AirTrain JFK

AirTrain JFK
Henry W. Hessing, P.E.

ABSTRACT: THIS PAPER DESCRIBES THE LONGEST SEGMENTAL GIRDER CONSTRUCTION ERECTED IN THE NEW YORK CITY ENVIRONS.

Constructed: 1998 – 2003
Project type: Light rail line
Cost: USD 1 900 000 000
Location: Queens, New York
Owner: Port Authority of New York and New Jersey
Contractors: Skanska USA Civil and Bombardier Inc.
Design: STV Incorporated
Mueser Rutledge Consulting Engineers
Figg Engineering Group
1. INTRODUCTION

The fully automated JFK Airtrain was designated a finalist in the competition for ASCE’s 2005 Outstanding Civil Engineering Achievement Award. The $ 1.9 billion Airport Access Project connects John F Kennedy International Airport (JFKIA) located in Jamaica, New York with two major intermodal connections –Long Island Rail Road (LIRR) and New York City Transit (NYCT).

2. DECISIONS

The reason to construct a light rail system was to meet JFKIA growth forecasts. Design/Build/Operate/Maintain (DBOM) project delivery method was selected in order to fast track the normal Design/Bid/Build process. Air Rail Traffic Consortium (ARTC) was determined to be the low bidder and consisted of the contractors and designers noted above.

The Federal Aviation Authority (FAA) issued its Record of Decision on the Environmental Impact Statement for the approval of JFK’s Light Rail System (LRS) in July 1997. Ground breaking took place in September 1998. The system opened on December 17, 2003 the centennial of the birth of aviation.

3. DEFINITION OF LIGHT RAIL

The Transportation Research Board Committee on Light Rail Transit defines light rail as “a mode of urban transportation utilizing predominately reserved but not necessarily grade separated rights of way. Electronically propelled rail vehicles operate singly or in trains. LRT provides a wide range of passenger capabilities and performance characteristics at moderate costs.”

4. LIGHT RAIL AT JFKIA

The light rail system at JFKIA is called AirTrain JFK. AirTrain makes frequent stops around the airport – including the airline terminals, parking lots, hotel shuttle areas, and rental car facilities.

4.1 STATIONS AND ROUTES

The JFK Airtrain stations are fully enclosed, heated and air-conditioned with platform doors, wide escalators, large glass enclosed elevators, moving walkways to airline terminals, and 240-foot platform lengths. Ten stations serve on and off airport.

The system consists of three overlapping routes:
· the Howard Beach route;
· the Jamaica Station route; and
· the Airline Terminal route.
The Howard Beach route starts at Howard Beach and stops at Lefferts Blvd, while the Jamaica Station route starts at Jamaica Station on the Long Island Railroad (this station stop is called Sutphin Blvd. on the subway). Both routes meet at Federal Circle, then loop counterclockwise around JFK Airport, serving 6 CTA environmentally controlled stations:
· Terminal 1 (the first station in the loop);
· Terminals 2/3;
· Terminal 4;
· Terminals 5/6;
· Terminal 7; and
· Terminals 8/9.
The Howard Beach and Jamaica Station routes return to Federal Circle, then split, going back to their respective termini. The Airline Terminal route serves 6 terminal stations, operating in a clockwise loop, in the opposite direction to the Howard Beach and Jamaica Station routes.

4.2 CONNECTIONS

4.2.1 Long Island Rail Road Connection

The Long Island Rail Road (LIRR) operates approximately 700 trains per day through the Jamaica train station. It is one of the busiest rail stations in the world. Construction of the connection between Airtrain and the LIRR required nighttime and weekend work, and was accomplished one platform at a time. Access is provided to LIRR and the “E”, “J”, and “Z” subway lines.


NYCT Connection

The connection at Howard Beach, Queens included renovation of the “A” train subway station creating an intermodal station. Nighttime and weekend work were required as this heavily traveled subway line provides direct access to the west side of Manhattan.

5 DESIGN AND CONSTRUCTION CONSIDERATIONS

5.1 PERMITS

A review and analysis of the jurisdictions of over forty public and private agencies was performed and tabulated along with a description of their individual requirements. From this analysis, it was concluded that eleven (11) different types of permits were required from four (4) agencies.

For each permit, ARTC determined the name of the permit, issuing agency, described the permit, highlighted the application requirements, determined the permit fee, determined the regulations or stipulations with cost and schedule implications, estimated the permit due date and schedule duration. A schedule of required permits by location with application dates was prepared. Environmental permit applications were the first to be obtained.



5.2 CLEARANCE ENVELOPE

Definitions: The clearance envelope is the space in which no physical parts of the system, except the vehicles are placed, constructed or protrude. The static envelope is the outline of the physical dimensions of the vehicle in a stationary position. The dynamic envelope is the outline of a moving vehicle on tangent track experiencing normal body roll. The maximum vehicle dynamic envelope is the dynamic envelope that is modified for maintenance factors such as wear to both wheel and rail, freeplay between the two, and for primary and failed suspension. The maximum vehicle dynamic envelope considers lateral, vertical and rotational displacements under the required specified conditions of the design criteria on tangent track. All envelopes are normally referenced from the top of the (low) rail and the centerline of track.

Calculations were performed to determine the static envelope, dynamic envelope, maximum dynamic envelope which was based on Bombardier’s design vehicle, a future vehicle, the design vehicle, clearance envelope, effects due to curvature, effects due to superelevation, construction tolerances, seismic clearance, running clearance in order to determine minimum track clearances.

With minimum clearances known, horizontal and vertical alignments and clearances could be designed. As there are many factors that come into play, as design of alignments is an iterative process.

5.3 UTILITIES

5.3.1 Relocations

The typical guideway span varies between 80 and a maximum of 120 feet. This meant installing approximately 450 concrete foundations along the 8.3-mile route. As the Van Wyck expressway is a major north south arterial, primary relocations included drainage, electrical and communications. On the airport, utility relocations included drainage, sewers, force mains, gas, water, power electric, communication lines, and thermal distribution (chilled and dual hot water) lines used to heat and cool the airline terminals. Every effort was made to survey and identify all utilities in the preliminary design phase. Known utilities were marked in the field prior to excavation. Test trenches were excavated around the perimeter of each pile so utilities could be verified. The angle of every utility was measured, plotted and verified. Unknown utilities were encountered. These had to be identified for relocation design and construction.

5.3.1 Electrical

27 kV feeders, along with one main substation distribute power to seven substations for traction power and nine substations to operate the passenger terminals.

5.3.2 Drainage

The New York City environs receive approximately 44 inches of precipitation per year. As most of the right of way required for the light rail system passed over paved areas, introduction of the elevated guideway would not increase runoff.

The original cross section indicated individual plinths to support track. During design, this was changed to a continuous concrete plinth for ease of constructing and removing formwork. Determining the low points in the vertical alignment and collection before expansion joints became the basis of locating scuppers. Runoff went from the scuppers through 12 - inch diameter plastic pipe installed in the center of concrete columns to the existing below grade drainage systems.

6.0 CONSTRUCTION

6.1 Construction Staging Maintenance of Traffic

Construction staging and maintenance of traffic meetings were held twice a week for this project and once every two weeks for coordination with other on- airport projects which included reconstruction of Terminal 4 – the International Arrivals Terminal and reconstruction of Terminal 7 – British Airways Terminal.

Construction staging in an operating airport meant temporary and permanent loss of parking spaces. This was a major concern of the airport as customer satisfaction is of high importance. To mitigate these losses, every effort was made to minimize the construction area and length of time required.

Construction along the median of the six - lane, Van Wyck Expressway required maintaining three lanes of traffic during peak hour traffic. Existing roadway lighting was removed and a travel lane was constructed in the shoulder areas. This required adjustments to the on and off ramps and retaining walls along with new drainage installation. New lighting fixtures were installed. This allowed traffic to be diverted to two of the existing and the new right lane constructed in the shoulder areas in order to maintain three lanes of traffic in each direction.

Daytime work was performed in the median and the abandoned left lanes in both directions during off-peak hours when one additional lane could be taken so long as two lanes were maintained for the traveling public. Night work required three full lanes in operation in both directions at all times.

6.2 Pavement Restoration and Reconstruction

ARTC prepared a summary of pavement design criteria, in accordance with design standards used by the agency having jurisdiction over each roadway, for the expressway mainline, ramps, service roads, local streets and airport roadways, and vehicle types. This was the basis of the Pavement Design Criteria for restoration and reconstruction.

7. SUBSTRUCTURE

7.1 Seismic Design Considerations

Liquefaction is a phenomenon in which the strength and stiffness of a soil is reduced by earthquake shaking or other rapid loading. Liquefaction and related phenomenon have been responsible for tremendous amounts of damage in historical earthquakes around the world.

Liquefaction occurs in saturated soils, in which the space between individual particles is completely filled with water. This water exerts a pressure on the soil particles that influences how tightly the particles themselves are pressed together. Prior to an earthquake, water pressure is relatively low. Earthquake shaking can cause water pressure to increase to the point where soil particles can readily move with respect to each other. When liquefaction occurs, the strength of soil decreases and the ability of a soil deposit to support bridge foundations is reduced.

Deep loose sand characterizes the soil conditions at JFKIA. Soil borings indicated the potential for liquefaction up to a depth of 20 feet under a seismic event with peak rock acceleration of 0.15g. Additionally, the water table is high.

Besides calling for conventional design for forces and displacements, the seismic design criteria also required that additional limitations be met by the foundations and superstructure in order to allow the system to return to operation shortly after a seismic event meaning repairs would be limited to track work only.

7.2 Piles

Piling is an arrangement of beams installed in the ground that provide a foundation for substructure units. These beams for the most part consist of either steel H beams (H-piling) or hollow steel tubes that are filled with concrete and sometimes reinforcing steel (Cast-in-place piles). When piles are used, they are designed to carry the entire load of the substructure unit under which they are placed.

For years, experts in the pile foundation profession have recognized the advantages of a uniformly tapered pile over a vertical-straight-sided pile. "It may be concluded that the taper has a substantial beneficial influence and that for piles of equal embedment in a given sand, a tapered pile will have substantially greater ultimate bearing capacity than a straight-sided or cylindrical pile." Special Report 36— Highway Research Board

“Underpinning & Foundation Constructors, Inc. was awarded a contract to install more than 5,500 150-ton and 200-ton capacity piles to support the 8.3 mile long guideway. Underpinning invented a new pile type using a tapered steel lower section (25 feet) with steel pipe upper section (45 – 75 feet) and called it the Tapertube. These piles are 50 percent thicker than monotube piles, which allows them to be driven to higher driving resistances at lower stresses. The heavier steel also allows piles to be driven quicker once underway. The work was performed using hydraulic driving equipment built in Finland. The high mobility of the pile rigs, combined with highly efficient hammers, allowed for rapid installation in the tight confines of the active airport roadway system and in the center median of the heavily traveled Van Wyck Expressway.” – Underpinning & Foundation Constructors, Inc. web site

Piles were topped with 20 foot by 20 foot by 5 to 8 foot deep concrete footings. Cast in place concrete piers sat upon the footings and varied in size up to 45 feet in height and six (6) feet in diameter.


8.0 SUPERSTRUCTURE

Segmental Girders

The Request for Proposals (RFP) required the successful bidder to prepare the final design. Preliminary design envisioned single and twin – box concrete girders. The alternate was a composite steel box with a composite reinforced steel deck slab.

The final design for the guideway superstructure was precast segmental construction utilizing seismic isolation. The primary defining features are single-cell or dual cell box girders with cantilevered deck slab. Tendons are arranged in top and bottom slab for cantilever construction, match-cast joints between segments, and multiple shear keys. The single cell box supports a single tract while the dual box cells support a dual track configuration. Post tensioning tendons were applied across span closures to create multiple span continuous units.

Seismic isolation was achieved by using lead-rubber bearings that allow the superstructure to “float” during a seismic event. For non-seismic loading the bearing was fixed laterally relative to track centerline with movement limited to 1/8 inch. The contractor developed an elastic restraint system that would withstand non-seismic loads with a factor of safety but would fail at design level seismic loads, thus freeing the structure to float and avoid damage from seismic forces.

Preliminary design envisioned overhead launching trusses in the form of erection gantries. Most of the guideway was constructed span by span with cranes and erection trusses for safe maintenance of vehicular traffic. Portions on tight curvature or longer spans were built in balanced cantilever.

9. TUNNEL

Cut and Cover Tunnel

It was required that the elevated light rail system descend approximately 35 feet below grade to pass underneath the airport’s taxiways. It then has to rise to pass over the VanWyck Expressway, one of two arterial highways that provide ingress and egress to the central terminal area (CTA). Cut and cover construction was implemented. Since eighty percent of the tunnel was below the water table “bathtub” construction utilizing chemical grouting was employed in constructing the foundation. Pumps are required twenty-four hours per day.

10. TRACK

The track way features running rails, safety walkways, traction power, and communication ductbanks. The track that AirTrain JFK cars ride on is a combination of direct fixation track and ballasted track. Direct fixation track was originally developed for the Bay Area Rapid Transit (BART) system in San Francisco in the late 1960s. Since that time, direct fixation has become the most popular method for installing track on elevated concrete structures and in underground tunnels. This system uses two steel plates with a thick rubber layer between, which creates a sandwich-type configuration. The sandwich assembly is called a direct fixation fastener, or DF fastener, because the DF fastener is bolted directly to the concrete, forming the track bed. The DF fastener uses a Pandrol Clip to secure the running rails in place. A Pandrol Clip is a G shaped piece of metal used to attach the running rails to the crossties. Pandrol is the manufacturer’s name and their rail fastening products are used worldwide.


The DF fastener is bolted to a raised concrete pad known as a plinth pad. The concrete forms for the plinth pad are set to the final elevation needed for the running rails and also provide superelevation of the tracks on curves. Superelevation means that one rail is set higher than the other rail in curved areas. Raising one rail allows the train to bank into turns much like a car on a highway. This allows the train to negotiate turns with greater passenger comfort.

Ballasted track is the conventional method of constructing at grade track and consists of using railroad ties to securely connect the two sections of running rail upon which cars travel. The ties and rails are held in place by crushed stone called ballast. AirTrain JFK uses the most modern version of ballasted track. Instead of using wooden railroad ties, AirTrain JFK uses precast prestressed concrete ties. The running rail is 115-pound rail, which is one of the standard rail types used throughout the railroad and transit industry. Instead of using railroad spikes to connect the running rail to the tie, AirTrain ballasted track also uses Pandrol Clips to attach the running rails to the concrete ties.
The distance between AirTrain JFK running rails, referred to as the track gauge, is the United States standard of four feet, eight and one half inches. AirTrain JFK ballasted and direct fixation track meet US Federal Railroad Administration requirements.

Slattery Skanza’s tract division assembled and installed1 500 foot long continuous rail strings and placed direct fixation tract, linear induction motor rail and power rail.

11. TECHNICAL DESCRIPTION OF TRAIN OPERATIONS

11.1 Driverless System

AirTrain JFK is designed to be a fully automated driverless system. Computers control train movements using a moving-block signaling system. AirTrain JFK has two modes of operation: automatic train operation, utilizing the computer system, and manual operation which allows a driver to move trains for maintenance activities at a maximum speed of 15 mph, which is controlled by a speed governor. When operated in either of these modes, a train is controlled to ensure a safe speed on all sections of track including all curves. During the testing phase, some tests were run in manual mode with the speed governor disabled. In this situation, there is no speed restriction. The train speed is controlled solely by the train operator similar to manual train operations at other railroad and transit properties. Operating a train beyond the maximum15 mph speed, requires a higher level of operational skill and a more detailed knowledge of the track alignment.

11.2 Cars

Each car has four pick-up shoes to obtain power from a 750-volt, direct-current power rail comparable with NYCT and LIRR systems. AirTrain JFK has a fiber-optic communication network, which links all of the stations and terminals to the Operations Center (OMSF). This allows for station dynamic signage, full public address and closed circuit television. AirTrain JFK cars have two linear induction motors (LIM) and two propulsion inverters (conversion of direct current to alternating current). Braking is performed by regenerative dynamic service brakes, which are supplemented by electro-hydraulic disc brakes. AirTrain JFK vehicles are also equipped with emergency track brakes.

The cars have been constructed with steel underframes and aluminum roofs, sidewalls and bulkheads. Each car has two self-steering steel trucks with four wheels per truck. A linear induction reaction rail is located between the running rails. The reaction rail is an aluminum and iron plate that carries no electrical current. It reacts with the linear induction motors on the AirTrain JFK cars to produce an electro-magnetic force that propels the cars.

12. SUMMARY


DBOM shortened design and construction time by several years. The shortened time duration was reflected in lower overhead costs and a reduction in overall project costs. In the first year of operation, the PA estimated that 2.6 million passengers used AirTrain JFK.