Potain MDT 368 Tower Crane Masts Become Permanent Addition To Historic Minneapolis Bridge During Restoration

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Potain MDT topless cranes were built into the piers of the bridge, as traditional anchoring solutions would have required too much space. (Photo courtesy of Manitowoc.)

Minneapolis’ iconic Third Avenue bridge, which first opened in 1918 and features a distinctive S-curve design and five concrete arches, is currently undergoing a top-to-bottom restoration where the masts of Potain cranes were built into the very foundations of bridge. The innovative solution was the result of the bridge’s proximity to the St. Anthony Falls spillway, which precluded the use of conventional barge crane options, and load-bearing concerns from heavy all-terrain or crawler cranes on old-fashioned reinforced concrete arches. General contractor Ames Construction and engineering subcontractor FINLEY Engineering Group proposed using the existing bridge piers to support Potain’s tower crane.

“We had to find the safest, most effective way to drop the towers into the piers—in other words, embed a section of mast into the box column, then bolt on the rest of the tower crane as normal,” explains FINLEY Engineering Group Principal Engineer Craig Finley.

Foundation Integration

The project coordinators calculated the bridge could have a Potain MDT 389 on pier five and three Potain MDT 368 tower cranes on piers two through four, and these cranes could handle all of the desired loads during restoration. After investigating how the tower bases could be mounted without damaging the bridge, it was decided to reinforce the column walls to prevent stress on the towers or pier walls. Finally, sections of Potain tower crane masts were installed and secured with concrete and rebar.

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Potain’s MDT 368 was chosen, in part, because it features the Crane Control System (CCS) and Top Site geofencing. (Photo courtesy of Manitowoc.)

Strategic Application

In January 2021, the three Potain MDT 368 cranes were erected by Dawes Rigging & Crane Rental, while the MDT 389 was installed in August. From the various positions—and with a maximum jib length of 246 feet (75 meters)—the cranes are configured to avoid overlapping. The Potain MDT cranes are also set with hook heights from 72 to 120 ft (22 to 36.5 m) to limit stress, though both models allow for hook heights well over 300 ft (91.5 m). The MDT 389 and three MDT 368 cranes are tasked daily with moving heavy construction materials across the bridge.

“We quickly learned to love the towers’ ability to work 180 degrees and out to the midpoint of the span—all of a sudden, it changed the way we looked at towers,” Finley says.

Source: Manitowoc