C&C Consulting Engineers served on a team responsible for performing a comprehensive inspection of the Tobin Bridge over the Mystic River. Owned and operated by the Massachusetts Port Authority, the Tobin Bridge is a complex steel truss bridge with multiple spans .
This deck truss is composed of two side trusses with two decks in between the trusses. The top deck carries southbound traffic from Chelsea to Boston while the bottom deck carries northbound traffic. The decks are supported by steel members: purlins which rest on stringers that are supported by floor beams. The floor beams frame into vertical members of the trusses via gusset plates.
On October 12, 2007, two members of C&C led by Mr. Christian D'Annunzio were on the lower deck in a scissor lift checking the connections of the floor beams to the truss members. The gusset plates at the truss typically have scattered areas of rust and minor section loss. Often, this rust runs vertically along the interface of the truss member and the gusset plate. As our inspectors were scraping the rust scale, they found something significant. At floor beam 16, a vertical crack along the interface of the gusset plate with the truss member was hidden by the expanding rust scale. Once the rust was cleaned thoroughly, the crack was found to run simultaneously from the top and the bottom of the gusset plate. What once had been 8 feet of vertical gusset plate was reduced to 3 feet of solid plate. Massport was immediately contacted, lanes were closed for buses and trucks, and emergency repairs were implemented within a week.
The inspectors of C&C were pleased and proud to have contributed to the safety of the Commonwealth of Massachusetts.