Sky Train Transit network takes shape at Phoenix airport

The structure of the new Sky Train transit network is taking shape at the Sky Harbor International Airport in Phoenix. When complete, the elevated rail system will transfer passengers between the airport's busiest terminal, Terminal 4, and the Metro Light Rail station and East parking lots. Scheduled to begin operations in early of 2013, much of the overhead structure is already in place thanks to steel erection work being done by Bragg Crane Service and its Liebherr LR 1300 crawler.

In September Bragg's Phoenix division completed the erection of the steel structure at Terminal 4. Working for Texas-based Pro Steel Erectors, Bragg used a Liebherr LR 1300 lattice boom crawler crane to lift and install more than 1,100 metric tonnes (1,200 tons) of steel.

The LR 1300 was used with 68m (223 feet) of main boom, 124 tonnes (273,400 pounds) of counterweight and 57 tonnes (125,700 pounds) of car body weight, according to the company. A 28m (92 foott) derrick was rigged with a further 75 tonnes (165,300 pounds) on a suspended counterweight tray to make the heavy lifts at 46m (150 foot) radius.

To operate the crane within 30m (100 feet) of airplanes required that Bragg address special issues to satisfy the airport's strict requirements. Boom height, working hours, security and underground tunnels were just a few of the obstacles addressed prior to the mobilization of the equipment, the company said.

The type of matting used was an issue because wood chips are a hazard to airplane engines. Bragg's solution was to use rubber conveyor belt sections acquired some of its customers in the sand and gravel industry. These mats helped protect the 600 mm (24 inch) thick concrete and eliminated the risk of loose particles infecting the jet engines, the company said. Another benefit of the matting solution was that it could be quickly rolled out at the beginning of each shift and rolled up at the end. To allow the airport to keep more gates open during the day, Bragg's crews worked only at night, from 10 p.m. to 6 a.m.

Configuring the crane with the derrick and counterweight tray allowed navigation of the underground tunnels and provided more flexibility - using the tray for the heavy lifts and disconnecting it to handle the smaller lifts with more efficiency.

In a separate section of the project, Bragg is also erecting 131 precast concrete girders in two phases. In the first phase, in August 2010, Bragg set 79 girders in nine days. In the second phase, Bragg crews set 52 girders in a week and a half. These girders span up to 30m (100 feet) and weigh between 40 and 63 tonnes (45 and 70 tons). For these lifts, Bragg used 300-ton truck cranes.