Architecture Images- Central Business District
King George Building (formerly American Express Building)
|John Andrews International Pty Ltd|
|corner of King and George Streets.|
|Late 20th-Century Late Modern|
|Iconic seventies building with filigree glazing grid that was unfortunately replaced in the nineties (it blocked out a lot of sun...). Its funky '70s character remains, with the modern inclusion of indoor gardens, etc.|
Statement of Significance:
The former American Express Tower, completed in 1976, is a significant building in the career of John Andrews, a leading Australian architect who is recognised internationally for his innovative designs (Criterion H.1). Though the aesthetic of the building has been altered by subsequent developments, it continues to make a vital contribution to the texture and aesthetics of the City of Sydney through its bold triangular form and unusual use of off-form concrete (Criterion E.1). It is an important example of a speculative office building which, in an innovative way, integrated modernist aesthetic ideals and the economic imperatives of the 1970s urban property development with environmental and civic amenity (Criterion A.4) (Historic Theme: 5.4 Working in offices). The building also demonstrates unusual urban design considerations through its siting and triangular form, which allow greater penetration of sun and light to the street level, and consequent improvement of pedestrian amenity at a major city intersection. The collaborative process of design, which involved the builder in the development of the architectural concept, is also considered innovative for its time (Criterion F.1).
The building is a thirty storey office block located on the corner of king and George Streets, Sydney. The building has thirty-two storeys, is 127 metres high and the floor to floor dimension is 3.97m. The tower was constructed by gang forming which was self jacking and therefore did not require an overhead crane. The stair and service cores of the building are expressed externally in off form concrete with curtain glass walls between. The original external sun shading system mounted on a detached space frame has been removed. The building is situated on an irregularly shaped corner site (being a consolidation of several older sites) at one of the city of Sydney`s busiest pedestrian thoroughfares and articulates a sensitive concern for pedestrian amenity. The triangular form of the building has the advantage of opening up the entire corner, allowing greater penetration of sun and light to the street level. The plan of the building is an innovative solution to problems posed by the site`s shape. The circular core shape was evolved to facilitate ease of observation of an arriving elevator car. The building makes a dynamic contribution to the urban fabric of the City of Sydney and demonstrates Andrews innovative design talent and environmental consciousness.
The building was designed by John Andrews International Pty Ltd, a highly reputed firm of architects with a large body of work in North America and Australia. It has been recognised nationally and internationally as an outstanding creative work of the 1970s. It was completed in 1976 and originally known as the King George Tower, then the American Express Tower and is now known as 388 George Street. The client, the AMP Society, required a building with a positive identity that would provide a special environment for pedestrians and officer workers alike. In 1982 it received a Sir Zelman Cowen award commendation and in 1983 shared the Royal Australian Institute of Architects (RAIA) Sulman award. The builder was Sabemo Pty Ltd, the Project Manager Hooker Commercial Developments Pty Ltd and Structural Engineer Wargon Chapman and Associates Pty Ltd.
Condition and Integrity:
The building is in good condition but reduced integrity having been much altered since 1976. The bold external form has been maintained but the Andrews aesthetic has been changed. No statutory protection applies to the buliding. (1999)
74-82 King Street, corner 378-394 George Street, Sydney.
Architecture and Urbanism No 41, 74 :0500
John Andrews : The Canadian Architect, June 1976 vol 26, No6,
An Informal Discussion with John Andrews :
John Andrews : Architecture a Performing Art,
Jennifer Taylor and John Andrews, Oxford Unipress, 1982 :
The King George Tower in Sydney l`industria Italiana del cemen to No6 - 1980 :
NSW Builder, Vol 6 , No1 February 1977.
King George Tower 388 George Street Sydney.
Apperly, R., Irving, R., & Reynolds, P., 1989. "A Pictoral Guide to Identifying Australian Architecture", Angus & Robertson, North Ryde.
Clarke, S. September 1991. "The American Express Tower, Draft Classification Card.
Hill-Travis, P., July 1996. "The American Express Tower, Draft Classification Card".
Taylor, J. & Andrews, J., 1982. "John Andrews: Architecture, a performing art", Oxford University Press, Melbourne.
Taylor, J. 1990. "Australian Architecture Since 1960", 2nd ed., RAIA National Education Division, Red Hill.
Architectural Review, Vol. CLXIV, Sept 1978, p.140.
Sydney Morning Herald, 20.8.77, 4.7.79.
Name King George Tower
- Architect John Andrews International Pty Ltd
- Structural engineer Wargon Chapman and Associates Pty Ltd
- Service engineers D.S. Thomas and Partners
- Builder Sabemo Pty Ltd
Function Commercial office building
Location Sydney, NSW
Type office building with parking
- Plan shape triangular with core elements at edges
- Number of stories 35levels above ground , 2levels basement car park
- Total floor area 45,552.9 sq m
- Net rentable floor area 38,240.7sq m
Relationship to ground ground level pedestrian plaza with diagonal shortcut across the site, underground parking
material reinforced concrete
- type flat plate slabs (link)with drop panels in some areas
- pattern square grid two way acting
- floor slab span 7.6m
- material reinforced concrete
-shape there are three separate core elements the major core element is semicircular,
two other smaller elements are situated at other sides of the triangular floor shape
- types square columns
- material composite structural steel/concrete
footings conventional reinforced concrete pad footings
King George Tower is located at one of the busiest locations in Sydneys CBD. The site was formerly the McDowells department store and there is a site area of 3,342.2sq m.
The design considerations for the site related to the original use on the site, the McDowells department store . It was noted that many people would use the old department store as a short cut so that they did not have to negotiate the busy footpaths around the edge of the site . One of the design considerations then at the ground level was to try to incorporate a shortcut across the site . At the time of the towers construction there was also a considerable desire from the council to incorporate an underground pedestrian system which would be connected to the railway system.
The client required a building which would provide office space of the highest quality and a building that maximized the use of the site as was allowed by the regulations, the client also desired a building that was to be distinctive and well recognizable .The tower was designed with a total rental office space of 38,000 square metres and an efficiency of 89% on open floor planning was achieved.
One of the major requirements for the client was to maximize the site coverage and utilization. The triangular floor plate was used to allow for the required setbacks for the site, calculated as the mean setback from each street to the diagonal facade of the tower. The placement of the stairs on the tower were designed to allow for a more efficient use of the floor space and the placement of the core meant that a difficult and hard to plan part of the site was well utilized.
The structural design requirements for the office areas were for open plan floor areas but the column grid has created problems with some of the partitions of the offices and this is further complicated because of the triangular floor layout. The floor to floor height 3.7m was achieved using in situ flat plate slabs 230mm thick, which were supported on 1.2m square columns reducing to 500mm square at the upper levels. These are on a 7.6m grid creating a frame system which is stiffened by a major semi-circular servicer core and the two minor stair cores. The cores are connected at mid and upper plant levels by major perimeter beams that are two storeys in height.
In addition, office floor slabs are required to carry an applied load of 4.5 kPa plus 1kPa for partitions and ceiling.The ground floor slab was designed to carry a live load of 5 kPa and the car parking 3 kPa.
The site is situated on a foundation of Sydney sandstone which provides an adequate bearing. The water table was not an issue in the site.
The tower was constructed using a modification of the standard slip form arrangement for the core areas . This modification was called self jacking gang -form technique which meant that the desired rough band sawn timber finish would be achieved on the concrete core areas.
An alternative system was proposed and tested as a prototype. The slip-form was completed in bands equating to the floor levels so as to give definition to the reading of the building and minimize unsightly differences in finish. These forms were stripped and cleaned 4 days after pouring and prepared for the next 3.7 m pour. The form work was of varying textures and sizes to further minimize differences in finish between pours - which could be due to the concrete itself or climatic changes. The self jacking gang-form technique was a refinement of this process post contract.
The self jacking gang-form process adapts conventional slip form to perform a self climbing function. Overhead jacks fixed to a rigid platform lift the forms. The moulded external forms act as support for the concrete below, bolted to the form ties. After pouring the forms are jacked up and re-secured, loads transferred to the new concrete. External shutters are raised via chain blocks and the forms for the level above are fixed to the new concrete, and so on. This frees the crane for other building works. Stripping time is reduced to 16 hours and the same form work is used throughout the job over 32 levels. Concrete was poured via crane and hoist with pump backup.
The key requirements that influenced the selection of structural solutions were (a) an efficient floor system that maximized the allowable site index (b) floor system that minimizes the floor to floor height and was not intrusive into the services zone. (c) speed of construction to enable early tenant occupancy
Structural Alternatives and System Selection
The following structural alternatives were considered for the floor system based on the above key options.
large span flat plate slabs up to a ten metre grid
flat slabs incorporating large drop panels
one-way beam, one-way slab solution
banded beam and slabs
All the alternatives were assessed for their economic efficiency and the original desire for a ten metre grid was found to be uneconomic. The 7.6 metre grid with two-way flat plate slabs was chosen because of its economy in financial and constructability terms. The relatively small structural grid allowed a cast in-situ concrete frame with no need for drop panels or beams, nor any need for pre-stressing or post-tensioning. Thus the building was constructed using only conventional building techniques.
The concrete chosen for the building was to be a warm toned concrete. The selection of bare faced concrete for the core elements of the tower would give the tower a distinctive visual appearance and was very much a part of the current architectural movement at the time.
The use of flat plate slabs means that the floor structure would not intrude into the services space for the airconditioning and other services requirements. They are also easy to form and construct minimizing the difficulty of construction .
The flat plate floor slabs would be supported upon a grid of columns. The columns are reinforced in situ concrete and are placed on a 7.6m grid. At the ground and public concourse areas these round columns are 1.2m in diameter. At the upper office levels the round columns are reduced in diameter to 500mm. At some areas the columns would require shear capitals to support higher stresses in some areas
At the facade edges 900mm deep edge beams would be desired to create the required spandrel panels for fire protection up the face of the tower. The column grid would be set back from the facade edge and the slabs would cantilever out from these. The spandrel panels would also provide support for the stainless steel space frame supporting the polycarbonate sunshading. The spandrel panel also meant that floor to ceiling glazing for the office floors could be used. Today the BCA does not allow this type of solution due to more stringent fire regulations.
Final Structural Solution
The floor system chosen for the tower is an in situ reinforced concrete flat plate slab 230mm deep. At the edges the slabs are formed into a 900mm deep edge beam which forms the required spandrel panel and also provides the support for the sunshading system.
The floor slabs are supported on a 7.6m column grid which was found to be the most efficient solution. At some points shear capitals were required on the columns to support the floor loads at areas of high stress. The columns changed in size ranging from 1.2m diameter for the lower levels reducing to 500mm at the upper tower levels.
The columns of the building are set back from the perimeter of the building and this means that the floor slab cantilevers out to the line of glazing. The 7.6m column grid is continued down to the basement levels and this spacing is also suitable for these car parking floors.
The major semi circular core is of 300mm reinforced concrete walls, as are the walls to the minor stair cores. The cores are connected by major perimeter beams which are two storeys in height and located at mid and upper plant levels, this connection means that a frame is created providing the means to resist the lateral loads upon the building .
The structural elements that contribute to the different functional systems are: Structural types: in situ concrete flat plate floor slabs, internal concrete columns , core
material -reinforced concrete
material - reinforced concrete
- pad footings, raft slabs
materials - reinforced in-situ concrete
The triangular configuration of the plan was a design decision based upon maximizing potential views and sunlight penetration by opening up the entire corner. By locating the major core at the back of the site at the apex of the triangular plan structural stability as well as maximum floor efficiency was achieved.
The reinforced concrete cores located at each apex of the triangular plan produce a frame to resist lateral loading on the building. The major core houses the lifts , toilets and the major services, whilst the two minor cores house fire stairs and they are much smaller in size.
The desire to use flat plate slabs led to the need for the columns to be placed at a regular grid. For efficiency reasons the final grid chosen was 7.6m square.
The major external design decision to incorporate a stainless steel space rame to support polycarbonate sunshading was a solution by the architect to reduce the heat load upon the glazing without losing the outlook from the offices. To support this sunshading , 900mm deep spandrels were used. The sunshading responds to the particular orientation of the facade by having vertical cut off to the South Western elevation and horizontal cut off to the North and East elevations.
King George Tower , Constructional Review August 1976
American Express Tower , Architecture Australia ...
Eric Smith, Acer Wargon Chapman & Assoc, Oct 1996
Thanks to http://www.arch.usyd.edu.au/kcdc/caut/html/GPT/front.htm