Tricky Ways to Pull Down a Skyscraper

不知不覺，安靜環保：日本人教你巧拆摩天大樓

HENRY FOUNTAIN 2013年06月19日

Taisei-Seibu JV

在東京，一架挖掘機正從內部逐層拆毀一家酒店。

東京——拆除一棟大樓有許多方法，其中一些場面壯觀：從內部爆破，讓大樓自行坍塌，或者用一個兩噸重的落錘把大樓砸成碎片。

但擁擠的東京有許多過時的高層建築，在回收利用和環境方面也有嚴格限制。在這裡，日本公司正在完善一些堪稱「隱形拆除」的方法。一些高層建築從上往下拆除，拆除工作隱藏在移動的棚架後面，而其他建築自下而上拆除，整棟樓用千斤頂慢慢降低。

有時，這些方法似乎違反了地心引力規律，或者至少有違常識，因為那些建築雖然看似毫髮無損，但卻在慢慢收縮。這些方法能讓工地更乾淨，更安靜。隨着老舊建築變得過時，且最好的解決辦法是將它們推倒重建，這些技術最終可能會在紐約以及其他城市得到青睞。

東京最近一棟受到隱形拆除處理的高樓是赤坂王子酒店 (Akasaka Prince Hotel)，這是一棟40層的高樓，其正面很獨特，呈鋸齒狀，俯視着東京繁華的商業區之一。自去年秋天以來，大樓內部的鋼筋混凝土結構就一直在被逐層拆 除，從接近樓頂的樓層開始，採用液壓剪和其他一些重型設備。大樓每10天收縮大約兩層樓；本月，整棟大樓將徹底消失，取而代之的將是兩棟新樓。

拆除赤坂王子酒店所用的系統是由大成建設株式會社(Taisei Corporation) 研發的。該公司一位名為市原秀紀(Hideki Ichihara)的經理表示，這種方法能帶來環境效益，而且能夠對金屬、混凝土和其他可回收材料進行更高效率的分離。另一個優點是視覺上的：正在逐漸消 失的建築在儘可能長的時間裡看似什麼都沒發生。「我們不想讓人們真的看到拆毀作業，」他說。

市原秀紀是在冬末的一天在這家酒店內部說這番話的，當時， 在他頭頂250英尺（約76米）的地方，工人們正在拆除兩個樓層，他們拆下外部的鋁和玻璃，切割鋼樑，粉碎混凝土塊。但路人看不到任何拆除作業——最上面 的四層被一個棚架包了起來，棚架套在完好的樓頂上，表層覆蓋著模仿酒店外觀的面板。

那兩層樓被拆除後，藉助15根臨時柱子上由計算機控制的千斤頂，樓頂和棚架頂蓋慢慢下降。然後，這些柱子被轉移到下面樓層的新位置，工人們開始拆除接下來的兩層樓。

拆除高層建築的更傳統方法是在建築物周圍搭建覆蓋整棟樓立面的腳手架，但讓樓頂暴露在外。相比之下，棚架頂蓋能降低噪音，減少粉塵。「所有作業都在有蓋的區域進行，」市原秀紀說，「噪音水平比傳統方法低20分貝，施工區域排放的粉塵減少了90%。」

不過，除了棚架頂蓋外，大成建設株式會社的系統和其他方法相似，都是從上往下拆除大樓的。另一家日本公司鹿島建設株式會社(Kajima Corporation)則開發出一種自下而上的拆除辦法，即在底樓對大樓的鋼柱進行切割，拆除一個樓層後，用千斤頂降低整棟建築。由於所有拆除作業都在地面或靠近地面的地方進行，因此不需要在大樓的頂部安放重型設備，或部署工人。

「我們的想法是，讓大樓盡量保持完整，」鹿島建設株式會社 一位名叫水谷良(Ryo Mizutani)的負責人說。該公司在1月完成了皇宮附近里索那瑪璐哈大廈(Resona Maruha)的拆除，那是一棟24層的辦公大樓。巨型液壓千斤頂支撐着大樓的40根柱子，工人們每次把柱子切去30英寸（約合76厘米），以便讓整棟樓 慢慢降低。

里索那瑪璐哈大廈建於1978年，赤坂王子酒店建於1982年。一座30、40年的老建築，如果能得到適當維護，通常應該還有多年的使用壽命。比如，已有82年歷史的帝國大廈(Empire State Building)在經過大規模裝修後，仍然運行良好。

但東京的建築物受到變化無常的商業地產市場的影響，高房價、不斷演變的設計標準和其他因素共同營造了興旺的拆除市場。

20世紀70年代，日本經濟的繁榮發展促使東京出現了大量沉悶、雷同的建築物。如今，其中很多建築物已經變得陳舊，由於要安裝信息技術設備，那些相對低矮的天花板（層高標準在1990年上調）使室內空間變得更加局促。

赤坂王子酒店是由日本最著名的建築師之一、現代主義風格的 丹下健三(Kenzo Tange)設計的，這棟外觀閃亮的建築物的天花板也比較低矮。隨着越來越多外資高檔酒店湧入東京，這家酒店終於被經濟壓力壓垮。（原地將建起新的建築 群，包括寫字樓和零售面積，住宅大樓，在高達590英尺的大樓的最上面幾層還會有豪華酒店套房。）

東京的情況可能是獨一無二的，但紐約和其他城市或許最終也 會面臨拆除一些高樓的需要。紐約諮詢公司Terrapin Bright Green最近的一份研究指出，曼哈頓的很多辦公大樓需要全面整修或者拆除。這些建築是在20世紀50年代末到70年代初期間建成的，天花板比較低矮，柱 距較窄（致使樓面布局受限），供暖和空調系統效率低下。

目前還不清楚美國的拆除承包商是否會採用日本的方法，即便是在東京，很多建築物也是用較為傳統的方法拆除的。（若採用新方法，籌備項目的成本會比較高，但拆除作業往往比傳統方法省時。）

全國拆除協會(National Demolition Association)前主席、拆除公司——勃蘭登堡產業服務公司(Brandenburg Industrial Service)市場總監比爾·穆爾(Bill Moore)表示，一家意大利承包商曾試圖向美國公司兜售一種與大成建設類似的頂部加蓋系統，但收效甚微。穆爾表示，」我們的環境法規沒有那麼嚴格，」而 且可以通過洒水有效抑制粉塵。

穆爾表示，有一點非常清楚：不會通過使用精確放置的炸藥進行內部爆破，也不會使用落錘。出於安全及環保考慮，紐約基本上禁用這兩種方法，儘管官員們在本月批准了10多年來首個內部爆破計劃，目標是大致孤立的總督島上一座老舊的海岸警衛隊(Coast Guard)公寓樓。

東京也不允許進行內部爆破，那裡比紐約還要擁擠。但東京大 學(University of Tokyo)環境研究所(Institute of Environmental Studies)副教授清家剛(Tsuyoshi Seike)表示，推動新拆除方法發展的主要因素是2002年生效的一部回收法律。

除了鋼、鋁、銅等價值較高的金屬外，該法還要求回收廢棄的木材和混凝土，即便拆除項目承包商需要為此付費。「人們開始重視回收，」清家剛說，「拆除領域的情況已發生巨大改變。」

他表示，為了提高效率，需要就地分離可回收利用的材料。通過創造可控的作業環境，日本的這兩種拆除方法都能實現材料就地分離。

水谷良表示，鹿島建設的方法還有一項優勢，那就是在對建築結構進行拆除前，不必單獨將石棉等有害物質從現場移除。相反，隨着這些材料被逐層剝離，它們可留在原來的樓層上，直至該樓層降至地面後被安全運走。

翻譯：陳亦亭、許欣

Tricky Ways to Pull Down a Skyscraper

By HENRY FOUNTAIN June 19, 2013

Taisei-Seibu JV

An excavator demolished a hotel in Tokyo from inside, floor by floor.

TOKYO — There are many ways to demolish a building, and some of them are spectacular: blowing it up from the inside so it collapses on itself, or smashing it to bits with a two-ton wrecking ball.

But here in Tokyo, a cheek-by-jowl city with many outdated high-rises and tough recycling and environmental restrictions, Japanese companies are perfecting what might be called stealth demolition. Some tall buildings are dismantled from the top down, the work hidden by a moving scaffold, others from the bottom up, the entire structure being slowly jacked down.

At times the techniques seem to defy gravity, or at least common sense, for although the buildings appear intact, they slowly shrink. The methods, which make for a cleaner and quieter work site, may eventually find favor in New York and other cities as aging skyscrapers become obsolete and the best solution is to take them down and rebuild.

The latest Tokyo high-rise to get the stealth treatment is the Akasaka Prince Hotel, a 40-story tower with a distinctive saw-toothed facade overlooking one of the city’s bustling commercial districts. Since last fall, its steel and concrete innards have been torn apart, floor by floor, starting near the top, by hydraulic shears and other heavy equipment. The building has been shrinking by about two floors every 10 days; this month it will be gone, to be replaced by two new towers.

Hideki Ichihara, a manager with Taisei Corporation, which developed the system being used to tear down the hotel, said the technique had environmental benefits and allowed for more efficient separation of metal, concrete and other recyclable materials. Another advantage is visual: The vanishing building looks normal for as long as possible. “We want people not to really see the demolition work,” he said.

Mr. Ichihara was speaking in the bowels of the hotel on a late winter day while, about 250 feet above, workers were demolishing two floors, removing the exterior aluminum and glass, cutting up the steel beams and pulverizing the concrete slabs. But none of the work was visible to passers-by — the top four floors were shrouded in a scaffold that hung from the intact roof and was covered in panels that mimicked the facade.

When the two floors are gone, the roof and scaffold cap slowly descends, thanks to computer-controlled jacks on each of 15 temporary columns. Then the columns are lowered into new positions, and the workers start taking apart the next two floors.

The cap helps keep noise and dust down compared with more conventional methods of demolishing tall buildings, which involve erecting a scaffold all the way up and around the structure but leaving the top exposed. “All the work is inside the covered area,” Mr. Ichihara said. “The noise level is 20 decibels lower than the conventional way, and there’s 90 percent less dust leaving the area.”

Aside from the cap, though, the Taisei system is similar to other methods in that the structure is taken apart from the top down. Another Japanese company, Kajima Corporation, has developed a bottom-up approach, cutting a building’s steel columns at ground level and jacking the entire structure down as each floor is removed. Since all the demolition work is done on or near the ground, there is no need to place heavy equipment, or workers, at the top of the building.

“The idea is to keep the building as intact as possible,” said Ryo Mizutani, an official with Kajima, which in January finished demolishing a 24-story office tower, the Resona Maruha building, near the Imperial Gardens. Huge hydraulic jacks supported the building’s 40 columns, and workers cut 30 inches from each column, over and over, to allow the structure to be slowly lowered.

The Resona Maruha building was completed in 1978, the Akasaka Prince tower in 1982. Ordinarily, a building that is 30 or 40 years old should have many years of life left, if properly maintained. The Empire State Building, for example, is 82 and doing just fine after major renovation work.

But the Tokyo buildings fell victim to the vagaries of commercial real estate here, where high property values, changing design standards and other factors have conspired to create a bull market for demolition.

The boom in Japan’s economy in the 1970s spawned scores of dull, cookie-cutter office towers in Tokyo. Now many of those buildings are obsolete, with relatively low ceilings (height standards were increased in 1990) that have become even more cramped by having to accommodate the infrastructure of information technology.

The Akasaka Prince, a gleaming showpiece designed by one of Japan’s most famous architects, the modernist Kenzo Tange, had low ceilings, too, but it also succumbed to economic pressures brought on by the influx of more upscale hotels run by foreign companies. (The new complex to be built on the site will include office and retail space, residences and, on the top floors of a 590-foot tower, luxury hotel suites.)

Tokyo’s situation may be unique, but New York and other cities may eventually face the need to demolish some high-rises. A recent study by Terrapin Bright Green, a New York consulting firm, suggested that many office towers in Manhattan needed to be overhauled or demolished. These structures were built from the late 1950s to the early ’70s and have low ceilings, tight column spacing that limits floor layouts, and inefficient heating and cooling systems.

It is unclear whether demolition contractors in the United States will adopt any of the Japanese methods; even in Tokyo many buildings are demolished in more conventional ways. (With the new techniques, setting up the project can be more expensive, but the demolition often takes less time than with conventional methods.)

Bill Moore, a past president of the National Demolition Association and marketing director of Brandenburg Industrial Services, a demolition company, said that an Italian contractor had tried to interest American companies in a top-cap system that is similar to Taisei’s, to little effect. “Our environmental regulations are not that strict,” Mr. Moore said, and dust can be effectively contained by spraying with water.

One thing is clear, Mr. Moore said: Implosion by use of precisely placed explosives would not be used, nor would a wrecking ball. Both methods are largely forbidden in New York because of safety and environmental concerns, although this month officials allowed the first implosion in more than a decade, of an old Coast Guard apartment building on largely isolated Governors Island.

Implosion is also outlawed in Tokyo, which is even more densely packed than New York. But the main impetus there for the new demolition techniques was a recycling law that took effect in 2002, said Tsuyoshi Seike, an associate professor at the Institute of Environmental Studies at the University of Tokyo.

In addition to valuable metals like steel, aluminum and copper, the law required that wood and concrete waste be recycled, even if the demolition contractors had to pay to do so. “People started to take recycling seriously,” Dr. Seike said. “And things have changed quite drastically with demolition.”

For greater efficiency, recyclable materials need to be separated at the site, he said. By creating controlled work environments, both Japanese methods allow for on-site separation.

Mr. Mizutani said his company’s method had an added advantage in that hazardous materials like asbestos did not have to be removed from the site separately, before the structural demolition began. Rather, as the materials are stripped from each floor they can be left there until that floor reaches the ground and they can be safely carted away.