Thursday, July 26, 2007

Behind Every Failure Lie Many Successes

My elder daugter’s blogging about her meeting with Matthew Pearl, the author of The Dante Club and The Poe Shadow, her very first in her third sojourn in US, reminds me of a similar experience that I had, oh may be more than ten years ago, back in Malaysia.

It was a technical talk organized by the Institution of Engineers, Malaysia of which I am a member. And the speaker was Prof. Henry Petroski (it took me about 5 minutes to scour the depth of my mind recess to dig out the name during this morning’s drive to work, no small feat for a man past the half century mark).

But I could not recall where he is from. So a google-check shows that he is teaching at Duke. He is a rarity among engineers who write books, let alone a popular one at that. As a group, engineers are probably the least literary inclined. I suspect that has something to do with our training in the analytics, though by no means engineers form the only professional group well-honed in the business of analytical thinking.

That’s perhaps the reason too why engineers are seldom featured in novels, TV series, and movies. Engineers are too stoic, too matter-of-fact, or even sedate to instill any excitement, despite having an integral role in making the world turn day in and day out.

Engineers are the proverbial back-room boys (and girls). Unlike lawyers, doctors, and even architects who come into constant contact with people in their line of work. To quote Marilyn vos Savant of the Ask Marilyn fame serialized in the Parade Magazine, Engineers are an unappreciated lot.

Anyway, I digress. Back to Prof. Henry Petroski. He has written many books and the one that I have read then, which became my only autographed copy, is To Engineer Is Human. Obviously this is a play on the famed adage: To err is human, to forgive divine". I have forgotten the contents of the book, other than the byline in the title: The Role of Failures in Successful Design.

While God forbide that engineers should design something purposely to fail, we do learn a lot more from a failed design than a successful one. The most famous engineering failure, not in terms of casualty because there was none, but in terms of the evolution of an actual engineering “catastrophe”, is the collapse of the Tacoma Narrows Bridge in Washington State.

The Bridge was the third longest of its genre, suspension bridges, when it opened on July 1, 1940. It collapsed in a windstorm about four months later, earning the moniker the Galloping Gertie because of its rolling, undulating behavior during service. To get a taste, albeit, a vicarious one, of the “choppy” ride across the bridge, here is one version:

Motorists crossing the 2,800-foot center span sometimes felt as though they were traveling on a giant roller coaster, watching the cars ahead disappear completely for a few moments as if they had been dropped into the trough of a large wave.”

Top two: Swing it to the left, and swing it to the right!
Bottom two: Breaking up and a huge splash.
(Stills captured from the video referenced below)

The collapse of the bridge is due to a phenomenon called resonant excitation. Every structure has its own natural frequency and when the structure is vibrated, say by wind, close to its natural frequency, its response is magnified many times leading to structural collapse. The entire episode of the bridge deck going through its wild swings and eventual disintegration has been captured on film and can be viewed here. It has since become a popular demonstration of resonant behavior in schools and colleges all over the world.

The bridge was replaced in 1950, after a lapse of ten years, built to a better design that still stands today.

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