The Arch
The Arch is a 65-floor 231 meter (758 foot) tall skyscraper located in Hong Kong.
This huge building is composed of two towers joined at the center by a "club house”. The entire complex, composed almost entirely of residential units, was designed by architectural firm Sun Hung Kai Properties limited and developed by Ove Arup partners.
According to Mr Allen Woo the sales and marketing manager at Sun Hung Kai real estate agency the general practice, for achieving a clear height of 2.6 to 2.7 metres, a floor-to-floor height of 3.9 to 4.0 metres would be required. However, because of high wind load in Hong Kong for such a super high-rise building, every increase in building height by a metre would increase the structural cost by more than HK$1 million (129 thousand USD).
Therefore a comprehensive study was conducted and finally a floor height of 3.6 metres was adopted. With this issue alone, an estimated construction cost saving for a total of 58 office floors, would be around HK$30 million (3 million USD). Yet at the same time, a maximum ceiling height of 2.6 metres in office area could still be achieved with careful coordination and dedicated integration.
The building consists of connected twin towers. The Arch was chosen as one of the best new skyscrapers receiving 15 voting points.
THE DESIGN
The site of the arch was a newly reclaimed area with a maximum water table rising to about 2 meters below ground level. In the original brief, a 6 storey basement is required; therefore a diaphragm wall design came out. The keyword to this project was time.The diaphragm wall design allowed for the basement to be constructed by the top-down method making it possible for the superstructure to be constructed at the same time as the basement, thereby removing time consuming basement construction period from the critical path.
Wind loading was another major design criterion for the Arch building as it is situated in an area influenced by typhoons. Not only must the structure be able to resist the loads generally and the cladding system and its fixings resist higher local loads, but the building must also perform dynamically in an acceptable manner such that predicted movements lie within acceptable standards of occupant comfort criteria. To ensure that all aspects of the building's performance in strong winds were acceptable, a detailed wind tunnel study was carried out by Professor Alan Davenport. The total Gross Floor Area of this project is 100,000 square metres and contains some 1,000 apartments.
From an architectural point of view, this arrangement provided better floor area utilisation, offering an internal column free residential area with a clear depth of 9 to 13.4 metres and an overall usable floor area efficiency of 81%. Furthermore, all air-conditioning ducting, electrical trunking and piping gathered inside the core area were squeezed into a very narrow and congested corridor ceiling void.
THE SITE
The 999-year leasehold site has an area of 2,269 metres squared.
The ground level public area along with the public sitting out area forms an 8,400 metres squared landscaped garden with richly ornate fountain, trees and artificial stone paving dedicated for public enjoyment.
CONSTRUCTION
Steel structure was more commonly adopted in the high-rise building. In the original scheme, an externally cross-braced framed tube was applied with primary/secondary beams carrying metal decking with reinforced concrete slab. The core was also of steelwork, designed to carry vertical loads only. Later after a financial review by the developer, they decided to reduce the height of the superstructure by increasing the size of the floor plate so as to reduce the complex architectural requirements of the tower base which means a high strength concrete solution became possible.’ added Mr Woo.
In the final scheme, columns at 4.6 metres and 1.1 metres deep floor edge beams were used to replace the large steel corner columns. Climbing form and table form construction method and efficient construction management were used in this project. The most attractive point is that the reinforced concrete scheme saved HK$230 million (29 million USD) compared to that of steel structure. In the reinforced concrete structure scheme, the core was a similar arrangement to the steel scheme and the wind shear was taken out from the core at the lowest basement level and transferred to the perimeter diaphragm walls. In order to reduce large shear reversals in the core walls in the basement, and at the top of the tower base level, the ground floor, basement levels 1 and 2 and the 5th and 6th floors, the floor slabs and beams were separated horizontally from the core walls.
Another advantage of using reinforced concrete structure was that it was more flexible to cope with changes in structural layout, sizes and height according to the site conditions by using table form system.
CONCLUSION
Hong Kong is one of the most densely populated cities in the world and residential buildings with more than 30 storeys are common sight here. With advanced design and construction technique many of them are soaring over 50 storeys high in the local skyline.
The rapid growth of the local residential market, both in terms of quantity and property value in the 90s, had presented a perfect setting for developers, architects, engineers and builders to deploy innovative designs, efficient construction methods and new building materials and equipment to satisfy market demand. Through the process, local building professionals have accumulated invaluable experience and knowledge in the design, engineering and construction of high rise residential buildings. The same experience and knowledge can be shared by professionals in other parts of the world.
Kowloon area is now one of Hong Kong's highest class residential areas, with a high number of foreigners. The real estate prices usually influence the rest of Hong Kong's.
PROFESSIONAL TEAM
Grand Award / Residential Category
Project Team Members
Client/Developer: Sun Hung Kai Properties / MTR Corporation Ltd
Project Manager: Sun Hung Kai Real Estate Agency Ltd
Project Architect: Sun Hung Kai Architects and Engineers Ltd
Main Contractor: Sanfield Building Contractors Ltd
Structural Engineer: Sun Hung Kai Architects and Engineers Ltd
Building Services Engineer: Parsons Brincherhoff (Asia) Ltd
