Sydney Architecture Images- Central Business District

Chifley Tower

architect

Kohn Pedersen Fox Associates  and Travis Partners

location

Chifley Square, Cnr Hunter, Phillip and Loftus Streets, Sydney

date

1988-93

style

Late 20th-Century Post-Modern

construction

reinforced concrete, granite cladding. 240m/787ft 50 floors

type

Office Building

notes

A nice touch of post-modern art-deco exuberance in an otherwise boxy city. Built when KPF were at their prime.
 
 
 
 
 
 
 
  Above image copyright Simon Fieldhouse
 
 
The international commercial city is based on the premise that it is more profitable to develop air space than it is to develop land space. For Sydney, Chifley Tower is one of the most expensive projects to date, with an overall cost approaching $1 billion. Incorporating technology seen in their East Wacker Drive project in Chicago, the American firm of Kohn Pedersen Fox grafted on the picturesque romantic skyscraper stylism found in early 20th Century American office towers.

The lift cores, microwave technology and rooftop mechanical plant are contained in a turret feature topped by a flag pole creating a dramatic outline on the skyline, a feature avoided by earlier modernist towers.

With 4-metre high floor-to-floor heights, the building has been designed to accommodate high technology communications and services. Three electrical substations, with provision for another two, power the building with uninterrupted electrical supply suitable for computers. To counteract building sway in high winds, a steel block weighing 400 tonnes is suspended from eight 75mm diameter steel wires, suspended from the top of the building. This giant pendulum is connected to a hydraulic dampened gravity system which in turn restrains the building’s movement in high winds.

Information appearing in this section is reproduced from Sydney Architecture, with the kind permission of the author, Graham Jahn, a well-known Sydney architect and former City of Sydney Councillor. Sydney Architecture, rrp $35.00, is available from all good book stores or from the publisher, Watermark Press, Telephone: 02 9818 5677

The project is a compositional exercise in the assemblage of parts, each part drawing the meaning from a particular aspect of its surrounding context. The timing of this commission coincided with Australia’s winning the American Cup.

The dominant feature is the glass sail facing Sydney Harbour. Besides the implied symbolism of Australia’s victory, it embodies the spirit of the city of Sydney. The wedge-shaped site on which this building site was formed by the collision of old and new city grids. The resulting complex geometry needed resolution. Similarly, the pedestrian scale and the incomplete geometry of Chifley Square to the south needed attention. The site is also an edge site, highly visible from the harbor and the stretch of Botanical Gardens and the Domain park to the east.

At its base, the building is composed of parts that define the streetwall; as it rises it shifts in scale and wall articulation, finally orienting itself to the larger city grid at the top. The exterior material also changes from the primary expression of stone to the glass sail on the east, recognizing the building’s edge position in the city context. Pedestrian movement around the base is allowed to find a natural series of paths through the arcades and galleries introduced at street level, leading to the completed civic space at Chiffley Square.
The Bond Corporation set out to offer tenants Australia’s first 6 star commercial building. Architectus undertook the project in association with Kohn Pedersen Fox of New York. The design was principally developed in New York whilst the detailed design and documentation was completed by Architectus.

The Chifley Tower represents one of the most advanced commercial office developments in Australia with 80,000 m² of floor area over 42 levels. The building is an all-steel structure including drywall core construction. A 400 tonne steel tuned mass damper at the top of the tower is used to minimise building movement.

The development includes Sydney’s most exclusive retail arcade, comprising two levels with a ground level food court. The space allocated to the car park consists of a 4 level basement for tenant self-park (390 cars) and a truck dock making room for 23 trucks. The urban design of the building responded to the local context by aligning height setbacks with nearby buildings and completing the 1950s planning of Chifley Square.

The design of the building was used as an example for building form guidelines in the Central Sydney Strategy Plan 1988. The comprehensive analysis of the environmental effects, together with the building’s outstanding design resulted in a record development approval within 14 weeks.

The building has now become the focus of Sydney’s financial and legal communities.

Structural info-

Project
Name Chifley tower 
Project Team 
- Architect Kohn, Pederson, Fox, Travis McEwen Group 
- Structural engineer Flack and Kurtz Australia and New York and Thornton Thomasetti. 
- Service engineers Flack and Kurtz Australia and New York and Thornton Thomasetti. 
- Builder Multiplex Construction (NSW) 
Function Commercial office building, with retail on lower levels. 
Year 1992 
Location Sydney, NSW 
Cost Development value $1.2 billion and construction value $425 million. 

Building 
Type Highly serviced office building with parking, two levels of retail, two levels of trading floors and conference rooms. 
Form 
- Plan shape rectangular with multiple setbacks and curved facade to the East with a central irregular polygon shaped core. 
- Number of stories 53 levels above ground, 4 levels basement and 5 service levels 
- Total floor area approximately 90 000 sq m 
- Net rentable floor area 72,268 sq m 
- Number of modules 3 rectangles, one cured polygon and one central irregular polygon shaped core 
Relationship to ground ground level pedestrian entrance, underground parking, two levels of retail and a below ground loading dock. 

Primary Structure 
material all steel frame with concrete floor slab on steel decking permanent form work 
floor system 
- type steel beams, composite metal deck/concrete floor 

- pattern beams radiating between the core frame and the outer columns, one-way floor slab 

- beam clear span 10-15 m, typically 12m 

- floor slab span 2.5-3 m 
core structure 
- material steel braced frame with Boral Gypsum drywall cavity shaft wall 
- type braced steel (350 MPa) 
- shape irregular polygon 
support structures 
- types internal columns on the perimeter, out rigger system 
- material structural steel 
footings spread footings and rock anchors 


Design requirements 
Chifley Tower occupies one of Sydney's most expensive sites, bought by the Bond Corporation in 1988 for $306 million. It is one of the most elevated sites in the city with harbour views never to be built out. Its 6,438.6 square metre site is close to the Domain and the Botanical Gardens and the traditionally government precinct of Sydney. 

The footprint of the building follows the curve of the 1930's scheme for the Parisian style statue square. To relate to the scale of this square, the podium is only built to a five storey height on this line and, to minimize overshadowing on the nearby gardens, the tower is positioned on the North West corner of the site. This is also a response to the site geometries and the immediate built context. 

Aesthetic reasons and council height restrictions step the building back at various levels, creating the American Post Modern appearance crucial to its image on the skyline.Form relates to the orientation of views, and the high technology service requirements. The building must accommodate the highest level of technology for financial services and legal communities, major trading corporations, stockbrokers, insurance and investment houses. Office space had to be column free with 24 hour access to the most advanced electronic communication and information systems, and there had to be flexibility for changes in technology, including easy penetration of the core. The internal fabric had to be flexible to accommodate the interior architectural changes of future tenants.The core had to be as compact as possible to increase the lettable floor area. 

Above the podium level of shops and restaurants, Chifley Tower steps back to a highly articulated facade of non- parallel sides, multiple setbacks and a mixture of curved faces which enliven the Sydney Skyline. Of the 48 levels; basement 1-4 is parking, plant and loading dock, ground level is lobby and retail, level 1-4 is retail, restaurants, office support convention facilities and plant room, levels 5-39 is offices, levels 40-44 is executive rooms, levels 42-43 is the plant room and the cooling tower is located on the roof. In the low rise section the floor area of on average 1624 sq.m offers 79.9% efficiency. Mid rise, with a 1526 sq.m average floor area, the efficiency is 81.0% and the high rise section offers 79.9% efficiency with1293 sq.m floor area. 

The tower plan consists of 4 quadrants. In the East an elliptical shaped office area with curved facade suitable for harbour views, catching the sunrise for international trade work. The layout allows for maximum offices with natural light. Floor to ceiling heights are a generous 2700 mm for such a prestigious building, on trading floors reaching 3200 mm. The floor to floor height is 4075 mm generally. 

The core is a polygon plan of steel frame with a Gypsum dry wall cavity shaft system. The plant rooms are restricted to the top floor, level 4 and the basement. The span of each quadrant from the core is a clear 12-15 m. Smaller functional modules in the car park allow a column spacing of approximately 8.5m-13m as required by the geometry of core conflicting with the geometry of the site. In the retail area the column grid is 7m by 7m again bending to the complex geometrical requirements of the site boundaries. In the space beneath the tower the columns follow the perimeter, often multiplying to form arcades and mark entrances, articulating the facade and adding to the aesthetics of the form. The floor slabs have been designed for a 3kPa live load with 7.5 kPa in the compactus zone. The design allows for a wind load of 50m/s ultimate on a 1000 year return with a maximum lateral deflection of H/400=226/400=0.565 m for a 50 year return. The facade is anchored directly into Hawkesbury Sandstone with a bearing capacity given by the council at 5 MPa. 

One of the driving forces behind the selection of the structural system for the Chifley Tower was speed of construction. Since the site was bought for $306 million, with 15% per annum interest rate, the interest was around $1 million per week. Higher construction costs had to be balanced by considerations of sooner rental returns. 

For a building of this height angle being so light in steel, vibration control had to be built into the structure. There had to be 2-2.5% dampening for serviceability and 6% being the ultimate level to achieve. Fire resistant levels for structural adequacy is to be 180 min for all elements. 

A 20 storey building occupied part of the site prior to construction. To save time, construction was started on the empty part of the site before the old building was demolished. Thus construction and demolition were occurring within 10 metres of each other. 


Structural Solutions 
The key requirements that influenced the selection of structural solutions were (a) an efficient floor system selection for column free space, (b) floor system that minimizes the floor to floor height and allows integration of structure and services, (c) speed of construction to enable early tenant occupancy (d)maximum flexibility for new technologies eg. multiple openings to the core, on roof communication space, and careful integration of structures and services, (e)facade designed by architect determined a column grid not necessarily the most efficient for the distribution of loads, (f) flexibility in the interior architectural arrangement so that tenants could accommodate internal stairs, voids etcetera, into their occupied space after the architects design. 


Structural Alternatives and System Selection 

According to the engineer, Matthew O'Hearne of Flack and Kurtz engineers, experience in dealing with the requirements given in the brief led almost immediately to a choice of steel as the primary structural material. Even though the initial material and fabrication cost is higher, the composite steel and concrete floor system was selected as overall economies can be achieved, included early return on investment. 

Steel had the following advantages necessary to fulfill this buildings' brief: 

1) a steel frame core allows for multiple penetrations required by technologies expected in this development and tenancy 

2) speedy erection for faster return. Steel sections could be ordered long before structural designs were finalized. This allowed efficiency in material supply. 

3) steel accommodated for the multiple setbacks and facade articulation. 

4) ability to puncture beams and transfer load to free up space to accommodate tenants requirements. 

5) lightweight 

6) use of standard, off shelf components for ease of modelling, testing and off-site manufacture 

7) steel Bondek 2 acts structurally to thin the slab but also as form work so that the floor belowis clear for other trades to move in and do work. 

Choice of 350 grade steel was determined by pre-ordering requirements but had advantages of 

-overall 25% weight saving 

-smaller columns, shallower beams 

-fewer elements to install 

-less fire spray 

For buildability the floors were designed not to be propped. Thus they are 25% over-engineered with 530 UB beam allowing for additional live load capacity of 1-2 kPa. 

The disadvantages of steel; 

1)higher initial fabrication costs although returns are brought earlier. 

2) requires fire protection, sprayed with retardant such as vermiculite or concrete 

In consideration of concrete; 

1) core penetrations are more difficult and reduce the structural efficiency 

2)a framed tube, required, would interfere with the facade detailing already determined by the architect 

3) a braced frame or shear wall becomes inefficient over 40 stories 


The use of steel beams for the floor systems also permits the integration of structure and services, with the services zone being within the horizontal zone for the structure. There is thus no need to increase the floor to floor height to accommodate the service ducts. The air-handling ducts penetrate the webs of the beams, where the shear forces to be resisted by the web are not critical. 

The composite steel/concrete construction has a number of advantages which results in reduced construction time. The steel deck for the composite construction provides a working platform during construction, and eliminates the need to either prop or strip form work and the attendant delays resulting from these operations. 

The exposed steel , however, requires fire protection. In this project the cost of fire rating the structure was considered to be small in comparison to other costs, and did not influence the selection of this system. 

Final Structural Solution 

The floor system for the tower is of composite construction and consists of radially arranged UB530 universal steel beams - spaced at 2.5m to 3 mat the core and at 3.2m supporting concrete floor slabs cast on permanent steel Bondek 2 form work. Composite steel beams span the 10-15m between the core and the outer columns. The steel beams placed between columns are supported at the perimeter by steel spandrel beams, that span between the columns. 

The central irregular polygon core is of steel frame construction. The floor slab and the core are tack welded together.The columns on the perimeter of the building are at 10m spacing and are of steel construction.The car park has in general a 8.5 m column grid and a flat slab floor system. The footing for the core is a raft slab and for the columns are pad footings.Outriggers tie the perimeter columns into the core to direct axial forces caused by wind pressures. Transfer trusses allow for facade setbacks and geometry changes. 

The structural elements that contribute to the different functional systems are: Structural types: composite steel deck and concrete slab floor with steel beams and a steel outrigger system tying the perimeter columns into the steel framed core.
material: composite steel/concrete, steel. 

Structural type: core
material -structural steel with drywall cavity cladding. 
Structural types: - raft slab and rock anchors
materials - reinforced concrete slab, steel anchors


Design Decisions 
The decision to choose the plan consideration is influenced by orientation of views and an aesthetic articulation of the building relating to the surrounding context. The shape and the facade articulation means that beam arrangement is not necessarily the most efficient. 

The floor system was selected to eliminate propping of the metal deck during construction and to allow flexibility of penetrations while maintaining a generous floor to ceiling height. 


The car park grid of generally 8.5m was selected to accommodate three cars between the columns. Flat slab construction was selected as it is an efficient and cost effective system for this span and minimizes floor to floor heights, thus reducing the depth of excavation into the sandstone. 

Cranes: Three cranes were required to construct this building in the necessary time, operating in a 2000sq.m. area. Models had to be constructed to work out the geometry to maintain a safe site. The structure had to support their horizontal and vertical loads. Every fourth floor is engineered for horizontal loads. The cranes can lift up to 25 Tonnes, necessary with 4 T/m column sections and 8T base plates. 

Tuned mass dampener: A 400 Tonne pendulum swings out of phase with the building to reduce movement in high winds. This transforms mechanical energy into heat via a hydraulic system. In a 5 year return wind (34 m/s) the winds are dampened around 1-2.5% and acceleration is decreased by 0.03 to 0.02g. The steel plate is hung from 8 eleven meter long cables anchored at level 46. A tuning frame slides along the cables, adjusting their active length and thus its period. Eight hydraulic cylinders push fluid through a control valve and heat exchanger. Torsion is restricted by an anti-yaw yoke. 


References 
- Architecture Australia Sept/Oct 1992 

- Architecture Australia Jan/Feb 1994 

- Architecture Bulletin April 1991 p67 

- Architecture Bulletin July 1991 p53 

- Architecture Bulletin April 1993 p67 

- BCME October 1993 pp40-42 

- Building Owner and Manager, National Magazine for the Building Owners and Manager's Association of Australia. 

- The Building Economist Sept 1992 

- Chifley Tower, Promotional brochure. 

- Interview with Matthew O'Hearne of Flack and Kurtz, Sydney. 

- Interview with Kohn, Pederson, Fox, Travis McEwin Group. 

- Specifier Architecture and Interiors Vol 2 no 2 May 1993 

- Steel Profile "Tall Building Expression" date unknown. 

Thanks to http://www.arch.usyd.edu.au/kcdc/caut/html/GPT/front.htm 
 
 

 

www.sydneyarchitecture.com 

links

http://www.chifleytower.com.au/default.asp