四大令人嘆為觀止的大橋

Bridges have been around ever since humans began to move themselves—and their goods—from one place to another. Early bridge engineers had to do little more than fell a tree across a ravine1） or stream， but they soon discovered that they could span greater distances and haul heavier loads by putting more time and energy into their structures. What follows is a survey of some of the most breathtaking bridges of the modern era.

自從人類開始將自己及自己的物品從一個地方移動到另一個地方，橋梁就一直存在了。早期的橋梁工程師所能做的僅僅是砍倒一棵樹，將其架在峽谷或溪流之上，但是很快他們就發現，通過在橋梁架構上花費更多的時間和精力，他們可以跨越更大的距離，運送更重的貨物。下面讓我們縱覽一些現代最讓人嘆為觀止的橋梁建筑。

Millau Viaduct

The Eiffel Tower， which looms over2） the Paris skyline， measures 324 meters high from its four-footed base to the tip of its flagpole3）. Now imagine tearing the tower from its moorings4） and carrying it southeastward， through the Massif Central region of France to the Cévennes Mountains. Now imagine setting the tower down in the Tarn Valley， a deep gorge5） surrounded by high， rolling hills near the town of Millau， France. Now， finally， picture lining up six more similar towers and stringing a roadway across the valley. Look！ This is the Millau Viaduct， a massive bridge that opened in 2004 to carry the A75 motorway south to Béziers.

In reality， the highest point of this cable-stayed bridge6） is taller than the Eiffel Tower by 19 meters and only a little bit shorter than the Empire State Building （381 meters tall， if you're wondering）. A car traveling over the span is actually suspended 271 meters above the valley. Drivers who overcome their fear of heights can shave 100 kilometers and four hours off the long trip from Clermont-Ferrand to popular destinations along the Mediterranean Sea. The bridge also reduces pollution by relieving congestion7） that used to occur as cars queued up to cross a much older and smaller bridge in Millau.

米洛高架橋

埃菲爾鐵塔赫然聳立在巴黎天際線上，從它的四個塔墩到頂桿的尖端有324米高。現在想象一下，把這座鐵塔從它的泊地拔起，朝東南方向搬運，穿過法國中央高原地區搬到塞文山脈。現在想象把鐵塔安放在法國米洛鎮旁的塔恩河河谷——一個被高聳的、連綿起伏的山脈所環繞的幽深峽谷——之上。現在，最后試想一下再把六個相似的鐵塔與之排成一列，連接成一條橫跨塔恩河河谷的道路。瞧！這就是米洛高架橋。這座大型橋梁2004年通車后把A75公路向南延伸到了貝濟耶鎮。

事實上，這座斜拉橋的最高點比埃菲爾鐵塔還要高出19米，只比帝國大廈（高381米，如果你想知道的話）矮一點。一輛在橋上穿行的汽車實際上是被懸置在山谷之上271米的高空。那些克服了恐高癥的司機可以把從克萊蒙費朗駛往地中海沿岸那些有名的旅游勝地的長途旅行縮減100公里（四個小時）。米洛高架橋還能緩解以前車輛在米洛排隊過一座更古老、更小的橋時經常發生的交通擁堵，從而減少污染。

Gateshead Millennium Bridge

In a bascule bridge8）， one or two pieces of the bridge deck， known as leaves， swing up to provide clearance for boat traffic passing underneath. They open quickly and efficiently but aren't the most elegant pieces of architecture. This was the challenge facing engineers when officials in Gateshead， England， announced a contest in 1996 to design an innovative cycle and pedestrian bridge to span the Tyne River. The new structure had to allow ships to pass underneath without blocking the view of other nearby bridges or interfering with cultural activities taking place on either bank.

The winning design solved the problem， not with a bascule-type system， but with a never-seen-before tilting9） mechanism. Here's how it works. The bridge is made up of a pair of steel arches. In its \"down\" position， one arch forms the deck of the pedestrian and cycle path. The other arch sits at a 90-degree angle to the first， with cables strung between the two to provide support for the deck. When the bridge needs to move to its \"up\" position， eight electric motors tilt both arches as a single structure. As one arch lowers， the other rises to act as a counterbalance.

When the 126-meter-long bridge opened in 2000， 36，000 people lined the banks of the river to watch the bridge's inaugural10） tilt. And in 2007， its likeness appeared on a new pound coin from the Royal Mint.

蓋茨黑德千禧橋

在豎旋橋上，一塊或兩塊被稱作橋翼的橋面板向上擺起，從而為從橋下經過的船只騰出通航空間。這些橋翼可以快速高效地張開，但并不是建筑中最巧妙的部分。在1996年英格蘭蓋茨黑德當局宣布舉辦一場競賽來設計一座跨越泰恩河、供自行車和行人使用的創新型橋梁時，這成為當時工程師們所面臨的挑戰。新的建筑必須要能使船只在橋下通過時既不阻礙人們觀賞附近的其他橋梁，又不妨礙河兩岸舉行的文化活動。

最終勝出的設計解決了這個難題，不過不是通過豎旋橋活動桁架一類的結構，而是通過一個前所未見的傾擺機構。它是這樣工作的：該橋由一對拱形鋼橋組成，當它在“下擺”的位置時，其中一個拱橋形成供行人和自行車通行的橋面，另一個拱橋與前者成90度角豎起，由連接二者的那些鋼索為橋面提供支撐。當大橋需要移動到“上擺”的位置時，兩個拱橋會成一體在八臺電動機的作用下傾斜。隨著一個拱橋下降，另一個會升起以起到平衡作用。

當這座126米長的大橋在2000年投入使用時，36，000人站滿了泰恩河兩岸，想要觀看該橋的首次傾斜。2007年，該橋梁的形象出現在了英國皇家鑄幣局新發行的一英鎊硬幣上。

Octavio Frias de Oliveira Bridge

S?o Paulo， Brazil， just down the coast from Rio de Janeiro， is known for its extravagance11）. It's an international city， with a flourishing nightlife and a lively arts scene. It's also Brazil's financial hub—home to some of the wealthiest people in the country. Because of these qualities， it's not surprising that the S?o Paulo inhabitants designed and built one of the most unique bridges in the world.

Named after the Brazilian media mogul12） Octavio Frias de Oliveira， the cable-stayed bridge spans the Pinheiros River， which bisects13） the western side of the city. The bridge is only 900 meters long and not particularly high at 138 meters， but its design features two curved decks that cross each other through an X-shaped supporting tower. The two roadways， suspended from the tower by 144 cables， link the S?o Paulo districts of Brooklin and Real Parque.

Motorists crossing the bridge at night enjoy a spectacular show courtesy of LED lights. The lighting system enables bridge authorities to illuminate the X-shaped tower with different colors for commemorative dates or for special events. But it's not all about special effects. A series of 140-watt bulbs shine on the roads to ensure the safety of drivers.

圣保羅奧利維拉橋

坐落在里約熱內盧海岸線邊的巴西城市圣保羅因奢侈而聞名。它是一座國際化大都市，有著繁榮的夜生活和生動有趣的藝術場景。它也是巴西的金融中心，巴西一些最富有的人就居住于此。考慮到這些特性，圣保羅的居民設計并建成世界上最奇特的橋梁之一也就不足為奇了。

這座斜拉橋以巴西傳媒界大亨奧克塔維奧.弗里亞斯.奧利維拉之名命名，橫跨將城市西部一分為二的皮涅魯斯河。雖然橋身只有900米長，138米的高度也算不上特別高，但這個設計的特點在于兩個弧形的橋面穿過X型支撐塔相互交錯。這兩條路由支撐塔上的144條鋼索懸于空中，連接著圣保羅市的布魯克林區和雷亞爾公園。

夜間駕車通過大橋的司機會欣賞到壯觀的LED燈光秀。橋梁管理部門能利用燈光系統為紀念日或特別活動采用不同顏色的光點亮X型支撐塔。但這并不全都為了特效，沿途還會有一連串的140瓦燈泡照明來確保司機的安全。

Oresund Fixed Link

Building a single-purpose bridge is a complex engineering feat. Now add other complicating factors， like a bridge to carry both trains and cars. And join that bridge seamlessly with an immersed tunnel. These were the design requirements facing engineers when they began planning how to connect Denmark and Sweden across the ?resund Strait. Their solution was one of the largest infrastructure14） projects in European history： the $3 billion ?resund Fixed Link.

The Fixed Link actually consists of three major parts. If you're traveling from Copenhagen to Malm?， Sweden， the first thing you encounter is an immersed tunnel 4 kilometers long. Back at sea level， you emerge from the tunnel onto Peberholm， a Danish artificial island built from material dredged up15） during construction. After Peberholm， you access the final leg of the Fixed Link， a cable-stayed bridge stretching for 8 kilometers and ending on Swedish soil.

Collectively， the ?resund Fixed Link is a miracle of modern engineering. It is the world's longest cable-stayed bridge for both road and railway. Its towers are 204 meters high and provide a navigational16） clearance of 57 meters under the main span. The bridge features two levels， with the railway running along the lower deck and the roadway on the upper.

厄勒跨海大橋

建造一座單一用途的橋梁需要復雜的工程技藝。現在再加入其他復雜的因素，如橋梁要使火車和汽車都能通行，并且橋梁要與水下隧道無縫銜接。這些就是工程師們當年開始計劃如何跨越厄勒海峽將丹麥和瑞典連接起來時所面對的設計要求。他們當時給出的解決方案是歐洲歷史上最大的基建項目之一：耗資30億美元的厄勒跨海大橋。

厄勒跨海大橋實際上由三個主要部分構成。如果你從哥本哈根啟程去瑞典馬爾默旅行，你首先遇到的將會是一段四公里長的海底隧道。出了隧道回到海平面之后你會來到佩博霍爾姆島（一座使用施工期的挖掘物建造的丹麥人工島）上。過了佩博霍爾姆島之后你會進入跨海大橋的最后一段—— 一座長達八公里終止于瑞典國土的斜拉橋。

總的來說，厄勒跨海大橋是現代工程的一個奇跡。它是世界上最長的既有公路又有鐵路的斜拉橋。它的索塔有204米高，主橋跨下的通航凈空尺度達57米。橋的特色在于分為兩層，下層是鐵路橋面，上層是公路。