Can a contractor really set pins for steel in concrete within 1/16th of an inch?
> Can a contractor really set pins for steel in concrete within 1/16th of an inch?
Come on Thad, you know the answer to that. Even surveyors struggle with it. That's why steel has big holes in it for when they do anchor it somewhere in the right spot.
I'd be more concerned about grade. Goof that up and some things do go down hill. And steel that gets cut too short. They can always cut/paste a long beam, but I don't think they have figured out how to stretch the short ones. Oppsies, sorry ma'am.
JT,
Sometimes, if it's really critical, an as-built survey will be done on the freshly-poured-in-concrete bolts before the base plates are welded to the columns. There's quite a bit of adjustment there, if necessary.
Base plate holes are typically drilled 1/16" larger than the bolts they get set over, and the bolts can be knocked around a bit because there's always at least 1" of space at the bottom to pour the non-shrink grout after the columns are plumb.
Dave
> Can a contractor really set pins for steel in concrete within 1/16th of an inch?
I'd say it depends on who the contractor is. I recently watched a team set the steel for the new Harry Potter steel coaster at Universal Studios Florida, using the latest Total stations. They were waiting around one morning apparently doing nothing, instruments all set up...I asked them what they were doing. They said they were waiting for the temperature to rise another 6.5 degrees, before everything would be aligned for the next piece to go into place!
I can be done...but you would probably need a monitoring total station (1/2 second or better), perfect field procedures, and perfect field conditions. This level of accuracy is common when laying out machinery in chip factories, etc.
We laid out column lines last year using a 1 second Leica MS50 to 1/8" of the plans. It was a pain in the ass but we did it...had to reset two lines after finding them slightly out of tolerance but we got it.
Tom
