This project was entered in the LSAA 2018 Design Awards (Cat7 Special Applications, #7432)
Application: Cable-net arbour walkway incorporating artwork panels, vines & foliage and feature lighting, linking the New Perth Stadium with the parklands precinct and the main transport infrastructure hubs of Swan River Pedestrian Bridge and the Stadium Train Station.
PROJECT DESCRIPTION:
A 350m long architectural tensioned cable-net structure, supporting indigenous inspired artwork panels, crawling vines and plants and feature programmable LED lighting. The Arbour walkway was designed to guide the major pedestrian flows on game day from the main transport hubs at either side of the stadium precinct. The cable-net structure snakes around half of the stadium and is supported by bespoke steel arches with tapered bases. In total over 3,500 artwork panels, perforated with designs inspired by local indigenous groups, are supported by nearly 15km of stainless steel cables and clamps. At the bases of the arches, vines and crawling plants grow from garden beds and in time will rise up and over the precinct pathways below.
DESIGN / FABRICATION / INSTALLATION BRIEF
The aim of this project was to provide an access Arbour to the new Perth Stadium that was a memorable and distinctive experience in itself. The Community Arbour was required to facilitate the movement of large numbers of people from public transport ensure whilst providing views of the iconic Stadium in it’s prominent position beside the Swan River.
Our design enhanced the communication to Stadium and recreational precinct users that the area was a world-class venue. It complemented the landscaped environment and Stadium as a visually-appealing structure while ensuring functionality and durability. The open and flowing design enabled users to have broad vistas of the Stadium, Swan River and CBD skyline.
Each steel arch was unique with constantly changing radii. The arches were required to appear very light at ground level. Tapered sections were used to achieve this, with induction bending of steel sections used to achieve the complex geometries desired by the project architect. Connections needed to appear seamless; various design details and cover plates were prototyped and reviewed by the project team prior to deciding on the best solution for this project. The end result makes the 25m wide sections appear as though they are a single piece of steelwork with no seams or joins.
Many variants of artwork forms were required for the folded aluminum panels with multiple fold angles, shapes and artwork styles all required. The natural shape of the cable net further increased the number of unique panels due to the large number of different hole spacings generated. We designed the cable clamps to allow a varying force through the cables so that all cable spacings could be kept standard. This allowed for the panel clamp locations to be the same distance apart for every panel leading to a large increase in repeatability of panels simplifying both fabrication and installation.
STRUCTURAL SYSTEMS
The structure comprises 43 individual arches from 15-25m wide and 8-10m tall at the apex. At the ends of the walkway the arches incline outwards and have the unbalanced cable net forces braced by diagonal struts back to ground. These struts also have tapered ends to mimic the architecture of the arches. The cable net is prestressed between the arches; catenary cables at the sides resist the transverse cable tensions, longitudinal cables are broken at each arch individually. Artwork panels clamp to the cables and both the panel weight and wind loading are the primary load cases on the structure. To increase redundancy of the structural system, cross-bracing is used every 5 to 6 bays so that in the event of damage the majority of the structure will remain unaffected and any loss of tension will only have a localized effect.
A key structural solution was to have variable tension through the transverse cables to allow the longitudinal cables to be kept at a constant distance apart. The cross clamps linking the cables were designed to resist an out of balance load to enable this to happen. This change enabled the number of unique panels to be dramatically reduced leading to a large saving in fabrication and installation time.
MATERIALS
The artwork panels were made from perforated and folded aluminium, chosen for its lightness, workability and excellent corrosion resistance given the location. Anodizing of the panels was chosen to achieve the colour required; this was a large challenge on the project as consistency of coloured anodizing through 3,500 panels was difficult to control. Powdercoating would have been more reliable for colour, but the risk of damage to painted panels on site during installation was high and anodizing provided the most durable finish for the project.
The cable net, fittings and clamps were stainless steel grade 316 and passivated for superior corrosion resistance – essential given the estuarine waterfront location.
The primary frame was structural steelwork, as expected for a structure this size. Due to the lack of induction bending of large pipe diameters in Western Australia, steelwork was sourced overseas. Coating was to the same specification as the rest of the stadium project, with a high performance International Paints specification used.
FABRICATION
Structural steelwork was rolled using induction bending to achieve the complex and varying radiused used in each arch. As the final geometry of the steelwork was dimension critical to ensure that the cable net would be installed successfully, comprehensive check measurements of every steel arch was undertaken and verified prior to steelwork leaving the factory. To allow extra tolerance in the footings a detail was devised to provide extra adjustment in bolt centres in case of concreting issues. Full as-constructed surveys of the footings were undertaken prior to steel installation so that any offsets or movements required could be clearly communicated to the steelwork installers.
Three different fold angles for panels were used so folding jigs were made to ensure that each panel would be made to the same geometry.
COLLABORATION, CONSTRUCTION AND MAINTENANCE
A scaled prototype frame including a cable net section, panel clamps and 6 artwork panels was built on site for review and sign off by the project team. This led to some detail modifications as we collaboratively workshopped fabrication and erection methodologies consecutively with the architectural finishes. This mock-up also gave the lighting team a testing bed to trial different types of lighting and programming equipment and to quickly visualize how this would appear on the final project.
The project ran mostly consecutively from one end of the arbour to the other. Once sufficient cross bracing had been installed between arches, the cable net could progress installation while the steel was moving forwards several bays ahead. A key interface area was around the middle point of the arbour where the main goods, workers and plant entry to the stadium bowl was located. This area had to be kept operational during site working hours which meant that all install works in this area were undertaken out of ours to ensure there was no impact on the main stadium construction. The arbour was designed with a height raise here to allow for truck and fire vehicle access to the stadium when complete.
Credits:
Entrant: MakMax Australia
Role played by Entrant: Designer, Engineer, Installer
Location: Perth, WA
Completed: December 2017
Client: Brookfield Multiplex (WA)
Architect: Cox / Hassell
Engineer: MakMax
Specialists: Maffeis Engineering
Builder: MakMax
Fabricator: Structural Dynamics / Unique Metals
Ref Gallery: 2018_Images/Award_Entries/7432_Perth_Arbour_Walk DPID 273
