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The Manhattan Bridge's $500-million rehabilitation is nearly complete
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The Manhattan Bridge knows how to dance. Like all suspension bridges, it was built to dip and rise depending on the relative weight of vehicles and trains crossing each side of the span. The carefully calibrated steel sway can be a thing of awe and even beauty -- but it also can be the greatest culprit of wear and tear.
Two decades ago, such wear prompted state and city engineers to suddenly close the landmark East River crossing for a long weekend, so they could more closely examine the damage done by the twist of the roadway. They discovered that engineer Leon Moisieff's inexplicable decision to design the bridge with two sets of train tracks running along its outer decks (rather than down the center, the standard for suspension spans) forced the bridge to endure more dramatic twisting than it would have otherwise. As it stands, the bridge dips up to eight feet when a train crosses it if there is no train on the opposite side serving as a counterbalance.
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| Lotfi (left) and Tarpey examine some steelwork |
"This bridge is a living, breathing thing," says James Tarpey, the resident engineer who has overseen the Manhattan Bridge's rehabilitation since 1990. It's flexible, he says, "but it's made of steel, not rubber."
Fifty-six thousand tons of steel, to be exact, including the towers, cables, center span, and approaches. And though it's efficiently handled the roadway's natural twist since it opened to traffic in 1909, it also has suffered the rust, corrosion, and excessive fatigue damage of a bridge that was neglected over the years due to state budget constraints and the city's 1970s fiscal crisis.
From three-quarter-inch steel beams worn paper-thin to vertical wire suspenders turned red with rust, the bridge was destined for a major fix-up in the early 1980s. "Thankfully, the original engineers designed the bridge with a lot of redundancies," says Tarpey, who explains that its sound original engineering and construction has enabled contractors to keep half of the bridge open to traffic while making repairs.
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| More than 3,000 construction workers have helped with the rehabilitation |
Tarpey works closely with Reza Lotfi, the New York City Department of Transportation's engineer in charge of the bridge. The pair knows virtually everything about the Manhattan Bridge's $500-million rehabilitation, which began in 1982; each agrees that even with work remaining, the structure is already more sound than ever.
"During the whole project we've said, 'Since it's got to be done, let's do it right and use the right materials and make it last,'" says Lotfi. "I feel really good about where we are. We've accomplished a lot."
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How Does it Work?
To fully understand how the Manhattan Bridge works, it's important to understand its design. The span has two levels. The lower deck has two outer train corridors, a center roadway with three reversible lanes, and a pedestrian path and bikeway on each of the outer edges. The upper decks are above the train corridors, and each consists of two lanes for vehicular traffic. There is no upper roadway along the center of the bridge. A cross-section of the bridge appears U-shaped -- and makes clear why the weight of trains and traffic on the outer edges can make the span twist.
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Lotfi's greatest undertaking was installing a support system that would bolster the bridge and accommodate its lopsided twisting. The solution involves installation of steel cross braces in the shape of an X to the underside of the roadways. The braces stiffen the span but do not stop its natural twisting.
Other completed projects within the rehabilitation include reconstructing the Brooklyn and Manhattan approach spans and main cable anchorages, rehabilitating subway tunnel entrances, stiffening all steel trusses, and installing new roadway floors and train tracks. The arch and colonnade on the Lower Manhattan side were also repaired, cleaned, and relit to restore their polished appearance as a triumphal gateway (one of only three in the country, although the others are also in New York, at Washington Square Park and Brooklyn's Grand Army Plaza).
Work on the south upper and lower roadways also is finished, and north side work is slated for completion by spring 2004 -- great news for the 600,000 subway riders who will regularly benefit from the restored shortcut over the East River. Spring also will mark the opening of a new bicycle-only path on the bridge's north side, at which time the south side path will be designated for pedestrians.
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| One of the four, 2,000-ton cables that's embedded in the east anchorage |
After installing finishing touches such as a new "intelligent transit system" electronically linking the bridge to city traffic-advisory command centers, only two major projects remain: rehabilitating the center roadway and replacing vertical suspenders.
Serving as testament to Lotfi and Tarpey's diligence is the restoration of the bridge's distinct ornamental details, like the cast-iron canopies that hang from the towers above the pedestrian and bike paths, the decorative balconies around each tower, and the eight trademark globes that distinguish the bridge for miles around. Workers also are refurbishing the historic bronze plaques that will reside under the canopies and at the span's pedestrian entrances.
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| The north path will be open exclusively to bicycles |
"The challenge was to restore the bridge to accommodate modern transportation, and to carry on what it was intended for," says Lotfi. "It's also to save the bridge's appearance -- not just for how it looks, but because of how it fits against the skyline of the city."
"It makes a tremendous difference just to see the bridge restored to its original color, instead of it being rust-colored," Tarpey says, and agrees with Lotfi that "Manhattan Bridge blue" is most likely based on the color of traditional Dutch delft tiles.
Tarpey adds, "I mean, everything on this bridge was falling apart, and now it's back to its original beauty."
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