405 Bourke Street is a new commercial development located in the heart of the Melbourne CBD. Designed by renowned architect Woods Bagot, the project is set to feature a 40 storey, 180 metre building combining office and retail spaces.

The tower is to be built in and around the constraints of the site. Existing car park structure, light easements, 399 Bourke Street building and the existing east retail and car park areas all provided constraints to the design as well as the constructability of the proposed tower.

The north-east portion of the tower cantilevers over the existing 399 Bourke Street via the use of three mega trusses. Each mega truss, approximately 28m long x 12m deep, consists of 2mx2m steel cross sections filled with concrete which form a distinctive feature of the building.

Extensive works and re-planning within the existing 399 Bourke retail zone were required with the design team to ensure the structural integrity of the existing structure was maintained and the client’s expectations realised.

Year Completed:
Expected completion 2021
Building Metrics:
Total Area: 61,500
Levels: 40

Brookfield Foundry Landowner Pty Ltd
Woods Bagot
Robert Bird Group Services:
Structural engineering
Civil engineering
Construction engineering

Key technical challenges

  • The primary tower structure consists of a composite slab and beam structure. Due to the long beam spans and thin slab, extensive analysis for footfall vibration was required to ensure the structure achieved code requirements and client expectations.
  • Working with the existing structure and developing design solutions that strengthened rather than demolished.
  • Extensive co-ordination with the mechanical engineer to develop a strategy that minimised beam penetrations and beam notches.
  • Differential shortening analysis with consideration of mega truss, steel structure, concrete structure and existing structural elements

Environmental performance

  • 5 Star Greenstar
  • 5 Star NABERs Energy and 4 Star NABERs Water ratings.

Key technical innovation

  • Design of mega column and mega piles to resist the large concentrated truss loads. Specialised piling rigs were required to construct the 2100mm diameter mega piles required to resist the truss loads.
  • Developing a strategy to resist the mega truss uplift forces with the use of special high strength reinforcement.
  • To maximise the office floor column grids, HISTAR 460 HD columns were adopted in the design. Column cross sections are relatively small with thick web and flanges, as large as 140mm thick. HD Columns are fabricated and transported from Luxembourg.

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