Bolt and Nut Specification Issue 1

[MikeB8993]

I'm working on an upcoming railroad bridge project and we have received a bid question from a contractor. The structure is a RR bridge with welded plate girder and a steel plate deck. The general notes for our plans states "Bolts connecting the deck plate to the girder shall be F3125 Grade 1852, Type 1 tension controlled bolts. Nuts shall conform to ASTM A563, lubricated. All nuts for the deck plate to girder connections shall be locknuts." The contractor states they contact several bolt suppliers and were told the combinations of these will not perform well. I was brought on this project late in the design cycle so I don't know where this note for pulled from. Any clarification and/or advice on what the issue is?


Thanks!

 

[BridgeSmith]

I think the main issue is the requirement to use "locknuts". Grade 1852 bolts are twist-off (AKA tension -controlled), and as such, the only way to properly install them is fully tensioned, using A563 Grade DH nuts (for Type 1; DH3 for Type 3, AKA weathering steel). An A563 locknut would be unnecessary, and I don't think they exist.

All of the pertinent requirements are in the ASTM F3125 spec., so just specifying ASTM F3125 Grade 1852 is correct and complete.

 

[dvd]

Portland Bolt lists A563 locknuts available as either an Anco lockwire style or a prevailing torque style with deformed threads. I would think that the prevailing torque locknuts would take some of the torque required to snap the TC tang, and thus the TC bolt would be improperly tensioned. Not sure how much torque is required to run down an Anco lockwire locknut, but I suggest contacting Lok-Mor regarding their Anco locknuts to discuss use with TC bolts.

 

[BridgeSmith]

I stand corrected. However, it doesn't appear to me that the available locknuts would be compatible with TC bolts, since the locking mechanisms would interfere with getting the proper tension at the twist-off torque.

Fully tensioned bolts shouldn't need locknuts, anyway. TC bolts with standard A563 Grade DH nuts are used on RR and highway bridges every day, and to my knowledge none have had a problem with the nuts coming loose.

 

[HowTooAnsys]

The issue is a misunderstanding between the project specifications and the contractor's suppliers.

Call for F3125 Grade 1852 Type 1 tension control bolts (TC bolts) with lubricated nuts (ASTM A563).
Problem: TC bolts are designed for specific tension and don't need separate locknuts.

Advice

Clarify with the contractor that locknuts are not required with TC bolts. They provide their own locking mechanism.
You can consult the project engineer who wrote the original note to confirm TC bolts are intended and locknuts are a mistake.

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[MikeB8993]

Thanks for the feedback guys! I removed the sentence for locknuts with the TC bolts. This note was originally taken from another project and this issue was resolved through an RFI on the other project but was never corrected on the plans. Will be more careful next time when pulling notes from another project.

 

[rb1957]

such is the way of so many things ... something initially incorrect was corrected by some other paperwork but not incorporated into the original (why? we know what we're doing) then the original gets reused without the correction.

"Hoffen wir mal, dass alles gut geht !"
General Paulus, Nov 1942, outside Stalingrad after the launch of Operation Uranus.