The Reading Community School District outside of Cincinnati, OH is getting a new 215,000-square-foot school building that reports indicate is the largest school in the state to be made entirely of precast concrete. In precast construction, large, prefabricated concrete panels are trucked to the construction site and assembled like a large puzzle into walls and floors around a steel frame. It’s an attractive building method because it can rapidly accelerate the construction schedule, getting projects done much faster than with traditional construction.
Mack Industries, an Ohio maker of custom precast products, got the contract to supply the precast for the school, and they called on ALL Erection & Crane Rental to supply the crane and operator for this past summer’s critical step of placing the precast concrete sections that make up the school’s floors. This phase required configuring all three floors as well as the roof.
Installing the floors came with multiple challenges, the foremost being that all the exterior walls had already been set. This meant the crane would have to be positioned outside the three-story walls and the operator would not be able to see inside to where he was setting the floor pieces. Each piece, called a plank, is large and heavy – approximately 30 feet long, 8 feet wide, 10 inches thick and weighing 20,000 pounds.
Initial framing for many of the interior walls was also complete. Combined with the finished exterior walls, this made setting the floors similar to a large-scale version of the classic board game “Operation” – performed with your eyes closed.
The practical choice
Jared Willis, project supervisor for Mack Industries, said ALL Crane’s involvement was invaluable, starting before the first crane ever arrived at the jobsite.
“I assumed we would need a traditional crawler for the job,” said Willis. “But Brian Meek, the sales supervisor from ALL Crane, suggested a hydraulic mobile crane. It ended up saving us a lot of money and made a lot more sense for our site.”
Meek recommended the Liebherr LTM 1220-5.2, a 265-ton mobile all-terrain crane with a telescoping boom length of 197 feet. The unit is outfitted with VarioBase, Liebherr’s unique system that enables each individual crane support to be extended to an arbitrary length. This increases the lifting capacities and extends the working range.
Thus, the LTM 1220 has the ability to achieve hoist heights of up to 328 feet and outreaches of up to 288 feet, making it ideal for clearing the school’s walls and reaching deep into every section of the structure.
“They would have needed a huge crawler to handle that kind of weight,” said Meek. “It just wasn’t practical given the constraints of the site. I’m always considering what makes the most sense for the customer. It’s a matter of safety and productivity. With the Liebherr LTM 1220, we could get them the capacity they needed, they could place it exactly where it needed to be and it came at a much better price for them.”
Strategic lift plan
When it was time to set the floor pieces, the ALL Crane operator would pick a plank off the truck, raise it above the exterior walls, carefully swing over to the correct zone of the floor, then begin to slowly lower it in place. The installing crew from Mack Industries was inside, relaying instructions to the crane operator via radio to help guide it to the precise position. Each day, 35 to 40 planks were set in place.
“The LTM 1220 had the right mix of capacity, reach and adaptability to tight spaces to make this job go smoothly,” said Meek. “It was the right choice for this job because of the efficiency and flexibility it brought to the site.”
The Mack and ALL Crane teams also worked closely together on pre-lift planning. In the weeks leading up to the lift, Meek was a frequent visitor to Mack Industries headquarters as teams from both companies employed CAD drawings and 3D lift planning software to plot out every step. The process helped Mack organize deliveries, so the crane operator had the exact concrete planks needed each day, and it mapped exactly where the crane needed to be to set each zone of the floor.
When finished, the school for pre-kindergarten through 12th grade will house more than 1,700 students on the site of the Reading school district’s former high school. The $43 million project began June 2017, with completion scheduled for August 2019.