As part of MassDOT’s ABP, DTC designed and rated a new single-span bridge to replace a structurally deficient 92’-3” span bridge. The original steel girder-floorbeam-stringer system was replaced with a prestressed concrete Deck Bulb Tee Beam superstructure. The eight (8) new precast beams, which also serve as the bridge deck, have a 93’-0” span length and are supported by the original granite block and concrete abutments that were modified.
In order for Deck Bulb Tee Beams to form a continuous superstructure, concrete closure pours between the beams are needed. For this bridge project, Ultra High Performance Concrete (UHPC) was used for the closure pours. UHPC is capable of attaining an allowable compressive strength in excess of 20,000 psi. This system eliminates the need for a separate deck placement, which reduces the time of construction. This was the first MassDOT project that implemented both Deck Bulb Tee Beams and UHPC so there was close coordination between DTC and MassDOT’s Materials and Research Department to develop a workable Special Provision. Strain gages were installed inside two (2) of the Deck Bulb Tee Beams to acquire data that was analyzed by DTC for a period of two (2) years following the completion of construction.
Structurally sound portions of substructure from the original bridge were able to be salvaged, which reduced the overall project cost. At both abutments, the stem walls had to be demolished and replaced to accommodate the new superstructure. The north abutment required the installation of micro piles to support the new loads while the south abutment is constructed on bedrock. Retaining walls were added at three (3) corners of the bridge for slope stability.