Project Overview
In the Big Apple, bridges are essential for traveling between the city’s boroughs. And while many iconic bridges in New York City—including the Brooklyn Bridge, Manhattan Bridge, and others—are best known as thoroughfares for automobile traffic, they also serve pedestrians and cyclists. When the 2780-ft-long Robert F. Kennedy (RFK) Bridge, which links the boroughs of Manhattan, Queens, and the Bronx, required significant upgrades, including pedestrian access improvements, the Metropolitan Transport Authority (MTA) partnered with precast concrete producer The Fort Miller Company and engineering firm COWI on a precast concrete solution involving multiple product types and ultra-high-performance concrete (UHPC).
Walk (and Bike) This Way
The existing scissor stairway connecting the RFK Bridge sidewalk to the grade below represented a 50-ft climb, and MTA officials sought a new design to help encourage additional bike and foot traffic and meet Americans with Disabilities Act (ADA) requirements. This project posed considerable logistical challenges for the contractor, Walsh Construction Group: the jobsite was in a population-dense area, and it had a small footprint constrained by several barriers, including a highway, a river, and another bridge. These issues were addressed thanks to the use of an assortment of precast concrete components, including haunches, deck panels, ramp panels, and architectural retaining walls.
“MTA chose precast concrete components over cast-in-place wherever practical to achieve an accelerated schedule and reduce the time impact on this project,” said Joshua French, vice president of estimating, sales, and marketing for the Fort Miller Company. “Using precast concrete also reduced the amount of traffic coming into and leaving the project site. This was a huge benefit due to the difficult access and the limited amount of space available.”
Given the location and changes in elevation, designers chose an innovative switchback design for the pedestrian and cycle bridge. This design features precast concrete haunches, which were connected to the side of the existing cast-in-place highway bridge piers using UHPC. With UHPC, cure time was significantly reduced, enabling faster erection, and the need for elaborate formwork and scaffolding at the project site was eliminated. The team also used UHPC when installing the precast concrete deck panels for the pedestrian and cycle bridge, taking advantage of color matching to provide seamless transitions from panel to panel across the deck. Closer to ground level, crews installed architectural precast concrete retaining wall panels; these panels were then backfilled and topped with precast concrete ramp panels that were joined with color-matched, UHPC field-cast connections.
Despite minimal available space at the jobsite, the project team leveraged precast concrete to carefully coordinate the delivery and staging of the precast concrete deck elements. This led to a shortened construction timeline and saved money by minimizing on-site labor costs.
The result is modernized access to the bridge. “This project brings the RFK Bridge’s original structure and access up to modern ADA standards,” French said. “Once fully implemented, it will more efficiently and safely connect Manhattan and Randall’s Island.”
Mason Nichols is a Grand Rapids, Mich.-based writer and editor who has covered the precast concrete industry since 2013.
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