The $342 million new Nowra bridge remains on track to be across the Shoalhaven River by the middle of the year.
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The final V-shaped pier on the northern side of the river was completed on Wednesday, with the finishing touches just needing to be put in place on the top.
The South Coast Register was lucky enough to be 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.
"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.
Around 25 people are involved in each deck launch - headed by the hydraulic jack driver - there are also workers at each large bearing on each pier where the non-friction mat is continually fed through.
"The structure slides over the pad, it comes out the front side, the workers walk it around to other side feed it back through - the sliding surface is also painted in grease," he said.
"The low-friction pads are essential to allow the bridge to slide easily into place."
They are so slippery, launching can't be undertaken in heavy winds "as the bridge could just slide off".
"We have large guides on each side which hold the bridge in place," Mr Whiddon said.
Incredibly during the launching process the team can actually "slightly steer" the bridge.
"The bridge will wobble a bit and the guys on every second pier and mainly the advancing pier are able to steer and guide the structure to ensure it's going in the right direction," he said.
"Alternatively we can increase or reduce pressure from either of the jacks as required, which can also direct the structure."
When each launch is finished the bridge is locked into position by the friction pad behind the hydraulic jacks on the southern side of the river and the side guides hold it in place.
"That way it can sit there in all types of wind conditions," Mr Whiddon said.
Underneath the bridge deck, it was amazing to see the size and curve on the structure which will also aid in drainage.
When completed, all water run off from the bridge will be captured and treated before being returned to the river system.
While watching the construction, if you've wondered what the blue and white metal structure heading the northern end of the bridge is?
It's known as the launching nose - its role is to reduce the weight of the travelling structure to allow it to safely reach the next pier.
"Imagine the segments, each 1500 tonnes they have the capability of starting to deflect and could run into the pier instead of being on top," Mr Whiddon said.
"The launching nose's length is three quarters of the span, so it takes the load to allow it to reach the next pier comfortably.
"When the bridge gets into final position, we remove the launching nose."
The launching nose comes off in three segments, with one segment removed each time one of the final three deck pieces are put in place.
Meanwhile, while the decks are being finished, work is continuing around the site.
The installation of the road separation barriers and the pedestrian traffic on the bridge decks has begun, while pavement layers have started on Illaroo Road, with locals getting a final view of what the road's profile will look like.
Work has started on the removal of the 22,000 tonne rock platform around the southern piers.
The 130m long and 45m wide platform, affectionately known as "Fulton Hogan Island" is being removed and the rocks being sorted at the southern end of the project site and will eventually be reused in other areas of the project.
And once the final decks are in place, work will begin on building up the roads on either end of the bridge.
A bridge is like a living structure
Did you know that bridges are often compared to living structures?
All bridges wobble, in fact if you sit stationary in traffic on either of the older Nowra bridges, you can feel movement.
"All bridges move," Mr Whiddon said.
"Most people don't realise it because you don't often come to a stop on a bridge.
"If a large truck comes across this new bridge at the same time you might feel it, but it will wobble less than the concrete bridge and a lot less than the old Whipple truss bridge.
"Bridge structures are like a living structure - they are designed for the movement and need that movement.
"Why a lot of bridges, particularly the timber bridges when we take traffic off them, deteriorate a lot quicker is because they don't have that movement.
"They need movement to keep them in that working order and condition.
"Even the action of traffic running across a road, removing general leaf litter is an advantage. It can lead to less deterioration of the structure."
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Robert Crawford
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
