This is a brief article giving an overview of one method for rigging light gauge steel modules. This process was performed by BOXY, the parent company of US Frame Factory.
BOXY LLC used a basket weave technique to rig two 52′ Long by 12′ Wide by 10′ tall modules. These modules were made entirely with a cold-formed steel frame. There were two temporary 2×10 wood runners installed along the side of each module to distribute the load and protect the metal framework. There was minimal deflection noticed during the craning process. There was noticeable cracking in the drywall above windows and doors, but most likely that damage was from the transportation process and not from the craning process. There are also other methods of rigging a module like top rigging, but those methods are not covered here.
Framing of the Modules
These modules were framed up with 600S200-54 at 16 OC minimum in the floors and a 600T125-54 track on the edges. The walls were 362S162-54 at 16 OC with a 362T125-54 track. The ceiling was 600S162-43 at 16 OC. The floors had a 3/4″ T&G plywood installed with adhesive. Aerosmith pins 5574PG 2-1/4 X .144 HELICAL PINs were used for installation. The long walls had EXP exterior gypsum and the endwalls had plywood sheathing. Part of what made this modular setup possible was the onsite hallway that would be constructed with panels at the jobsite. Additionally, the roof was stick framed at the job site.
This rigging setup consists of a top main spreader bar with two halos at the ends and a smaller spreader bar in the middle. Once distributed at 5 points along the unit, this allowed for about 10′ of separation between each strap and 5′ at the ends of the modules cantilevered. One complicating factor is that the small spreader bar was directly connected to the crane lifting hook, so chain falls had to be used to get the correct length. The weight of each unit was estimated at 20,000 ibs and was measured just under 20,000 ibs, so that put the weight per strap at approximately 4,000 ibs. We used 2″ x 40′ 2 ply nylon straps. Each strap was rated for 12,400 ibs in a basket configuration. The main spreader bar used was a mod 50 with mod 12s used as the spreader bars. The spreader bars were just slightly larger than the unit so as to not cause any squeezing on the walls and ceiling of the unit.
We also installed wood 2x10s on each long side of the module at the bottom and bolted it into the track for the cold-formed steel with 1/2″ bolts. The wood was supposed to transfer the load of the straps across the light gauge steel. We were afraid of web crippling on the track used to frame the bottom of the units. In retrospect we are not sure it was necessary, but it was still a nice feature to have.
This is an alternate design that was engineered for the project by IntegriCert. We did not use this option because we were able to use off-the-shelf Modulift’s modular lift components. Compared to fabricating our own rigging system, it made a lot of sense to utilize a prefabricated system that was cheaper.
Post Transport and Crane Damage
There was minimal damage on the interior post transport. Some of the doors and windows showed cracks in the drywall at the opening, but most of them did not have any cracking. Most corners of the drywall were also in good shape as well. Further improvements to this system would be to butt a 16 ga corner or other supporting brace where we noticed damage.
The total cost was $4,942.62 of rigging from Delta Rigging, $3,120.00 for the crane and one rigger, and $4,880.00 to hire the two extendable deck trailers with drivers to carry the long 52′ modules. That totals $12,942.62 spent on rigging, crane, and transport of the modules or approximately $11.31 per sqft to facilitate the process of shipping the modules. That does not include the infrastructure and cost of prepping the modules for transport. One issue we faced with transport was that the deck of the trailers was curved, so we had to shim the modules for transport. Make sure to protect straps for transport as straps rubbing against a metal edge will break.
If you have any further questions, feel free to reach out to our team at US Frame Factory.