Ferrymead Bridge

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INFRASTRUCTURE AWARD - Commendation

Ferrymead Bridge, Christchurch

 

Submitted by:  Opus International Consultants

Owner:  Christchurch City Council

Consulting Engineer:  Opus International Consultants

Contractor:  HEB Structures

Sub-contractor:  BBR Contech

 

Summary:

The original Ferrymead Bridge was extensively damaged following the 2010 – 2011 earthquakes. The strategic bridge, located on a primary lifeline route, needed to be replaced quickly with a robust structure resilient to ongoing earthquakes and an aggressive marine environment.  This location presented a most challenging bridge site, with highly liquefiable ground to 25m depth, steeply dipping bedrock and complicated by strong basalt interspersed with weak pyroclastic deposits.

Opus conceived a two span reinforced concrete bridge supported by reinforced concrete piles cement grouted into the underlying rock.  The innovative development and use of a pressure grouted pile – rock interface using Tube-a-Manchette methods was fundamental to safely achieving the seismic resilience required, in an active seismic environment.  The risks arising from the active seismic environment were carefully assessed and managed by programming the sequence of pile construction and providing temporary props, before completion of the superstructure.

High seismic demands resulted in heavily congested reinforcing pushing the boundaries of concrete and were overcome by using self-compacting concrete with fly ash for the pier headstock.  Concrete and deterioration modelling based on the previous bridge’s performance ensured durability and optimum cost for the new design.Overcoming obstacles through innovation, design excellence and close collaboration with HEB and their specialist subcontractor resulted in significant risk reduction and client savings.

 

What the judges said:

Providing a resilient replacement bridge for this ‘lifeline’ arterial route required some special design and construction considerations.

With a foundation comprising highly liquefiable ground to 25m depth and steeply dipping bedrock with variable composition, there were some complexities to deal with.

The two-span bridge contains innovative pile construction technology that firmly sockets the piles into the underlying rock to resolve this challenge – thought to be the first application of contact grouting of pile sockets in New Zealand.  The central pier is located clear from either river bank, providing a robust superstructure and piers resistant to lateral spreading.

Special concrete design and detailing further enhances the robustness and durability of the structure.   With a focus on safety from seismic events both during construction and in the future, the design and construction innovations of this elegant bridge have ensured that this road will remain a functional and important piece of lifeline infrastructure.