User:Syhum/Zakim Bridge

The Zakim Bridge

The Leonard P. Zakim Bunker Hill Memorial Bridge is a steel and concrete cable-stayed bridge located in Boston. The bridge carries ten lanes of traffic into and out of Boston. It was commissioned to replace the old Charles River Bridge as part of the Big Dig and was open to traffic in 2003. Designed by Christian Menn, it is an elegant and efficient solution to the problem of replacing the old bridge because of its methods of construction, structural form, and symbolism.

Structural Description

Cable-stayed bridges are mainly supported by their towers. The cables are anchored to the towers and are connected to the road deck. When forces are applied to the road deck, they are carried up through the cables as tension forces. Then, the towers carry the forces down as compression until they reach the ground. Cable-stayed bridges do not need to have two towers like suspension bridges do.

Both the deck and the cables are made of steel. The span between the two towers is 227 meters. The two side spans are 84 meters each, making the total length of the bridge 436 meters. The total cost of construction was $115 million.

Qualifications as Structural Art

When considering the bridge as structural art, certain characteristics can be examined: efficiency, elegance, and economy (3 E's), and social, symbolic, and scientific (3 S's).

Efficiency

Although the bridge is very close to other surrounding highways and ramps of the MBTA, it is efficient in its use of space. It was built without having to divert traffic from the roadways running parallel to it across the Charles River. The bridge was built by the cantilever method from its towers, enabling it to be constructed without erecting supports in the middle of the river or other scaffolding. This allowed nautical traffic to proceed uninterrupted and saved both time and money.

Elegance

The towers of the Zakim are asymmetric; one is taller because of the elevated roadway. The white concrete of the bridge is lit up with blue lights at night, making it a beautiful and elegant sight in the Boston skyline. It is frequently used as a backdrop in local news segments.

Economy

In terms of money, the Zakim Bridge is cheaper when comparing the cost per square meter of the deck to other cable-stayed bridges. The Pont de Normandie in France cost $465 million , and although it is longer, the cost per square meter is almost double that of the Zakim’s. The Ting Kau Bridge in Hong Kong cost HK$1.94 billion, and the cost per square meter is also much higher than that of the Zakim’s.

Social meaning

The bridge is a quick and efficient way for suburban commuters to get in and out of Boston quickly. While it was being built, surrounding traffic went uninterrupted, which was a huge advantage to travelers.

Symbolic meaning

The bridge was named after Leonard P. Zakim, a civil rights activist, and in remembrance of the people who fought in the Battle of Bunker Hill. Leonard Zakim worked against racism and poverty in Boston and was seen as a bridge to all peoples; his work is symbolized in the bridge. Being named after the Battle of Bunker Hill also reminds people of local history and the bravery of the people who fought there. Physically, the bridge is reminiscent of the Bunker Hill Monument and the USS Constitution, both of which are located nearby.

Scientific meaning

The Zakim Bridge is an efficient use of steel and concrete in transporting vehicles across the Charles River. Overall it is a safe structure, although there have been instances of ice falling from the cables and hitting vehicles below.

As a bridge that was built without disrupting the surrounding traffic, that was efficient in its use of materials, and that beautifully represents the history of Boston, the Zakim Bridge is both and elegant and efficient structure. It is also an economical structure when compared to other cable-stayed bridges around the world and provides a safe, accessible route into Boston. Because of these traits, it is a bridge that is loved by the public and has come to be an important part of the Boston skyline.