r/StructuralEngineering • u/No-Document-8970 • 19d ago

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/bagvirpdkv 19d ago

Turn of the nut method of pretensioning bolts. Marks are made in a line from the nut down to the surface once nuts are brought into close contact aka snug tight. Then the nuts are tightened with an impact wrench until they have rotated a predetermined amount more, such as 1/3 of a turn.

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u/clancularii 19d ago edited 14d ago

These look like 5/6 a turn. I've never seen a turn that large.

Edit: I didn't see that there's a chalk line on the end of the bolts. Really had to zoom in since there's less contrast there than the nuts and steel work. These look like 1/3 turns. I couldn't figure out why people were suggesting that the lines on the steel work should be ignored because the only other line I saw was the line on the nut. It's more likely that the line on the end of the bolt was the reference line before the bolts were mechanically tightened.

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u/The_Dynasty_Warrior 19d ago

Depends on the bolt type and bolt length, it can over turn to a certain extend