Newmarket Viaduct
Encyclopedia
Civil engineering
Civil engineering is a professional engineering discipline that deals with the design, construction, and maintenance of the physical and naturally built environment, including works like roads, bridges, canals, dams, and buildings...
features' of New Zealand
New Zealand
New Zealand is an island country in the south-western Pacific Ocean comprising two main landmasses and numerous smaller islands. The country is situated some east of Australia across the Tasman Sea, and roughly south of the Pacific island nations of New Caledonia, Fiji, and Tonga...
, is a six-lane State highway
New Zealand State Highway network
The New Zealand State Highway network is the major national highway network in New Zealand. Just under 100 roads in both the North and South Islands are State Highways...
viaduct
Viaduct
A viaduct is a bridge composed of several small spans. The term viaduct is derived from the Latin via for road and ducere to lead something. However, the Ancient Romans did not use that term per se; it is a modern derivation from an analogy with aqueduct. Like the Roman aqueducts, many early...
in Auckland
Auckland
The Auckland metropolitan area , in the North Island of New Zealand, is the largest and most populous urban area in the country with residents, percent of the country's population. Auckland also has the largest Polynesian population of any city in the world...
, the country's largest city. Carrying the Southern Motorway
Auckland Southern Motorway
The Auckland Southern Motorway is the major route south out of the Auckland Region of New Zealand. It is part of State Highway 1....
over the Newmarket
Newmarket, New Zealand
Newmarket is an Auckland suburb to the south-east of the central business district. With its high building density, especially of retail shops, it is considered New Zealand's premier retailing area, and a rival of local competitor Auckland CBD...
suburb area southeast of the CBD of the city
Auckland CBD
The Auckland CBD is the geographical and economic heart of the Auckland metropolitan area. Bounded by several major motorways and by the harbour coastline in the north, it is surrounded further out by mostly suburban areas...
, the 700 m long viaduct is up to 20 m high in places. Due to concerns about its ability to withstand earthquake
Earthquake
An earthquake is the result of a sudden release of energy in the Earth's crust that creates seismic waves. The seismicity, seismism or seismic activity of an area refers to the frequency, type and size of earthquakes experienced over a period of time...
s and its increasing inability to cater for peaktime traffic demand, it is being replaced with a stronger and wider structure over several years, starting in 2009.
History
Original structureThe viaduct was finished in 1966 for NZ$2.26 million, and was constructed as New Zealand's first pair of balanced cantilever bridge
Cantilever bridge
A cantilever bridge is a bridge built using cantilevers, structures that project horizontally into space, supported on only one end. For small footbridges, the cantilevers may be simple beams; however, large cantilever bridges designed to handle road or rail traffic use trusses built from...
s. With its long spans, the s-curvature and the varying superelevation of the motorway, it is a complex structure even today, and at the time was ground-breaking design for New Zealand.
While considered a successful design, it was built to far lower earthquake standards than which other New Zealand structures now fulfill, being built to survive only a 1 in 500 year return period
Return period
A return period also known as a recurrence interval is an estimate of the interval of time between events like an earthquake, flood or river discharge flow of a certain intensity or size. It is a statistical measurement denoting the average recurrence interval over an extended period of time, and...
earthquake. It could have received significant damage in an earthquake as common as once in 200 years. This made the structure the weakest strategic transport infrastructure link in the Auckland area, with a potential collapse cutting off all motorway transport to the South. Also, during design, temperature stresses
Creep (deformation)
In materials science, creep is the tendency of a solid material to slowly move or deform permanently under the influence of stresses. It occurs as a result of long term exposure to high levels of stress that are below the yield strength of the material....
were not yet understood to a sufficient degree, leading to increased wear on structural elements.
The limited earthquake stability, together with increasing traffic demands (over 200,000 vehicles a day, more than on the Auckland Harbour Bridge
Auckland Harbour Bridge
The Auckland Harbour Bridge is an eight-lane box truss motorway bridge over the Waitemata Harbour, joining St Marys Bay in Auckland with Northcote in North Shore City, New Zealand. The bridge is part of State Highway 1 and the Auckland Northern Motorway...
and the most traffic on a section of road anywhere in New Zealand), led to the planning for a new viaduct structure, which will be able to withstand an earthquake with a 2,500 year return period. Other factors were the very low safety barriers (which once allowed an out-of-control truck to fall onto its roof 15 m below, in 2004), which are also insufficient to prevent debris from falling onto the properties beneath, and the fact that the existing viaduct is a prohibited route for overweight vehicles, forcing more trucks through the city streets.
Major maintenance of the existing structure was also considered as an option. However, the structural elements of the existing viaduct did not lend themselves to easy strengthening, and even a reconditioned viaduct would only have provided an estimated life expectancy of 40-50 more years. With a proposed new structure costing only around 15% more than a repair, and expected to last for over 100 years, it was decided to go for a full replacement.
Proposed structure
The new Transit New Zealand
Transit New Zealand
Transit New Zealand was, from 1989 to 2008, the New Zealand Crown entity responsible for operating and planning the New Zealand State Highway network...
structure is estimated to cost NZ$ 150 million, and cleared planning hurdles
Resource consent
A resource consent is the authorisation given to certain activities or uses of natural and physical resources required under the New Zealand Resource Management Act . Some activities may either be specifically authorised by the RMA or be permitted activities authorised by rules in plans...
quicker than expected, leading to hopes that it would be possible to build it in time for the 2011 Rugby World Cup
2011 Rugby World Cup
The 2011 Rugby World Cup was the seventh Rugby World Cup, a quadrennial international rugby union competition inaugurated in 1987. The International Rugby Board selected New Zealand as the host country in preference to Japan and South Africa at a meeting in Dublin on 17 November 2005...
. Originally, the three-year duration project was expected to start in 2009/2010. Factors that influenced the quick decision process were the lack of any archeological evidence in the construction area, as well as the lack of substantial numbers of residential properties affected by the new structure.
The new structure will be built in a way to minimally affect the traffic flow on this crucial motorway link, by first constructing a new viaduct of four southbound lanes to the north-east of the existing structure, then demolishing the existing three southbound lanes, before constructing the three new northbound lanes in the gap and finally demolishing the three old northbound lanes. It was originally considered whether to build a 'steel box' or a 'concrete box' structure, though both would look similar to the existing viaduct structure. It was eventually decided to construct a segmented structure built from 468 pre-cast concrete sections constructed off-site in East Tamaki
East Tamaki
East Tamaki is a suburb of Auckland, New Zealand. This is a mixed residential, light industry and retail area which is growing rapidly. Prior to the 1960s this was largely a dairy farming area. A landmark is Smales Mountain which in 2010 has the remains of an old Pa, a stone field garden, an early...
, and moved into place with a lifting gantry truss.
Tonkin & Taylor and URS New Zealand, as part of the Northern Gateway Alliance, have been assigned to develop the new bridge, and one of their design targets includes full recycling of all material during the project. The consultant team is also to use the experience gained at the Waiwera Viaduct in this new project. However, estimated costs in June 2008 had risen to NZ$187 million, and was unclear whether the funds can be made accessible quickly enough to achieve the ambitious schedule of finishing the bridge in time for the 2011 World Cup. In October 2008, funding was confirmed, but the estimated price has now increased to NZ$195 million, with rising prices for fuel, construction materials and labour cited as the reasons. While still ahead of schedule, only part of the viaduct replacement is expected to be completed in time for the Rugby World cup in 2011.
The new viaduct will feature better noise protection for the surrounding communities, thanks to noise-absorbing asphalt, solid concrete crash barriers, and partial noise walls. Some further urban design improvements will also be part of the project, such as a volcanic-themed walkway from Gillies Avenue down towards Newmarket (connecting to Clovernook Road).
Construction
Construction began in earnest in April 2007, with the first foundations for the up to 18m high piers of the southbound part of the new viaduct. A bracing structure under the section carrying over the railway line was established over Easter 2009, and a 140m long, 800 ton heavy launching gantry was erected above the Newmarket skyline, which will move into place new sections and stabilise parts to be demolished (with the demolition considered the most difficult part of the project). The southbound addition is to be finished by the end of 2010, while the northbound section will likely take at least until March 2012. During construction, sight screens will reduce visual distractions of passing drivers, though the construction will still require narrowing of the traffic lanes and reduction of the maximum speed on the viaduct to 70km/h. A number of temporary support girders around the structure will also be required to safely cater for the stresses put on the structure while parts of it are demolished and rebuilt.
Construction will involve building the new southbound viaduct first, then demolition of the old southbound viaduct, followed by the construction of the new northbound section in the resulting gap, before the old northbound section is finally demolished. This will ensure that except for short interruptions, normal motorway capacity will remain available throughout the construction period. After this, further work will also take place around the viaduct, including the construction of a volcanic-themed walkway from Gillies Avenue to Broadway (via Clovernook Road) and an upgraded footbridge over State Highway 1 at Mt Hobson Road.
The new viaduct will be composed of 468 separate bridge deck sections, produced in a precast
Precast concrete
By producing precast concrete in a controlled environment , the precast concrete is afforded the opportunity to properly cure and be closely monitored by plant employees. Utilizing a Precast Concrete system offers many potential advantages over site casting of concrete...
facility in East Tamaki
East Tamaki
East Tamaki is a suburb of Auckland, New Zealand. This is a mixed residential, light industry and retail area which is growing rapidly. Prior to the 1960s this was largely a dairy farming area. A landmark is Smales Mountain which in 2010 has the remains of an old Pa, a stone field garden, an early...
.
Over 150 people are employed directly by the project.
External links
- Newmarket Connection (official project website, NZTANew Zealand Transport AgencyThe New Zealand Transport Agency is a New Zealand Crown entity tasked with promoting safe and functional transport by land, including the responsibility for driver and vehicle licensing and investigating rail accidents. It was created on 1 August 2008 by the Land Transport Management Amendment...
) [District Plan Modification 193] (required for the new viaduct, includes various related reports, Auckland City CouncilAuckland City CouncilAuckland City Council was the local government authority representing Auckland City, New Zealand, and was amalgamated into the Auckland Council on 1 November 2010. It was an elected body representing the 404,658 residents of the city...
)