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Florida Bridge Contractor Automates Rebar Tying to Shave Labor and Days off the Timeline

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Davie, Fla.-based Shelby Erectors is a bridge rebar contractor, competing and winning in Florida’s market for government highway and transportation projects.

Founded in 1997, the company now employs about 100 and has a backlog of $25 million. The company works extensively on bridge projects, including the $2.3-billion, 21-mile-long Orlando I-4 Ultimate project. They have also completed rebar work on the Starship Launch Mount 2 for Space-X.

In projects over the last two years, they have leveraged new technology from Pittsburg-based Advanced Construction Robotics that automates the tying of rebar, freeing up crews for other tasks. This has delivered a measurable return in terms of cost and timeline savings, and has helped Shelby Erectors win business, including rebar work on the Wekiva Parkway project on Florida’s beltway. The Advanced Construction Robotics TyBOT robot self-locates, self-positions and ties up to 1,100 intersections per hour.

Shelby Erectors also plans later in 2022 to implement IronBOT, a rebar placing robot that carries and places rebar bundles weighing up to 5,000 pounds, enabling rebar contractors to increase productivity by up to 250%.

Robot for Rebar

Bridge ironwork, constructing the rebar framework that reinforces a concrete bridge, is not easy. Even before rodbusters can put iron rebar in place according to the structural plan, it must be hauled over to the deployment site manually. This requires a crew of several rodbusters to grab up lengths of rebar, sharing the load. Then comes the arduous process of tying the rebar together for rigidity, which means hours spent bent over the steel framework, inviting back problems.

That is why Shelby Erectors was featured on Dirty Jobs with Mike Rowe, and also why the company is an early adopter of new technology that automates the most arduous and unpleasant parts of the rodbusters charged with erecting structural steel to reinforce concrete.

Given its Florida location, Shelby Erectors sees pretty steady business all year long, and COO Jack Nix says that in the winter, they see northern rodbusters traveling south to complement their native workforce. But there is still room for automation to help the tech-forward company get more out of its rodbuster crews.

“Our company is 100% paperless—we don’t shy away from technology,” Nix said. “Two years ago, we saw an article about this rebar-tying robot, and were curious. I had a big job I was going to bid—and I thought that might be a good fit for that job. And then the people from Advanced Construction Robotics showed up and did a demo. They literally drove to my home in the Florida Keys and demoed the product in my driveway. It was clearly a viable product that might work for us.”

Nix was intrigued in large part because tying rebar is difficult and dangerous. That motivated Nix to make the investment and advocate for adoption by the teams of rodbusters.

“Anybody who has ever tied a rebar deck will tell you it is a backbreaking process, and hard manual labor,” Nix said. “If that machine can take some of the backbreaking work away from the workforce, that is valuable. We implemented TyBOT two years ago in December, and we found that any technology comes with some resistance. You have to get your old timers to buy in and want to use it.”

While Nix said the early days of adoption presented some challenges, the speed and productivity of TyBOT have paid dividends.

“The TyBOT can tie productively 800 to 1,000 ties an hour versus 150 and 200 ties for a worker,” Nix said. “What would take four to five people to do can now be done with one robot supervisor and the robot. This saves you the labor, and allows you to take that same workforce and use them to do the work of placing steel. It also has given us 25% to 30% savings on schedule, so we can turn projects faster which is attractive to project owners.”

At any one time, Shelby Erectors has had one and sometimes two TyBOTs deployed at a given time.

“We see that this is the way of the future of the construction market,” Nix said. “We need to lay and place the steel, but then the robots handle bulk tying. Then, we send our crew on to place more steel and one person drops back to manage the bulk tying work.

TyBOT may save the company between 200 and 300 manhours per job, which is significant in Florida where wages are relatively low, but an even better value according to Nix in northern states where wages are higher.

“Now, we can go from needing a five- or six-man crew to a two- or three-man crew,” Nix said. “It will change the way contractors can work together on these projects. Now, we can go faster than the prime can get ready for.”

Hurdles to Overcome

Advanced Construction Robotics had to solve a few problems to make TyBOT work well in Florida. According to Nix, the cameras on the robot uses to sense rebar intersections tended to fog up given the high humidity. Solutions to other challenges had to do more with people than technology, though.

“One challenge is getting the general willing to use this,” Nix said, adding that TyBOT requires certain steps in the project to be re-ordered. “Tie bot runs on the screed rail. The general has to have that up prior to doing rebar installation—and this changes the schedule and how the work flows. It does not change the project cost, just the sequencing.”

The robot will still tie rebar that is not straight—just so long as it sees the joint. So Nix said it was important to ensure rebar is level and plumb before tying commences.

“Another problem we had was that the chairs the rebar sits on, if they are not spaced correctly, it might mistake the chair as an intersection and tie that,” Nix said. “So we have to make sure we are setting up and framing the work correctly, and make sure it is all straight before we start tying.”

Nix stressed that because the technology is new, rebar subcontractors may have to sell the value to generals—which is essential since generals need to adjust other elements of the project to accommodate TyBOT.

“We have been telling generals this technology will help us improve or maintain the schedule,” Nix said.

“This is what we need from you with regard to the screed rail, which has to be in place earlier.”

Nix said his company also had to come to an understanding of where the robots do and do not make financial sense, and how to fill the role of the robot supervisor, who wears a waist-mounted controller.

“For us, we originally thought we could use a full-time robot supervisor, but what happened then is our robot would catch up with our placement crews and then that operator would be idle,” Nix said. “What we are doing now is training our actual rodbusters to run the robot. Then that robot operator just jumps back to the placing crew when the robot catches up.”

Projects, Nix found, must meet certain criteria for scale before the robots drive a return.

“We have tried using TyBOT on just about anything, including smaller projects,” Nix said. “But when you account for the cost and hassle of mobilizing the robot to the site, you find that on single span bridges, it is not a good fit. We found it takes a minimum of two or three spans or more and a 40-foot width or wider—there is not enough production otherwise to justify it.”

TyBOT Specs and Tech Stack

TyBOT is a gantry-mounted robot that can operate on a rail between 9.5 feet and 100 feet wide. It is powered by a Cummins Onan generator that can run continuously for 12 hours without refueling, using a 16.5 AWG poly coated single snap wire to complete up to 1,100 ties per hour. TyBOT requires a minimum bar chair height of one inch and can tie bars with intersections as small as 3-by-3 inches. It can accommodate up to #8 or #9 rebar, and while it has not been used on fiber reinforced rebar in the field, tests on this material have been successful according to the company.

A truly autonomous robot, TyBOT does not need a building information modeling (BIM) design file, or other digital information about the project. Nor has it been trained to perform its job through machine learning. Its dual camera system can see the intersections of rebar, and the robot can then execute ties either a 100% or 50% pattern on bottom and top mats. The cameras are equipped with a light ring, enabling TyBOT to work in the dark. Snow and other obstructions on top of the rebar can stop the robot from working, however.

While TyBOT does not require Internet access to operate, a 4G cellular connection enables Advanced Construction Robotics to support and upgrade the robots.

Robots-as-a-Services (RaaS)

Like Dusty Robotics, Advanced Construction Robotics is among the emerging construction technology companies operating on what amounts to a robots-as-a-service business model. Robotic capacity is sold on an annualized subscription basis or in the case of TyBOT, through piecework. According to Advanced Construction Robotics CEO Danielle Proctor, pricing ranges anywhere from 20 to 25 cents per tie, including the tie wire.

Contractors do get help adopting the technology, including training and support. With training, an employee should be competent with the technology after three to four days of use. During that initial phase, Advanced Construction Robotics has a technician on site with the customer.

“Currently, we are teaching our customers how to self-supervise the robot,” Proctor said. “In the event we have customers that do not want to self-supervise, we do have a fleet of robot supervisors.”

IronBOT Speeds up Process

While TyBOT has proven reliable on projects, enabling smaller crews and faster completion, productivity gains could increase even more with the addition of IronBOT, which automates the arduous task of lifting and then placing up to a 5,000-pound load of transverse and longitudinal rebar.

“IronBOT is going to be a game changer,” Nix said. “We have been up there to see the prototype of IronBOT and gave them feedback and suggestions. We are in discussions with them and will probably be one of the first users of IronBOT. This is what we do—all we do is rebar placement.”

According to Proctor, the way the robot supervisor for IronBOT interacts with the robot will change over time.

“But at first,” she said, “the supervisor will tell the robot what spacing to use. The machine can hoist up the entire bundle, up to 5,000 pounds, go to where you want to place, and the robot will begin placing that rebar at that spacing. In some applications, the spacing stays consistent or if it changes, the supervisor will tell IronBOT to change and to what spacing.”

This means IronBOT is not reliant on access to geopositioning data or a cellular signal to operate, nor does it require access to BIM.

As a former rodbuster himself, Nix says he hopes this helps those currently in the field have longer, better careers.

“Iron work, rodbusting, is one of the hardest trades in construction,” Nix said. “It is very physically demanding. The use of this technology and the placement of the decks on the hardest portion of building a bridge—that does not just reduce labor demand, but it eliminates back-breaking, carrying,-bent-over time. This will allow people to have better, longer careers where they are not getting physically beat up. We need to keep our infrastructure going, build and rehabilitate what we have. Robots take some of the physicality out of this, which can help us entice some of the next generation into this industry even as we improve construction schedules and lower cost.”

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