Sydney Architecture Images-The Inner West

Olympic Park Rail Station

architect

Hassell

location

Olympic Park Homebush Bay

date

1996-8

style

Late 20th-Century Late Modern

construction

steel

type

Government
 
 
 
 
 
 
 
 
Project 
Name Sydney Olympic Train Station, Homebush 
Client Olympic Co-ordination Authority 
Project Team 
- Architecture and Landscape Architecture Hassell Pty. Ltd 
- Structural engineer and Civil Engineering Tierney & Partners 
- Service engineers and Environmental Engineering Connell Wagner 
- Project Managers and Contractors Leighton Contractors 
- Acoustic and Sound Engineers Robert Fitzell Acoustics 
- Graphic Design and Signage Emery Vincent Design 
- BCA consultants Trevor Howse and Associates 
-Energy Advice Solarch 
Function Train terminal/Transport Link 
Year 1998 
Location Homebush, NSW 
Cost $95 million 

Building 
Type Train Terminal 
Form 
- Plan shape rectangular - 200m x 35m 
- Overall Height platform to roof top - 21m 
- Basic roof module single span vaulted 'leaf' roof truss 
- Number of modules 18 modules spaced at 12m 
- -Additional roofs 14m long arched entrance canopy, 5.5m wide side awning 

- Floor area 7000 sq m 
Relationship to ground 6m deep excavation "below" ground, 15m high roof canopy from ground level 

Primary Structure 
material 
- roof steel 

- base concrete 
roof structure type 
- type single span vaulted 'leaf' roof truss 

- pattern repeated folded vault configuration 
support structures columns, buttresses, arched trusses 
footings pads, slab on ground, rock anchors 

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Design requirements 
When Sydney won the bid to stage the 2000 Olympics, the main sporting venues had been the subject of initial master plans. However, there had been no real work undertaken for the development of transportation as well as the site planning for Homebush Bay. 

In late 1993, an international design workshop was convened to canvass ideas for the site. HASSELL was appointed as the design team to prepare a new urban design plan. In the 1995 Master Plan, a loop rail link and proposed an underground station in the centre of the Olympic site was adopted. 

The Olympic Co-ordination Authority (OCA) required a facility that formed a "gateway" to the site as part of the public facilities and public domain at Homebush Bay. It has to be of a world class stature with demonstrated design excellence and become a recognisable building of which the public would be proud. The site has dimensions of 35m by 200m. The station has to be 500m away from the Stadium and 100m west of the main Olympic Plaza. It also has to be located immediately south of the showground precinct. 

This structure was required to handle crowds of up to 50,000 people per hour arriving and departing. The Station has to operate in 3 different modes: 


1. Normal mode - to operate as a normal station 
2. Major event mode - accommodating up to 30,000 people per hour (e.g. Easter Show) 
3. Olympic mode - accommodating up to 50,000 people per hour 
The Station should be operated and managed effectively in accordance with international safety standards. Performances and durability of the materials used have to be considered. In addition, the design has to meet the defined environmental policy of the OCA. It also has to provide high equity of access to all user groups. 

The main requirement was to produce a building where it expressed its structure and function. To create a building of world class stature through the refinement and development of elements within the building expressing its form, structural material and light. 

The roof structure should safely carry the expected dead, live and wind loads. The footing system should be capable of transferring the loads safely to the foundation. The ground condition at the selected site consists of medium strength shale on the western and central areas of the site and low strength shale on the eastern side, which is generally close to the surface. 

A number of clear design intentions were established for the project following initial interpretation of the brief and site. These can be summarised as follows. 


To ensure absolute clarity and legibility for the Station passengers. 
To view the project as "below ground" rather than "underground" ie to consider it as an open air structure. 
To allow an awareness of the external environment. 
To celebrate the act of arrival and departure 
To rely to the maximum extent on natural lighting and ventilation 
To give a clear sense of direction in the architecture 
To explore the traditions of the great traditions of station design, expressing the drama of event, the manipulation of light and the expressions of structure 
To separate the base and canopy of the building 
To provide a seamless link to the public domain 
To provide a strong, singular image for the Station 
In a site dominated by large and tall architectural elements, the Station could not compete in terms of vertical scale. The answer was to give it horizontal scale, and celebrate light and space to achieve a memorable experience for the passengers alighting from the underground loop. 

Thus the design challenge was to provide a strong and solid "base" which identified and integrated with the surrounding public domain, and a delicate and light canopy which gave a visible presence to the Station within the site. 

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Structural Solutions 
In a site dominated by large and tall architectural elements, the Station could not compete in terms of vertical scale. The answer was to give it horizontal scale, and celebrate light and space to achieve a memorable experience for the passengers alighting from the underground loop. 

Thus the design challenge was to provide a strong and solid "base" which identified and integrated with the surrounding public domain, and a delicate and light canopy which gave a visible presence to the Station within the site. 

Alternative Structural Systems 
Design studies explored various concepts to cover the space in a free spanning structure. The basic idea was that of a barrel vault. In addition,the building having a wide span of 36m, needed some depth in the structure. 

Faceted Vault (click to see sketch design) 

In this alternative system, all the arched trusses are joined to one another, thus the whole system braces itself. However, the architect wanted to have a break at the top joints so as to let light in. Thus, the final single span vaulted 'leaf' roof truss with 10mm gap between the top arches. 

Overlapping Shells (click to see sketch design) 

The canopy is made up of single arches, which are placed at an angle with the higher end facing east. The shells vary in size from the smallest on the eastern end of the building to the biggest on the western end. The problem with this alternative was the different sized elements, which meant it was expensive to create. Moreover, it is preferable to have more northern light than eastern light entering the building. This structure, being open at one end, requires some form of vertical support. However, this was not architecturally desirable, thus, this alternative was omitted. 

Overlapping Planes (click to see sketch design) 

The canopy is made up of rectangular planes, which are placed at an angle with the higher end facing west. These planes vary in size from the smallest on the eastern end of the building to the biggest on the western end. The reason this system was omitted was because it was architecturally unsound. 

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Final Solution 
The concept of a series of single span vaulted roof trusses which gave a leaf like expression with a ribbed underside was developed and studied using physical models before being tested by Tierney and Partners through computer modelling. By linking these together, a stable yet simple structrural system was acheived. 

Under this protective canopy, all other elements within the Station were treated as items of "furniture" and the emphasis was on spacial clarity with maximum visibility and minimum clutter. 

The structural elements that contribute to the different functional systems are: 

Structural types: arched truss, column 

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Design decisions 
A single span system was selected in order to achieve a column-free and spacious concourse. Natural lighting and ventilation required the extensive use of glazing and favoured a columnar structure to a walled one. 

As the building does not get much light in from the sides because of its enclosed form, there was a need to make it naturally lit. It was decided to open up center of the arched truss by having a double ridge to let light through. Our climate is not suitable for alot of glass exposed to the sun, thus a strip of glass approximately 100mm wide is enough for the opening. Sunlight runs on the long dimension of the station, therefore, a deep rhythm of light casts right down into the station, especially during the middle of the day. Light incidence also occurs when sunlight enters at an angle in the cross section. 

Architecturally, the Station is not purely about structure but also about expressing the form of the building. 

Bracing of the arched trusses could have been done by having highly rigid joints, which meant that all elements have to be welded together.The other option was to brace the leaf using a stressed skin.As there was a desire to express the principle spanning members (Ribs) and suppress the secondary systems (bracing), the decision was to brace the arched trusses by a system of struts, with cross bracing between the purlins which are hidden by the ceiling. As a result, a greater sense of expression of the structure and the form of the barrel vault was acheived. 

There was a need to allow for reflection of light on the ceiling surface especially at night. With the bracing hidden the ceiling can perform an acoustic role by having perforations and absorbant materials behind. Thus, the importance of sound reinforcement and speech legibility in the Station is emphasised. 

The architect actually preferred to have deeper section on the arched truss, which meant a higher ceiling with narrower divisions.Thus the canopy would have some form of depth rather than merely a pattern. However, this was not possible because of not wanting to expose the bracing as a simple and clear reading of primary structural members was desired. 

Equally, the double 'V'pin joints which are very visible from the concourse level, required a combination of structural and architectural effort to achieve a sound and visually pleasing feature. This is achieved through the eccentricity of truss chords in relation to the pin which added complexity to the joint. 

The finishes of the building materials were also considered architecturally. All materials were to be exposed as what they are. However, a distinction between structural and non-structural elements are also made. For example, precast cladding to walls are white cement while the structural columns between the non-structural walls will be of gray cement. 

In terms of construction, the structure of the station made use of standards parts and materials in order to reduce cost and yet acheive the required architectural expression. 

A rapid assembly process was developed by Leighton Contractors in consultation with the design team. This process has been possible due to the repetitive nature of the structural and constructional elements. The structural steel, which has been fabricated by Affassi in Melbourne, has been delivered in partly assembled components to the site following painting in Sydney. The trusses are assembled with purlins and safety mesh, into 2 components. These are then transported into place on the progressively erected pre-cast concrete columns, by a mobile crane. 

An arched truss spans 35m and is made up of a vertical twin arch at the ridge (the leaf spine) and inclined arches at the bottom (the leaf's borders). Tubes were the best solution to cater to the curving geometry. Thus, 355CHS were used for the arches. Moreover, strong visual continuity as well as the expression of structure are read from the continuity of the tubes. 

A services gap of approximately 900mm sits around the concrete box between the precast cladding and the cut wall. 

Roof drainage runs through stainless steel pipes which sit within the pre-cast columns. Rainwater is then discharged underground exactly at the point where bending moments are greatests in the columns.Thus, a lot of structural problems had to be solved in the design of this junction, by the structural engineer. 

Access and egress are directed toward the west of the station. A combination of stairs,ramps and lifts were used for vertical access. Internal ramps run along the northern and southern edges of the concourse, while the lifts and stairs are located to give even distribution of crowds. The latter arrangement was derived to meet the requirements of the Access Committee. 

The 'box' accomodates three platforms. The central platform serves all arrivals and departures under normal operating modes, and is dedicated to arrivals, when in major event or Olympic modes. The central platform can also be dedicated to departure time when no arrival trains are scheduled, which will occur in major event conditions. The system that these platforms adopts dictates the planning of the concourse and platform levels. 



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Efficiency and Economy 
In terms of economy, the use of Speed Deck 500 for the roof cladding was a cost-effective solution that accommodated the complexed shapes of the roof, which is of varying radius and width, and warps along the span of both the leaf and the barrel part of the roof. The fixing of the cladding had to be modified to provide adequate capacity as well as architectural performance under non-standard support conditions. 

In response to the requirement for the building to be of word class stature standard details and materials were developed and refined to raise the building above the ordinary. On the other hand, complicated (non-standard) details were avoided to reduce cost down to a manageable figure. 

Time factor was an important issue in the development of the Station. The design team together with its consultants had to produce a structurally efficient building which can be put together in the shortest time possible. This was achieved by having most of the components prefabricated and partially assembled. These components are then assembled on site. They were able to install two trusses per week, while the precast lining to the station box is installed in parallel to the creation of the roof. 


References 
ACSE Seminar (1997) The New Sydney Showgrounds and exhibition halls at Homebush bay, The Association of Constulting Structural Engineers of NEw Sotuh Wales ( The Structural Branch of the NSW branch division of the Association of Consulting Engineers Australia) Friday August 29, 1997 
Maher, Ken (1997 ) Olympic Park Railway Station: Design Concept Hassell Pty Ltd. 
(1998) BPN February Issue, Article: Roofing pg 18, 
On Track (1998) Olympic Coordination Authority, March 1998 
Haskell, J. (1994) Strong Design Sets the Standard at Homebush, Architectural Bulletin, Nov, pp. 6 - 13. 



Drawing references 
Drawings were referenced courtesy of Hassell Pty Ltd (Architects) and Tierney and PrtnWagner (Structural Engineers)
  www.sydneyarchitecture.com 

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