Case Study: A Jointless Structure to Replace the Belt Parkway Bridge Over Ocean Parkway

This paper presents the design of a 65.8 m (216 ft) long three span continuous, jointless bridge using the semi integral abutment concept to relieve the substructures of most of the seismic forces. As part of their capital program, the New York City Department of Transportation (NYCDOT) proposed to replace the rapidly deteriorating Belt Parkway Bridge over Ocean Parkway in Brooklyn, New York in 1999. On the basis of a competitive selection process, the Granite Halmar (contractor)/ Gannett Fleming (designer) team was selected for this replacement project, under a Design-Build contract. The bridge carries the Belt Parkway, a regional corridor traveled by 166,000 vehicles daily, over Ocean Parkway, a scenic landmark in south Brooklyn. The existing bridge was a two span steel multi girder structure with a wall type center pier and full height reinforced concrete abutments. The proposed bridge is a three span structure, longer and wider to span over the proposed service roads on Ocean Parkway underneath and to accommodate full width shoulders on the bridge. The three spans are 18.9 m (62 ft.), 32.8 m (108 ft.) and 14.1 m (46 ft.), respectively, for a total length of 65.8 m (216 ft.). The abutments consist of a single row of pipe piles supporting a concrete cap beam, and the piers are multi column bents with concrete capbeams supported by minipiles. The design incorporated the semi integral abutment concept, with the backwall cast integrally with the deck and the deck joint moved over to the approach slab beyond the abutment. In addition, the bridge was made continuous for live load at the piers by introducing girder splices over the piers. The structure was fixed at the west pier and allowed to expand at all other supports. Under a regular design, the continuity in the superstructure along with the fixity only at one pier would have resulted in extensive seismic forces on that one pier. However, under this proposed semi integral abutment concept with the backwalls cast integrally with the deck, the passive pressure generated by the embankment behind the backwalls was utilized in absorbing the seismic forces, thereby reducing the resulting seismic forces at the fixed west pier. In addition to eliminating deck joints, the use of stainless steel reinforcement, and the use of precast (Inverset) deck elements considerably enhanced the service life of the bridge, beyond the 50-year life required by NYCDOT. Due to staging of construction, the superstructure of the first half the bridge was erected in ten days and the second half of the bridge was also completed in record time. The bridge replacement was completed by November 2004, a month ahead of the already aggressive schedule.