I recollect someone providing a link to an AISC document a few weeks back describing inconsistencies in clearances between the steel and concrete specifications (
Here it is typically 2mm clearance in general, 4mm for base plates, and I think up to 6mm for larger bolts in base plates: assuming you are referring to bolt hole clearance. For using an impact wrench typically need at least 55mm clearance from any face, and recommended minimum of 100mm between faces if hand access required, if the issues are clearance for tooling and access.
B.Tech (mfg & mech), MIIE, gradTIEAust
From: William.Sherman@CH2M.com [mailto:William.Sherman@CH2M.com]
Sent: Friday, 8 August 2008 07:31
Subject: Large diameter bolt clearances
Any suggestions for references for tightening clearance requirements for large diameter anchor bolts (>1.25" diameter)?
William Sherman - CH2M HILL /
Principal Structural Technologist
Structural Global Technology Leader - Water Business Group