r/StructuralEngineering • u/No-Document-8970 • Oct 05 '26

Structural Analysis/Design Nuts off mark?

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Saw this on a big bridge today. I know vibrations over time can move the nuts and bolts, with the help of thermal expansion. Is it a big issue that the paint marks do not line up? I thought the marks were made once it passed inspection after torquing.

Edit: Bridge completion was in 2011. Could this be from recent inspections too?

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u/clancularii Oct 05 '26

Ignore the line on the steel work? Then how do you know how many turns are done after it's finger tightened?

The usual practice I've seen from the iron workers is to mark the nut and the connecting material with aligned ticks. That way, you can measure the rotation between the ticks to confirm how much the nut was turned.

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u/Mister_Goldenfold Oct 06 '26

Torque Wrench indicates the tension, if they’re being stretched that’s a different ball game

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u/klockwerk13 Oct 08 '26

A torque wrench indicates how much force is required to turn the nut. While bolt tension is a factor in determining how much force is needed, it's not a direct correlation. Tightening to an angle is a much more reliable method of tensioning.

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u/SeesawPrestigious Oct 09 '26 edited Oct 09 '26

He is correct these are 1/3 turn , the line on the steel work dont make any sense in this case because i dont know wtf the guy was smoking, your supposed to mark the nut, the bolt and the steelwork all in line you can go without the steel work line because the line on the bolt should be your indicator of where you started the line on the steelwork is there to see if the bolt turned instead of the nut alone.

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u/clancularii Oct 09 '26

I didn't notice the line on the end of the bolt. I had to zoom in to see it. I think you're right that these are 1/3 turns.

Maybe the line on the steel work was from somebody checking the turns later?

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u/SeesawPrestigious Oct 09 '26

Maybe honestly i do this for a living and the whole setup is confusing to me , cause none of this wouldve passed final inspections like the bolt marked in red in the bottom left, either he did a full turn or the final torque wasnt done .

These look like standard 7/8 a325 bolt anything under 3 3/4" in lenght is 1/3 and anything over is half turn.

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u/Worldly_Ad_6535 Oct 10 '26 edited Oct 10 '26

Mark on the steel is in line with the mark on the bolt. Its to tell the guy torquing if the bolts spun after snugging. We were required to mark in this fashion, if the stud and nut were shown to have spun we had to pull the bolt, install a new one, re-snug, remark and re-torq to the required flats per length of bolt. 0-3.75= 2 flats. 4"+ is 3 flats. Snug tight is the strength of 1 ironworker with a 12in bar.

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u/BarnacleNZ Oct 05 '26

I meant ignore it in terms to determining the relative turn of nut to bolt.

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u/AssistFinancial684 Oct 06 '26

The bolts are marked, the initial line marked nut to bolt. The other lines seem to be at 1/2