Wednesday, August 27, 2003 Civil Engineering
Civil engineers aren't necessarily polite. They may, however, have an interest in the following about the Brooklyn Bridge:But on August 14, the night of the blackout, the 28-year-old computer technician for the architectural firm Kohn Pedersen Fox experienced something he'd never felt before. Packed shoulder to shoulder with pedestrians, he could feel the Brooklyn Bridge sway so much that if he stood still he couldn't keep his balance. Then there was the groaning.
"I looked over to the right and thought, What in the world is that noise?" says Prince. "It was coming from the cables, and I didn't want to find out. I picked up my pace four-times and I was gone."
Prince's experience has been echoed by many who crossed the Brooklyn Bridge during the massive blackout trek. In fact, the New York City Department of Transportation acknowledged that it received numerous reports from concerned residents. On the bridge, pedestrians reported feeling seasick, having to weave as they walked, and hearing noises ranging from creaking to grinding.
In the last two years borough dwellers working in Manhattan have twice been forced to evacuate, and both times the bridges have played a pivotal role in the exodus. After the chaos of 9-11, walking home during the recent blackout seemed almost trite. But with the rising number of incidents that force the city to empty by whatever means necessary, we are placing a burden on the Brooklyn Bridge that has some engineers concerned. They argue over whether the 120-year-old bridge was designed to handle hundreds of thousands of pedestrians at one time and what damage age has wrought, despite periodic repairs.
But John A. Ochsendorf, a structural engineer who is also an assistant professor of building technology at M.I.T, raises the key point: "There haven't been many times in the life of this bridge when it's been packed with pedestrians."
One issue on which engineers can agree may shock most people: Contrary to logic, pedestrian traffic is actually heavier than vehicular traffic. Pack people into the same square footage of a car or SUV, and the humans weigh more than the vehicle.
What's more, pedestrian movement interacts with a bridge�vibrating it, in the words of several engineers�in a much more chaotic and little understood way. While cars and trucks move their weight in a smooth, uniform manner, pedestrians constantly shift weight from side to side and strike the bridge in an up-and-down motion. Witnesses observed the bridge reacting to both types of pedestrian stress on the day of the blackout. The Village VoiceVery interesting article. Not sure if it's the usual leftist doomsaying, or a real issue. It does, apparently, have nothing what-so-ever to do with global warming. -- posted by Chuck at Wednesday, August 27, 2003 | E-mail | Permalink | Main |
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