RedditPP Mascot

RedditPP

r/StructuralEngineering • … • u/Superbead

Do structural bolts work loose over time in steel connections, especially in tall buildings?

Non-SE here, helping a couple of guys model the structure of the original NYC World Trade Center. There're plenty of the original drawings out there. Regarding bolted connections, many of them state similar to:

> All bolted connections shall be high strength friction type, except where specifically noted as A307.

Most of these connections appear to be 'pinned' rather than moment-resisting. The towers were designed to sway, so there presumably would have been some slight movement throughout the day in these connections.

I've seen one explicit detail about the bolt threads being purposefully damaged with a chisel (or welded) to stop the nut backing off, but most appear to be expected to be tightened up and then hidden away for the rest of time.

Do these bolted connections ever loosen with the natural movement of a tall building?

— 0