Why hammer red-hot steel into a bridge? - Video

Why hammer red-hot steel into a bridge? ????????

That's a rivet, heated to about a thousand degrees. One man braces it while a gun squashes the other end into a second head. But the secret starts after the hammering stops: as the rivet cools it shrinks, squeezing the plates together. The catch is that nobody could control how hard each one gripped, so from the 1950s high-strength bolts took over. Inspectors still strike suspect rivets on the side of the head with a hammer. If one moves, it's replaced. Would you trust a hammer to check a bridge?

Sources:
Fisher & Struik, Guide to Design Criteria for Bolted and Riveted Joints, 1st ed. (rivet heated to about 1800°F; "As the rivet cools, it shrinks and squeezes the connected plies together"; the force "was not controlled and varied substantially"; first high-strength bolt specification January 1951): https://boltcouncil.org/files/1stEditionGuide.pdf
SNCF Group history page (rivet heated to 1,100 degrees, struck to deform it): https://www.groupe-sncf.com/en/group/history-archives/rivet-eiffel-railway-bridge
Hot riveting, trainmuseum.org ("As the rivet cooled, it shrank"): https://trainmuseum.org/hot-riveting
Wikipedia, Rivet (clamping force on cooling; high-strength bolts largely replaced structural rivets): https://en.wikipedia.org/wiki/Rivet
Dennis DeBruler, Industrial Scenery blog, 2018 (the force "varies from rivet to rivet")
Iowa DOT Special Provision SP-236022, 2023 (strike with a 40 ounce hammer on the side of the head; loose if it can be felt to move)
Washington State DOT Bridge Design sheet 6.4-A16 (same test, on suspect rivets, "not to sound every rivet"): https://wsdot.wa.gov/publications/fulltext/Bridge/Web_BSD/6.4-A16.PDF
Wisconsin DOT inspection manual, Part 5 Chapter 3 (hammer sounding of bolts and rivets)

Footage (YouTube): Railway Bridge Technical; Local Train BD.
Stock (Pexels): Gowri Manoj.
The cooling rivet shot is sped up. The hammer test picture is an AI-generated illustration. The voice is AI-generated.

#shorts #secretreasons #rivets #bridges #railway #engineering #interestingfacts