Bank of China Tower, known as the tallest building in Hong Kong and Asiafrom 1989 to 1992, is 1,209-foot and it is a fitting building. The “Tower”sits in the central business district, a ribbon of land densely packed withbanks and office buildings squeezed between mountain and harbor.
It is oneof the busiest, crowded, active, frenetic cities in the world. Afterexperiencing it, I was attracted by its visual context and its specialfeatures, as this modern building has a flexible layout, reflectiveglasses, sustainability in architectural design etcpicI.M. Pei, the architect of Bank of China Tower, tends to use large,abstract forms and sharp, geometric designs. His glass clad structuresseem to spring from the high tech modernist movement. His reliance onabstract form and materials such as stone, concrete, glass, and steel, hasbeen considered a disciple of Walter Gropius.
Nevertheless, he is moreconcerned with function than theory. Pei wanted to create a structure thatwould represent the aspirations of the Chinese people and symbolize goodwill toward the British people. His buildings are a unique testament tohow the convergence of two great traditions, the Asian and the European,can create new aesthetic standards – timelessness in stone and glass. Hehas used the urban, modern style to create the building, such as steelframe and glass curtain wall. Bank of China Tower is the most noticeablebuilding in Hong Kong, not only the number of stories but is also the onlybuilding that stands out from the rest of the other buildings because of itextraordinary shape.
First of all, let us look back to 1883, William Le Baron Jenney inventedthe first “skyscraper construction” building, in which a metal structuralskeleton supports an exterior wall on metal shelves (the metal frame orskeleton, a sort of three-dimensional boxlike grid, is still used today).
His earliest surviving metal-skeleton structure, the Second Leiter Buildingof 1891, stands at the southeast corner of State and Van Buren streets inthe Loop. The granite-face facade is extremely light and open, suggestingthe metal frame behind. The building looks so modern that it comes as ashock to realize it is more than a century old. On the other hand, LudwigMies van der Rohe’s structural and spatial concepts are analyzed throughhis three major building prototypes, specifically the skeleton framebuilding, both in its high- and low-rise manifestations, and the clear-spanbuilding. His most important projects are also examined, not only asisolated functions, but within the context of urban space.
The ‘Seagram’building in New York, hailed as a masterpiece of skyscraper design, whichprofoundly influenced the form and architecture of the office building, andthe open space in the city. The extruded metal and glass curtain wall ofSeagram and its use of tinted glass became widely replicated. After theSeagram building was completed and it encourages street-level open space inassociation with high-rise buildings.
According to Ken Yeang, skyscraper, as a city-in-the-sky, in a novel designapproach that resembles urban design and planning as against the design ofa conventional building in a high-rise structure. It is a new verticaltheory of urban design. It also suggests ideas for the diversification ofvertical land uses, the creation of public realms and places-in-the-sky,vertical landscaping, creating high-rise neighborhoods, vertical townscape,vertical transportation and accessibility.
Structure engineer Leslie Robertson describes the tubes as “bundledvertical space trusses.” Almost the entire gravity load of the buildingflows through the structural diagonals behind the “Xs” of the facade tofour corner columns. There is a fifth central column that splits into atetrahedron at the twenty-fifth floor with branching legs that passinterior loads to the comer columns adding stability close to the base andthe great clear span of the lobby.
The diagonals, intermediate minor columns and beams, and stiffening trussesin different planes are framed into the primary comer columns. Thecomposite action steel and concrete comers lock the structural elementsinto a space frame structure, and this is what sets this building apartfrom others.
The “Tower” is sustainability in architectural design. Reduce in energyconsumption is not the only strategy of sustainable design. The resources/ materials conservation as well as the environmentally pleasant design aregood examples that can be observed in Bank of China Tower. Five principalcolumns hold up the 70-storey building with one at each of its four cornersrisen to different heights and a central column transferring loads downfrom the tower top to the 25th floor and then diagonally out to the cornercolumns. This structural system requires less major diagonal elements andlighter structural membering.
Reinforced concrete, instead of complex andexpensive welded steel connection, was the element to envelop the joint atwhich vertical, horizontal and diagonal members of the steel frame cometogether from different angles. The 3-dimensional space truss togetherwith the concrete joint let the tower use only 60% as much steel as aconventional skyscraper frame normally has used.
It has a flexible layout. The triangularly trussed 3-dimensional structuregives column-free interior space that allows future change in officelayout. This saves energy and resources.Talking about the lighting,atrium and the inclined roofs (skylight) allow more natural lighting andtherefore save energy for artificial lighting: The 15-storey atrium runningfrom the ground floor to the building’s first sloped roof makes possiblethe diffuse of natural light down to the banking hall. “Sky lounge” on the70th floor topped by an inclined triangular cap is also flooded by naturallight.
The building is covered by reflective glasses. The whole building isenclosed by silver-coated reflective glass framed in natural anodizedaluminum. Such skin not only reflects the images of changing sky and city,but also the bright sunlight so that heat gain and cooling loads (i.e. energy consumption) were effectively reduced.
Masking effect of water gardens is found, the whole building has rotated by45 degree, forming triangular spaces (water gardens) at either side of theentrance. The flowing water helps to muffle the noise from the busy trafficroads nearby and makes the entrance area more environmental friendly andwelcoming.
Composite design allows the geometry of the structure to be molded to thegeometry of the facade. Pei insisted that the corners of the facadediagonals come to a point at the absolute edge of the building. Thealuminum cladding does just that. Behind the virtuoso precision of thecurtain wall, the structure does what it has to do to hide itself.
The building rises as a great cantilever out of the ground that mustwithstand lateral forces as a horizontal cantilever withstands verticalforces. In Hong Kong these are considerable. The tower will withstanddouble the wind loads of New York City – typhoon winds of 143 mph at thetop and four times the equivalent earthquake load of Los Angeles.
Cantilever loads are greatest at the fixed end. The foundation is cast-in-place hand-dug concrete caissons with perimeter concrete diaphragm walls. The base of the Bank of China Tower is stabilized by two steel-plate sheartubes. These surround the service cores from foundation to fourth floor.
Steel plates are generally less than one-half inch thick. These providethe whole lateral force system from story four down. The shear coresinclude the elevators aid the bank vault areas where the steel is coveredby over three feet of concrete. There are thinner concrete overlayselsewhere on the steel-plate shear tubes for interior building cladding.
The “Tower” was very much an international effort. “Green coated”reinforcing bars, used in selected areas of the building to combatelectrolytic action, were a “first” in Hong Kong. The bars were purchasedin China, shipped to Abu Dhabi for epoxy coating and then to Hong Kong.
The curtain wall was bid by firms in West Germany, Japan, and the UnitedStates. The West German firm won the contract. The building turns to different colors as the day goes by. Because of itssteel frame and glass curtain wall, it reflects the day light. In themorning, the building’s color is glossy sky blue and at night is both blackand gray with some night lights reflected from other building’s lights.
While visually striking as a sculptural form, the tower was also anengineering breakthrough. By using an enormous version of a conventionalthree-dimensional truss as the basic structure, Pei was able to transferstress to the four corners of the building, making it far more stable thanit would have been if built according to the column-and-beam method.
The Bank of China Tower differs in structural concept from the traditionalbuildings around it and looks it. It is not politely nor politicallycontextual. It stands out as what it is, an ingenious architectural andstructural solution symbolizing the Republic of China. The two are entirely different building concepts with little basis forcomparison. Foster’s Hong Kong Bank is a highly hand- and machine-craftedjewel. It is tied into the great money market electronic network of worldfinance. The Bank of China Tower is a branch bank building in which mostof the space is for rent, a commercial building. The Bank of China willoccupy floors one through seventeen and sixty-eight through seventy. Fifty-one floors are “spec. space” designed to be competitive on the Hong Kongmarket.
The Bank of China Tower is very much a building of our time. The EmpireState Building and the Chase Manhattan Bank Building were designed beforecomputers entered the building field to make number crunching cheap. Atthat time building forms were often changed to fit calculations. Ideaswere discarded because they were too expensive to calculate. For years, as steel and concrete increased in strength, the changes wereincorporated into building thinking as only improved versions of weakersteel and concrete. Their design was limited by conventional thinking.
Columns could be made a bit smaller but no matter how much the strength ofsteel is increased the modulus of elasticity (stiffness) changes verylittle. This means it becomes a better tensile material but not a greatdeal improved to withstand bending. Concrete has the oppositecharacteristic. Its compressive strength increases its tensile propertiesonly grow as the square root of its compressive strength.
The Bank of China at least involved fung shui. The people, representing anofficially atheistic society were steadfastly opposed to the practice andrefused to have the traditional analysis done. Not surprisingly, freelanceadvice began to proliferate almost as soon as the design was made public.
As if the unhappy history of the site was not curse enough, the localgeomancers noted that the masts stop the tower could be interpreted eitheras chopsticks held vertically in an empty rice bowl, or as the sticks ofincense used to memorialize of the dead. Far worse were the X’s made bythe cross bracing that was to be expressed on the facades. Localauthorities noted immediately that, at best, the X’s evoked the marktraditionally drawn on a failing student’s exercise by a calligraphyinstructor. At worst, they suggested the custom of hanging a name tagaround a condemned man’s neck and slashing an X through it to signify thathe was “finished”.
Coping with the unusual shape was a powerful motivation, an inspiration, inthe development of this new concept. The system is now tested and readyfor application to a wide variety of building systems.
picIt shows how the bank of china is joined together in 3 dimensionsOne has the impression it was over designed and excessively detailed. Incontrast a structure as elegantly rational as the Bank of China Tower fitstogether in any language. So, Bank of China Tower is worthwhile to havefurther investigations. I have tried to discover what I have experienced,instead of observing some architecture I have never seen before.
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