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The $342 million new Nowra bridge is almost within reach of crossing the Shoalhaven River.

Sixteen of the 19 bridge deck segments have been cast and launched over the 360-metre Shoalhaven River span.

It is hoped segment 17 will be poured this week, weather permitting and the project remains on target to reach the northern side of the river in mid-year.

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Each bridge deck segment, 19-20 metres, requires 360 cubic meters of concrete, equivalent to 60 concrete trucks.

After each segment is poured, the concrete is left to cure and then it is pushed across the river using hydraulic jacks.

During the segment launch, PTFE (Polytetrafluoroethylene, same as Teflon) coated pads are used to help the bridge slide across each of the piers.

Across the project, piling for all 39 piles is complete.

Each pile requires around 45 cubic metres of concrete, equivalent to eight concrete trucks.

All eight pile caps have been installed, with work continuing on the placement of concrete within the last pile cap on the northern side of the river and eight of the nine bridge piers have been completed.

All 39 bridge planks on the new Bomaderry Creek Bridge have been installed and decks poured, with bridge widening work continuing.

Work is also well advanced on Illaroo Road with some of the sealing work now underway.

For all the statisticians out there:

The new bridge will carry four lanes of northbound traffic and the existing concrete bridge (opened in 1981) will be used for southbound vehicles.

The project will eventually provide a new four-lane bridge over the Shoalhaven River and upgrades to 1.7km of the Princes Highway, including upgraded intersections and additional lanes.

The new bridge is needed to replace the existing 1881 wrought iron whipple truss bridge which is in poor shape, has restrictions on over-mass and over-height vehicles, has high ongoing maintenance costs and can only carry highway traffic for a limited time.

The whipple truss bridge will be retired from road use and repurposed after the new Nowra Bridge opens.

An announcement on the future use of the bridge is expected in the next couple of months.

ACM was given a behind-the-scenes look at the bridge's construction, including access under the bridge as the massive deck segment, which weighs around 1500 tonnes, was launched into place.

Two Powerful hydraulic jacks, one on either side of the deck structure, are used to push the deck into place, onto the top of the V-shaped piers.

Massive bearings on each pier allows the deck to slowly move into position, sliding over special low-friction pads.

The deck segments are launched from the southern side, with the whole bridge progressing in turn, moving 20 metres at a time.

Mind you, moving that 20 metres can take up to four hours, and you really can't see the segment actually moving - it only moves between 200 and 240 millimetres at a time.

Transport for NSW Nowra bridge project manager, Ryan Whiddon, said once completed the bridge will weigh around 28,000 tonnes.

"Each time the bridge segment is moved the jacks lift the structure up 18 millmetres and it is then slowly moved forward between 200 and 240mm before the bridge is lowered, the jacks retract and the whole process is repeated again and again," he said.

Each deck segment requires 360 cubic metres of concrete, equivalent to 60 concrete trucks.

"The bridge is attached to one main superstructure. When we cast each segment, it's attached to the segment before," he said.

The next deck segment is ready to be cast, while the metal reinforcement of the superstructure of the following segment is already being constructed.

That gets dragged into the mould at the same time as the bridge segment progresses.

While each segment usually takes around two weeks to be completed, cured and moved into place, the final one will actually take around four weeks as it has extra work that has to be completed.

"We have gone with the incrementally launched methodology in this bridge because it is a lot safer to build the bridge on land than over the waterway," Mr Whiddon said.

"By building everything on land when the bridge is launched over the river we have our hand rails in place for the safety of workers, our other safety systems are also in place and our work is all done at a lower working at heights profile."

The massive stainless steel bridge bearings on each pier, which come from Italy, transfer the load through from the superstructure (the decks and spans on top) of the bridge, to the substructure of the bridge (piers and piles below), transferring the weight down to the bedrock below, which is about 55 metres below the water level.

Each bearing currently has a mirror-polish finish stainless steel sliding plate to allow the structure to easily be moved into place.

Once the bridge is fully completed and in position, the structure will be jacked up on each bearing and the sliding plate removed and replaced by a permanent plate.

The bearings are designed to last the 100-year lifespan of the bridge and are massive when compared to the two bearings on each pier of the adjacent existing concrete bridge.

Although the new bridge will only be four lanes wide, it has been engineered and constructed to be able to take up to the weight of six lanes of traffic.

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Robert Crawford is a senior journalist at the South Coast Register, for Australian Community Media . Everyone's got a story, what's yours? Email robert.crawford@austcommunitymedia.com.au

Robert Crawford is a senior journalist at the South Coast Register, for Australian Community Media . Everyone's got a story, what's yours? Email robert.crawford@austcommunitymedia.com.au

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