In a single-point bridge failure, one component breaks and brings down an entire structure. See how this happened 52 years ago to West Virginia’s Silver Bridge.
How West Virginia's Silver Bridge Fell in 1967
Published: October 16, 2019
Onscreen: The Silver Bridge, West Virginia, 1967
Narrator: It was nicknamed the Silver Bridge because of its shiny coat of aluminum paint. But unknown to the people that used it, its design contained a serious flaw.
On December 15, 1967, Peggy Huber was driving towards the Silver Bridge.
Peggy Huber: Traffic was heavy. It was Friday and near Christmastime. I got behind a dump truck. And it was moving so slow it stopped right at the light where the bridge was, and I was behind it. And I had reached down to turn the radio dial, and I heard this awful noise, and when I looked up, the bridge was just like a TINKERTOY®, waving, and it just fell. It just sounded like a bunch of metal. It was very loud.
Jack Fowler: It collapsed, I think, at 4:58, so it was a busy time. There was 31 vehicles that fell.
Narrator: The collapse killed 46 people. It remains the worst road bridge disaster in American history.
To find out what had caused the bridge to fail, investigators search the riverbed for wreckage.
Fowler: They brought in a whole bunch of divers, and they would bring pieces up, and of course they would examine it, to see if it would fit in any way.
Narrator: The bridge was an eyebar suspension bridge. Giant bars, up to 55 feet long, with a hole called an eye at each end, were linked together with steel pins. Crucially, each link of the suspension chain contained only two eyebars.
Fowler: And they finally found one of the eyebars that was broken, split. And when they examined it, they found that there had been a hairline fracture in it.
Narrator: Nearly 40 years of corrosion in the steel had triggered a fracture that ripped the eyebar from its pin. The weight of the bridge proves too much for the remaining eyebar, pulling it with an extreme force that tears the link apart. The failure of this single point triggers an unexpected domino effect, causing the entire bridge to collapse.
In the United States alone, around 18,000 bridges have been identified as “fracture critical.” This means if one component fails, part or all of the bridge would probably collapse.
Why Bridges Collapse
Produced and Directed by: Martin Gorst
Digital Producer: Ana Aceves
© WGBH Educational Foundation 2019