Building Bridges Badly

[Payne]

   OK! A quick history/engineering lesson, then on to the sermonising!

   Some of you will be familiar with this story already, to you, I apologise.



   The Millenium Bridge was one of the many engineering projects intended to mark the begining of the new millenium in the U.K. It was intended as a new foot bridge over the river thames in London between St. Pauls cathedral and the Tate Modern art gallery. A design was chosen that was stylish, showed off the best of British engineering talent and was functional, both as a practical bridge and also to fit in with the landmarks as best as possible.

   The design chosen was a suspension bridge with a difference. Instead of the usual arrangement, the cables suspending the bridge would lie along side the bridge under extreme tension, instead of above it, which is more usual. This would have obvious advantages in keeping the bridge attractive without impinging on the actual view of the riverside. It would also pose great technical challenges which would prove Britain was still a front runner in engineering.

   The project actually went well, with only slight delays, and only going a little over budget. Nobody really bitched too hard about this, those that did didn't matter.

   On opening day, however, great consternation and gnashing of teeth! As thousands walked over the new bridge, they reported the bridge "wobbled". It was plainly visible on television cameras at it's worst, and some of the more nervous members of the public felt very scared and/or sea sick. Fearing a collapse or worse, the bridge was immediately shut down, pending a solution.

   Turned out that it was the volume of traffic on the foot bridge. As a step is taken, a small amount of side ways force is exerted. With a lot of people on the bridge, that can add up to a lot of sideways force at any given moment. The engineers had been aware of this but had discounted it, believing that these moments of force would cancel each other out, resulting in a stable bridge.

   Unfortunately, they were wrong. The sideways forces DIDN'T cancel each other out quite exactly. Due to the lightness of the bridge, the engineering that had the suspension running allongside the bridge and the very mobile mass placed on top of the structure made it easy for the bridge to begin a small wobble.

   As more people became aware of this wobble, they locked into step to individually try to overcome it, making it wobble more, making more people lock into step and so on.

   Eventually the bridge was fixed by placing large tanks of oil under the bridge to absorb any excess movement, a quick and easy fix to what could have been a serious problem.


   There that wasn't TOO bad was it? I hope some of you are still with me.

   Conclusions:

   1- A simple error in a basic stage of planning can lead to dramatic problems in the finished article. Never due overlook an "obvious" fact, it may make your end result wobble.

   2- A simple fix could be, and was made. It did however compromise the initial concept of the design, even if only superficially. Some people still call it the "Wobbly Bridge" for example, and even if it's not really as noticible, the bridge no longer has that "airy" aura about it.
   3- A mass of humans confounded "intelligent" people by acting entirely as would be expected. Any structure, physical or metaphorical, needs to take the human factor into account as much as possible.

   4- If you look hard enough, there are lessons in any story. Even stories about overconfidant engineers.

   5- Because there has to be five. Right? Huh? Right?

[Triple Zero]

nice story

it also shows a nice lesson about emergent behaviour: lots of small agents acting according to local rules (the interlocking of steps) can bring forth a higher-level effect (moving in sync, making the bridge wobble dangerously).

[Payne]

Well, I'm actually a little bit disapointed with this, my metaphors started to get a little mixed up at the end.

It was originally supposed to be more about n00b posting, rocking the boat.

Then it kind of failed into the n00b's posts themselves.

Hence the wek conclusions.

Still it works on some level, i think. Just a pity I don't know what that level is, and that level will probably be as Electronic Toilet Paper that rats will chew and make into lovely Papier Mache bijou residences.

[Triple Zero]

well you could've fooled me

[Darth Cupcake]

I recall seeing that bridge while in London and feeling like it looked awfully out of place, what with London being full of "old" and "stately."

Your point is valid, I think. I just rather enjoy:

A design was chosen that was stylish, showed off the best of British engineering talent and was functional, both as a practical bridge and also to fit in with the landmarks as best as possible.

...

With a lot of people on the bridge, that can add up to a lot of sideways force at any given moment. The engineers had been aware of this but had discounted it, believing that these moments of force would cancel each other out, resulting in a stable bridge.

WAY TO SHOW OFF THE BEST OF BRITISH ENGINEERING TALENT, CHAPS

[Payne]

Well, all in all, it WAS an achievement, I actually quite like the bridge, certainly from an aesthetic point of view.

It's just a pity that they couldn't get it right first time, which ultimately is one of the points of this. I think.

[East Coast Hustle]

I recall seeing that bridge while in London and feeling like it looked awfully out of place, what with London being full of "old" and "stately."

Your point is valid, I think. I just rather enjoy:

A design was chosen that was stylish, showed off the best of British engineering talent and was functional, both as a practical bridge and also to fit in with the landmarks as best as possible.

...

With a lot of people on the bridge, that can add up to a lot of sideways force at any given moment. The engineers had been aware of this but had discounted it, believing that these moments of force would cancel each other out, resulting in a stable bridge.

WAY TO SHOW OFF THE BEST OF BRITISH ENGINEERING TALENT, CHAPS

do you know why the Brits drink their beer warm?




because the same people that build their cars also build their refrigerators.

[Darth Cupcake]

And all this time I thought they drank it warm because they just take no pleasure out of life.

To support my point, I cite the argument "their food."

-DC
Likes steak, not charred hunk of what was once a carbon-based life form

[Payne]

Well yeah. It should really be pointed out that these were English engineers for the most part.

If they were Scots, the thing would have taken out half of London...

[East Coast Hustle]

And all this time I thought they drank it warm because they just take no pleasure out of life.

To support my point, I cite the argument "their food."

-DC
Likes steak, not charred hunk of what was once a carbon-based life form

that's what happens when you make mortal enemies with the country that invented cuisine.