BergerWorld: 2nd Quarter 2008

The North Adams Bridge, located in historic Berkshire County, Massachusetts, was constructed in 1940 to carry MA Route 8 over the Hoosic River and the Boston and Maine Railroad. The 815-foot-long structure consists of 13 simple, non-composite, steel stringer approach spans and one simply supported truss span. The substructure consists of reinforced concrete abutments and reinforced concrete bents supported on bedrock and wood and steel piles. The Berger Group was selected by the Massachusetts Highway Department to evaluate the existing structure and recommend improvements.

The Team first performed an in-depth inspection, testing and evaluating the bridge, including seismic evaluations, fatigue checks and an extensive subsurface exploration program. Berger also performed an inspection and material testing program for the bridge deck, superstructure and substructure components to determine the extent of structure deterioration. In addition to detailed visual inspection, destructive and non-destructive testing was conducted on the deck slab and substructure components to establish concrete strength and chloride content. These include a half-cell potential survey, sonic/ultrasonic measurements and Ground Penetrating Radar (GPR) of the deck. The half-cell potential survey was conducted to assess the severity of steel corrosion and measure further corrosion risk; the sonic/ultrasonic data was used to evaluate the mechanical/strength characteristics of the concrete by identifying areas of low velocity/low strength; and the GPR data was used to identify areas of moisture infiltration/entrapment indicative of delaminating and cracking.

Next, Berger prepared a report summarizing their findings, including recommendations to replace the existing simple span girders with continuous spans to eliminate most deck joints, utilizing staged construction to ensure the maintenance of traffic during construction and, because the bridge is located in a historical district, minimizing any adverse impacts to the historic Heritage Park and surrounding businesses. Berger also prepared recommendations for approach roadway geometric and safety improvements, traffic management plans and detailed construction staging plans. Finally, Berger prepared final designs for the replacement of the bridge in its entirety, including steel rolled beams and plate girders which support a reinforced concrete deck and rigid frame. The reconstruction of the $22 million historic bridge is expected to begin in 2008 and be completed in 2012.