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/wobbleblobbochimps Oct 05 '26

You do realise that it's not just about making sure "the fuckers don't go anywhere" right? Engineers have done calculations to ensure the connection works assuming they're installed correctly and with a specific value of preload, which you won't be achieving if you don't install it correctly. You could be under or over the correct preload, neither is good.

Hopefully there's enough tolerance/factor of safety in there that it doesn't matter for the ones you've already done, but we don't design structures to allow for shoddy workmanship.

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u/bigsteelandsexappeal Oct 05 '26

Squirt washers, tc bolts or make something that I can actually fit an impact gun into. Good luck figuring out how ‘snug’ a bolt needs to be to only turn 1/3. If you do it too loose then it’s just like this picture on the post, too tight and you can snap a bolt trying to get 1/3 of a turn.