said Walsh.“ The first was developing and engineering the load-handling concept and rigging to move asymmetrical, stress-sensitive, long-leadtime elements. The second was making sure the same rigging would work equally well both for the crane that would load the pieces from land onto the barge and for the barge-mounted crane that would later lower them to the lake bed for final assembly by divers. The third challenge was making sure that the land-based crane could work safely near the earth-andsheet-pile dock.”
Firm Footing
One of Dearborn’ s key jobs on this project was making sure the ground at the bargeloading site would support the 550-U. S.-ton capacity Liebherr LTM 1450-8.1 all-terrain crane that would be lifting the tridents and Cross T connector from land onto the barge.
To do that, Dearborn conducted a geophysical investigation and crane placement survey to locate and map any subsurface voids, underground
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Top Left: A wireless load cell at each corner of the spreader told the pressure on a trident’ s concrete pipe.
Top Right: Each trident and the Cross T connector pieces were set in specific spots on the barge for the 1-mile ride out into Lake Michigan.
Bottom Right: Engineering analysis and 6-foot-by-12-foot-by-8-inch outrigger pads gave firm footing and made sure ground reactions didn’ t affect undergroudnd utilities or the seawall.
utilities and structures such as seawall tiebacks and unconsolidated soils.
The survey also enabled Dearborn to assess whether the ground could support the crane reactions from lifting pieces that weighed more than 90,000 pounds with rigging.
Dearborn’ s investigation used visual inspection, an aerial drone to inspect the seawall and a handheld radio detector and ground-penetrating microwave radar to check the ground to a depth of 12 feet.
The study revealed the locations of the buried tiebacks that support the sheet-pile seawall as well as underground utilities.
Avoiding all of those dictated in part where the crane could sit. Dearborn’ s analysis also recommended that the crane’ s four