Manhattan West Platform, New York City, New York
SEGMENTS, FALL 2013, VOL. 58
The Manhattan West Platform project (Fig. 2) is the first phase of Brookfield Properties’ Manhattan West development project, comprising 5.4 million square feet of premier office, mixed-use and public space.
In order for the Manhattan West development to become a possibility, the Owner determined that a platform to segregate and safely separate the tower construction from the active rail yard was necessary. This active rail yard consists of 15 tracks operated by Amtrak, Long Island Rail Road (LIRR), and NJ Transit that carry roughly 1,400 trains daily from Penn Station throughout the northeast. This constraint required a solution to erect some type of ‘protection shield’ that can span approximately 240' across these 15 tracks over an area approximately 480' wide. Between 2010 and 2012, a solution was developed that changed the construction strategy from a multi-span steel platform with numerous footings and intermediate bents located between active train tracks to a precast segmental bridge concept that could span roughly 240' over the entire yard while minimizing track level work.
The platform consists of 612 precast segments, each averaging 55 US Tons. The platform is broken down into 16 spans, 10 of which are composed of 39 segments, and 6 of which are composed of 37 segments, in order to accommodate the core for the future NE tower. Constraints for the segments mainly included a weight restriction of 58 US Tons in order to truck them from the precast yard to the jobsite in midtown-Manhattan. The average span is 30' wide and contains 20ea 37x.6" strand bonded tendons and 14ea 31x.6" strand bonded tendons, with provisions for 4ea additional 31x.6" strand future tendons. Each span contains nearly 100T of PT and once fully assembled, weighs on average 2,400 US Tons.
In order to fabricate, assemble and erect these 16 spans, Brookfield hired Rizzani de Eccher, USA Inc. (RdE USA), a General Contractor that specializes in match cast precasting and erection of precast segmental bridges.
To cast the 612 segments required for the project, RdE USA combined their expertise and equipment with Jersey Precast, a local precast facility in New Jersey. RdE USA purchased 5 moulds from Deal, a member of the de Eccher Group that specializes in the design, engineering, and fabrication of customized bridge erection equipment. There are 3 typical moulds that will be used to cast 452 segments, 1 variable mould used to cast 128 segments with varying web thicknesses, and 1 pier segment mould used to cast the 32 pier segments. The first segment was cast on January 8, 2013.
The span-by-span launching equipment has also been designed and engineered by Deal. The equipment is currently being fabricated in the company’s native Italy. The LG is designed to transport and set the individual segments, utilizing an overhead winch gantry, across a Temporary Protection Platform (TPP) that consists of a steel girder bridge with two intermediate bents that are founded between the active rail road tracks. Once the 39 or 37 segments are stressed and the span is self supporting, the overhead gantry will lift the span and travel transversely to set the span in its final position over the rail road. Moving the span over the open rail yard is scheduled to occur during a two hour window on Sunday mornings, due to the de-energizing requirements as well as the large train volume through this area. Once the spans are erected in their final position, a 6" slab will be cast over the entire platform. This space will serve as an outdoor plaza and will provide pedestrian access to the Manhattan West Development upon completion.