ASPIRE is a quarterly magazine published by PCI in cooperation with the associations of the National Concrete Bridge Council. The editorial content focuses on the latest technology and key issues in the Concrete Bridge Industry.
Issue link: http://www.aspiremagazinebyengineers.com/i/439391
PROJECT Platform Spans Manhattan Innovative launching gantry sets 2400-ton beams to create platform spanning 15 rail lines for high-end development in the sky by Phil Marsh, McNary Bergeron, and Andrea Travani, Rizzani de Eccher USA Precast concrete bridge components continue to offer solutions to new challenges, achieving longer spans and greater load capacities. Those capabilities were optimized for a unique project in Manhattan, in the heart of downtown New York, N.Y., that used bridge construction technology in a novel fashion. It features 2400-ton segmental concrete box beams spanning 240 ft to create a platform from which will rise two 1000-ft-tall, class A office skyscrapers, a 60-story luxury condominium tower, a boutique hotel, mixed-use retail space, and an expansive pedestrian plaza linked to the new High Line Park on Manhattan’s west side. This innovative and challenging solution was devised when Brookfield Office Properties sought to connect the two portions of its 7-million-square-foot development that spanned 15 railway lines and related electrical services near Penn Station in Manhattan, where development area is scarce. The developers wanted to create a platform on which they could build a parking structure topped by a public plaza with two high-rise office buildings flanking the site. Officials contacted the Manhattan West project construction manager to discuss the possibility of using a launching gantry to build a 240 by 480 ft steel platform over the existing rail lines, located in an open trench 55 ft below street level. The idea was to use some overhead equipment to avoid disrupting activities at track level. Because of the high level of activity at track level, no columns or supports for the platform could be built at rail level. But the steel solution was problematic due to the weight of the girders. Instead, RdE came up with the idea of a segmental platform to span the gap and contacted the construction engineer to start working on the design of this record-length bridge. The future office buildings’ columns will not bear on the platform itself. The core structures of the building will be founded on bedrock, while the curtain-wall columns will penetrate through deck openings in the platform and extend down to track level. The smaller columns for the parking structure will bear on the platform and support the pedestrian plaza above it. The site provided major challenges. The project would have to be built in the heart of Manhattan over some of the busiest railway tracks in the world without touching down at track level. Crews had to absolutely ensure the integrity of the girder setting process, to ensure no slippage or accidents would interfere with the rail service. Rail service outages to allow work at track level were available for no more than 2 hours at a few limited times. Transverse Launching Gantry The design features sixteen 2400-ton segmental beams, each comprising 37 to 39 match-cast precast concrete segments that span the 240-ft opening between the two sides of the development. The beams were set in place with a custom-built launching gantry that worked from overhead to construct and set a beam. The gantry ran on rails running parallel to the abutments that supported the beams. PROFILE MANHATTAN WEST / NEW YORK, NEW YORK PRECAST PLATFORM DESIGN ENGINEER AND CONSTRUCTION ENGINEER: McNary Bergeron & Associates, Broomfield, Colo., and Old Saybrook, Conn. OVERALL PROJECT CONSTRUCTION MANAGER: Turner Construction Co., New York, N.Y. MANHATTAN WEST PROJECT CONSTRUCTION MANAGER: Rizzani de Eccher USA, Bay Harbor Islands, Fla. and Pozzuolo del Friuli, Italy SUBSTRUCTURE DESIGN ENGINEERS: Entuitive, Toronto, Canada PRECASTER: Jersey Precast, Trenton, N.J.—a PCI-certified producer POST-TENSIONING CONTRACTOR: Tensacciai, Milano, Italy