clarity / bolted connection type / inspection of 1

[boffintech]

The specification for Structural Joints Using High-Strength Bolts requires that the EOR indicate the connection type. See below.

As the special inspector on a project am reading through the drawings, specs., etc. The EOR states in the general notes: “Bolted connections shall be type N (bearing type with threads included in shear plane) with minimum ¾” diameter A325 bolts.

What does this mean? Snug-tight, pretensioned, or slip-critical?


SECTION 4. JOINT TYPE
For joints with fasteners that are loaded in shear or combined shear and tension, the
Engineer of Record shall specify the joint type in the contract documents as snugtightened,
pretensioned or slip-critical. For slip-critical joints, the required class of slip
resistance in accordance with Section 5.4 shall also be specified. For joints with fasteners
that are loaded in tension only, the Engineer of Record shall specify the joint type in the
contract documents as snug-tightened or pretensioned. Table 4.1 summarizes the
applications and requirements of the three joint types.

 

[Teguci]

Bearing type and slip critical type are mutually exclusive.

Use of N or X after the bolt type indicates a bearing type (N-threades included, X-excluded). Bearing type bolts are to be installed snug tight.

Slip Critical is a pretensioned bolt with a specified surface preparation. Slip Critical and pretensioned bolts shall be installed snug tight and then the nut is further turned to apply a permanent stretching on the bolt. Use of SC after the bolt type indicates slip critical type.

 

[nutte]

Pretensioned does not necessarily mean slip critical. Bolts in bearing-type joints can also be installed pretensioned; the joint is not slip critical in this case.

 

[spats]

He specifies that they are bearing-type connections. Page 16.1-103 of the ANSI/AISC 360-05 Specification states that "Bolts are permitted to be installed to only the snug-tight condition when used in bearing-tyoe connections". So unless the EOR says otherwise, I would assume snug-tight only.

 

[nutte]

Prior to the passage you quote, page 16.1-103 says that bolts shall be pretensioned. Then it says that for the specific case of bolts in bearing-type connections, snug-tight bolts are permissible. Pretensioned is the default, not snug-tight.

This is all academic, though. Somebody needs to tell the inspector which it's supposed to be, as indicated in the original post. It's not up to him to guess.

 

[spats]

nutte,

It says pretension "except as permitted below". Therefore, for bearing-type connections, the "default" is snug-tight.

 

[nutte]

We disagree on this point. With that in mind, how should an inspector be expected to figure out what it's supposed to be? The EOR needs to provide the requirement.

 

[connectegr]

This is an elementary bolting question. No offense intended, but how do you become "special inspector" of any steel project without knowing this? What are the inspector qualifications?

There is nothing confusing in the specification requirement.

http://www.FerrellEngineering.com

 

[connectegr]

Generally bearing connections require only snug-tight installation. However, certain conditions may require pretensioning. Refer to section 4.2, RCSC Spec.

http://www.FerrellEngineering.com

 

[boffintech]

spats states that that unless the EOR says otherwise, he would assume snug-tight only.

However, I have to agree with nutte; pretensioned per table J3.1 is the default, not snug-tight.

Reason: the last sentence of the paragraph reads, "Bolts to be tightened to the only snug-tight condition shall be clearly identified on the design and erection drawings."

As connectegr correctly noted there is nothing confusing about the specification requirement: when a certain connection condition exists, bearing-type, snug-tight is permitted when clearly identified by the EOR on the design drawings.

The drawings I'm looking at do not clearly identify any connections as only snug-tight therefore all of the A325 bolts placed to date are out of compliance with the design drawings.

Interestingly enough, if the design drawings had referenced the new 2010 version of the Specification for Structural Steel Buildings I'd agree with spats.

Reason: the 2010 version reads, "Bolts to be tightened to a condition other than snug tight shall be clearly identified on the design drawings."

 

[spats]

Evidently they realized the error of their ways and corrected it in the 2010 specification.

I am also a registered Special Inspector in the state of Florida, and I would certaining not reject connections made to date without clarifying the requirements with the EOR. As connectegr states, bearing connections are normally snug-tight only. I always clarify this in my specs by directly stating that all bearing connections are to be snug-tight only unless otherwise noted.

 

[boffintech]

connectegr, to answer your question, I'm very resourceful.