Construction of an iconic replacement for the Orrs Bridge in Cumberland County, Pennsylvania, features the TyBot robot completing the strenuous rebar ties, saving time and labor.

“What TyBot enabled us to do on this job was to keep the schedule,” says LaMar Childs, President of LB Construction Enterprise in Spring House, Pennsylvania, the rebar subcontractor on the bridge project, adding, “It’s a heck of a machine.”

The original Orrs Bridge, crossing Conodoguinet Creek in Hampden Township, was built in 1957, and in recent years, started falling into disrepair. The old bridge used a five-span, adjacent concrete box beam design, which over time, developed issues with structural integrity.

About 10,000 vehicles cross the 315-foot-long bridge daily, the most of any bridge in the county. The county reduced the allowable weight on the bridge several times, but decided with so much traffic and the need for emergency vehicles to be able to safely cross, it would be best to replace it.

“We’re the fastest growing county in the State of Pennsylvania, and this bridge is in the heart of the fastest growing part of the county,” says Kirk Stoner, Director of Planning for Cumberland County, adding, “It’s a challenging project.”

The new bridge curves across the creek, downstream from the old bridge. Like the former bridge, the new one will have one lane each direction. It also will have shoulders and a pedestrian sidewalk.

Federal funds paid for about 80 percent of the replacement cost, with the state contributing 15 percent and the county 5 percent, funded through an increase in vehicle registration fees. The county has a six-year, $40 million bridge capital improvement plan.

“This is our biggest project to date,” Stoner says. “It’s a high-profile project with a lot of eyes on the project.”

The county’s engineer Herbert, Rowland and Grubic Engineering & Related Services [HRG] of Pittsburgh designed the new curved structure and provides construction administration and inspection. It was curved to improve sight lines and visibility, limit speeds on the bridge, and eliminate a tight corner and a 45-degree incline where the old bridge connects to the road system.

“The curve was a little bit more difficult to build,” says Matt Lena, an Engineer with HRG. “It’s a much gentler curve than the two sharp road approach curves prior to the existing bridge.”

Before construction could start, the county had to relocate a species of endangered freshwater mussels in the bridge area.

Deblin Construction of Mechanicsburg, Pennsylvania, received the $7.9 million contract and work began in April 2019. COVID-19 precautions led to work stoppages in the spring of 2020, but Deblin still expects to complete the bridge this year, Stoner reports.

“It was nice building this bridge offline, so we can maintain traffic on the existing bridge,” Lena says.

The new prestressed concrete spread box-beam bridge is supported by concrete piers, which will have an architectural treatment form applied to create the appearance of stone. The abutments will receive that same treatment, which will help the bridge blend into the landscape, Stoner says.

Deblin installed Portadams, an engineered reusable coffer dam system, and dewatered the work area with continuously operating pumps. Workers accessed the work areas from dry land on either side of the bridge. Half of the bridge was completed at a time, and then the Portadem was removed. There was no marine operation.

The concrete beams were placed and then work commenced on the deck, which included the use of TyBot, the rebar tying robot. The robot tied 40,000 knots, connecting the rebar across the deck of the Orrs Bridge, prior to crews pouring concrete. The robot can successfully complete about 1,000 ties an hour, while a human averages about 100 ties. People still need to feed TyBot wire and make ties at the outer edge of the bridge, which are hard for the machine to reach.

“It was neat to see it in action,” says Nathan P. Silcox, Hampden Township Commissioner.

While connecting the new bridge into the existing road system, traffic will be detoured for about a month. “Everything has been going great,” Lena says.

Once the new bridge opens to traffic, in October 2020, crews will demolish the old one. “We are happy the project has come together so well, and that it will be done on schedule,” Stoner says.

Advanced Construction Robotics (ACR), an affiliate of Brayman Construction Corp. of Saxonburg, Pennsylvania, developed the TyBot robot a couple of years ago, after Stephen Muck, Chairman and CEO of Brayman, who recognizing a shortage of skilled labor, thought robotics could help. He teamed up with Jeremy Searock, now Co-Founder and President of ACR, to develop a robot to tie rebar.

“The technology was ready to go from academia to industry,” Searock recalls. “It solved a problem and proved to the industry that robots are not science fiction, but real products that can provide schedule savings, improve safety, and save costs.”

TyBot uses computer vision as sensors and artificial intelligence as it looks for rebar intersections and ties them. It is not remote controlled, and contractors do not give it a plan.

“Just like a person, TyBot sees the intersections and ties them,” Searock explains.

Childs began evaluating the different tasks the company’s workers perform about six years ago, looking to reduce strain on employees.

“Installing rebar can be back-breaking work,” Childs explains. “There are also a lot of repetitive task elements in tying rebar, especially doing bridge decks.” Knowing that, Childs began researching how to reduce the strain but keep up the speed of tying. That led him to TyBot.

Use of TyBot for the Orrs Bridge required comprehensive planning to ensure the work flowed, Childs adds. Crews need to order and place enough rebar to stay ahead of the machine.

“When I talk with workers, they tell me they are not as worn out,” Childs says. “There is still an element of making sure it is doing what it is supposed to, but it takes a lot less manpower and time.”

Childs estimates TyBot saves 50 percent to 65 percent of the time it takes to tie rebar, perhaps more, depending on the bridge’s configuration. Using TyBot also has reduced falls and other injuries, offering employees’ a longer career and increased morale. He adds that TyBot is easy to mobilize.

TyBot can be leased or bought by contractors across the country. ACR can deliver it and offers a test drive program. “These technologies give contractors the opportunity to transform their business,” Searock says.

Stoner says the county is open to contractors using new technology, but choosing to use something like TyBot is up to the contractor. “This is a prominent bridge,” Stoner says. “The end product will be picturesque. It’s a gateway bridge.”

Advanced Construction Robotics newest product, IronBot will carry and place the rebar and can work in tandem with TyBot to place and tie. “When used together, you will be able to do twice the work for half the time,” says Jeremy Searock, Co-Founder and President of ACR. It will be available in 2021. Additional details will become available in the next couple of months.