Since the opening of Sea Cliff Bridge in December last year the bridge itself has become a major attraction for visitors to the Illawarra including drivers, cyclists and pedestrians.
Sea Cliff Bridge was originally designed to include a 2.5metre wide shared pedestrian /cycleway as a local connection between the villages of Coalcliff and Coledale. However, the unprecedented use of the pedestrian/cycleway has highlighted the need for the Roads and Traffic Authority to review the way the bridge accommodates all users, and in particular pedestrians and cyclists.
As a result of these investigations several changes will be made to improve safety for pedestrians whilst still accommodating cyclists.
Facilities on the bridge will be enhanced by:
providing a signposted footpath instead of a shared path. This will minimise the potential conflict between pedestrians and cyclists, whilst still allowing children (under 12) and cyclists supervising children to use the path.
removal of the rub rail on the back of the barrier dividing the footpath from the road, creating an additional 400mm space for pedestrians to further widen the footpath.
providing two 1.2m wide shoulders on the bridge marked for cyclists. The bridge line marking will be changed to reduce the width of the vehicle lanes and increase the width of the shoulders to allow cyclists to stay on the roadway.
removing the raised edge line markers to reduce the road hazard for cyclists.
adjusting the drainage grates to sit flush with the road surface to allow on road cyclists to use the full shoulder.
These works will increase safety for both pedestrians and cyclists by providing a widened shoulder allowing cyclists to stay on the road and avoiding conflict with pedestrians.
These changes will be implemented by the end of September 2006.
Project overview
Lawrence Hargrave Drive was closed in August 2003 to allow the construction of a more permanent solution to the rock fall problem that has plagued this section of road for more than a century.
The section including the new Sea Cliff Bridge was reopened on 11 December 2005.
The new Sea Cliff Bridge
The new Sea Cliff Bridge has two 3.3 metre-wide lanes with 1.2 metre-wide shoulders. A separate footpath has been built next to the traffic lanes on the eastern (seaward) side. The two-lane bridge spans the southern amphitheatre and the middle headland.
Sea Cliff Bridge is made up of two sections using different construction techniques. A balanced cantilever section (similar to the Mooney Mooney and Pheasants Nest bridges) extends from the existing road at the southern headland and curves to join an incrementally launched section (similar to the Woronora Bridge). This joins the existing road at the middle headland.
The bridge, to the east of the existing road, provides a long-term solution for all road users. The project also includes various geotechnical and stabilisation works along the cliff line.
The balanced cantilever section
Using the cantilevering method, the superstructure of bridge is built from the piers by means of cantilevered formwork. The structure advances (symmetrically) from a short stub on top of each pier in segments of about 3 m to 5 m length to the mid span or to an abutment. Using this technique allowed building out over the sea without the need for supporting formwork.
Bridge features include:
Curved, 455 metre long balanced cantilever bridge along the coastline.
Built up to 45 metres to the east of the existing road to bypass the unstable cliff line and rock falls.
Road level 41 metres above the sea level at its highest point.
Four piers and five spans – first and last 70 metres long with central spans 105 metres long.
The incrementally launched section
The incremental launching method consists of casting 15 metre to 30 metre long sections of the bridge deck at the northern bridge abutment. The completed section was then pushed out across the piers and the next section was then cast onto it. The bridge deck slowly advanced south with the first section having been pushed the full length of the bridge.
Features of bridge include:
Multiple span curved 210 metre long bridge bypassing the middle headland to join the balanced cantilever bridge.
Built 25 metres east of the existing road.
Seven piers and seven spans, the first 24 metres and the others 31 metres long.
Slope stabilisation and road works
Slope stabilisation included rock removal, rock bolting and meshing.
Loose rock and weathered seams on the cliff line were stabilised.
A rock overhang above the existing road on the northern headland was removed.
A catch ditch and diversion banks to divert any rock falls and mudflows away from the road were constructed.
The new pier locations and sections of retained road are protected from undercutting and further regressions by rock armouring and sea wall along the coastline.
Other features of the design
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