Snug Tight for Bolt Installations

[BigH]

We have a Bailey Bridge to install. Specs say snug fit plus 1/3 rotation (120 deg). From a practical point of view, how does one arrive at the "snug tight" condition - and know that is what it is!

 

[Drumchaser]

BIGH

From our spec.s (S.T.A.) ...not sure if it is ASTM AASHTO etc.

SNUG-TIGHT - "The conditon when the nut is in full contact with base plate. It may be assumed that the full effort of a worker on a 12" wrench results in a snug tight condition."

Hope this helps

 

[Qshake]

BigH, I concur with Drumchaser on the matter of full effort of a ironworker using a typical spud wrench. This is outlined in, I beleive, AISC and certainly in the Fisher/Kulak book Guide to Design of Bolted and Riveted Joints.

I agree that it is subjective but that's what it says.

Regards,
Qshake

Eng-Tips Forums:Real Solutions for Real Problems Really Quick.

 

[BigH]

Terima kasih! (thanks)

 

[BigH]

Another - any specific pattern of tightening (like you would on a car tyre?)

* *
* *
* *

??

 

[Drumchaser]

Snug-Fit? or actual tensioning?

Tensioning (after SF) - "Start at the most rigid part of the connection and proceed to the free edges."...return the wrench to re-tension previously tensioned bolts that may have relaxed as a result of subsequent tensioning of adjacent bolts"

this also appears to be subjective (in your case)

FYI - most of our stuff arrives from the fabricator with nuts and bolts (in place)for shipping only. These have to be replaced with ASTM A325 / A490 etc.

HAve no experience with Bailey Bridge. Military application? Thought they were 1 laners?

 

[bridgebuster]

From my experience Snug tight + one-third means fully tensioned.

Below is a link to the NYSDOT Steel Construction Manual's section on bolting. I copied the definition of snug tight but take a look because there are some tables on required pretension and proper inspection procedures.

https://www.nysdot.gov/divisions/engineering/structures/manuals/scm/repository/scm08_section10.pdf

"Bolts shall be tightened to the minimum required tension described in Table 1001.5a by the turn-of- thenut
method. Enough bolts shall be installed and brought to a snug tight condition to ensure that the parts
of the joint are brought into full contact with each other. Snug tight is defined as the tightness attained
by a few impacts of an impact wrench or the full effort of a person using an ordinary spud wrench. This
represents approximately 150 foot pounds [200 N m] for bolts ? inch (M22) in diameter and larger.
Following this initial operation, bolts shall be placed in any remaining holes in the connection and
brought to snug tightness. All bolts in the joint shall then be tightened additionally by the applicable
amount of nut or head rotation specified in Table 1001.5b. During this operation, there shall be no
rotation of the part not turned by the wrench."

 

[Qshake]

BigH - Starting inside and working your way out is a good way to go. My experience is on large gusset plate joints and there is a good deal of drift pins and fit-up-bolts to deal with while bolting up joints. So if you impact a bolt up near a pin or fit-up bolt where the plies don't remain flat and snugged together you will need to revisit those bolts first installed after you remove the pins/bolts.

So I always worked with the ironworkers to go in an orderly fashion from inside out and clockwise so that we can easily remember what was done first.

Regards,
Qshake

Eng-Tips Forums:Real Solutions for Real Problems Really Quick.

 

[BigH]

Thanks to all. Good responses.

 

[HgTX]

http://www.boltcouncil.org/files/2004RCSCSpecification.pdf

If you do the "pre-installation verification" test, that serves more or less to verify snug-tightness, because if it wasn't snug you won't get the required result.

Hg

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