In the mid-1930s, two familiar spires towered above the morning fog.
1930 年代中期,
Stretching 227 meters into the sky, these 22,000-ton towers would help support California’s Golden Gate Bridge. But since they were currently in Pennsylvania, they first had to be dismantled, packaged, and shipped piece by piece over 4,500 kilometers away.
兩座世所周知的高塔 聳立在晨霧之上。 向上延伸 227 公尺,直達天際, 這些 22000 公噸重的高塔 能協助支撐加州的金門大橋。 但,因為它們目前位在賓州, 必須要先將它們拆解、裝箱、 一塊一塊運送到 至少 4500 公里以外的地方。
Moving the bridge’s towers across a continent was just one of the challenges facing Charles Ellis and Joseph Strauss, the project's lead engineers. Even before construction began, the pair faced all kinds of opposition. The military feared the bridge would make the important harbor an even more vulnerable target. Ferry companies claimed the bridge would steal their business, and residents wanted to preserve the area's natural scenery. Worse still, many engineers thought the project was impossible. The Golden Gate Strait was home to 96-kilometer-per-hour winds, swirling tides, an endless blanket of fog, and the earthquake-prone San Andreas fault.
將金門大橋的塔移到大陸的另一端 只是查爾斯‧伊利斯 和約瑟夫‧史特勞斯 面臨的其中一個難題, 他們是該建設計畫的主任工程師。 在動工之前, 兩人就面臨了各種反對聲浪。 軍方害怕金門大橋 會讓這個重要的海港 變成更容易受到攻擊的目標。 渡輪公司宣稱金門大橋 會搶走它們的生意, 而居民則想要保存 該地區的天然景觀。 更糟糕的是,許多工程師認為 這個計畫是不可能的任務。 金門海峽有時速 96 公里的強風、 渦流浪潮、無邊際的大片濃霧、 以及容易發生地震的聖安德斯斷層。
But Strauss was convinced the bridge could be built; and that it would provide San Francisco’s commuters more reliable passage to the city. He was, however, a bit out of his depth. Strauss’s initial plans to span the strait used a cantilever bridge. This kind of bridge consists of a single beam anchored at one end and extended horizontally like a diving board. Since these bridges can only extend so far before collapsing under their own weight, Strauss’s design used two cantilevers, linked by a structure in the middle. But Ellis and his colleague Leon Moisseif convinced Strauss to pursue a different approach: the suspension bridge.
但史特勞斯深信 建造這座橋是可行的, 且它可以讓舊金山的通勤者 有更可靠的進城通路。 但,他是有點自不量力了。 史特勞斯最初的計畫是 用懸臂橋來跨越海峽。 這種橋樑的構造是 有一根樑柱固定在一端, 接著水平延伸出去, 就像跳水板一樣。 這種橋樑只能延伸到一個長度, 再長就會因為本身的重量而垮掉。 因此,史特勞斯用兩座懸臂橋, 中間再做一個連結用的結構。 但艾利斯和他的同事 里昂‧莫伊賽夫說服了史特勞斯
Where a cantilever bridge is supported from one end a suspension bridge suspends its deck from cables strung across the gap. The result is a more flexible structure that’s resilient to winds and shifting loads. This kind of design had long been used for small rope bridges. And in the 1930s, advanced steel manufacturing could create cables of bundled wire to act as strong steel rope for large-scale construction. At the time, the Golden Gate Bridge was the longest and tallest suspension bridge ever attempted, and its design was only possible due to these innovations. But cables and towers of this size could only be built at large steelworks on the country’s east coast.
採用不同的方法:吊橋。 懸臂橋是由一端做支撐, 吊橋的橋面則是用 串接的纜繩懸吊起來。 建造出的結構會比較有彈性, 可以適應強風和不斷改變的承重。 這種設計長期以來都是 用在小型的繩橋上。 1930 年代,先進的製鋼技術 可以將金屬線捆紮起來, 製成堅固的鋼繩, 供大型建物使用。 在當時,金門大橋是史上 所有嘗試建造的吊橋當中, 最長也最高的一座, 它的設計之所以能夠實現, 就是因為這些創新。 但這種尺寸的纜線和高塔, 只能在美國東岸的大型鍊鋼廠建造。
While the recently completed Panama Canal made it possible to ship these components to California, reassembling the towers on site didn’t go quite as smoothly. It was relatively easy to find a stable, shallow foundation for the north tower. But building the south tower essentially required erecting a ten-story building underwater. Since the strait’s depth prevented them drilling or digging the foundations, bombs were dropped on the ocean floor, creating openings for pouring concrete. A seawall was built to protect the site from powerful currents, and workers operated in 20-minute shifts between tides. The towers had so many compartments that each worker carried a set of plans to prevent getting lost. And at one point, an earthquake rocked the south tower nearly 5 meters in each direction. Strauss took worker safety very seriously, requiring hard hats at all times and stretching a safety net below the towers. But not even these precautions could prevent an entire scaffolding platform from falling in 1937, carrying ten workers to their deaths.
雖然近期完工的巴拿馬運河 能將這些元件運送到加州, 在工地重組這些高塔的過程 並沒有那麼順利。 相對之下,為北塔找到 穩定的淺地基還比較容易。 但,要建造南塔, 基本上就需要在水底 建造十層樓高的建物。 因為海峽的深度, 地基無法用鑽的或挖的, 取代做法是將炸彈投到海床上, 炸出裂口,灌入混凝土。 而建造防波堤的目的, 是要阻擋該地的強力海流, 且工人得在浪潮之間的 20 分鐘施工。 這些高塔由非常多部分組成, 每位工人都得帶著 一組平面圖,才不會迷路。 有一回發生了地震, 讓南塔朝著兩個方向晃動 各將近 5 公尺 。 史特勞斯非常重視工人安全, 要求隨時戴著堅固的帽子, 並在塔的下方拉起了安全網。 但就算有這些預防措施,也無法防止 1937 年整個施工架平台垮下來。 造成 10 名工人死亡。
Once the towers were complete, workers spun the cables in place, hung suspenders at 50-foot intervals, and laid down the concrete roadway. The bridge was finished, but there was still one more task ahead: painting it. After production, the steel had been coated with a reddish paint primer it maintained throughout construction. But the Navy had been pushing hard to paint the bridge a tactical black and yellow. Consulting architect Irving Morrow actually thought the primer itself paired nicely with the strait’s natural backdrop— and he wasn’t alone. Citing numerous letters from locals, Morrow’s 30-page pitch to paint the bridge “international orange” beat out the Navy’s plans. And today, this iconic color still complements the strait’s blue water, green hills, and rolling fog.
高塔完工之後,工人 便把纜線裝設完成, 每間隔 50 呎就有一根吊繩, 接著再舖設混凝土路面。 大橋完成了,但還有 一個任務等在前面: 上漆。 鋼材在生產出來之後 就塗上了紅色的底漆, 建造過程都一直保留著這些底漆。 但海軍一直在逼促 要為了戰略考量將大橋 漆成黑色和黃色。 顧問建築師厄文‧莫羅 認為底漆本身 和海峽的天然背景很搭—— 而且並不是只有他這麼認為。 莫羅的 30 頁提案引用了 許多當地人的信件, 建議將大橋漆成「國際橘」, 擊敗了海軍的計畫。 至今,這代表性的顏色仍然很能融入 海峽的藍色海水、綠色山丘, 及翻滾的海霧之中。