As a bridge-design class, movable bridges have four distinct
types. All four types are well-represented in New York City, with 12 bascule
bridges leading in number, followed by the seven swing-span bridges, four
vertical-lift bridges and two retractile bridges. All 25 bridges are under the
control of the NYCDOT.
Most of these bridges are of early 20th century vintage and
the NYCDOT acknowledges that the lack of a consistently good preventive
maintenance program for the past 75 years has impaired some bridges' moving
functions. To correct these bridges' malfunctions and some potential safety
hazard issues, NYCDOT is currently rehabilitating six of them, including
replacing some bridge sections on the Third Avenue (swing) Bridge that crosses
over the Harlem River. The bridge carries one-way southerly directed traffic
starting in the Bronx by access ramps at Third Avenue, East 135th Street,
Bruckner Blvd. and Lincoln Avenue Crossing the Harlem River and into Manhattan,
the bridge has exit ramps to East 128th Street, East 129th Street, Lexington
Avenue and the Harlem River Drive.
The Third Avenue Bridge was erected in 1898 at a cost of
$2,794,268, replacing an existing swing bridge that was obsolete. Early in the
1900s an electric-powered motor replaced a steam-powered system for rotating
the bridge's swing-span midsection, thus enabling craft and cabin cruisers to
pass through to the other side of the bridge.
Despite the major construction and rehabilitation performed
on the bridge in the mid-1950s, the NYCDOT recently decided some bridge sections
needed to be replaced, including the swing-span midsection. It recently let a
contract for $118 million to rectify all issues and work began in October 2002.
NYCDOT projects the project will be completed by April 2005.
The project is being accomplished in five carefully planned
stages so traffic can use some of the bridge's traffic lanes, albeit with
traffic-flow efficiency compromised. At the later stages, a temporary bridge
will serve the traffic while the existing bridge is shut down for the replacing
of the midsection. With stage one completed in March of this year, stage two is
now under way. This report deals with these first two construction stages and,
more specifically, with the construction of the new piers.
The Third Avenue Bridge is a cantilever truss bridge with 31
spans that includes the 300-ft-long swing-span midsection. Its overall length
is 2,800 ft and it features two divided, 26-ft-wide dual traffic lanes that
form the complete roadway. Running parallel on either side of the roadway are
two 9-ft-wide sidewalks.
The engineering firm Hardesty & Hanover LLP,
headquartered in New York City, is heading the design and details of the
project for the NYCDOT. Pointedly, the project calls for the replacement of the
swing-span midsection and 1,351 ft of approach spans. The firm also designed
the temporary bridge, which will be built sometime next year.
Drilled shafts by choice
For building the new poured-in-place concrete piers, it was
decided by Hardesty & Hanover that the drilled shaft method be used. A
total of 22 shafts are being sunk by the installed pipe/excavation method with
each shaft being 6 ft in diam. and a nominal depth of 110 ft.
The contractor for this project is Kiska Construction
Corp.-USA, which has been involved in the rehabilitation of many other New York
City bridges over the past 12 years. Kiska brought in a foundation drilling
specialist, HUB Foundation Co. Inc., for installing the pipe (caisson),
excavating the ground inside the installed pipe, drilling a socket into the
bedrock, installing rebar cages and placing the concrete to fill the pipe
(shaft). This set of rounds essentially completes the construction of one
HUB, a 37-year-old company from Harvard, Mass., had
specialized in pile driving in the earlier years of its existence but has been
focused on shaft drilling since 1990. Jim Maxwell, president, said he purposely
redirected the company toward foundation drilling and has completely gone out
of the pile-driving business. His reason for these actions is based on his
belief that the shaft-drilling technology will become more popular as design
engineers and project owners realize the attributes associated with this
According to Maxwell, one of the attributes is the
elimination of noise pollution that is associated with pile-driving activities.
When installing pipe (caissons), the vibratory hammer transmits its vibrations
to the pipe at amplitude level that creates relatively little projected noise.
Eliminating the noise is especially important if the pile driving takes place
near residential areas, hospitals or nearby commercial venues. Depending on the
construction conditions, shaft-drilling methods can be competitive with
pile-driving methods, he said.
With the company's firm commitment to foundation drilling,
Maxwell sits on the board of directors of the International Association of
Foundation Drilling, Dallas. This organization has an in-house training school
where HUB people are trained. Maxwell said with drilled shaft applications
increasing he readily acknowledges more formally trained contractors will be
needed to meet this growing demand.
King Kong returns to Manhattan
"This is the most challenging project I have
encountered. And it takes big, high-producing equipment to carry it out
efficiently. In fact, I brought King Kong back to Manhattan," said
Maxwell, smiling. King Kong is the name of a big vibratory hammer being used on
Here is why big equipment is needed to install the pipe. For
each pier there are two 50-ft-long pipe sections required, where one is stacked
vertically and welded on top of the other for building the shaft and acting as
the concrete form for placing ready-mix concrete. The pipe wall is .75 in.
thick and made from type A-252 grade-2 steel.
Once the first 50-ft length has been driven with the
vibratory hammer, the ground inside the pipe is excavated using a drill rig
fitted with an auger drill bit. Following the excavation, the same drill
penetrates 20 ft deeper below the bottom of the installed pipe to stir up the
ground. This ensures there are no obstructions to be encountered when driving
the pipe farther down once the second 50-ft section is stacked and welded in
place. Essentially, the two pipes are welded for making one pipe length from
its top to the bedrock. When the pipe meets the bedrock, a socket is drilled
into the bedrock 10 to 15 ft and the pier is anchored with the poured-in-place
For vibrating the pipe into the ground, two heavy-duty
machines were brought together. Maxwell was very careful in selecting this
equipment for the project. In the future, the equipment will be used on other
projects as well. One of the pieces is the APE King Kong model 400
hydraulically operated vibratory hammer with a patented clamping system used
for large-diameter caissons. It is one of the bigger hammers offered in North
America. The hammer manufacturer, American Piledriving Equipment Inc. (APE),
Kent, Wash., offers yet a larger model, the APE 600. APE has its own school for
training contractors comprehensively on pile driving and deep foundation
applications. There is even a distance learning course that can be taken over
A vibratory hammer with a 4,000 in./lb moment capacity was
first tried on the project prior to the delivery of the King Kong, but Maxwell
said no appreciable production results could be achieved. By comparison, the
APE 400 eccentric moment capacity is 13,000 in./lb. Maxwell said the production
results using the King Kong have been outstanding. A 50-ft length is driven
into the ground in about 10 minutes unless significant obstructions are
King Kong is big in every sense of the word. It has to be
built heavy-duty to ensure it will stay together despite the high eccentric
moment output and its drive force of 360 tons. The suspended weight of King
Kong is over 18 tons.
The other half of the pipe-driving equipment is a new
Liebherr HS 895 HD hydraulic crawler crane, which HUB Foundation recently
bought. The value of the new duty-cycle crane is it can do anything a
conventional lift crane can do and yet perform duty-cycle work that the lift
crane cannot do well. Simply, it is a more versatile crane.
One of the unique features of Liebherr duty-cycle cranes is
the available built-in power packs. They are available in different capacities,
depending on the applications. This crane has one of the biggest
output-capacity power packs available from Liebherr to ensure an oil delivery
rate that is commensurate with the King Kong hammer's demand. The maximum
hydraulic oil delivery rate is 264 gpm which is powered by the crane's 805-hp
engine. The high horsepower and oil delivery capacity are ample to power the
power pack and all other crane functions simultaneously.
A built-in power pack has two main advantages over the
traditional set-alone type. It frees up the space normally required to station
a set-alone power pack. Instead this space can be used for work activities or
storage. The added work/storage areas are especially welcome when the crane is
working from a barge, as it is on this project. Another important advantage of
the built-in power pack system is it is controlled from inside the cab by the
operator and is part of the crane's maintenance program.
So far, the choice of using the drill-shaft method has
proven to be successful.
Since the crane can be used for duty-cycle or lift work, it
can be used as a lift crane between drill-shaft projects. Maxwell will be
renting the crane to Kiska once he has completed this project's pier work.
Kiska wants the crane to remain here for lift work at the bridge project
because the company can eliminate mobilization costs. Next year, Maxwell will
come back to do some additional pier construction, so leaving the crane here
will mean no additional mobilization costs.
With the Third Avenue Bridge project going so well, the
NYCDOT, as well as other government agencies and private-sector owners, are
sure to use this system on their projects.
Contractor calls in super hammer for shaft drilling