Robert Bird Group’s concept design is coming to life as Circular Quay Tower in Sydney is making its ascent. When complete, this new office tower will be over 260m tall and will be the second tallest in Sydney.

Lendlease hosted a design competition in 2017 and RBG and Foster + Partners co-created this striking competition winning concept using an engineering led approach.
Some unique town planning constraints, along with the site shape and location created the canvas for RBG to get the creative juices flowing. We used our topology optimization process to establish an outline of the form, followed by sketching to provide further conceptual definition, before a final stage of design refinement using our genetic algorithm optimisation process.

A natural form emerged, resembling the veins in a leaf, and one that we hope will make a special contribution to Sydney for the owners, occupiers and the public.

The architectural competition brief was to create a world class office building taking advantage of the site location, views across the Harbour and the many local amenities. A slender tower geometry was well suited to a side core arrangement that allowed the views to the Harbour, Sydney Opera House, the Sydney Harbour Bridge and Barangaroo to be enjoyed from long clear span floors.

With the eccentric core position, RBG proposed an external frame as the most efficient way to frame the structure for gravity and lateral load carrying systems. In collaboration with Foster + Partners we applied our digital design technologies together with the traditional process of conceptual sketching to create the elegant engineered architectural design that emerged.

Lessons Learnt

Topology and genetic algorithm optimisation methods can help engineers to create elegant, organic new forms of structural expressionism.


The organic exo-skeleton system saved a considerable amount of concrete and CO2 compared to a conventional concrete core with outrigger system while also generating significant net area gains:

  • Total Concrete Saving: 5,699 m³
  • Net CO2 Saving: 2,462 tonnes
  • Area Gain: ˜25 m²/ floor

Project Metrics

Project Value:
$1.5 billion AUD
Year Completed:
Due 2023

Project Metrics

Lendlease Building Pty Ltd
Foster + Partners
Robert Bird Group Services:
RBG developed the conceptual design for Circular Quay Tower and undertook Structural Engineering and Construction Engineering services.