Twist-off bolts

[MikeE55]

If the contractor uses a twist-off bolt in a connection where slip-critical is not required, is there any problem with having the bolt only tightened to the snug-tight condition? I can see where this might confuse someone who inspects the job, but I don't see any other problem.

 

[evelrod]

Most TS bolts have a 'button' or rivet head and would preclude the use of a suitable wrench to "hold the roll" and thereby make "snugging" questionable. Also, any inspector worth his salt would reject such an operation.
Having said that, I am aware of certain methods of removing the sprue or tang in order to install the fastener so as to indicate "properly torqued". I am not blind. I know this happens---it's still ill advised and illegal!
Moreover, why would one wish to use an expensive TS where a cheap A 302 would suffice?

Rod

 

[MikeE55]

Thanks for your reply. The TS bolts were installed by mistake in connections that were not meant to be slip-critical. The inspector did catch that the bolts were improperly installed, but asked me to make an engineering decision on whether they could left in the snug-tight condition. I would like to see them all tightened completely, but don't want to create unnecessary expense. I am inclined to think that if the plies of the connection are snug, there is no further reason to torque the bolt.

 

[evelrod]

In my area (Los Angeles, CA.) you would be required to replace the high strength bolts with A 302 or properly torque the TS bolts. If, in your case the torquing of the existing bolts will not compromise the connection, it might just be cost effective to just do it. If your talking about hundreds then, you might consider replacing them.
I would advise you to check into codes before signing off something like this.

Rod

 

[Rjeffery]

As an inspector, I would have to have the TC bolts Tensioned (not torqued). The tool that tensions these type of bolts is the only way to properly install them. the connection can't tell me if it is slip critical or not. so I have to assume (yes I said, assume)that the higher grade of bolt was installed for a reason but will do no harm if it is not. (I can't or will not try to second guess an engineer.)

There should be no additional expense involved in tensioning the TC bolts until the splins are torn. If they are removed and replaced with a lower grade bolt there is an expense in that i would not allow the TC bolts to be reused. I can't tell if they were over torqued!

 

[evelrod]

I retired in 98 so what I remember may be out of date by now. In the beginning when these TS type (TC Tension Control, if you prefer) were just starting to be used in the Los Angeles area, there was a published torque spec for them seperate from normal A 325 --- I can't seem to recall, a senior moment I rekon, but it was a number less than spec for A 325 and it said something like "if it does not roll at *** then it should be considered properly torqued". Having said that, I ran afoul of several Smith-Emery folk that disagreed---I learned many years ago that the golden rule is "Thou shalt not p*** off thy inspector"! I personally (yeah, right) never cheated a connection, but if I removed a hard bolt that was only finger tight or wrench tight, with inspector approval, I would always reuse them.
It is not at all uncommon to find hard bolts where soft were specified and as long as the hard bolts were brought to the torque/tension spec for the HARD bolt, no harm , no foul. Sometime, as I said above, it was not cost effective to do so and in that case, I would have them switched out.
Most inspectors (well maybe not the ones for Cal Trans ;-)) would work with you. L.A. has some very knowledgeable inspectors and it never pays to get into a p****** contest with them.

Rod