10 steps to build new Grafton bridge
ROADS and Maritime Services have released a breakdown of the construction process for building the second river crossing at Grafton - broken down into ten steps.
- The $240M project helping bring Grafton back to life
- REVEALED: Construction timeline for new Grafton bridge
- EXPLAINED: Bridge design changes to improve flood mitigation
- VIDEO: Take a virtual tour across the new Grafton bridge
For more information on the project, visit: www.rms.nsw.gov.au/graftonbridge
Piling is done by drilling deep into the ground (to solid rock), this hole is then filled with reinforced concrete to give a strong foundation for the new structure.
A temporary jetty will also be built to allow for precast bridge girder sections to be loaded onto a barge for transportation to the river.
The size of the bored piles will range from 1.2 metres for land-based piles, up to three metres for river based piles.
Five foundations will be built in the river, and five on land.
Permanent steel casings will be placed from the pile at the base of the river, to above the water line to allow for concrete columns to be formed in the river.
Steel reinforcing bars can be seen protruding from the piles. These will help to form the connection between the river piles and the piers that hold the bridge above the water.
The piers provide a structural connection between the foundation in the river and the bridge above.
This will start with tying reinforcing steel for inside the concrete pier.
The shape of the piers has been chosen as similar to the existing crossing, so as not to detract from the heritage and status of the steel truss bridge.
This will then be filled with concrete, the shutters removed, and final connection to the bridge box girder sections prepared.
This will be performed by a large tracked crawler crane, located on the river barge.
Workers near the top of the pier will help to guide the segment safely into position.
With the first girder secured, thick steel cables are threaded through, ready for the next piece.
Essentially, this means that the bridge will have the precast girder sections from the barge, installed on alternating sides of the pier to balance the load over the pier.
The girder sections will be tied together using the thick steel cables, and stressing the cables between adjoining sections.
Super-T girders have been chosen on the outer spans to maximise clearance to Greaves Street on the northern side and to provide flood capacity on the southern side.
Seven Super-T girders will be placed side-by-side to form the span and a deck poured on top to match the top surface over the bridge.
Finally, the bridge will be completed with an asphalt surface, new road barriers, lighting, signage and line marking.