High Strength Bolting - Pre-Installation Verification Requirements

[hocha]

I am managing construction on a project in California with a pre-engineered metal building. The shop drawings show pretensioned joints with ASTM A325 Bolts. The contractor is planning to use the turn-of-the-nut method to tension the bolts and is arguing that pre-installation verification is not required.

I have pointed out the specific language in the "Specification for Structural Joints Using ASTM A325 or A490 Bolts" requiring pre-installation verification (which is also included on the submitted shop drawings). However, recently, the contractor provided me with a letter from the engineer of record (licensed Civil, but not a licensed Structural, Engineer) for the pre-engineered metal building waiving the requirement for the pre-installation verification. Is this allowable?

Thanks in advance for your comments.

 

[paddingtongreen]

I would say no, get an approved Field Change Request changing the drawing.

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

 

[connectegr]

Pre-installation verification is required for turn-of-the-nut, per the current RCSC Specification. We have discussed removing this requirement in the next edition, but there is not sufficient support for the change. In addition to verifying that the installer understands the steps required of the installation process and defects in the lot of bolts may be discovered.

However, the EOR can wave or supplement the pre-inspection requirement. This is a liability accepted by the EOR. I am not sure how the EOR for a California project is not an SE, but this may be related to the size of the project.

http://www.FerrellEngineering.com

Providing fabrication and erection efficient structural design of connections. Consulting services for structural welding and bolting.

 

[NS4U]

connectegr, you sound like you are on the RCSC committee. I am curous how the EOR could wave this requirement? The RCSC language is quite clear that preinstallation verification testing is required. it seems like such an unneccsary liability to wave this requirement.

on a seperate note, i have worked on a number of projects with pretensioned bolts and always make sure the preinstall verification testing is done... whether they're installing 5 bolts or 500. given how strong the RCSC langauge is, I would never think of waiving this requirement.

on another note, turn of the nut is what I've typically seen and I would agree that if, they follow the nut rotation requirements of RCSC, it seems unlikely that they would not make the required pretension. personally, I have yet to see a bolt that didn't develop the specified min. pretension when providing the required nut rotation in RCSC.

 

[paddingtongreen]

@NS4U,
"personally, I have yet to see a bolt that didn't develop the specified min. pretension when providing the required nut rotation in RCSC."

Do you have some means of testing the installed tension? The Turn of the Nut method can be misleading if the bolts have not been properly snugged beforehand. If not snugged, a bolt with full tension may lose some when the adjacent bolts are pulled up

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

 

[NS4U]

paddington- that is a differenet issue. i completely agree with you that if you have a series of bolts close together, the order that you pretension the bolts is critical and you can certainly relax the tension in other bolts if you don't pretension in a logical order. this is the same logic that requires you use a star pattern when tightening lug nuts on your car's tire.

your concern though, is applicable to every type of bolt tensioning method, not just turn of the nut, and the preinstallation testing does not capture this affect since it only tests a single bolt, not a series of bolts in a joint.

regarding the different levels of "snug tight" i agree with you. snug tight to one iron worker is different than snug tight to another iron worker. this is why preinstall testing is important. it allows the ironworker to understand how tight the joint needs to be in ordrer to be considered snug tight. if they dont snug up the joint enough, they will see that turning the nut 1/2 turn, or so, won't develop the required pretension.

that being said, snug seems to be a more or less universal term and I have found that even though the amount of snug can very from person-to-person, the amount of pretension you add by turning the nut 1/2 turn or so past snug more than compensates for the variation in snug.

But, that doesn't mean I will waive the preinstall testing reqs, even if that are using turn of nut!

 

[connectegr]

I did participate on a workgroup for this very issue. Even the workgroup could not reach a consensus on eliminating the pre-installation verification. The primary concern was issues with the quality of the bolts. But, obviously there is some concern with not destinguishing one installation method as preferred or more consistent than the others. I don't know why a EOR or inspector would want the liability of waving the procedure. Many engineers are not familiar with the spec and take the word of the contactor, than it is am un-necessary requirement.


Correctly marking the bolts is also necessary to properly inspect the installation.

http://www.FerrellEngineering.com

Providing fabrication and erection efficient structural design of connections. Consulting services for structural welding and bolting.

 

[paddingtongreen]

RCSC says that a nut is snug tight if given the full effort of an ironworker with a stsndard spud wrench or a few impacts of an impact wrench.

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

 

[chicopee]

If the Certs were from American maufacturers, would pre-installation verification be needed?

 

[paddingtongreen]

Back in the late 70s, early 80s, we were designing and construction managing a nuclear power plant. The steel erector wanted to use TS bolts (this was a brand back then, there were also TC and TF brands). Since they hadn't been used on a nuke before we instituted a test program wherein a percentage of each heat were busted on the Skidmore; I had to analyze the results (I was responsible engineer for all of the steel on the job). It was easy because, of the hundreds of bolts, not one came in light. I don't know when the requirement was introduced into the specification, I didn't know of it till this thread. I wonder if we triggered it, we had someone on the nuts and bolts committee.

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

 

[connectegr]

paddington...
The current RCSC provides a little better description of snug-tight in the current edition. RCSC '09 8.1 all bolts in the joint have been tightened sufficiently to prevent removal of the nuts without the use of a wrench"

http://www.FerrellEngineering.com

Providing fabrication and erection efficient structural design of connections. Consulting services for structural welding and bolting.

 

[paddingtongreen]

Thanks. I went to the site and it showed me the 2004 version. That is a much safer description.

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

 

[ToadJones]

"The current RCSC provides a little better description of snug-tight in the current edition. RCSC '09 8.1 all bolts in the joint have been tightened sufficiently to prevent removal of the nuts without the use of a wrench" "

This certainly seems much less restrictive than the old "full effort" method.

 

[paddingtongreen]

It does mean that use a wrench and that they have to re-check the early bolts to see if they've been freed up by the subsequent bolts.

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

 

[hocha]

Thanks for all the input. I also discussed with the Owner's Engineer. The consensus on this end aligned with most of the responses. The EOR can waive the requirement for pre-installation verification (as he is assuming the liability), and I, as the CM (Owner's Agent), no longer have leverage to enforce a pre-installation verification.

However, the EOR has no idea where the contractor procured his bolts from (and cannot judge whether they are counterfeit) so I really do not understand why he would take on this liability. In any case, I am much more interested in preventing a potential failure than I am knowing who is liable for the failure if it occurs. So I have asked for details on the bolts that are going to be used. Wish me luck...

As an aside, the Owner's engineer told me that an actual structural license is only required in CA under a few cases (design of schools, hospitals, etc.). A civil license (with a structural background) is sufficient in most other cases.