Hi, I just have a few questions regarding the installation of structural steel columns onto pedestal foundations with anchor bolts.

If for instance a module with 6 main columns and feet is placed onto a corresponding arrangement of 6 foundation pedestals (each with four anchor bolts), shims are used to ensure the proper elevation of the module when initially setting. After this module is placed and levelled on these shims the foundations must still be grouted.

My questions are:

1) are the nuts tightened after the base plate is grouted to the foundation? (i.e. is the module simply sitting on the shims before grout?)

2) what method should be used to tighten these nuts? (turn-of-nut, only snug-tightening?).

3) In CSA S16-01, section 25.3.2 Erection (Column Bases and Anchor Rods) it states that anchor rod nuts are only to be tightened snug tight. Why? Is this after grout or before?

Also, to me it does not make any sense (from the perspective of bolted connection design) to pretension ANY type of bolt against small point loaded shimS. You want the clamped material to be stiffer than the bolt so that small deflections will be taken by the clamped material and not the bolt (with mild steel shims this is likely not possible).

Any input is greatly appreciated!

Nuts are torqued after the grout is set. Tightening is usually just snug tight for structures, they have no tendency to unwind. Vibrating equipment might be different.

For every answer, someone will say it is wrong.

Michael.
Timing has a lot to do with the outcome of a rain dance.

Answers:
1: Yes
2: Snug Tight
3: Snug Tight... they will not normally loosen... You could be using a more recent version of S16...

Dik