Inspection of Snug-Tight Bolts

[abusementpark]

For bolted steel connections in which the only requirement is for the bolts to be snug-tightened (i.e. no pretension requirement), how does an inspector typically determine whether or not the bolt is properly snug-tightened?

 

[Ron]

For a snug-tight condition (a pre-cursor to tensioning by turn of nut method), there is no way to tell other than to watch and/or turn a few bolts with a spud wrench.

 

[connectegr]

"Turn of the nut" applies to pretensioned bolts and does not apply to snug tight. The inspection must verify that all plies are in firm contact. The inspector should observe the installation and check a random sampling. The appropriate pretension is described as the "strength of an iron worker".

http://www.FerrellEngineering.com

 

[abusementpark]

For a snug-tight condition (a pre-cursor to tensioning by turn of nut method), there is no way to tell other than to watch and/or turn a few bolts with a spud wrench.

Is this why a lot of engineers call for pretensioned requirements like tension control "twist off" bolts? It is easy to verify that the snug-tightened requirements (and then some) have been met.

 

[connectegr]

Snug tight is not an exact science. But it does not have to be. As I mentioned the important factor is that all plies are brought into firm contact. Requiring un-necessary pretensioning has it's own issues. Not the least of which is the increased cost. Another anomaly can "bolt banging". I would not recommend pretensioned bolts simply for an inspection guideline. Require a proper installation quality control practice.

Reserve the specification of pretensioned bolts for slip critical connections. This should only be necessary for certain loading conditions or additional erection tolerance.

http://www.FerrellEngineering.com

 

[csd72]

Agree with connectengr, snug tight has been doing us well for centuries.

As well as the cost issue, providing pretensioned bolts can make a very big difference on how a connection behaves. Fin plates can start transferring moments, welds that were designed to be lightly loaded can become more highly loaded, there is less allowance for shrinkage or equalising of bolt shears through shear ploughing e.t.c. e.t.c.