桥桥桥桥桥桥桥！中国人如何建起1000000座桥梁？
在这张中国地图上，如同血管一般遍布全国的不是公路，不是铁路，而是一座又一座的桥梁，时至今日，在中国大地上已有各类公路桥梁超过 96 万座，而在长达 40000km 的高铁里程中，更有将近一半都是桥，他们跨越高山大川，连通城镇村庄，让中国成为了一座幅员辽阔的桥梁博物馆，那么我们为什么要建设如此众多的桥梁？这个问题当我们换个视角便能找到答案。
On this map of China, what is like blood vessels all over the country is neither highway nor railway, but one bridge after another. Till now, there are over 960,000 highway bridges of all kinds in China. And of the 40,000 kilometers long high-speed railways, nearly half are bridges. They cross mountains and rivers and connect towns and villages, making China a vast "bridge museum". So, why should we build so many bridges? By changing our perspective, we will be able to find the answer to this question.
在你眼前这片土地上，西部的高原山地峡谷纵横，东部的丘陵平原江河蜿蜒，原因的海线上又是岛屿散布海峡，海湾分隔两岸，太多的天堑阻挡着人们的交通交流，甚至出路，人们该如何才能跨越这一切？在接下来的视频里，你将会看到一部中国桥梁的跨越式，而首先我们必须从最经典的一种桥开始说起。
On this land in front of you, horizontal valleys cut across plateaus and mountains in the west, while the meandering rivers flow through hills and plains in the east. On the sweeping coastline, islands are scattered, and the two sides are separated by straits and bays. With too many natural moats, obstructing the traffic, communication, and even people's way out. what can we do to get over it all? In the following video, you will see a spanning of a Chinese bridge, but first we must start with the most classic bridge.
## PART 1 架梁为桥
这是一种古老的桥形。2 墩架一梁，是为梁桥，而相邻支座中心点的水平距离便是跨度，也正是它体现了一座桥梁的跨越能力。1937 年，中国人自行设计建造的第一座现代化大桥便是梁桥，尽管他在建成后仅仅 89 天就被射击大桥的毛一生先生亲自炸毁，但却依然为 10 万多人打开了逃离战火的生命之路，这就是杭州钱塘江大桥。它的最大跨度约 66 米，相邻 2 吨上共架一梁，称为简支梁桥，而如果将它的梁体加以延伸，形成多墩架一梁，便进化为连续梁桥，由于梁体连续不间断，前后可以相互约束，因此拥有更高的承载力，桥梁跨度也随之提高，例如武汉长江大桥最大跨度达 128 米，在他的帮助下，中国人第一次跨越了长江天堑，可对于当时的中国而言，这些钢桥是如此先进，如此昂贵，基本只能用于铁路建设，好在一种新技术在国内逐渐普及，它的原理十分巧妙，在混凝土中置入预先被拉伸的钢筋，利用钢筋的收缩欲望去平衡外力，量体便能承受比原先更大的荷载，从而支持更大的跨度，人称预应力混凝土技术。相比钢铁，混凝土显然便宜多了，于是在预应力技术的加持下，大量公路桥梁纷纷登上历史舞台，当前跨度已达到 180 米。
This is an old type of bridge. With two piers and one beam, it becomes the "beam bridge". And the horizontal distance between the center points of adjacent supports is its "span". It is also the span that reflects the spanning capacity of a bridge. In1937, the first modern bridge designed and built by the Chinese was the beam bridge. Although it was blown up by Mr.Mao Yisheng who designed the bridge, only 89 days after completed, it still opened the way of life for more than 100,000 people to escape the war. This is the Qiantang River Bridge in Hangzhou, whose maximum span is about 66 meters. With one beam on two adjacent piers, it is called "simple-supported beam bridge". And it lits beam Iis extended to form "one beam on multiple piers", then it evolves into a "continuous beam bridge". Since the beam is continuous and uninterrupted and the front and rear can be mutually restrained, the load capacity is higher and the span of the bridge also increases. For example,the Yangtze River Bridge in Wuhan has a maximum span of 128 meters. With its help, Chinese people crossed the Yangtze River for the first time. But for China at that time, these steelbridges were so advanced and expensive that could basically only be used for railway construction. Fortunately, a new technology was gradually popularized in China which has very ingehious principles. By placing pre-stretched rebar into the concrete, and using the rebar's "shrinking desire to balance the external force, the beam can therefore bear a larger load than before and thus support larger spans. It is called "prestressed concrete technology". Compared with steel,concrete is obviously much cheaper. So.with the support of prestressing technology, a large number of highway bridges have entered the history stage, and the current span has reached 180 meters.
时至今日，梁桥的应用已十分广泛，更是形成标准组件，可以工厂制造，现场组装，即便单跨跨度有限，但成百上千胯前后相连，便可以横贯江河湖海，甚至已经 165km 的长度，彻底取代路面，成为世界最长桥梁，不过想要继续提升跨度，梁桥势必要迎来一场进化。
Till now, beam bridges have been widely used. Moreover, they form standard components which can be built in factory and assembled on site. Although the single span is limited, when hundreds or thousands of spans are connected back and forth, they can cross rivers, lakes and seas, and even completely replace the roadway with a length of nearly 165 kilometers, becoming the world's longest bridge. However, to continue to improve the span, beam bridge is bound to usher in an "evolution".
## PART 2 似梁非梁
这种桥具有和梁桥极其相似的外形，但它的量体和桥墩被固结成为一个整体，因此可以同甘共苦，共同抵抗量体的弯曲，这就意味着在桥墩的协助下，量体可以达到更大的跨度，或是选择更加轻薄的桥面，这就是钢构桥。
This type of bridge has a very similar shape to the beam bridge. However, its beam and piers are cemented together as a whole, so they can "share weal and woe" to resist the beam bending together. It means that with the help of the piers the beam can achieve a larger span or choose a lighter and thinner deck. This is the "rigid frame bridge".
但美中不足的是，这种桥对热胀冷缩十分敏感，如果桥墩过于倔强，量体便无法放飞自我导致变形无法释放，为此工程师们为钢构桥设计了更高的桥墩，让它变得柔软灵活，以释放量体的变形，尤其在高山峡谷地带，这种高桥墩再合适不过，于是众多高大挺拔的桥梁拔地而起，桥墩从桥面直插谷底，最高已突破 190 米，相当于一座 60 多层的高楼。
But the downside behind this is that this kind of bridge is very sensitive to thermal expansion and contraction. If the piers are too "stubborn", the beam will not be able to "let go of itself", and eventually, the deformation can not be released. Therefore, engineers have designed higher piers for the rigid frame bridge to make it "soft and flexible" and to release the deformation of the beam. This kind of high pier is perfect especially in mountains and valleys. So, many tall and straight bridges rise up from the ground with piers plunging from the deck to the valley floor of which the tallest is up to 190 meters, equivalent to a 60-storey building.
不过，在平原之上，高耸入云的桥墩亦无用武之地，为了降低桥梁高度，同时保证桥墩的柔性，就需要给墩柱进行瘦身，或采用特殊的桥墩形态，然而桥墩要薄，桥梁要稳，成本还要低，三者互相制约，让跨度超过 3 百米的钢构桥屈指可数，即便如此，2006 年建成的重庆石板坡大桥复线桥最大跨度达到 330 米，一举成为世界上跨度最大的预应力混凝土连续钢构桥。
Nevertheless, on the plain, the towering piers are no longer useful. In order to reduce the height of the bridge while ensure the flexibility of the piers, it is necessary to "slim down"the piers or adopt a special pier form. However, to make the piers thin, the beam stable, while the cost low is a restriction itself. It leads to numbered rigid frame bridges with a span of over 300 meters. Even so, the Double-line Bridge of Shibanpo Bridge in Chongging completed in 2006 whose maximum span reached 330 meters, becomes the prestressed concrete continuous rigid frame bridge with the largest span in the world.
不过梁桥也好，刚过桥也罢，倘若面对峭壁深谷或是桥下交通的需要，竖直的桥墩无处安放时，该怎么办呢？
However, be it a beam bridge or a rigid frame bridge, when facing the circumstance of cliffs and deep valleys, or the need for traffic under the bridge, the vertical piers will have no place to be set. What can we do about it?
## PART 3 长虹卧波
此时人们需要的是一种一跨而过的桥形，比如拱桥。
At this time,people heed a kind of bridge that can span over the distance such as "arch bridge".
对于中国人来说，拱桥再熟悉不过了。
For Chinese people, the arch bridge is all too familiar.
被写进小学课本的赵州桥，1400 多年来，几经洪涝地震，其主体结构却依然完好。
The Zhaozhou Bridge, which was written into elementary school textbooks, still remains its intact main structure over 1400 years of floods and earthquakes.
这种拱结构要求两端不仅要向上托起桥身，还必须提供强大的水平推力，正是这样的推力牢牢抵抗住汞的变形，从而提高了拱桥的跨越能力。
This "arch" structure requires that its two ends not only hold up the bridge but also provide a strong horizontal thrust. And it is this thrust that firmly resists the deformation of the "arch", thus increasing the spanning capacity of the arch bridge.
这是拱桥独特的优势，却也是挑战。
This is the unique advantage of an arch bridge but also a challenge.
若遇上松软脆弱的地基，两端便无法提供如此有力的支撑。
If faced up with soft and fragile foundations, the two ends cannot offer such strong support.
人们只能尽量减轻桥梁自重来保持拱桥的稳定。
People can only try to reduce the weight of the bridge to maintain the stability of the arch bridge.
例如由我国首创的桁架拱桥，纤细的混凝土拱架让侨生更加轻盈，最大跨度达到 330 米。
For example, the truss arch bridge pioneered by China has a slim concrete skeleton which makes the bridge lighter, and its maximum span reaches 330 meters.
又或是在拱和梁的焦点间设置一细感，以细感的拉力代替制作的推理，成为细杆拱。
Or set up a"tie rod"in the intersection of the arch and the beam, to replace the push at both ends with the pull of the tie rod. This is the tied arch".
而随着普通混凝土拱桥达到跨度极限，越来越多的新式拱桥开始涌现。
As ordinary concrete arch bridges reach their span limit, more and more new types of arch bridges are emerging.
比如将混凝土填充在钢管中，为它增加一层保护壳，从而比普通混凝土更加坚固牢靠。
Such as filling concrete into steel pipes to add a"protective shell"to it, making it stronger and more reliable than ordinary concrete.
同时钢管还能作为施工骨架，大大降低了拱桥的修建难度。
At the same time, the steel pipes can also be used as a construction skeleton, which greatly reduces the difficulty of building arch bridges.
更有甚者，以填充完毕的钢管为骨架，在外层再次包裹混凝土，则演变为一种硬骨头拱桥，人称进兴骨架混凝土拱桥。
More than this, using the filled steel pipes as the skeleton, then wrapping the concrete again on the outer layer, it can evolve into a "hard bone arch bridge", namely the concrete arch bridge with stiff skeleton.
如今这种桥的跨度已突破 400 米。
Now the span of this kind of bridge has exceeded 400 meters.
而随着我国钢铁产量跃居世界首位，桥梁建设逐渐走出了舍不得用钢的时代。
With China's steel production jumping to the world's first, bridge construction has gradually stepped out of the era of "reluctance to use steel".
钢拱桥也随之崛起，它能与横架钢构等结构进行组合，创造了一个又一个工程奇迹。
Steel arch bridges have also emerged. which can be combined with truss rigid structure and other structures, creating one engineering miracle after another.
时至今日，拱桥的跨度已达到 575 米，超过了一个躺岛的中国尊。
Up to this day, the span of the arch bridge has reached 575 meters, more than a lying-down "China Zun".
而接下来登场的角色即将帮助我们突破 1000 米跨度大关。
And the next role on the scene will help us break the 1,000-meter span mark.
## PART 4 钢铁琴弦
这是今天的上海浦东。
This is today's Pudong, Shanghai.
早在 30 多年前，这里还没有林立的高楼。
More than 30 years ago, there were no tall buildings here.
为了发展，人们迫切的需要一座跨江大桥。
In order to develop, people desperately needed a bridge across the river.
可是黄浦江两岸相隔近 4 百米。
However, the two banks of the Huangpu River are nearly 400 meters apart.
而当时的中国，还从未有桥梁达到如此跨度。
At that time in China, no bridge had ever reached such a span.
即便难度可想而知，同济大学的李国豪校长和项海帆教授，依然力主自行建造这座黄浦江第一桥。
Even if the difficulty was conceivable, President Li Guohao and Professor Xiang Haifan of Tongji University still insisted on building the "first bridge over the Huangpu River"by ourselves.
项教授写道，上海是我国的东大门，黄浦江大桥应成为上海市的标志，传名于世，建造黄浦江大桥，不但是 1000 万上海人民的夙愿，也是上海桥梁工程界的梦想，在学校我们也一直以此激励桥梁专业的学生们。
Professor Xiang wrote, Shanghai is the eastern gate of China. The Huangpu River Bridge should become the symbol of Shanghai and be known to the world. The construction of the Huangpu River Bridge is not only the long-cherished wish of 10 million Shanghai people, but also the dream of Shanghai's bridge engineering community. At school,we have always used this to inspire bridge majors.
最终，在 1991 年已不到国外方案一半的造价，上海南浦大桥正式通车，开启了我国自主建设超大跨度桥梁的先河。
Finally,in 1991, with less than half of the cost of the foreign scheme, Shanghai Nanpu Bridge was officially opened to traffic, setting up a page for China's independent construction of super-span bridges.
这座大桥两端伫立着两座约 50 层楼高的高塔，梁、塔与桥面间以 180 根钢索相连，如同一根根倾斜的钢铁琴弦，故名斜拉桥。
Both ends of the bridge stand two towers about 50 storeys high. The two towers are connected to the deck by 180 steel cables like tilted steel strings. Hence it is named"cable-stayed bridge".
但对于斜拉桥来说，这样的跨度仅仅是小试牛刀。
But for cable-stayed bridges, such a span is only a"small test".
根根拉索向上提拉，竭力阻止两体向下弯曲，如同有了一个隐形桥墩，极大地提高了桥梁的跨度潜力。
The cables are lifted upwards, trying to prevent the beam from bending downward as it has "invisible plers", which greatly increases the span potential of the bridge.
更重要的是，与生俱来的对称形态，让斜拉桥更容易实现自锚。
More importantly, the inherent symmetry of the form makes it easier for the cable-stayed bridge to "self-anchor".
稳定的三角结构，则具备更强的抗风能力，这在无地可矛和风力强大的海上得天独厚，逐渐成为众多跨海大桥的标志。
The stable triangular structure has a stronger wind resistance which is unique in theanchorless" and windy sea, gradually becoming the symbol of many sea-crossing bridges.
加之工程材料和计算方法的革新，现代斜拉桥从诞生起，仅用了 50 多年，便完成了 1 千米的跨越。
Together with the innovation of engineering materials and calculation methods, since the birth of modern cable-stayed bridges, it took only more than 50 years to complete a 1,000-meter span.
然而角度倾斜的拉锁将沿着两体轴向产生水平的轴力。
However, the angularly inclined ties will generate horizontal "axial forces" along the axial direction of the beam.
随着跨度延伸，拉锁势必增加，这种轴力也将逐渐累积，直到量体不堪重负。
As the span extends, the ties are bound to increase, and this axial force will also accumulate gradually until the beam is overloaded.
雪上加霜的是，当拉索越来越长，越来越倾斜，巨大的自重令其弯曲下垂。
To make matters worse, as the ties get longer and more inclined, the huge self-weight makes them bend and sag.
再难以紧紧拉住庞大的量体，这便注定了斜拉桥的跨度极限。
It is no longer possible to tightly pull the huge beam, and predetermines the span limit of cable-stayed bridges.
可谓是成也斜拉索拜也斜拉。
It can be said that "the success of the cable-stayed bridge is also the failure of the cable-stayed bridge."
因此若要向 2 千米跨度发起冲击，只能指望最后一位选手了。
Therefore, to make a push for the span of 2,000 meters, we can only count on the last player.
## PART 5 跨度王者
在我国西南山区现代桥梁出现前，人们往往只能依靠原始的方式出行，比如索桥或吊桥。
In the mountainous region of southwest china, before the emergence of modern bridges, people often had to rely on primitive ways to travel, such as rope bridges or suspension bridges.
但他们的建造者和使用者一定想象不到这种桥会在今天达到 1700 百米的跨度成为桥梁界的王者。
But their builders and users must have never imagined that this kind of bridges can reach the span of 1,700 meters today and becomes the king of bridges.
这就是现代悬索桥。高耸的桥塔，弯曲的主缆，坚实的锚碇，共同组成了他最基本的沉重体型。
This is the modern suspension bridge. Soaring bridge towers,curved main cables and solid anchorages constitute its most basic load-bearing system together.
和古老的索桥不同，现代悬索桥拥有格外坚韧的主缆。
Unlike old rope bridges, modern suspension bridges have exceptionally tough main cables.
以位于江苏的五峰山长江大桥为例，它的主缆以直径 55mm 的高强钢丝为基本材料，127 根为一数，352 数为一览。
Take the Wufeng Mountain-Yangtze River Bridge in Jiangsu as an example: Its main cable is made of high-strength steel wire/witha diameter of 5.5 millimeter as the basic material, 127 wires in a bundle, 352 bundles to one cable.
双缆并行承载的钢梁重量超过 7 万吨，相当于 1000 架满载的 c919 大飞机。
With double cables in parallel, the weight of the steel beam carries exceeds 70,000 tons, equivalent to 1,000 fully-loaded C919 aireraft.
相比如此巨大的量体，桥上往来的车流都显得微不足道。
Compared with such a huge beam, the traffic on the bridge seems insignificant.
于是桥面不再像古老的索桥因外力上下波动。
So, the deck is no longer like the old rope bridge fluctuating up and down due to external force.
甚至足以同时通行四列高铁列车，成为世界第一座高铁悬索桥。
It even allows four high-speed trains to pass at the same time and becomes the world's first high-speed rail suspension bridge.
并且和斜拉桥不同，悬索桥的吊索垂直于墙面。
Moreover, unlike cable-stayed bridges, the slings of suspension bridges are perpendicular to the bridge deck.
因此无论跨度多长，都不会产生轴力挤压量体。
Therefore, no matter how long the span is, no axial force is generated to squeeze the beam.
这也是为何众多难以逾越的天堑都被悬索桥一一征服。
That's why many insurmountable dangers have been conquered one by one by suspension bridges.
而根据学者们的推算，悬索桥的跨度至少能达到 5000 米之多。
And according to scholars'calculations, the span of suspension bridges can reach at least 5,000 meters.
到这里，当我们再回看这张地图，也许会有不一样的体会，我们或许很难想象，一代代建设者们是如何突破地形、地质、水文、气象、材料、结构、通航、安全、寿命、造价、美学等种种条件的限制，即便在一穷二白的岁月里，也能创造出新的技术，实现一次又一次的跨越，但我们却能清晰地看到，这近百万座桥梁是如何见证着一个国家一路走来的历程，那是钱塘江大桥落成时，这个民族最深重的苦难，是南京长江大桥落成时，这个国家自立更生的决心，也是上海南浦大桥落成时，那份拼命追赶世界的渴望，今天当你走在中国任何一条公路或铁路上，极大概率将和不止一座桥梁相遇，而无论你是否知道他的名字，他们都将无声的伫立在这里，在大山之中，在江河之上，在海峡海湾之间，直至数 10 年，100 年甚至更加漫长的岁月，在这段岁月里，公路将通向天南，海北铁路将去往四面八方，不计其数的人们将从这里走过，而这片土地上的每个角落也终将彼此相连。
Now, when we look back at this map again, we may feel different. We may find it hard to imagine how generations of builders have broken through terrain, geology, hydrology, meteorology, materials, structure, navigability, safety, longevity, costs, aesthetics and other constraints. Even in the years of poverty, they were able to create new technologies and realized new leaps again and again. Yet we can see it clearly that how these nearly one million bridges have witnessed the history of a country along the way. It is the deepest suffering of our nation in the completion of Qiantang River Bridge. It is the determination of our country to be self-reliant in the completion of Nanjing Yangtze River Bridge. It is also the desire to catch up with the world in the completion of Shanghai Nanpu Bridge. Today, when you walk on any highway or railway in China, there is a high probability that you will meet with more than one bridge. And whether you know their names or not, they will all stand silently here in the mountains, over the rivers, between the straits and bays, for decades, 100 years or more. Durihg these years, highways will go far and near, and so will the railways. Countless people are passing by. Finally, every corner of this land will be closely connected to each other.
