Engines of Our Ingenuity

No. 220:
QUEBEC BRIDGE FAILURE

by John H. Lienhard

Click here for audio of Episode 220.

Today, a bridge collapses, and we ask why. The University of Houston's College of Engineering presents this series about the machines that make our civilization run, and the people whose ingenuity created them.

I'm looking at two photographs, both taken in late August, 1907. In one, a great cantilever structure extends almost 900 feet from its pier -- half a huge bridge over the St. Lawrence River -- 40 million pounds of structural steel reaching toward Quebec. The second photograph is not so pretty. It shows 40 million pounds of what looks like wet spaghetti, splashed across the ground, leading away from the pier and off into the water.

For eight years the Quebec bridge project had been under the direction of an American engineer. He was Theodore Cooper, the biggest name in bridge building. Cooper had never produced a true superlative, and his first move was to extend the span from 1600 to 1800 feet. That got the piers out of the water and on to dry land. But it also made this the largest cantilever span ever attempted.

The contract was let to the Phoenix Bridge Company. And soon many factors were gnawing at the design's integrity. The Company lacked funds for preliminary design and testing. Cooper's health was poor, and he limited his travel to the site. But maybe the largest problem was that he was just too highly regarded.

The Phoenix Company increased the span without recalculating stresses. They accepted the change on Cooper's reputation. And Cooper was inattentive to this lack of care. When the Canadians finally raised money to start construction, they suggested that stresses should be checked independently. But they backed down when Cooper angrily said, "We've lost enough time already!"

So work began. By 1906 it was clear that loads would be a lot higher than people had thought. By then everyone was overcommitted, and Cooper opined that the structure could take it. In 1907 some buckling was reported to Cooper, and now he began to worry. On August 27th, he finally sent a wire: "Add no more load to the bridge!" The Phoenix Company shrugged and went on working. The structural members must have been bent when they were installed, they said. They worked the next day without incident.

Then, at quitting time on August 29th, two compression members caved in and the rest of the bridge followed them. Eighty-four men were still on the bridge; eleven lived to tell about it.

Blame for the Quebec bridge failure diffuses out among a lot of people, all of whom were distracted from the job itself. And we see parallels in many modern disasters. Good technology has to be personal and self-expressive. This first Quebec bridge was to have been the great masterpiece of cantilever construction, yet no one really poured his soul into it. It collapsed because it wasn't buoyed up by the human spirit.

I'm John Lienhard, at the University of Houston, where we're interested in the way inventive minds work.

(Theme music)


Tarkov, J., A Disaster in the Making. American Heritage of Invention and Technology, Spring 1986, pp.10-17.


The Engines of Our Ingenuity is Copyright © 1988-1997 by John H. Lienhard.


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