The illusion of motion and an historical near disaster
Speaking of supposedly solid things that might move beneath one’s feet, I can’t help but wonder if there will be any noticeable movement of the Chesapeake Bay Bridge if I’m able to walk it this fall. I have heard some anecdotal accounts where people say they did feel that bridge move, but most of those are from people in vehicles. Which makes me wonder if many of them were simply imagining that they were moving…interpreting the feeling of wind buffeting their vehicle as being able to actually feel the bridge moving. I felt nothing while crossing the New River Gorge Bridge in a vehicle. I know someone who also swore up and down that he felt the Key Bridge moving every time he drove across it. I am also dubious about that, but of course, there’s no way to test that now. When I drove across it two years ago it was a mildly bumpy ride. Not rough, but just a very slight bouncing up and down in places on the main span. I attributed that to the road surface, which was full of patches and repairs (the bridge was scheduled to have its deck replaced this summer). I have actually seen this bouncing in some drive over videos of people crossing the Key Bridge. There was one of someone filming from in a semi truck where you can really see this apparent motion. So I’m not sure what to make of that. Was the bridge really moving that much, or was it due the truck bouncing up and down on the uneven road? Do people let fears and misgiving fuel this sort of apparent imagination with regards to crossing bridges? I suppose I might find out this fall while taking a stroll across the bay. But in that case, there will only be people on the bridge, no cars and trucks. Likely not enough weight and motion to produce dramatic movement, as there will only be a few thousand people at most. Well, OK, as long as they don’t start marching…. However, if there is a good breeze, I suppose that might produce some lateral movement that might be noticeable.
That reminds me of an event I read about and saw films of that happened in 1987, on the Golden Gate Bridge. A 50th anniversary celebration was to be held where the bridge was closed to traffic and people were allowed to walk on the road deck. The organizers were expecting several thousand people, but to their shock, some three hundred thousand people crammed themselves onto the bridge. This crowd put so much weight on the bridge that it began to sag in the middle, and yes, this was recorded in pictures and on film. It seems that celebratory event turned into an unplanned stress test for the bridge, which thankfully it passed. Engineers at the time said the bridge was not in danger of collapse. Apparently not too many in the crowd noticed this sagging, as otherwise there could have been one hell of a stampede of people trying to get off of the bridge. And if that had happened, there easily could have been many injuries and deaths. Which would have made a major contribution to the orange metal monster’s already astronomical body count of people who have jumped off of it. In addition to the thousands of deceased jumpers, there could have been hundreds (if not more) people crushed and trampled to death trying to escape from the bridge.
Since that time, such an event has never been repeated, and with good reason. Considering how close they came to a potential major disaster. This would never happen on the Bay Bridge, as the event organizers have always limited the amount of people on the bridge at any one time. And they will be walking, or running, as the case may be, moving from one end to the other, which will distribute the load.