A $1.4 Billion Project That Created a New Transit Hub and Improved Links to Six Subway Stations in Lower Manhattan Was Completed Last Year
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AUTONOMOUSTHE FULTON CENTER SYSTEMS WEALTH CREATION A $1.4 billion project that created a new transit hub and improved links to six subway stations in Lower Manhattan was completed last year. The engineer and freelance writer Hugh Ferguson talked to Craig Covil, Principal of Arup and New York Project Director, to find out the main challenges and how they were overcome. The Fulton Center is a $1.4 billion subway changing platforms had to use cramped glass pavilion, surrounding a giant eight- interchange in New York, that improves passages, or rise to ground level and cross storey dome structure capped with a connections between six subway stations in busy streets. Peak hour ‘dwell times’ for 53ft-diameter oculus, inclined to draw the Lower Manhattan and has regenerated an trains had become unacceptably high, maximum amount of sunlight down area badly affected by the 9/11 attack in reducing train frequency and increasing through the building to the lowest 2001 and the economic crisis of 2008. With congestion still further, and the system- subterranean level. It is lined with a large- Arup as lead consultant, the project wide knock-on effects could affect services scale installation, the Sky Reflector-Net, The northwest corner of the Fulton Center, showing the dome and the oculus rising above the steel and glass pavilion. At the rear is combined a wide range of engineering skills, all day. which involved a detailed collaboration the west end of the Corbin Building projecting on to Broadway, with the eight-storey ‘interstitial’ building in between © James Ewing from modelling pedestrian movements to A key to the solution was a new central between engineering, art and architecture. underground work in difficult ground and interchange building, the Fulton Center, on However, it was underground that the managing the project through a succession a site facing Broadway, through which most real engineering challenges lay. Some 30 m of stops and starts caused by uncertain of the 300,000 passengers using the below ground was sound bedrock, too deep funding. The Fulton Center opened in stations each day could be routed. This and too difficult to reach by piling. Near the November 2014, and was announced in facility was designed in conjunction with surface was a typical mixture of urban fill. In October 2015 as the winner of this year’s three architects: UK firm Grimshaw between, where almost all the work was to British Construction Industry International Architects; the preservation architect Page take place, was a treacherous mixture of Award. Cowley; and, HDR/Daniel Frankfurt. The sands and silts including Manhattan’s THE FULTON The principal purpose of the Fulton Center was required to be much more than notorious ‘Bull’s Liver’ soil, a vibration- Center project was to join up six stations on a functional transport interchange with sensitive stratified silt and fine sand. This is 11 separate lines that were expressly built by retail space above. New York needed an prone to consolidation, causing settlement competing private railway companies (1902– exciting, welcoming gateway building to under construction vibrations, and rapidly 1933) so that they would not join up. Lower Manhattan that would symbolise loses strength when disturbed or wetted: in Constructed in the early 20th century, the and catalyse the area’s regeneration. The its saturated state, it can quake like jelly CENTER, NYC entrances were narrow; passengers result is a simple three-storey steel and when shaken, and even flow like a liquid. 24 INGENIA INGENIA ISSUE 65 DECEMBER 2015 25 AUTONOMOUSTHE FULTON CENTER SYSTEMS WEALTH CREATION testing and analysis, and combined this with excavated beneath the station, and the PROJECT PLAN its knowledge of the behaviour of cast-iron exposed mini-piles replaced with CLASSIC BUILDING RESCUED A lot of the construction work for the project Along the south side of the Fulton Center linings of a similar vintage in London tube permanent columns. Meanwhile train ran the risk of disturbing the existing tunnels stands the Corbin Building, which was tunnels. This was done to assess the ductility speeds on the Subway were restricted, to and stations, most of which had been scheduled for demolition at the start of the of the iron and the structural integrity of the reduce vibration but also to reduce the constructed by ‘cut-and-cover’ and all of project. The narrow eight-storey building, large horizontal forces caused by sharp which were ‘floating’ in the sands and silts, tunnels and, in particular, to determine the braking. wedge-shaped in plan built in the 1880s including the Bull’s Liver. At the start of the maximum deflection that could be tolerated It was early in one of these weekend was dull grey from a century and more of project, temporary station closures had been in the lining: fortunately, the iron proved less possessions that a serious loss of ground grime, its distinctive pepper-pot roofs long planned, but this was ruled out because of brittle than anticipated. was detected around one of the mini-piles gone and its façade littered with iron fire the transport disruption it would have Here, as elsewhere on the project, as it was being placed – so serious that the escapes and with air conditioning units caused. So, all the work had to be carried out potential movement was modelled and parts subway operator had to be informed that hanging from windows. The architect was around a live railway operating 24 hours a of the stations and tunnels were fitted with the work would not be complete for hand- Francis Hatch Kimball, described by day, with 300,000 passengers passing deflection monitoring equipment. Sometimes over and train operations at 5.00 am the contemporaries as ‘the father of the through each day, and with just occasional and in some places, the tunnel tubes were following Monday. Resources were brought skyscraper’. Although modest by modern weekend closures. tending to sink, at other times to float in from other sites and by concerted standards, at the time of its construction in On top of this, the team had very little How the new Fulton Center interconnects six subway stations on 11 lines. Running north-south is the upwards. Phasing of the work proved critical, oldest and busiest route, the 4 and 5 Lines, built in 1902, which separates the new Dey Street concourse efforts, the hand-over was only delayed by 1888-9 this was (briefly) Manhattan’s tallest space at ground level beyond the confines from the new Transit Center building with the Corbin Building in front. Running east-west is the newest not just to control deflection in the tunnel, half an hour, the biggest impact of any building. Kimball was a pioneer in the use of of the Fulton Center site itself, and no full and deepest, the A and C Lines constructed as cast iron tubes in 1933, with a large cut-and-cover but to cope at all times with pedestrians mezzanine above © Arup event during the project. ironwork and terracotta, both materials street closures were permitted. using the stations and mezzanine, and traffic The first challenge was the station with using Fulton Street overhead. the A and C tube lines beneath Fulton Street The new Fulton Center ‘floats’ on a which had been constructed in the 1930s in concrete box, built with secant (interlocking) an unusual way. First, the two running pile walls and a 1.7 m-thick raft laid directly tunnels had been driven, under compressed on the carefully prepared sands and silts. The air just below the ground water level, and walls were propped temporarily by heavy lined with cast-iron segments; then the steel struts and permanently by the space between had been opened up to diaphragm effect of the Fulton Centre’s form the platforms; and finally a long concrete floors. A similar technique was used mezzanine area had been built over the top for creating the new, wide passenger by cut-and-cover, for pedestrian ramps and concourse underneath Dey Street – see corridors. The mezzanine needed to be subway schematic. rebuilt to accommodate new lifts and The trickiest part was connecting the two, escalators, with an original line of columns by opening up the area under the 4/5 Line down the centre removed and a new steel station as a passage. First, some 120 steel A-frame roof installed to transfer loads to the mini-piles up to 30 m long were sunk to side columns. support the old station box, which was just The greatest concern was the effect all resting on the ground with shallow this work and the change of loading would insubstantial foundations. Most of the new have on the running tunnels beneath: if the mini-piles were sunk between the tracks cast-iron lining cracked, water would come during weekend possessions. Jet-grouting A 3D CAD/ BIM model used by different construction disciplines to look at the mechanical, electrical, in and the tunnel could flood. Arup used the structural, civil and plumbing elements of the Center. The model was uploaded into Bentley augmented was used to create two cut-off walls directly old as-built records, as well as taking cores of reality software and then used by engineers onsite with iPads to compare site conditions with ‘as-built under the station, forming the side walls of Looking across Broadway at the narrow west elevation of the Corbin Building, and the dome with its design records’ © Arup inclined oculus and skylight under construction to the north © Arup the original cast-iron lining for laboratory the new passageway. Then the soil could be 26 INGENIA INGENIA ISSUE 65 DECEMBER 2015 27 AUTONOMOUSTHE FULTON CENTER SYSTEMS WEALTH CREATION Throughout the critical underground operations, the building was fitted with deflection monitoring equipment, the readings linked via software to hand-held devices so that MASSMOTION The Arup software MassMotion, though including doors, stairs and passageways.