Solution Summary: Autonomous Rebar-Tying Robotic System
An autonomous rebar-tying robotic system, such as the Tybot from Advance Construction Robotics, Inc., is an engineering control that may help reduce stooped postures, and stressful hand and wrist activity from manual rebar-tying operations during bridge construction. This system autonomously navigates bridge decks, identifies and ties rebar intersections, using robotics and artificial intelligence technology.
The TyBot can be transported in a truck (Ford F250 or equivalent) and 40-foot trailer accompanied by a quality control team (QCT). This transportation arrangement supports up to a 66 feet wide bridge. Larger bridges up to 100' wide will require additional loads to transport additional TyBot extension sections.
This system offers a tool-less assembly configuration which can set up in one to four hours depending on crew and available equipment. It integrates within existing bridge construction infrastructure as the unit utilizes the screed rail supports (figure 1) installed for the deck concrete finishing machine, which are required to be in place prior to TyBot arriving to the jobsite.
Figure 1. TyBot in operation on a bridge width over 100 feet achieved by utilizing a third screed rail. (Photo courtesy of Advanced Construction Robotics, Inc.)
The autonomous feature in this system does not require pre-programming or calibration as it finds the reinforcing steel intersections and perform the ties with a tie rate of up to 1,100 ties per hour. Prior to operation, the work crew will need to place the bars and tie enough of the intersections (approximately 10%) to secure it in place. As the work crew frames and ties bars, the TyBot begins tying any remaining intersections behind the work crew.
The TyBot has the flexibility to accommodate different:
- Precast system
- Bridge 10-100 feet wide
- Up to 12% grade and 12% super-elevation
- Can be set to tie 50% or 100% of intersection
- Compatible up to #8 x #9 bar
- Day or night operations
- Raining weather
The TyBot only requires one supervisor to monitor the performance (figure 2), reload the tie wire spool when necessary to ensure the robotic system does not impede safety protocols. In needed circumstances, the supervisor does have the ability to manually override the autonomous operation of the TyBot.
Figure 2. A supervisor monitoring the TyBot in operation on a 90-foot bridge. (Photo courtesy of Advanced Construction Robotics, Inc.)
The speed or square foot per shift that TyBot can tie will depend on the bar spacing and percentage of intersections needing to be tied. For more information and help for job specific estimates, please contact the manufacturer.
Stooped postures from bending over to tie rebars can cause low back disorders, such as muscle strain or a disc herniation (“slipped disc”), which is bulging of disc material possibly pressing on the spinal cord or nerves that go into the leg.
Stressful hand and wrist activity from repetitive rebar tying can cause musculoskeletal disorders (MSDs) such as muscle strains; tendonitis, which is inflammation of elbow and wrist tendons; or carpal tunnel syndrome, which is compression of a wrist nerve, resulting in finger numbness and loss of hand strength.
How Risks are Reduced:
An autonomous rebar-tying robotic system can reduce stooped postures and stressful hand and wrist activities by performing most of the rebar-tying tasks. However, please see ‘Additional Considerations’ below for potential safety risks while operating this equipment.
As is the case with any construction tool and equipment, users should follow manufacturer safety recommendations and comply with any applicable local, state or federal regulations.
The robot needs a stable platform to operate. Workers should verify that the platform is rigid and meets the specification of Tybot. A collapse could be fatal if rebar workers (placing the frame, tie-in the rebar) are within proximity of the robot is working.
While most of the work is done autonomously, workers securing the rebar should be aware of the distance between them and the robot to avoid catching and dragging-related risks.
Jean Christophe Le, MPH - CPWR The Center for Construction Research and Training
Bruce Lippy, PhD - CPWR The Center for Construction Research and Training
Chuma Nnaji, PhD, MBA - The University of Alabama Construction Innovation Integration Lab (CII-Lab)