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Overview
This bridge design is proposed to span the Waiohine River, as part of the Wairarapa Five Town Trail Network.
The design has been developed for Carterton District Council to better understand the best options and costs associated with connecting project the towns of Carterton and Greytown via cycle and trail.
The challenge was to design a single-span bridge to accommodate cyclists and walkers and also withstand a river known for its high flood levels.
To solve this, we designed a single-span suspension bridge with an upward curve. This design gives the bridge maximum clearance from floods and keeps the path clear for cyclists and walkers, without needing any piers in the river.
Getting there
Technical information
Superstructure design: The superstructure is suspended from high-strength Redaelli fully locked coil (FLC) cables, which are coated with a 5% aluminium + 95% zinc alloy for durability. The deck uses a proprietary, lightweight, and low-maintenance anti-slip FRP decking system with integrated anti-slip coatings.
Stabilisation: Parabolic wind cables restrain the superstructure laterally and help to stiffen the bridge. The bridge is longitudinally pinned at the southern end and free to slide at the northern end to accommodate movement.
Live load optimisation: We achieved a significant 35% reduction in live loading compared to conventional standards. This resulted in a direct saving on the cables, masts, and foundations.
Flood resilience: The bridge’s positive camber and a 1.2-m freeboard prevent floating debris from striking the structure.
Pedestrian safety: The design actively mitigates a phenomenon called “lateral lock-in”, where a bridge’s natural frequencies can cause it to oscillate dangerously. Our analysis used pre-stressed wind ties to ensure the bridge’s design falls outside this sensitive frequency range.
Safety: The bridge features wheel stops on either side of the deck to add safety for cyclists, wheelchair users, and small children.
Key specs
Type: Suspension bridge
Span: 155 m
Deck width: 1.23 m
Masts: Steel masts with a height of 5m
Balustrade: 1.2-m high with galvanised tubular rails and stainless steel wire rope infill
Key partners
We would like to thank the following organisations for their help and support in getting this project off the ground:
