Work is nearing completion on Chicago’s new 43rd Street pedestrian bridge, which will expand foot and bicycle access to the city’s lakefront. The ADA-compliant bridge features a curving S-shape that complements a similar bridge that opened in 2018 two blocks away at 41st Street.
Central Contractors Service, a member of the ALL Family of Companies, provided cranes throughout the bridge construction project and was also present in force for one of the final operations. It involved removal of the temporary safety trusses constructed alongside the new bridge arch, which served to protect the four METRA (commuter rail) and two Canadian National (freight rail) tracks below.
For this final operation, Central provided five separate pieces of equipment, in capacities ranging from 9 tons all the way up to 550 tons. The package included three all-terrain cranes, 550-USt Liebherr LTM 1450-8.1, 135-USt Liebherr LTM 1120-4.1, and 50-USt Liebherr LTM 1060-3.1, and two Broderson IC-80 carry decks with capacities of 9 tons each.
All this equipment was on the job site simultaneously for work related to the removal of the north and south trusses after the main bridge arch construction had been completed.
The temporary trusses had floor beams topped with wooden plank decking. Carry deck cranes were posted on the newly completed concrete bridge deck and used to lower these floor beams down from the temporary truss. Once the floor beams were removed, the all terrain cranes were used to remove the trusses.
The Liebherr LTM 1120-4.1 supported the east end of the north truss, while the Liebherr LTM 1060-3.1 supported and swung the west end of the truss out from underneath the newly constructed permanent arch. The weight of the truss was then transferred to the LTM 1450 in the air from the other two all terrain cranes. It swung and set the truss in a position where it could be dismantled. The Liebherr LTM 1450 was then relocated onsite to remove the south truss on its own.
Paul Urbanski, sales manager for Central Contractors Service, says the smallest equipment on the job, the 9-ton capacity carry decks, might have played the most important role in the operation. “We needed these small but powerful machines on the new bridge to perform the vital task of lowering the truss beams down to the ground,” said Urbanski. “Without them, we wouldn’t have been able to take down the trusses.”
Special engineering work was required to help ensure the new, finished bridge could support the weight of the carry deck cranes. Central Contractors Service worked with S&J Construction to compete the lift planning and general contractor FH Paschen also performed ground prep for the LTM 1450, enabling it to be positioned among the train tracks below.
In addition to Central’s cranes, also on the scene were S&J Construction ironworkers in man-baskets performing the truss disassembly as well as several METRA workers assuring that the tracks were kept clear of train traffic.
