The reduced footprint and floating counterweight meant that it is much more efficient for contractors to barge-mount a crawler crane. The crane can be on smaller water-based barges because the machine automatically adjusts its centre of gravity for each lift.
Kraemer North America recently used an MLC300 to help replace an 84-year-old truss bridge, the 756m Savanna-Sabula Bridge near Savanna, in the US state of Illinois.
The Savanna–Sabula Bridge was a truss bridge and causeway crossing the Mississippi River to connect the city of Savanna, Illinois, with the island city of Sabula, Iowa. The bridge was decommissioned last November when its US$80 million replacement – only a few metres downstream – was opened as the 750m-long Dale Gardner Veterans Memorial Bridge.
Construction of the new bridge involved placing two 292m-long outer plate girder spans and a central 167m-long tied-arch span. Kraemer realised that a barge-mounted crane solution would be necessary to access the lifts for the tied-arch span.
The company sought consultation from Dawes Rigging & Crane Rental about a crane that could be mounted on the tight working quarters of a barge, but still provide high-capacity lifts to great heights to aid in bridge construction.
Many contractors use Manitowoc RINGER cranes for a barge-mounted solution because the round RINGER shape stabilises the crane and distributes the machine’s weight.
However, Dawes suggested a newer crane. “With the variable position counterweight, the MLC300 is always finding a new centre of gravity based on the load that’s on the hook,” said Patrick Shea, project manager for Kraemer.
“This crane has helped us to achieve almost zero list while working on the barge, keeping every lift level while minimising the barge’s rotation. The VPC saves space, too. Most crawler cranes with the required length of boom would not have fit on the barge in the first place,” said Shea.
The MLC300 was erected on a barge in the Mississippi River measuring just under 21.5m by 30m. It lifted arch rib sections weighing about 70tonnes to just over 50m using 90m of main boom. All was accomplished from a 30.5m radius.
To meet the lift radius and pick weight requirements on the job, Kraemer’s MLC300 had its optional VPC-MAX attachment. This enhances the crane’s capacity and enables additional boom and jib length combinations.
The stability of the MLC300, which Kraemer rented from Dawes Rigging & Crane Rental, was exceptional, said Shea. “The whole time we used the MLC300, the barge listed by less than a degree.”
The old Savanna–Sabula Bridge was finally demolished in March.
