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是什么使桥梁如此坚固?

What Makes Bridges So Strong?

背景音乐
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是什么使桥梁如此坚固?
What makes the bridges so strong
喔!嘿!小伙伴们
Oh, Hi guys.
Scrips和我刚刚正在搭积木
Scrips and I were just playing with some blocks
你知道 这可能看起来不像
You know, it may not seem like it,
但是这就是我们居住的城市
but the cities in towns that we live in
它们都是按照同样的规则建造的
are all built using the same rules
这儿有一个模拟小镇
as a little pertain village over here
只是真实的小镇比这个要大那么一点
She said ” the real ones are bigger”
一个英国观众汉娜
and one of viewer Hanna from the UK
想知道是什么能让我们的建筑一直屹立不倒
want to know how somethings that we built still stay standing
所以她向我们提出了一个非常棒的问题
so she sent us a really great question
为什么桥梁都那么坚固呢?
why are bridges so strong?
真是个特别棒的问题
excellent question
有时 公路和铁路不得不穿过某些地方
Sometimes when a road or a railroad truck needs to go across something big
比如 河流或是深谷
like a river or a deep valley
专家会要求工程师设计建造桥梁以便穿越障碍
experts called engineers design and build bridges to do that job.
桥梁交通繁忙
and bridges can be really busy
例如 我们说的 世界上最繁忙的桥
take for example, what is said to be the world’s busiest bridge,
位于纽约的乔治·华盛顿大桥
the George Washington Bridge in New York City.
看哪 来来往往川流不息的车辆
Look at all those cars and trucks
它肯定要足够坚固才能承受如此多的人流车流
It has to be pretty sturdy to carry so many people and cars.
因为桥梁载重很大
For bridge carrying that much weight
所以需要用特殊的材建造料如钢铁
It has been built special material like iron and steel.
它不仅仅需要坚硬的材料来确保桥梁的坚固性
but it takes more than tough materials to make a strong bridge.
让我们一起看一看桥梁的建造原理
So let’s look at how bridges work.
一种构造非常简单的桥梁就是梁式桥
One very simple kind of bridge is called a beam bridge.
当我们提到简单一词时,它就是字面的意思
When we say simple, we really do mean simple.
为什么桥梁会那么坚固呢?
A beam bridge can be just a log that used to walk across the stream
或是指两个小障碍物之间铺的的硬板
or put a long ship of a carboard between two short blocks
这也是一座梁式桥
That’s a beam bridge too.
任何桥梁都要能承担一定的载重
All bridges can hold a certain amount of weight
如果桥梁载重过大会怎么样呢
for what happens if we put too much weight on the beam bridge.
我们来探索一下吧
Let’s find out.
实验中….
桥塌了
It collapses.
由于有大大小小的车辆通过大桥
so bridge that carries trucks and cars which are very heavy
因此它必须非常坚固
would have to be stronger
所以它必须非常坚固
that the bridge carries by people on foot
怎样才能建造比较坚固的桥呢
So how do we make stronger bridges?
人们逐渐认识到 利用一些特定的形状可使桥梁更坚固
While overtime people have learnt that a certain shapes can be used to make stronger bridges.
看这座铁路大桥
Take a look at this railroad bridge
要让火车通过 那它必须要足够坚固
It has to be strong because it carries trains.
你观察到什么形状?
What shape do you see?
对 就是三角形
That’s right, triangles
这并非是偶然的
and that’s not by accident
实际上 三角形使建筑更加稳固
The fact is triangles are really strong shapes for building
在三角形任意一边施加压力 那条边会弯曲
If you put force on one side of a triangle it bends.
但是在三角形顶点施加压力
But if you put force on its point
它形状保持不变
it keeps the shape.
那是因为另两边会产生下推力
That’s because the two sides of the triangle are pushed down by the force
底边产生水平拉力
and the bottom get stretched out to both sides.
每条边都受力 所以都不会变形
Each side feels the force but none of them bends.
这就赋予了三角形具有坚固不易变形的特性
And this makes the triangle a really sturdy and stable shape.
这就是你在桥梁构架中多见到三角形的原因
This is why you’ll see lots of triangles in bridges.
事实上车辆穿过的路面称为桥面
你观察到的桥面上方三角结构部分
both above of the part you actually travel along called the deck and below it The length showing a triangle that you see
是桁架
in a bridge is called the truss
桁架是大桥的延伸 车辆运输的方向
Truss is how the bridge spread out of the way that has to carry
并非一切桥梁都由桁架组成
But, now all bridges are made of trusses
如果桥梁不得不跨过宽阔的水域
If a bridge has to cross a really wide body of water
可建造桥体构架难度太大 成本也不菲
it might be too difficult or expensive to built a truss bridge
所以工程师设计另一种桥 悬索桥
So engineers designed another kind of bridge called the suspension bridge
一个特例就是加利佛尼亚的金门大桥
The Golden Gate Bridge in California is a great example of a suspension bridge
悬索桥利用拉力工作
Suspension bridges work by using a force called tension
拉力可使物体拉紧
tension is just pulling something tight
悬空的桥面是悬索桥的一部分
Suspension bridges are made of a deck that’s hung or suspended
它从桥一头到另一头 整个悬空水面
from one side of the bridge to the other
高高的索塔 支撑这些悬索
These cables are suport by tall towers
这样桥面既不严重下沉也不需要在两端固定
and neither how down telly or anchored on both ends
桥体受力被分散掉所以悬索桥才得以这么坚固
Suspension bridges are strong because of the force on the bridge gets spread out
来来往往的汽车 以及 满载的列车 其重量
The weight of the cars and trends of horses whatever is travelling aross it
对钢索产生拉力
pulls on the cables creating tension
钢索又对索塔产生拉力
Those cables that pull down of the towers
也对桥两段锚锭产生拉力 这样就支撑整个桥面
also pull on anchors on either end of the bridge to hold up the deck
我可以继续阐释桥梁精巧设计的工作原理
I can go on it about all kinds of clever bridges
但是 桥梁的坚固性不仅仅是 使用了坚实的材料
But, basiclly bridges are strong not only because tney are made strong with materials
也离不开工程师巧妙的创意和设计方案
but also because of the smart designs dreamed up and planned by engineers
这就是汉娜问题的答案 感谢汉娜以及关注我们的小伙伴
So things were asking Hanna and thank you for Hanna are within us social kids
拜拜 下次见
see you next guy
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视频概述

为什么桥梁如此坚固?为什么桥梁中多见三角形架构?

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视频来源

https://www.youtube.com/watch?v=oVOnRPefcno

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