If you walked across Central Campus in mid-February, chances are you saw an enormous crane near the Michigan Union. The crane was there to help workers install the first phase of the Courtyard Roof.
While the glass has not been placed yet, the "ribs" were put in place using an onsite crane located on the State Street side. The crane lifted the ribs up over the roof and placed them into the courtyard roof. The ribs -- measuring 64 feet by 48 feet -- were too large to bring through the building, according to Laura Rayner, project manager, Auxiliary Capital Projects.
The process was exacting and required equipment with specific abilities.
“The ‘ribs’ were assembled off site and then taken apart prior to delivery to insure that all the pieces would fit when they re-assembled them at the Michigan Union,” she explains. “Walbridge used a 265 hydraulic Liebherr 1220-5 -- an all-terrain mobile crane that has a maximum lift capacity of 220 tons, a maximum telescoping boom length of 197 feet and a long-folding fly jib extension of 141 feet.”
They also used a Potain HDT-80 tower crane, which is a self-erecting hydraulic tower crane that has a maximum lift capacity of 6.6 U.S. tons, a maximum hook height with horizontal jib that reaches out to 112 ft, and a maximum hook height of 176 ft with 148 ft length with a raised jib. The operating hook radius of the crane works within 148 ft, she says.
“All frames and loose pieces were properly marked and matched to the erection plans developed specifically for this project. Each piece was marked per the sequence and phase,” she says, adding that when the glass for the roof is installed, a similar process will take place.
Assembled during February’s freezing temperatures, the entire process took about a week to complete.