Mackinac Bridge Gets New Paint Job, Scaffolding
For the first time in the structure’s history the Mackinac Bridge’s towers are being stripped to bare metal and repainted. What also makes this project unique is the scaffolding that was developed to tackle the tower work.
The Mackinac Bridge, located at the Straits of Mackinac in northern Michigan and also known as the Mighty Mac, is the longest suspension bridge in the western hemisphere.
According to the Mackinac Bridge Authority, the Mighty Mac, which opened to traffic in 1957, is currently the fifth-longest suspension bridge in the world. The Mighty Mac’s total length runs 26,372 feet, with a 3,800-foot-long main span.
Researchers based out of Michigan State University recently began adding more data-tracking sensors to the bridge—sensors that will read data that can contribute to maintenance of the Mighty Mac’s structural components.
The paint platforms used on @MackinacBridge (engineered by Ruby + Associates, Inc.) were awarded the Best Neighboring State Project by The Structural Engineers Association of Illinois. The award recognizes "creative achievement in structural engineering"https://t.co/G1da7Au6Iz pic.twitter.com/9uYdKsnhXB— The Mackinac Bridge (@mackinacbridge) August 6, 2019
The first 20 prototype infrastructure sensors, originally installed in the beginning of 2016, were powered solely by traffic vibrations. For the next phase of testing, 2,000 sensors are to be installed to investigate large-scale deployment and provide useful monitoring data to the Mackinac Bridge Authority.
Repainting the Mighty Mac
The south tower—each of which stands 552 feet tall—was recently stripped of its lead-based paint, commencing the second phase of the project. According to The Detroit News, the old ivory-colored paint along the top section of the tower is first to be replaced, and the lower section of the tower will get the same treatment, with completion slated for the end of 2020. The paint work, a contract valued at around $6.5 million, is expected to have a lifespan of 35 years, including periodic maintenance.
To tackle the work, a movable scaffold system was designed by Ruby+Associates of Bingham Farms, Michigan, and fabricated by Moran Iron Works of Onaway, Michigan, ultimately used by Seaway Painting of Livonia, Michigan. Ruby+Associates won the Best Neighboring State Project Award at the Structural Engineers Association of Illinois 2019 Excellence in Structural Engineering Annual Awards for the scaffolding system.
The custom-designed platforms, used in the 2017-18 work painting the north tower, can enclose and move along the bridge’s towers. Workers were able to adjust the scaffolding as needed to account for the tower’s tapering toward the top of the structure.
According to the Mackinac Bridge Authority, the award nomination necessitated that the scaffolding design needed to be able to withstand winds that often exceed 100 miles per hour, as well as capturing paint and other materials. The new coating currently being applied is zinc-based. The contract to paint the north tower was valued at a little less than $6.3 million.
“As this is the first time in the bridge’s history when the towers have been stripped to bare metal and repainted, it makes sense that Ruby+Associates, Moran Iron Works, and Seaway Painting would need new, innovative equipment to get the job done,” said Mackinac Bridge Authority Executive Secretary Kim Nowack.
“We congratulate them on the award and thank them for their work preserving this infrastructure icon.”