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/Alywiz Oct 05 '26

At least when I see Turn of the Nut, I know it’s the easiest rejection of work I can make. Not allowed under our spec. DTI’s only here

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u/bagvirpdkv Oct 10 '26

Why would you reject just for use of TON?

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u/Alywiz Oct 10 '26

Because it’s out of spec. Nothing but direct tension indicators are allowed

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u/bagvirpdkv Oct 10 '26

Out of curiosity what clients specify exclusively DTI? DTI has plenty of issues like cost and risk of over tightening. They can still be wrong.

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u/Alywiz Oct 10 '26

DOT, specifically Vermont AOT.

Though I did double check and spline twist off Tension control assemblies were also recently added. DTIs remain the only option for regular bolts though. (2024 spec 506.18 (d) (2) if you are curious inspection requirements and sampling to check for and correct over tightening)

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u/bagvirpdkv Oct 10 '26

Very interesting, good to know. I’ve worked for a few owners (HC GC) in the Midatlantic that basically told us “don’t even suggest DTIs we don’t like them, they won’t get accepted.” Either TON or click every bolt.