Atlanta is home to 6 million people, internationally known corporate residents like Coca-Cola, CNN, and the Home Depot … and traffic. Lots and lots of traffic. Perhaps at the epicenter is the interchange that joins S.R. 400 with I-285, which sees an estimated half-million cars daily. Slowdowns of almost an hour are common.
Replacing the interchange has been discussed for well over a decade, and work has finally begun, spearheaded by a public/private consortium dubbed North Perimeter Contractors LLC. ALL Crane Rental of Georgia, a member of the ALL Family of Companies, was tapped to provide lift equipment for the expansive project.
The cranes will perform the important work of setting girders and beams. This aspect of the job mainly involves nighttime tandem picks, making for a project with a high number of critical lifts.
Many of the steel girders are super-sized, topping out at 180,000 lb and 180 ft long, or half the length of a football field. Because the interchange is vital to maintaining flow of metro traffic, it is remaining open while the new construction is going on alongside. When it is time to set the large girders, two all-terrain hydraulic cranes need to be positioned on the live roadway below to reach the new interchange sections being constructed above. Because of the periodic traffic interruptions, necessary for motorist safety, work is relegated to the less-busy overnight hours, roughly between 1 a.m. and 6 a.m.
The ALL team performs multiple critical lifts per night, several nights per week. ALL specified a rotating package of four cranes for the work, consisting of a 550-USt Grove GMK7550, a 300-USt Liebherr LTM 1250-6.1, a 300-USt Liebherr LTM 1300-6.2, and a 450-USt Tadano ATF 400G-6 all-terrain crane.
Cranes in the 300-ton weight class are typically configured with full counterweights, while the counterweights for the Tadano and Grove are adjusted situationally. The Grove GMK7550 has even been able to handle some smaller 80,000-lb beams on its own with a MegaWingLift attachment and 120 ft of luffing jib.
For the tandem picks, one crane is positioned in the median, while the second is placed on the opposite shoulder. The median crane moves first, followed by the shoulder crane. Both conduct a series of precisely coordinated swings to gradually position the beam for the lift. It must be raised 40 ft above the beam seats before coming to rest. The extremely long and heavy beams must be set within a half-inch of the placement target.
ALL’s operators are in constant radio contact throughout the process, with additional spotters from the North Perimeter Contractors’ team strategically positioned throughout the lift zone. “The operators have developed an intuition that allows them to maneuver seamlessly through the lifts,” said Irwin. “I’m really proud of our team.”
The process will be repeated scores of times from now until project completion.