Perini Corporation is one of the biggest contractors in the US, while O&G is a private construction services company headquartered in the the north east of the States. The two companies were responsible for the redecking project, while NAI designed the cranes.
Excluding the approaches, the bridge has a length of 3,770ft. The longest span is 701.4m (2,300ft), while the total length is 1,149.10m (3,770ft).
The 30 US ton gantry cranes primarily tackled the task of moving equipment from one side of the bridge to the other. They were designed to accommodate flexing of the bridge which even changed depending on the weight of traffic in a certain direction.
The cranes removed the original concrete filled steel grid deck – which was 4.5 inches thick – and installed new lightweight, orthotropic steel deck. They also had 3 US ton auxiliary hoists used to move traffic barriers.
The cranes worked both the length of the bridge and across it. Two gantries had runway lengths of 1,100ft, and two had runway lengths of 800ft so they could move forward and backward covering the length of the bridge. The crane’s girder (on which the hoist and trolley moved right and left) had a 70ft span crossing above the six lanes of the bridge. Traffic could flow under the cranes to avoid closure during construction.
In addition, the cranes were designed to negotiate the longitudinal slope of the bridge. The end truck motors were sized to allow the cranes to travel up and down a maximum slope of 4%, at full capacity. Full length catwalks were also built on each crane for easy access above active travel lanes.
Other obstacles were environmental; while designing, NAI had to consider the effects of wind, rain, snow and even ice. These were overcome with weatherproof removable covers over all motors and open gears. There were also heaters in all motors and panels to eliminate the threat of condensation build-up.
The cranes were designed to operate at capacity in winds up to 30 miles per hour, in below zero temperatures. Given that the cranes had to work successfully in outdoor conditions without a convenient power source, the cranes were self contained by incorporating a diesel generator mounted on each crane.
Traffic could flow under the cranes to avoid closure during construction bridge 1 Perini Corporation and O&G Industries teamed-up with North American Industries, Inc. (NAI) to design and manufacture four gantry cranes bridge 2 The 30 US ton gantry cranes primarily tackled the task of moving equipment from one side of the bridge to the other bridge 3 The cranes were designed to operate at capacity in winds up to 30 miles per hour, in below zero temperatures bridge 4 North American Industries has also recently custom-designed and installed a radio remote controlled 5 US ton pivoting circular crane – with a 53ft span – for the Institute for Advanced Vehicle Systems (IAVS) building at the University of Michigan, Dearbormichigan
