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Visitor information
Overview
This project is currently in the concept design stage.
Hornsby Park, Sydney, Australia comprises approximately 60 hectares of bushland and open space, about 1 kilometre west of the Hornsby town centre.
This site is home to several historical features and community activities, including early settler relics, the State Heritage listed Old Mans Valley Cemetery (Higgins Family Cemetery), remnant buildings of the quarry crusher plant and the existing upper Hornsby Park and Hornsby Aquatic and Leisure Centre (HALC).
The inactive quarry is in the Hornsby Diatreme, a unique geological feature that’s been studied by universities as one of the best examples in the country. Very few people have had the opportunity to appreciate its astonishing beauty and the natural bushland surrounding it. Transforming the site into a major recreational destination will allow residents and visitors to enjoy the stunning landscape, ecological communities and history that make this location so special.
The park offers every opportunity to be an attraction not only for the people of Hornsby, but the wider community.
As part of the council’s Hornsbyu Park Master Plan, it is installing a canopy sky walk, southern lookout, and this cable bridge.
A 2.4-metre-wide canopy sky walk and cable bridge will connect Hornsby Town Centre to the crusher plant precinct on a fully accessible pathway immersing visitors into the bush.
The canopy sky walk and cable bridge will sit approximately 25-30 m above the ground and will cover a total distance of approximately 400 m.
Hornsby Cable Bridge location
The bridge site is located 200m south-east of the existing Hornsby Quarry void.
Technical information
We consider a suspension bridge the most suitable bridge form because it suits the long span of the crossing and makes use of the readily available rock strata for anchoring.
We have designed a 160 m span x 2.4 m wide suspension footbridge.
We are proposing to use a 33 m steel mast at the western end and a 39 m steel masts at the eastern end of the bridge. The circular hollow section (CHS) steel masts will be formed from four legs which appear to splay open by an angle of circa 6 degrees from pier centre.
We believe these are consistent with the intention of the Clouston Associates RFT concept with some modification. These are more economic to fabricate, more robust, and minimise the overall footprint and thus the ecological impact of the piers. We also believe our proposed configuration is architecturally more consistent with the original “abstract tree” used to depict the bluegum high forest.
Superstructure
The superstructure will consist of three steel parallel flange channel (PFC) stringers spanning onto steel universal beam (UB) cross beams positioned at 1500 mm horizontal increments along the span.
The UB cross beams will be supported by spiral strand hangers spaced at 3 m along the bridge span and affixed to the cables with cable clamps.
The superstructure features equal angle plan bracing arranged in a Pratt truss configuration to span between the wind stay fixing points. The plan bracing enables load to span between wind-stay fixing locations and mast restraints.
Suspension cables
The superstructure will be suspended from the masts using high strength Redaelli™ fully locked coil (FLC) suspension cables. The cables will be connected to the masts with proprietary cable forks.
The cables will be coated with 5% aluminium + 95% zinc (AKA Galfan or Bezinel) to optimize durability. This system has been preferred over stainless steel because it proves a significantly more economical solution whilst still achieving a full 100 year design life for the assessed C2 corrosion category.
FLC cables have been preferred over spiral strand as they offer improved corrosion performance and axial stiffness compared to open spiral strand (OSS), with negligible increased cost.
FLC Galfan coated parabolic wind cables connected to cross beams via transverse wind-stays restrain the superstructure in the lateral direction. They also have a vertical component to help stiffen the overall superstructure and help control vertical vibration and improve overall user comfort.
Using a parabolic wind stay system – rather than multiple lateral wind ties anchored directly to the ground – significantly minimises the number of wind stay footings required and therefore the detrimental ecological impact.
Minimising impact to trees
Our goal is to minimise the removal of trees when installing the parabolic wind stays.
To help with this, we will peg out locations on site before clearing work starts, including all parabolic wind cables, lateral wind-stays, and backstay cables. Then, with the client and construction team we will walk through on site to determine and document how many trees might be affected.
Because the parabolic system is flexible in its geometry, we can adjust locations within reason to limit impact to trees.
Key partners
We would like to thank the following organisations for their help and support in getting this project off of the ground.
