Tandem lift on track22 July 2021
Installing a three-span pedestrian and cycle bridge does not sound a particularly hard job, but this one was to pass over the third-busiest set of railroad tracks in the United States with a hundred trains a day passing beneath.
For this project in Cleveland, Ohio, ALL Crane had to work closely with the Norfolk Southern Railway to get the critical work-clearance time that was needed to set the spans. Those times were scheduled in extremely brief, single-hour increments - the maximum tine that the railroad operators could halt train traffic for lifting work to be done.
ALL used two Liebherr mobile cranes in a tandem lift to set the final arch that topped off the structure. The cranes were a 450 t capacity LTM 1450-8.1 and a 250 t capacity LTM 1250-6.1. Initially the units worked independently in setting 38m spans that weighed 38.5t. But for one critical window they came together to help set the two halves of the arch and hold them in position so Youngstown Bridge’s ironworkers could execute a mid-air splice.
Plans for the lift were submitted months in advance to the railroad. Once submitted, no changes could be made to the lift. And, when the approved work time finally came, the team on the ground would have just an hour to complete the placement of the arch.
In the days leading up to lift day, Dan Lewis, project supervisor for Youngstown Bridge, had his team perform several pre-lift tests to make sure they would be ready to make the most of their time. “This gave our ironworkers the opportunity to fine-tune the rigging of each arch section,” he said. “This was important, given the time constraints. The team could know, well before the lift, that the two arches would be within a degree or two of each other at the splice point.”
The railway window was scheduled for mid-April then was suddenly moved up by three days. The ALL Crane team had on short notice to mobilize and assemble their cranes. When the predetermined hour arrived to set the two arch sections, nearly eight months of planning came down to sixty minutes. The LTM 1450-8.1 was configured with 48 m main boom at a 15 m radius and the maximum of 134 t of counterweight. The LTM 1250-6.1 had 40 m of main boom at a 10 m radius.
The two 38 m bridge side-spans had already been set on their respective abutments and on temporary structures toward the middle, with a 75 m centre span also resting on the temporary structures. By installing the arch, which would assume the bulk of structural support duties for the entire bridge, the temporary structures below could be removed and the bridge would be essentially complete. With the clock ticking off the allotted hour, crane operators held each arch piece in position as a dozen ironworkers, in man lifts and on the ground, swarmed to install scores of bolts at critical splice points. There was a minimum number of bolts that had to be installed for the structure to support its own weight, and this became a crucial milestone. It meant that, should the work window start to close, the bridge would be stable enough to stand on its own. If the milestone was not met, ironworkers would have to reverse course and disassemble the arch so they could try again another day.At the 35-minute mark, when the threshold was reached, everyone breathed a sigh of relief. Just 23 minutes later, at minute 58, the work was completed.