Mammoet Replaces Pittsburgh's Commercial Street Bridge in Under 24 Hours

Mammoet has successfully completed the installation of the new 10,000-tonne Commercial Street Bridge in Pittsburgh, USA, completing the critical bridge replacement operation in under 24 hours using its specialist skidding system. Working with Fay, S&B USA Construction, the prime contractor responsible for constructing the new bridge and demolishing the old one, Mammoet planned, managed and executed the lateral installation of the replacement bridge once the existing structure and demolition debris had been removed.

The installation was carried out using Mammoet's specialist skidding system—the same technology used to install the Chernobyl New Safe Confinement structure in 2016. A total of 42 skid shoes were distributed across four primary support runs, with each skid shoe independently controlled to lift the bridge from its temporary supports, precisely slide it into position and lower it onto its permanent bearings. The system's low height, high load capacity and advanced precision controls enabled the entire bridge to be moved 102 ft (31.1 m) in one continuous operation during a single day shift, while maintaining a tolerance of just one inch (2.5 cm) between the piers and abutments.

The skidding system was selected for its ability to withstand transverse forces while minimising stresses on the bridge during movement. To provide additional protection against twisting forces, a temporary frame was erected between the bridge and the skid shoes. Before the final installation, the team conducted a test slide, moving the bridge five feet (1.5 m) to verify deflections and ensure the system performed as expected. The project utilised Accelerated Bridge Construction (ABC) techniques, with the replacement bridge assembled alongside the existing structure over several months before being slid into its final position immediately after demolition. This approach reduced traffic disruption from nearly four years of intermittent lane restrictions under conventional construction methods to just 17 days of continuous, around-the-clock closure, allowing the existing bridge to remain operational until the final stage of the project.

The original Pittsburgh Commercial Street Bridge entered construction in 1948 and was completed in 1951. Carrying more than 100,000 vehicles every day, the bridge had undergone three rehabilitations—in 1980, 2006 and 2012—but eventually required replacement with a structure capable of carrying permit loads. The project marks the heaviest bridge ever moved by Mammoet in the United States and demonstrates the capability of its advanced skidding technology to execute complex bridge replacements within extremely tight timeframes. "We moved the entire bridge structure whole – the deck and the main support structures," said Mark Lane, Engineering Team Lead at Mammoet. "Our skidding system allowed for this type of solution to be feasible and provided the quickest means of replacing the bridge. "It has been a true global effort from our side to make this project happen. We've involved multiple offices and departments. We are now looking at utilising this system on several other projects now that it is in the US."