Modulift Beams Help Construct Modular Hotel in Seattle
Spreader beams were used in 19 different configurations in 200+ lifts. Photo: Mortenson
December 4, 2018 - Modulift spreader beams were combined with other rigging equipment in 19 configurations to make more than 200 lifts during modular construction of the citizenM Hotel in South Lake Union, Seattle, Washington, recently.
citizenM used a construction method that involved installing modules made by Modulift’s customer, Polcom, of Poland.
The seven-story building includes six floors of modular units, with each floor requiring 19 unique lifts. The beam and sling lengths for each lift were different, totaling 228 for the whole project.
Construction firm Mortenson, which has built more than 100 hotels across North America, was the project’s general contractor to assemble the modular building, which would eventually include meeting rooms, a living room, bar, gym, and luxury bedrooms.
Jack McCaskill, project engineer, from the Mortenson’s Seattle Operating Group, said that diversity of rigging was required because the modules varied in size.
The largest measured 10’ wide by 51’ long and weighed 45,000 lbs. Some modules had six lifting points. Others had eight. Not all those points were in line, and some modules had an offset center of gravity. Also, lifting heights increased as the hotel took shape, with the final story reaching 70’ above the street.
Modulift prescribed cascading rigs, consisting of spreader beams, slings, and shackles, as the most cost-effective below-the-hook solution.
For the eight-point lifts, a one-over-two-over-four configuration was used, consisting of seven spreader beams at different levels. The six-point lifts used a one-over-one-over-three rig composed of five spreaders at different levels.
Sue Spencer, technical director at Modulift, said: “Whenever Polcom begins a new product, they ship the equipment to site and we provide the rig drawings as their technical partner. This type of rig is flexible and nicely balanced. We could have come up with a custom designed frame, but this would have been heavier and more costly—and it would have been rigid rather than flexible. Also, because the customer has used our equipment on many module installations, they had the spreader beams required in their fleet. They only had to purchase a small quantity of spreader beam struts.”
Due to site constraints encountered once the project was underway, Modulift was called upon to modify five of the rigging arrangements. Spencer explained that alterations were necessary because of obstructions caused by scaffolding.
She added: “We had to redesign the rigs so they were much lower in height; we achieved it by reducing the sling angles above each spreader beam and in some cases at less than a 45° angle beneath. We also changed the types of connection slings to the spreaders to avoid any clashing between the slings and the beams due to lower [sling] angles.”
MOD 24, MOD 34, MOD 50, and MOD 70 spreader beams were all used during the project. The longest and largest was a 30’-long MOD 70. The smallest and shortest was a MOD 24 at 5’. The slings were predominantly chain slings with shorteners so that the lengths could be adjusted to accommodate the aforementioned offset centers of gravity, with polyester slings to connect to the beams for the lower height rigs.
McCaskill pointed out that the writing, visible on the side of the modules, identified the units by room number within the hotel. It was also used to communicate the sequence at which the modules needed to be set into place. He concluded: “Modulift has been outstanding, both in their efforts to help our project and in the quality of their work.”