For more than 50 years there were proposals for a suspended deck over the Flinders Street railway yards in Melbourne, utilising the large area of valuable land occupied by the railway tracks in one of the prime locations in Melbourne. In 1996 these proposals moved towards becoming a reality when Victorian Premier Jeff Kennett announced that the Jolimont railway yards would be “roofed” to form a large landscaped plaza with indoor and outdoor spaces to link the city to the Yarra.
An international architectural competition for the design of Federation Square, to become a new gateway to the Melbourne CBD was mounted with the brief for the project covering four integrated areas: a new civic square; a modern wintergarden; public performance and exhibition facilities and a cinemedia centre. The competition was won by Peter Davidson and Don Bates of Lab architecture studio.
Of the structures that make up Federation Square, the two most interesting are the Atrium and the Façade. The former forms a three dimensional framing system, glazed both inside and out while the latter features large facades with a variety of triangular patterns based on the pinwheel tiling concepts where each right angle triangle can be divided into five congruent copies of itself over and over again.
The Atrium is a large, high volume public thoroughfare and covered meeting place. The glass-enclosed galleria provides a sheltered extension of the Plaza and acts as the forecourt to the National Gallery of Victoria: Australian Art. Open at the north end, the 18m high by 20m wide Atrium allows 24-hour access across Federation Square linking the city to the river. The southern half of the Atrium steps down from the elevated level of the riverside promenade, and has been designed to operate as a casual chamber amphitheatre with an acoustic tuned interior.
The open-framed structure of the Atrium has been developed using parts of the same triangular geometry as the facades, but forms a three dimensional framing system, glazed both inside and out. A crystalline web of glass interlaced with steel and zinc creates the undercover promenade. Two massive curtains of glass hang from a self-supporting web of galvanised steel. The inner and outer layers of glass create a chimney effect, forcing the movement of air and producing a year round temperate climate.
Made up of around 800t of steel, the Atrium presented complex design and engineering challenges. Explaining, Dirk Zimmerman of Atelier One, structural engineers on the project says: “The Atrium is a three dimensional interpretation of the pinwheel grid - a fractal framework that forms the basis of an intricate variegated structure from a limited kit of parts. The primary structure is an irregular space frame formed from 200 SHS.
“Elements of the pinwheel grid are separated from outer and inner structural planes to form two surfaces. These surfaces are then linked together with a series of diagonal interconnecting members to form an homogenous open network of a structure.
“The structure is based on repeated individual frame or panel types, which are related to a 2.25m module, the length of the hypotenuse of each triangle in the pinwheel grid. As the frame itself is not triangulated all joints are moment resisting.
“The frame fabrication had to be very precise to allow for the accuracy of construction required to produce the moment connections and to support the outer and inner glazing.
“Although there is a lot of repetition among individual frames, members and connection types it is the geometry of all connections that continuously varies throughout the whole structure, requiring all connections to be individually designed and 3D-modelled for fabrication.”
Triangle - engineer’s best friend
Federation Square features large facades with a variety of triangular patterns. These are all based on the pinwheel concept where each right angle triangle can be divided into five congruent copies of itself over and over again.
Using this base, Lab + Bates Smart created unique facades by varying orientation, colour, geometry and material to great effect. This spectacle of colour and shape has now become the symbol of one of Melbourne’s most notable projects.
Connell Mott MacDonald was engaged by the façade contractors Permasteelisa to assist with the structural design of these complex facades. Albert van Grieken, national façade leader recalls: “While excited by the structural challenges and complex geometry, one of our earliest thoughts was that, in this case, triangles might not be the engineer’s best friend!
“The first task of engineering team, led by the national façade leader, was to understand the geometry and identify structural opportunities. The facades change direction at subtle folds and the patterns needed to visually lack obvious repetition. It was the architectural intent to connect individual triangles which are clad with stone, metal and glass to subframes to achieve the desired visual variety.”
Connell Mott MacDonald carried out extensive computer modelling and analysis of the deflections and distortions of the complex façade frames to meet the specified very tight joint width tolerances.
The final solution was to connect the individual glass, stone and metal panels to triangular aluminium panels which were then connected to steel mega-frames. The largest mega-panels are up to 6m long, 3m wide and weigh approximately 1t.
Many Melburnians would have wondered about the intended destination of these impressive colourful panels which were transported to site on large trucks.
Federation Square was selected as one of the 100 projects from around the world to be displayed at the 2002 Architecture Biennale de Venezia for its contribution to social and philosophical issues as well as for the quality of the architecture and its construction.
This is an edited version of an article that originally appeared in the June 2002 issue of “Construct in Steel”magazine, published by the Australian Steel Institute.