Construction of the largest and one of the most complex bridges under taken by Civilbuild is nearing completion.
The bridge is being built for Xstrata at their Liddell coal mine to carry massive coal trucks, excavators and other heavy machinery over the main northern railway line.
The position of the bridge and its design posed project engineer Frank Rossi and his team with innumerable challenges but all have been solved and the project will be completed on time.
The three span bridge is 44 metres long, 34 metres wide and designed to carry the weight of an 850 tonne excavator.
It consists of 56 girders, 18 super T girders per span and jersey parapet kerbs each 1.9 metres high to absorb the impact load.
All these components were built at Civilbuild’s pre-cast yard at Redhead.
The bridge is held in place by dead man anchors and 14 tie rod ends, stressed to 50 tonnes each.
The majority of traffic using the bridge will be large dump trucks, each weighing 500 tonnes when fully laden.
“Every scenario had to be looked at when designing and building this bridge including the worst case,” Frank said.
“The worst case scenario put to the engineers was a situation where the bridge was covered end to end with fully loaded coal trucks unable to be moved.
“The bridge has been designed and built to withstand those pressures.
“It has also been built to withstand the vibration forces from mine blasting nearby and that has required additional features not normally found in a bridge.”
Those problems were overcome with the sophisticated construction techniques available these days.
One of the real headaches for Frank and his team was construction over the busy rail line and fi tting into a tight time frame dictated by State Rail.
“Every three months the line is closed for three or four days for maintenance and those were our only windows of opportunity to work close to the line,” Frank said.
“We had to lift specially designed super T girders across the line and get them into position and to do that we had to bring a 400 tonne crane from Port Kembla.
“Everything had to dovetail from making sure the crane arrived and was in position on time to ensuring there were minimal delays in getting the girders into position.
“If we had not completed the work on time we would have had to wait another three months and that was just not on.
“Fortunately everything went to plan.”
When the crane left it was headed for a long, slow trip to South Australia for another job – at a maximum speed of just 80 kilometres per hour.