As part of the
NZ$500m Auckland Electrification Project,
which delivered an electrified rail network
to Auckland, KiwiRail commissioned WSP
to design the replacement of five bridges:
Browns Road, Jutland Road, Station-Lupton,
Morrin Road and Mt Wellington Highway
Road Bridges, which carry local roads over
the North Island Main Trunk (NIMT) rail line.
Innovative solutions were developed based
around the concept of using Accelerated
Bridge Construction (ABC) principles to
minimise the bridge construction periods
and associated disruption to road and
rail users. This involved the extensive
use of precast elements with innovative
techniques to connect the precast
To minimise the associated road works and
avoid resource consent triggers, slender
construction techniques were used for
the design of the bridge decks, including
a conventionally reinforced 325mm deep
twin portal and fully integral and simply
supported beams with slenderness ratios of
35 and 32 respectively.
The numerous stakeholders included local
boards and service providers, with Auckland
Transport, owners of the bridges requiring
replacement, as the key stakeholder.
Auckland Transport also represented the
interests of the local communities.
As the key stakeholder, Auckland Transport
was integrated into the project team and
worked collaboratively with KiwiRail and WSP
to determine best-for-project solutions. One
of Auckland Transport’s major requirements
was for the bridges to be widened to either
allow for separated cycle lanes or future proof
for planned route widening.
As Mt Wellington is a major arterial route and within 200m of SH1,
Auckland Transport required the project to maintain a minimum
of three operable lanes for the duration of the works, with the
exception of the Christmas weekend where this could be reduced
to two lanes.
For all bridges, except Mt Wellington Highway, Auckland
Transport was agreeable to using accelerated construction
framework with full road closure for the duration of the bridge
replacements, which was between 4-7 weeks.
Due to the close proximity of Browns, Jutland and Station-Lupton
Road Bridges to each other, only a maximum of two bridges
could be taken out of service at any one time.
Constructability through design was the key to the successful
delivery of this project and minimising any errors was
paramount. A decision was taken early on in the project to three
dimensionally model all of the bridges which provided extra
certainty that the dimensions of the precast elements were all
correct and allowed the project team to provide exact set out
information for individual bars where required. They also provided
the constructor with a visualisation of what they were to build.
A further step to increase the transfer of knowledge and
understanding on this project was the creation of detailed
construction sequence drawings. This allowed the constructor to
plan their resources appropriately and comprehend the design
philosophy of the structures.
WHAT SUCCESS LOOKED LIKE
Accelerated Bridge Construction was fundamental in achieving
KiwiRail’s project objectives of minimising cost and disruption,
while maintaining the highest standards of environmental and
health and safety principles.
The key to the success of the ABC design philosophy on
the project was the ability of the design team to integrate
constructability within the design solutions, and forming a
collaborative working relationship with the constructor.
The most innovative and impressive element of the project is the
detailing of a fully integral connection using ABC technology.
Integral bridges are normally considered more time consuming
to construct than the more conventional simply supported
structures. Given the whole of life benefits from removing bridge
joints and bearings this is an area of focus for New Zealand bridge