Narrator: Listen to part of a lecture in an engineering class.

旁白：听一段工程学的讲座

Professor: We've been looking at some engineering challenges of the past few decades.

教授：我们一直在研究过去几十年中的一些工程挑战

How engineers have to consider special demands like budget and time constraints when they're designing buildings and other structures.

工程师们在设计建筑物和其他结构时必须考虑的特殊需求，如预算和时间限制。

Today we're gonna focus on environmental challenges, problems engineers face from the great outdoors.

今天，我们将专注于环境挑战，工程师在户外面临的自然问题。

What comes to mind, Alice?

爱丽丝，你能想到什么吗？

Student: Well, if you're designing a building, you'd have to see what kind of soil or rocks you're dealing with.

学生：如果你正在设计一座建筑，你需要看看你面对的是什么样的土壤或岩石。

Professor:Good. What else? Mike?

教授：很好。迈克，你呢？

Student:Well, weather conditions.

学生：天气条件。

Professor:Okay, go on.

教授：好的，请继续。

Student:Like in a desert, the heat, the dry climate would probably affect the materials for the structure, even the design.

学生：比如在沙漠中，高温和干燥气候可能会对建筑材料甚至设计产生影响。

Professor:Okay. Now, a really good example of this, a challenge it took until the 1990s to figure out how to deal with is a bridge up in Canada called the confederation bridge.

教授：好。一个很好的例子是直到上世纪九十年代才解决的一个挑战——加拿大的联邦大桥。

This is a long winding bridge spanning a width of uh. Here. You can see it on this slide.

这是一座蜿蜒曲折的桥，跨度为……这里。你可以在这个幻灯片上看到它。

The confederation bridge connects Prince Edward island, which is off the eastern coast of Canada to the mainland.

联邦大桥连接了位于加拿大东海岸的爱德华王子岛与大陆。

And it has to cross a body of water 8 miles wide, the Northumberland strait.

它需要跨越一条八英里宽的水域，即诺森伯兰海峡。

Now this strait has some of the harshest weather conditions in Canada.

这个海峡拥有加拿大一些最恶劣的天气条件。

Talk about challenges for an engineer. Ice, wind, incredible cold.

对于工程师来说，这真是个挑战。冰、风、极其寒冷。

I grew up on Prince Edward island. I should know.

我在爱德华王子岛长大，应该很清楚。

Every time we take that ferry it was the only way to cross back then. There were long lines just to get on.

每次乘坐渡轮穿越海峡，那时候是唯一的方式，排队等候的人非常多。

And the ride was long, the schedule unreliable because of ice and winds.

而且旅程漫长，由于冰和风的影响，渡轮的时间表也不可靠。

Mike, you look puzzle.

迈克，你看起来很困惑。

Student:I don't get it. Why it takes so long for them to build this bridge.

学生：我不明白为什么建这座桥花了这么长时间。

I mean, sure it's cold up in Canada and all. But I remember some pictures in our book of bridges up in northern Europe where it's probably even colder than Canada.

我的意思是，当然加拿大很冷，但我在书里看过一些比加拿大更冷的地方的照片，那些地方也建有桥梁。

And they were built much earlier than the 1990s.

而且建得比二十世纪九十年代早得多。

Professor:Well, remember, temperature is just part of the picture.

教授：记住，温度只是其中的一部分因素。

You've got cold, icy winds over a lot of water along long stretch of freezing water.

你有寒冷、多冰的风和大量的水，沿着长长的结冰水面吹来。

It's not the longest bridge in the world. Well, it's the longest in Canada, but it is the longest bridge anywhere over water. that freezes

它并不是世界上最长的桥。它是加拿大最长的，但它是跨越冰冻水域的最长桥梁。

So this means you've got ice, huge masses of ice.And this ice goes floating down the strait and it has to get through.

所以这意味着有大量的冰。这些冰块会顺着海峡漂流而下，必须从中穿过。

So why is this a problem? Well, we've got to look at how most bridges like those European bridges you mentioned probably are supported.

那么，为什么这是个问题呢？好吧，我们得看看大多数桥梁，比如你提到的那些欧洲桥梁，可能是如何支撑的。

Remember when we looked at basic bridge design earlier in the year?

还记得我们今年早些时候研究的基本桥梁设计吗？

What was the basic shape of the piers? The supports for these bridges with long spans?

那些长跨度桥梁的桥墩，也就是支撑桥体的基本形状是什么？

Student:Well, they're like these columns, a row of cylinder shaped like columns supporting the span of the bridge.

学生：它们像柱子一样，一排圆柱形的柱子支撑着桥梁的跨度。

Professor: Okay, now think about it with these basic columns. Remember, we called them piers.

教授：好的，现在想想这些基本的柱子。记住，我们称它们为桥墩。

You've got a real problem, when sheets of ice start crashing up against them. Here, let me show you what I mean.

当冰层开始撞击它们时，你就有大麻烦了。让我给你看看我的意思。

Now imagine these sheets of ice floating down the strait. They're gonna run right into those piers and compress into these ice chunks and get stuck there.

现在想象这些冰层顺着海峡漂浮而来，它们将直接撞上这些桥墩并压缩成冰块，然后卡在那里。

So, what did the engineers do? Well, they know that once those chunks of ice form, that's it.

因此，工程师们做了什么呢？他们知道一旦这些冰块形成，那就没救了。

They can block the passage here where the boats would have to pass between the piers. Very dangerous.

冰块会在那里堆积，船只通过桥墩之间非常危险。

And there's nothing you can do to break up those chunks of ice once they start piling up like that.

一旦开始堆积，就没有什么办法能打破这些冰块。

Now, that's where the engineers' abilities to analyze the problem and come up with a design solution. That's where it all comes into play.

这就是工程师们的分析能力和设计解决方案能力发挥关键作用的地方。

And the ones who built the confederation bridge, wow, they really showed what they were made of.

建造联邦大桥的人，哇，他们真的展示了他们的实力。

They designed this special type of supporting piers, which were basically like the column shaped ones we've been looking at.

他们设计了一种特殊的桥墩，基本上类似于我们一直在看的那种柱状桥墩。

But for the bottom of each pier, they designed what they called shields, a protective base that turned the overall shape from a cylinder into a kind of inverted cone.

但在每个桥墩的底部，他们设计了一个保护基底，称为防护罩，将整体形状从圆柱体变成了倒锥形。

This was critical because the base, the cone part is where the pier comes in contact with the water and ice.

这一点至关重要，因为这个锥形部分是桥墩接触水和冰的地方。

Here. And take a look at the close-up of the base, so you can see what I mean.

这里。看看这个底座的特写，这样你就能明白我的意思。

So, now, when that sheet of ice approaches, instead of immediately getting crushed into those ice chunks, it starts to slide up this sloping part of the base, which changes the direction of the ice sheet from horizontal to upwards at a diagonal.

因此，当冰层靠近时，不会立即被压碎成冰块，而是开始沿着基座的斜坡向上滑动，从而改变了冰层的方向，从水平变为向上倾斜。

And this causes the ice to crack and break up into smaller pieces.

这导致冰层破裂成较小的碎片。

And this means that those ice pieces can keep on moving, pass the piers down the strait. And it doesn't all build up there at the bridge.

这意味着这些冰块可以继续移动，经过桥墩后顺流而下，而不是全部堆积在桥下。

Now, this wasn't the only problem the engineers had to deal with.

这并不是工程师们需要解决的唯一问题。

As I said earlier, the Northumberland straits, a big unobstructed area that acts like a natural wind tunnel.

正如我之前所说，诺森伯兰海峡是一个开阔无阻的区域，充当天然风道。