CCNZ / HIREPOOL CONSTRUCTION EXCELLENCE AWARDS 2015
‘Weathering steel’ bridges cement river’s sparkling reputation In 2014, a rickety pair of timber bridges on the Waitaki River bowed out after 132 years of service. In their stead emerged two magnificent ‘weathering steel’ constructions – a first for the South Island that will keep locals and tourists well serviced for another century.
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CONSTRUCTION EXCELLENCE AWARDS 2015
WINNER CATEGORY 3
PROJECT: Waitaki Bridges Replacement, Otago CONTRACTOR: McConnell Dowell
34 Civil Contractors NZ in association with Contractor magazine
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he $20.1 million road bridges (with pedestrian walkways) connect the hamlets of Kurow and Hakataramea. Built and engineered by civil construction firm McConnell Dowell, bridge design was courtesy of URS with geotechnical expertise from Tonkin & Taylor. McConnell Dowell’s engineering solution had to account for the variable nature of the Waitaki River. This body of water experiences high water flow and is prone to flooding. Under the hood of the bridges are piles that consist of 1.8 metre diameter concrete filled cylinders. Positioned along the length of both bridges, the piles are driven to a depth of 22 to 25 metres. They connect to bored concrete piers with moment transfer below river bed level. Project superintendent Mike Simpson says the piling solution supports granular river bed materials and is large enough that natural obstructions can be broken up and removed. Topping off the ‘steel ladder’ bridge construction are precast concrete planks and in-situ concrete decks. The upshot is two bridges that are arguably stronger than the eddies swirling beneath them! Uniquely, beams and decks are high strength ‘weathering steel’, especially sourced from China. Mike says these form a protective rust patina to almost eliminate corrosion. “The rusting process starts in the same way as conventional
