How the 8th Wonder of the World Failed Due To An Engineering Oversight | Massive Engineering Mistakes

The Kinzua Bridge looks like an impressive place to visit, and it's only about seven hours from me. Might make a trip out there - maybe add in Fallingwater, Cherry Springs, and Polymath Park for a nice, long weekend.

Today's video starts with a history of the Kinzua Bridge, then at about 5:00 shifts to the material science content.

As a quick tl;dr, the railroad trestle was originally constructed from wrought iron then rebuilt using steel to accommodate heavier, faster trains. In doing so, the bridge supports required thicker, steel bases. This meant either digging out the anchor bots or just using extension nuts. They chose cast iron extension nuts.

The video gets into tension tests, brittle vs ductile fracture, cast iron vs steel. It's a really nice, simple exploration of the failure.

If you want to read more, check out these resources...

• Article - The collapse of the Kinzua Viaduct: a combination of design oversight and material fatigue left a century-old railroad bridge vulnerable to an F-a tornado
• Article - Fall of the Eighth Wonder: the Kinzua Bridge
• Article - Lessons from the Kinzua: An Investigation Into the Collapse of the Kinzua Viaduct, a 103-year Old Railroad Bridge and Civil Engineering Landmark in Pennsylvania
• Photos - photos of the collapsed bridge (and one pre-collapse), captions provide a nice description of the crash itself
• Article - Kinzua Viaduct succumbing to age (2002 description of the pre-collapse bridge)
• Article - After 121 years, viaduct falls victim to tornado (2003, next-day report on bridge collapse)

Here's what the current state of the bridge looks like. They've turned what stayed upright into a gorgeous walk out to a viewing platform.