This Is How You Transform A Virtually Unusable Site Into A Viable Commercial Development
271 Spring Street, Melbourne was constructed on an almost unusable site. The 16-storey ISPT commercial development overcame a myriad of site constraints.
The building had to navigate two existing heritage buildings, an underground substation, two electrical easements and two double-stacked City Loop rail tunnels beneath the site.
The solution involved the use of a steel structural frame, reducing the building’s weight, and a creative approach to foundation design, minimising the building footprint, excavation zone and pile depths.
“We used engineering-led solutions which first responded to the site constraints and then informed the design. This allowed us to develop a building of sufficient size to warrant commercial viability,” says Arup Project Director, Richard Salter.
Complicating the build further was the need to upgrade the heritage-listed Mission Hall building to meet current codes and earthquake regulations. So, footing and floor replacement and structural strengthening were undertaken to improve the structural integrity of the early 1900's brick structure.
Reverse Engineering the Site Constraints
The design team created site maps delineating the areas that could tolerate either full loading, some loading or zero loading. These also highlighted areas sensitive to movements or that required strengthening or underpinning.
"The ground plane maps informed an analysis model to ensure any proposed solutions satisfied the constraints before proceeding," says Salter.
Integrated superstructure and substructure models allowed rapid development of a range of building stability options, allowing the exploration of various building geometries and attributes such as building height, materiality, floor plate size, and ease of construction.
The result was an alignment between architectural and engineering constraints to derive feasible building layout options.
Accommodating Irregular Load Distribution
The building's load distribution had to be tailored to suit the irregularity of the site’s ground capacity.
This required the building's stability core to be located on the side of the building, where loads could be tolerated, instead of in the centre.
A steel outrigger truss detached from the building’s core distributes loads to the areas of the foundations which don't pose an impact on the rail tunnels below.
Raking columns and in-plane floor truss structures absorb lateral thrusts and transfer them into stability structures which distribute them into the foundations.
Arup’s building services team used modelling innovations to fully coordinate the services into the steel frame solution, helping to reduce floor-to-floor heights enough to allow an additional floor to be added without exceeding planning height restrictions.
271 Spring Street's distinguishable facade is created by a unique awning pattern coupled with a raking facade that satisfies the planning set-back requirements and limits the visual impact of the overhang on the buildings below.
The design maximises floor plate size and creates a new contemporary workplace integrated from the ground floor into the heritage buildings, including an outdoor garden mezzanine space, and horizontal and vertical connectivity for improved team-based collaboration and performance.
As a result of the unique and innovative design that transformed the 271 Spring Street development into commercial feasibility, the building has taken home numerous awards, including:
- Best Tall Building under 100 metres 2020 Award of Excellence - CTBUH Awards 2020
- Development of the Year, Commercial Winner - The Urban Developer Awards 2019
- Victorian Commercial Architecture Award Shortlist - Australian Institute of Architects
- Australian Engineering Excellence Award 2020 - Engineers Australia.
271 Spring Street is a demonstration of the outcomes that can be attained by combining both human creative thinking and parametric modelling to overcome project constraints. The project team have transformed a seemingly unviable project by methodically balancing the commercial feasibility requirements with the preservation of surrounding structures, all the while paying homage to the site’s history through restoration and adaptive reuse of the century-old heritage buildings.