the column strength. But we don't want to drill though the column vertical bars as that would reduce the column strength too much. Is there any device that can approximately measure the thickness of the steel when the device is placed against the surface of the steel at the bottom of the hole.
Thanks.

 

[ztengguy]

you could try a xray and see if you can get a profile view where he is drilling and see if it will show the depth.

 

[ajk1]

x-ray to get profile view is an ingenious idea but I think would be very hard due to the circular shape.

 

[kingnero]

You shouldn't really think whether or not Xray is hard to do, you should ask a firm that provides these services... and you'll know for sure.

 

[ajk1]

Over the last 48 years I have been involved in the directig of radiographic work for well over 2000 X-rays, including over 1000 on one structure where had it carried out to locate the tendons so we could install repair bolts between the tendons. I am humble enough to know that does not make me an expert on radiography, but perhpas it does give me a bit of knowledge of what can and cannot be done and the limitations. In addition we did discuss the use of radiography with a specialist company at the commencement of the work and were advised that it would be difficult to impossible.