Bank of China Tower, Hong Kong

A new trend has emerged among the corporate world that has made people to look back on their workplaces and the built-in environment infused into it. Multinational organizations are adapting themselves to this concept of new generation work environment which can make the employees feel at ease and at the same time get inspired by the pleasant locale.The new age structures  are growing taller and taller making the way to reduce the footprint on the ground. One such tall structure which stands apart from its other counterparts, establishing its inevitable presence on the ground, is Bank of China tower, Hong Kong.

The Bank of China (BOC) Tower, which is located in Hong Kong's Central, is a masterpiece of renowned Chinese architect I.M. Pei. Construction of the building started in April 1985, which opened in August 1990. A 70-storey building 361m high, the BOC Tower is topped with two spires that account for its overall height of 367.4m. It is Hong Kong's tallest building and ranks fifth in the world when complete construction. Its unique design and impressive exterior make it one of the world's most outstanding architectures.

The design by I.M. Pei was inspired by the bamboo shoot, whose sectioned trunk propels higher and higher with each new growth. A symbol of strength, vitality and sturdiness, the BOC Tower also captures the bank's spirit of ambitious growth and striving to serve the community. Combining a traditional Chinese architectural concept with the use of modern building technology, the tower is formed by four triangular prisms of varying heights that result in a multifaceted exterior and seem crystalline in composition.

The Bank of China tower, with its unique rectangular shape at its base and triangular in shape from mid way to the top, rise to 70 storey high with gross floor area approximately 130,000 SQM and is considered as one of Hong Kong's landmark buildings. This distinctive form responds to the constraints of the site: the building appears more slender than a rectangular block of equivalent size and the slimming of its profile towards the top. At ground level, the tower is pulled back from the street to create a welcoming pedestrian environment that is fully accessible yet secluded from urban congestion. 

It is surrounded by a broad promenade, and flanked by cooling water gardens that muffle the activity and noise of surrounding traffic. Environmentally, its profile reduces wind deflections compared with a rectilinear tower of similar size, helping to maintain a comfortable environment at ground level, and creates external pressure differentials that are exploited to drive a unique system of natural ventilation. It was the tallest building in Hong Kong and Asia from 1989 to 1992, and it was the first building outside the United States to break the 305 m (1,000 ft) mark. It is now the fourth tallest skyscraper in Hong Kong, after International Commerce Centre, Two International Finance Centre and Central Plaza.

Plot Backdrop

After its brick-by-brick relocation to Stanley, the site was sold by the Government for "only HK$1 billion" in August 1982 amidst growing concern over the future of Hong Kong in the run-up to the transfer of sovereignty. Once developed, gross floor area was expected to be 100,000 SQM. The original project was intended for completion on the auspicious date of 8^th August, 1988. However, owing to project delays, groundbreaking took place in March 1985, almost two years late. It was topped out in 1989, and occupied in May 1990. The building was initially built by the Hong Kong Branch of the Bank of China; its Garden Road entrance continues to display the name "Bank of China", rather than Bank of China Hong Kong (BOCHK). The top four and the bottom 19 stories are used by the Bank, while the other floors are leased out. Ownership has since been transferred to BOCHK, although the Bank of China has leased back several floors for use by its own operations in Hong Kong. The Bank of China Tower's bold futuristic design has made it into popular culture. The digitally modified facade of the building is featured in the science fiction television series Star Trek: Voyager as the Starfleet "Communications Research Center". The building features alongside the Emirates Towers in the racing game ' Burnout Paradise' in the film Category 7: The End of the World, the tower is destroyed by a tornado.

Reminiscent of Willis

Architect I.M. Pei, founder and principle architect of I.M. Pei Architects designed the building with the structure of bamboo in mind. However the building looks nothing like a bamboo stalk, but more like a glittering tower of diamonds. The cross braces and triangular framework of the building are designed to withstand typhoons. Because of the strong framework of the building, there has less steel needed for the building's construction. The Bank of China tower is reminiscent of the Willis tower in Chicago that was the tallest building in the world for a long time. The difference is that the Bank of China tower is composed of triangular sections with triangular frames and the Willis tower is composed of rectangular blocks and has rectangles.

The glass facades of the building reflect the light and its surroundings, so it is like a bright and shiny white crystal, while the Sear Tower appears dark and ominous. When commissioned to design the Bank of China Tower on an intricate inland site, I.M. Pei was requested to create an unavoidably tall unique headquarters in a typhoon-prone region that would represent the aspirations of the Chinese people yet also symbolize good will toward the British Colony. The solution assimilates architecture and engineering simultaneously, involving an asymmetrical tower that informs both skyline and street.

The Bank of China Tower stands 70 stories tall, reaching a height of 1,209 feet. At the time of its opening in May 1990, it was the tallest building in Asia and still remains one of the tallest in Hong Kong. The trunk of this massive structure is representative of the growth patterns of bamboo, the symbol of hope and revitalization in the Chinese culture.

Silver blue facade reflects sky

The facade of the Bank of China Tower is clad in a laminated reflective curtain wall system with single layered clear floating glazing. The entire building is covered with silver blue reflective glass framed in aluminum. This helps to reflect the changing images of the sky and producing natural light to the whole tower.   Combining a traditional Chinese architectural concept with the use of modern building technology, the tower is formed by four triangular prisms of varying heights that resulted in a multifaceted exterior and seem crystalline in composition.

Constraints

Site Location-Firstly, the site was sloped approximately 30feet at the foot of Mount Victoria and was skewed out of alignment with the street grid. Its odd positioning was complicated by the fact that encircling elevated highways surrounds the site. Secondly, it was difficult to find appropriate spaces for the entrance and exits to the building. The site’s square configuration created logistical problems, as a building of the client’s desired size would front on to a municipal garage.

Physical Constraints Since the Bank of China had already purchased the site of the building, Pei had to incorporate its limitations into his design. The land was 6,700 square meters. The total floor area of the building was to be 1.4 million square feet (130,000 sq m), which 40% were to be designated Bank of China office space, and 60% would be rented out. The location of the site also posed as obstacles to Pei’s design. The obstacles were two-fold: it’s positioning in relation to other buildings and the location of physical thresholds.

Altering Constraints-Pei altered the physical constraints by negotiating a land swap. "The site was surrounded by a heavily trafficked roadway that they called a roundabout. There was no possibility to make an entrance. I had to find a way to gain access to the site. I proposed to create a new road at the back of our site: we obtained planning department approval after a long and difficult negotiation. That was the first thing I did" (Boehm, 2000, 105).Pei traded one corner of the site for another as shown in the diagram on the right. This re oriented the building so that it was parallel with its surroundings and made it possible for it to be rotated away from the garage.

Logic of Eccentricity

The tower is a stunning marvel in architectural geometry. It was designed as a cube rising out of the ground. As the structure grows skyward, the mass diminishes at the rate of one quadrant a time until it is reduced to a single triangular prism. 

Massing Model

Robertson the designer observes "A single eccentricity in a column will cause bending; but two ar more lines of eccentricity, joined by a uniform shear force mechanism, will counteract and therefore eliminate the bending". This principle was applied here.

Form and Function

According to Pei, "Both of my conditions - a land swap and the new road - were very important, because if a building isn’t properly sited, no matter how beautiful or how well it functions, it will not have the right context. Siting is the first major step toward architecture" (Jodido, 2008, p. 196).By manipulating the dimensions of the building site, the architect was able to create the optimal foundation for the bank while integrating it with the surroundings. It was through satisfying necessary functions of the building, such as providing a feasible entrance, that the form of the building was created - form as a product of function.

"In spite of its many short comings, the site had one important advantage. Because it was located just out of the airport flight path, the new building was not restricted by the height limit imposed on all the buildings to the north. A tall building would permit us to overlook some of the most prestigious buildings of Hong Kong, with a panoramic view of the harbor and Kowloon beyond. The next challenge was what kind of tall building, and how to make it structurally impressive" observes Pei (Boehm, 2000, p. 105). Charter Gardens

Analysis

The Bank of China Tower is located in Hong Kong, China which is a very humid, hot location.  The city of Hong Kong is also located on an island on the southern end of China. Being in this close of proximity to the South China Sea and the Pacific Ocean makes for a difficult location to construct a high-rise, especially one that has a mostly glass facade.  Heavy and excessive rainfall and winds are very common for this area, which can lead to such natural disasters as typhoons (hurricanes) and tsunamis.  Building a skyscraper in a location like this requires construction that can withstand severe winds, battering rains and potential flooding. This is why the building was modelled after a native material to this region, bamboo. Bamboo is a very resilient material that can withstand large horizontal forces and not break due to the microscopic "tubes" that make up the bamboo.  To design for something like this requires the building to have some "give" and take the horizontal wind loads and transfer them into vertical loads that can be supported by the vertical structural columns. 

The varying heights of the building and sloped roofs also help deflect some of the horizontal forces off of the building.  Since this region tends to be very warm and humid, an HVAC system that can cool such a large building is an absolute must.  However, a heating system is only a minor concern as only a small one is needed and can pull thermal energy from the ground.  The cooling system for this building contains several enormous chillers at the top of the building that force the cooled air down through the building via pressure and gravity.  Having a predominantly glass facade in such a hot location would normally be of great concern, however the glass used is specially treated so as to let in the proper amounts of light and heat without causing any additional excess problems for the HVAC system.

Steel columns to withstand typhoons

The structure is supported by five steel columns, four at each corner of the tower and one at the central point of the tower. The towers are lifted to different heights and the loads of the central column are directed to those found in the corners, forming a triangular frame. Most importantly Hong Kong is a typhoon prone zone with twice the seismic forces when compared to other cities, therefore the building as to be designed to withstand the wind pressure. The architect came up with the idea of using steel columns with hold the pressure exerted during environmental hazards.

The architect used composite mega truss that integrated two structural systems. These systems were designed to carry the buildings weight as well as resist horizontal wind thrust. A cross bracing vertical frame of the building carries the load to the four corner columns and there is a fifth central column that goes down to the twenty fifth floors where the loads are then transferred to the tip of the pyramid- like frame out to the columns. This allows the architect to design a lighter structure, because the diagonal elements required are less important, while the three-dimensional internal structure provides a clear floor that allows for future changes in the disposition of their use, thus saving energy and resources. . Computer technology played a crucial role to ascertain the complexities to overcome the wind loads. Without the help of technology it would have been difficult to form such robust structure. The top four and the bottom 19 stories are used by the bank, rest of the floors are leased to other people.

Sustainable Approach

Energy conservations are performed by adoption of high frequency ballast for light fittings at office and public areas; installation of heat reclaim chiller to preheat incoming water supply for winter space heating, and prediction of low annual air conditioning energy to save energy. They have also used infrared sensor water taps, motion sensor urinal and dual flush for ladies water closets to fulfill water conservation. In order to encourage public transportation facilities and reduce the carbon dioxide emission to the atmosphere, only 370 car parking spaces are provided for the building.

The Spires

Contrary to popular beliefs, the two spires atop the building are not lightning rods as their function is only decorative. The actual lightning rod is mounted on the spires to provide an extensive area of coverage made possible by the building's towering height. A 15 storey atrium is placed on the third floor to illuminate the Bank of China's banking hall, all the way up to a glass ceiling. The ample natural lighting has also given the banking hall much of its visual splendor.

Lighting adds elegance

Firstly, the site was sloped approximately 30 feet at the foot of Mount Victoria and was skewed out of alignment with the street grid. Its odd positioning was complicated by the fact that encircling elevated highways surrounds the site. The second challenge was the entrance and exit points of the structure, since the tower was in rectangular shape and was located in a traffic area of the city, it was difficult to find space for it and there was a logistical problem to solve it. Later the architect proposed a transverse route at the upper boundary of the tower to make it accessible to the people as well as provided a formal entrance to it.  The other challenge was the tower was located very close to the runway path, so the architect had to design very appropriately to grant the easy flow of airport activities. 

The tower is an iconic figure among the skyscrapers of the Hong Kong region and as made a contemporary mark during the millennium century. The ample lighting of the structure as also added more elegance to the tower and it glitters like a diamond during the day time by the reflection of the sunlight. Thus the tower will resemble the value of the city through its emergence among the other skyscrapers of the region. 

Salient Features

• This was the tallest building in Asia, and the tallest building outside of the United States, at the time of its construction.
• A small sky deck is open to the public on the 42nd floor.
• Style is based in grouping of four triangular glass and aluminum towers of varying heights that emerge from a square base granite podium, changing geometry in several silver reflective glassy prismatic pyramids-a sense of mineral quartz crystal.
• The mega structural steelwork is expressed externally by naturally anodized panels that form part of the curtain wall.
• Virtually every aspect of this building was planned and development challenged with new techniques from moving material to a height never before achieved outside of the USA, to glazing the largest 25mm thick pattern cut lights ever produced.
• First composite mega structure space frame high-rise building.
• This building is one of 18 buildings involved in the Hong Kong Tourism Commission's Victoria Harbour Lighting Plan.