A major bridge in Massachusetts is slated for immediate repair during the state’s 40-day inspection of all bridges following the I35W bridge collapse in Minnesota earlier this month.
Inspectors found two deteriorated support beams within the infrastructure of the Longfellow Bridge. These “jack beams” help support the deck system which holds up the actual roadway which spans 2,135 feet carrying approximately 28,000 motorists, 90,000 transit users and a significant number of pedestrians and cyclists each day.
In the past couple of weeks crews were working to remove several 200-lb loose decorative steel plates from the underside of the bridge. At the time officials said these pieces had no impact on the sustainability of the structure and that age was the primary cause.
This week’s discovery of the deteriorating support beams has crews working ongoing during the overnight hours to install supplemental support beams until the structure begins planned renovations. Inspections of every aspect of the bridge are also continuing.
Boston’s Longfellow bridge, which connects Boston to Cambridge via the Charles River was slated to go through a major rehabilitation and restoration project with the main goals to repair deteriorated parts of the structure and make improvements to its ramped approaches.
The primary objective of the rehabilitation project is to address the bridge’s current structural deficiencies, upgrade its structural capacity (where appropriate), and bring the bridge up to modern code. In particular, according to Mass Highway, the structural steel elements supporting the bridge deck have deteriorated and require upgrading, and the abutments will have to be modified slightly to allow the sidewalk approaches to meet Americans with Disabilities Act (ADA) accessibility guidelines.
Preliminary design work was scheduled to be complete last December and a full-scale renovation of the entire project was expected to begin in 2008 with a completion time of 42 months, according to the Mass Highway website.
The Longfellow Bridge is among two dozen Massachusetts bridges similar in design to the Minneapolis bridge.
The existing bridge was built in 1908, extended in 1956 and rehabilitated in 1959. The bridge consists of 11 original open-spandrel steel arch spans plus two later steel later steel girder approach spans at the Cambridge end. It has an overall length of 2,135 feet and a deck width of 105 feet, including a 27-ft fenced median occupied by the Massachusetts Bay Transit Authority’s Red Line. The bridge’s substructure is built of granite block masonry and consists of 10 hollow piers and two hollow abutments. The two central piers carry the signature pairs of neoclassically inspired dressed granite towers that have given the bridge its nickname - the Salt and Pepper Bridge.