Central Connector

<< Back to Central Connector designs

Grafton Bridge

A major part of the central connector (CC) project is a structural upgrade of Grafton Bridge to provide earthquake resistance and additional load-carrying capability.

The structural and seismic upgrade is not going to change the way Grafton Bridge looks or change its heritage status.

No allowances were made for earthquake resistance in the original design of Grafton Bridge. As the CC's design has developed, so too has the need to bring the bridge in line with modern earthquake design standards. The bridge will be strengthened to withstand a one in 1000 year earthquake.

As well as being an Auckland icon, the bridge is a vital pedestrian and traffic link. Heavy transport (eg vehicles weighing over 13 tonnes) cannot currently use the bridge, following weight restrictions imposed in 1970. The Link buses are currently the only bus traffic able to use the bridge, as they are a lighter design than standard buses.

The structural upgrade of Grafton Bridge will mean it can carry increased bus traffic, and be future proofed to handle new transport technologies, for example light rail.

Work on Grafton Bridge involves:

strengthening the bridge columns, using steel bar reinforcements (a technique also used on the Auckland Harbour Bridge)
strengthening the bridge beams, by applying a carbon fibre material to the existing concrete beams
installing new, reinforced concrete shear keys and deck lineage to resist horizontal earthquake forces
repairing cracks in the existing concrete and removing algal growth, where water has leaked through the bridge joints
applying a "modified cementitous coating" to prevent further corrosion. The coating provides protection from concrete carbonation (which affects most concrete structures)
replacing joints and bridge bearings.
site access from the Symonds Street cemetery is needed to do this work. There will be some scaffolding and some construction vehicles present in the gully at times.

History

Grafton Bridge was built in 1908 and was initially designed to carry horse-drawn traffic, early motorcars and pedestrians. At the time it was built, it was the longest reinforced concrete span bridge in the world and one of the first large concrete structures in New Zealand.

The bridge spans 98m across Grafton Gully, and is 43m above the gully floor at its maximum.

There is no doubt this is an area of important heritage value to Auckland. Careful and meticulous planning has gone into the design to ensure these heritage values are preserved as we work to achieve the CC's transport goals.

Other modifications since the bridge was built in 1908 were also aimed at preserving the bridge for future generations:

major reconstruction of approach beams in 1936
replacing joins and repairing cracks in the 1950s
handrail repairs and concrete coating in the 1990s
glazed canopies added in 2000.

Heritage areas to consider in this area include:

the Symonds Street cemetery, established c.1852, and closed in 1885 (apart for the burial of additional family members. The last burial was carried out in the 1950s.) The cemetery represents a significant collection of 19^th century funerary art and masonry, and survives as an important social record for Auckland, holding the graves of Governor William Hobson and Major George Pitt, as well as many other early Auckland citizens
vegetation in the formerly forested Grafton Gully. Remnants are considered to provide a valuable collection of plant stock, previously evident in the forests that covered the central city area, and typical of woodland cemeteries in the Victorian era
Grafton Bridge, subject to a heritage order under the New Zealand Historic Places Act 1993 and a category A scheduled monument and object of special value in the district plan. The bridge is also considered of international importance as an engineering structure of unique value
the bus shelter and public toilets building on the corner of Symonds Street and Grafton Bridge was built in 1910 and is listed with the New Zealand Historic Places Trust and being scheduled in the district plan.