NZ bridge uses stainless steel

KiwiRail design the first bridge in New Zealand to use stainless steel reinforcement.

During 2009 KiwiRail New Zealand identified the need to replace the Ngauranga Gorge Rail Bridge between Wellington and Petone.

All rail traffic on the Wairarapa Line between Masterton and Wellington, along with the high volume of local commuter trains must pass over this bridge. Rail traffic on the North Island Main Trunk Line can occasionally be diverted onto the Wairarapa Line and will also need to utilise this bridge.

This bridge allows for the out flow of the Ngauranga Stream into the Wellington Harbour, and is situated in a tidal zone.

Infrastructure assets such as bridges require a 100 year design life. Having seen the costly effects of concrete spalling first hand, KiwiRail recognised the potential life cycle costing benefits of using stainless steel reinforcing bar (rebar) for this project.

Tata Steel NZ provided technical and design evaluation information from European producer Outokumpu Stainless, and various industry organisations to assist KiwiRail with their decision making. After considering their options, Outokumpu’s lean duplex grade LDX2101 was specified.

Tata Steel NZ supplied a total of 57 tonnes of stainless steel reinforcing bar and tie wire for the project. The bulk of the material was supplied from European mill stocks and production in straight lengths for processing in New Zealand, with the balance being sourced from Australia’s specialist stainless steel rebar processor Lyndon’s Durinox, who cut and bent the material to specification.

Client: KiwiRail
Bridge Designer: Novare Design
Stainless Steel Rebar Supplier: Tata Steel NZ
Reinforcing Bar Processors:Lyndon’s Durinox

Steel & Tube Reinforcing
Pre-Cast Culvert Manufacturer:Humes Concrete
Construction Contractor:Brian Perry Civil
Post Tensioning:BBR Contech
Watch this site for construction updates.

Stainless steel is 100% recyclable, with a typical recycled content of 60 – 70%. This high level of recycled content has no adverse effect on mechanical properties or corrosion resistance. Stainless steel requires no coatings, is inherently fire resistant, and will not give off toxic fumes in a fire.