Name: 世界第八大奇蹟是如何因工程疏忽而失敗的？ (How The 8th Wonder Of The World Failed Due To An Engineering Oversight |Massive Engineering Mistakes)
Uploaded: 2021-01-14T10:10:15.000Z
Duration: 7 min 47 s
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關係子句

for this construction calamity, we head to Pennsylvania USA and a famous bridge that fell from grace.

It's utterly incredible that no one got hurt if a train was going over.

It doesn't bear thinking about what was once considered the eighth wonder of the world is now a relic of engineering oversight.

Completed in 18 82 at over 300 feet tall and 2000 feet long, Can Zoo a Bridge was the tallest railroad bridge in the world at the time.

This was pretty much the eighth wonder of the world.

Even with today's technology, this would be a challenge, let alone back in the 18 hundreds.

So toe actually achieve a viaduct over that size.

Building a bridge of this size out of stone or brick would have taken forever.

And using car Stein would have been too brittle, say, look too raw.

Time as a suitable material wrought iron had another advantage, too.

It's malleable, so they used sheets of iron to create an innovative support structure known as Phoenix columns, thes Phoenix columns who made out of wrought iron that was folded around and held together with rivets.

Revolutionary design was also quicker and cheaper to build, however, within a decade, locomotives double in weight.

This meant more strain on the bridge, and Maura vibrations at the time still was the strongest, lightest, most flexible bridge making material around.

So it sounds crazy but actually ripped the old conserve bridge down and rebuilt it in.

Still, no bridge meant no coal, so a quick construction was essential.

And in just a matter of months, 120 men erected.

The new bridge 90 days is all it took to completely rebuild the longest railroad bridge in existence.

New Steel Bridge used the original trestle design with large a frame supporting the pier on top.

It could now carry a CZ much cola's the steel mills needed.

But in an effort to save time, a decision was made that would turn out to be disastrous.

Rather than installing new steel anchor bolts toe hold the bridge in place.

They were too short, so engineers used extending nuts called collars to bridge the gap.

Replacing these anchor bolts would have taken forever, you would've needed to dig out.

Blast away would have been a real hassle.

So instead, they just put these collars over the top of it.

A time collar seemed a reasonable solution, but they hadn't completely factored in Mother Nature.

This quick fix did the trick, and the bridge carried freight and passenger trains for over a century without incident in 2000 to a maintenance team discovered corrosion on the bridges legs.

Two trains and pedestrians began repair works.

But in the summer of 2003 disaster loomed an epic tornado spiral towards the consumer gorge.

Structural engineer Brian Ember was on the restoration.

In July of 2003 I got a phone call Millie afternoon that a tornado had hit the bridge.

I jumped in my vehicle right away, made the trip and got here right about dusk, and it was clearly a tornado.

I met with the crew and made my way down here to the edge of the ravine and turned the corner, and the valley just looked filled with smoke like you would expect after a battle.

You could barely start to make the structure in the fading light, and you could see pieces steel emerging from the fog.

And then what was remains of structure still standing.

The 160 kilometre an hour tornado had sent a huge section of the bridge crashing to the valley floor.

So the next morning I went down in the valley and found these anchor bolts and couplings littering the floor everywhere of the valley where they had ruptured and failed at almost every single peer.

The choice not to replace the iron anchor bolts with steel was catastrophic.

To demonstrate steals, strength and flexibility, mechanical engineers Dr Mark Zubin and Dr Tim Tebow Olesky are using a load frame.

The one on the right is 10 18 steel, and the one on the left is cast iron.

You can kind of see that they look similar, so looks can be deceiving, and what we're going to do is test the two of them and see what happened.

Load frame measures the amount of force required to fracture the medal by pulling it from each end.

First up, the iron intention cast iron expresses a brittle behaviour, our behavior in which it will fail without one.

Now the steel there goes, the steel exhibits will be called ductal behavior.

You'll see the specimen narrow in the middle, and that's what we call yield behavior.

And essentially, the specimen is absorbing energy to allow it to handle Maur load, and therefore, in contrast to the cast iron, you're going to get a warning before it sails.

So although similar steel structure gives it increased flexibility, whereas iron can crack without warning, all those steel was clearly the stronger and more flexible material.

Iron anchor bolts didn't fail until the tornado of 2003.

The problem was that the original designer didn't think there was going to uplift, and uplift comes from wind blowing on the towers.

When wind blows on the tower, it wants to try and overturn it.

And so on this leg there would be uplift the original designer.

He used these because he didn't think there would be uplift when in fact there would be with 100 mile an hour wind.

 And it turned out to be inferior, especially after years of wear and tear, and it cracked a combination of extreme weather on the decision not to replace the anchor bolts over a century ago was the undoing of this epic piece of engineering. 