The job, overall, was a bridge realignment, as part of the Queensland Government’s $333 m Inner Northern Busway project. The INB is the heart of Brisbane’s busway network.
Explaining the project, Stuart Edwards, BOOM’s Business and Engineering Development Manager in Brisbane said The Leighton INB Alliance contacted BOOM, and several other heavy lift companies, seeking options for demolishing part of the existing Countess Street Bridge, to enable reconstruction of the new bridge.
“The two existing girders supporting the roadway were large concrete and steel components, cast in-situ. The estimated mass was 350 tonnes.
“For the new roadway alignment one of the bridge girders needed to be in a different location and running at a slightly different angle ... the new bearings were 5 m. away at the eastern end and 7 m away at the other end,” said Stuart.
Rather than see the job as a straight demolition and removal of pieces of the girder in the superseded position, BOOM’s then engineer, Craig McBarron, identified three options.
First, the contractors request of demolition and lifting out the heavy pieces, to enable a new girder to be built.
But this option was not adopted due to an extremely restricted working area, high cost and the impact on traffic over a relatively lengthy construction period.
Second, a relocation, of the existing bridge girder to the new alignment, by lifting and moving with high capacity cranes.
But, again, due to space restrictions and costs this process was not adopted.
Third, BOOM’s clever lower cost option ... relocation of the existing bridge girder with modular transport.
“We used two of our big heavy haulage prime movers – one set up with a ten row module (low loader) and another with an eight, row module, both modules equipped with purpose built frames and hydraulic jacks.
“The existing bridge girder that was to be moved was first jacked up and then the trailers with their trusses were backed under the girder and then the girder was lowered onto the frames mounted on the modules yet well clear of the original bearings,” explained Stuart.
The frames were stiff trusses each weighing ten tonnes and designed to carry a central point load of 200 tonnes.
The special trailers with jacks on the trailers were brought in from BOOM’s Singleton depot in New South Wales.
“We engaged the services of consulting engineers Qantec McWilliams of Brisbane to design the frame and H & M Engineering and Construction of Rutherford NSW to fabricate them.
“An independent surveyor was also appointed by BOOM to provide real time updates as the prime movers inched forward. This enabled early corrections to the path of the trucks and guidance during final placement.
“When inching the two trucks forward ,to get the girders into the required position, each end had to be located within a 20 mm tolerance when placing onto the new bearings,” concluded Stuart.
Photo captions
An aerial view of the job site showing the Countess Street Bridge. It was the girder closer to the bottom of the photo which was moved a few metres, saving the cost of demolition and building a new one ... an unexpected cost saving technique developed by BOOM.
The steel and concrete girder, pictured above, was lifted by hydraulic jacks, the low loader modules, with their frames on board, reversed in and the girder was then lowered onto the frames. The trucks then inched forward the few metres required to reposition the girder on the new bearings.
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The ever popular Stuart Edwards, Business and Engineering Development Manager at BOOM’s Brisbane Office receiving the Highly Commended Award for category A – Lift for Cranes over 60 tonnes, presented, by Michelle Grady, publisher of Construction Contractor magazine
An aerial view of the job site showing the
Countess Street Bridge. It was the girder closer
to the bottom of the photo which was moved a
few metres, saving the cost of demolition and
building a new one ... an unexpected cost saving technique developed by BOOM.
The steel and concrete girder, pictured above,
was lifted by hydraulic jacks, the low loader
modules, with their frames on board, reversed
in and the girder was then lowered onto
the frames. The trucks then inched forward
the few metres required to reposition the
girder on the new bearings.
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