Jim Stynes Bridge, Melbourne

Jim Stynes Bridge: a unique structural solution


Melbourne’s Jim Stynes Bridge employs a circular tensioned catenary to resist its unique load pattern.

 

  Project Details

  Architect: Cox Architecture 
  Head Building Contractor: Fitzgerald Constructions 
  Client: State Government of Victoria in partnership with the City
  of Melbourne 
  Design Concept: Cox Architects, Oculus 
  Structural Engineer: Aurecon Australia
  Non-destructive Testing: ALS Industrial, Gippsland NDT Services 
  Steel Detailers: Quantech Design, CADRAW Professional Drafting Services
  Steel Fabricators: Focus Engineering & Construction, Fitzgerald
  Constructions Australia 
  Transport to Site: Atkins Transport 
  Coatings Suppler: International Paint 
  High Tensile Steels: Interlloy 
  Steel Distributor/Manufacturer: BlueScope, Liberty 

 

The Jim Stynes Bridge is a shared pedestrian and cycle path located along the north side of the Yarra River, Melbourne, and named in honour of the late footballer. 

Designed by Aurecon, Cox Architects and Oculus, the bridge is a striking 125m long, lightweight structure that spans the Yarra River and sweeps beneath the Charles Grimes road bridge. The Bridge connects the Docklands precinct to the Melbourne CBD where a highway and road bridge had previously formed a barrier between the two. 

The structure relies on a structural system that offers an open, sweeping path while limiting interference with the adjacent riverside and elevated roadway it traverses. 

The curved nature of the path required a unique structural solution. The cantilevered deck, in conjunction with the curved truss, is trying to twist the bridge structure downwards under its self-weight and applied loads. 

The twist is resisted by a coupling force at the top and bottom of the truss. The coupling force is uniform along the full length of the structure. As a result, the coupling force at the top is resisted by a circular tensioned catenary. Only a circular shaped catenary is suitable to resist this load pattern. Similarly, the coupling force at the base is resisted by a compression arch.

Structural concept and realisation

The approach taken by Aurecon and its partners was to maximise lightness by creating a solution that took account of the fundamental requirements of context and function while minimising the impact upstream in extreme flood events. The bridge’s arc provides a smooth transition for cyclists, while allowing the structure to act in tension as a horizontal suspension bridge. 

The structural solution is a unique, horizontal, self-tensioned catenary that incorporates the truss in its design to resist the rotating force induced by the cantilevered deck and the curved truss. 

A 3D parametric model was built that enabled all possible constraints to be tested and allowed for different geometries of the structure to be easily modified. Using parametic modelling instead of traditional methods resulted in a significant time saving. 

Steelwork for the bridge was fabricated in 14 individual modules. Each module was constructed within the fabricators shop in sequential order and a trial of their connection to the next module was undertaken prior to delivery to site. This was important to reduce the risk of misalignment on site and cause delays to the project. The modules were then transported to site to be lifted into position and suspended by temporary chain blocks to allow for future adjustments of the bridge deck. 

Each module was spliced together with bespoke couplers nestled within the depth of the steel members. During the trial test runs in the steel fabricator shop, it was determined that turning each of the couplers simultaneously would be a difficult task to carry out over the river. 

To overcome this, the design team worked with the contractor to develop an innovative, slender split coupler that was capable of resisting the large tension loads. This allowed for each module to be manoeuvred into place with only one coupler requiring adjustment. Once in position, the split couplers were installed and any further minor adjustments were made. 

The success of the approach contributed to the project being named Winner of the Victorian and Tasmanian Australian Steel Awards 2016 for Engineered Structures.