User:Kellgill/Zakim Bridge
Zakim Bunker Hill Memorial Bridge | |
|---|---|
 Leonard P. Zakim Bunker Hill Memorial Bridge | |
| Coordinates | 42°22′07.5″N 71°03′47.5″W / 42.368750°N 71.063194°W |
| Carries | Interstate 93 and U.S. Route 1 |
| Crosses | Charles River, MBTA Orange Line |
| Locale | Boston Massachusetts |
| Official name | Leonard P. Zakim Bunker Hill Memorial Bridge |
| Characteristics | |
| Design | Hybrid Steel and Concrete Cable-stayed bridge[1] |
| Total length | 1,432 ft (436 m) |
| Width | 283 ft (86 m) |
| Height | 270 ft (82 m)[2] |
| Longest span | 745 ft (227 m) |
| Clearance below | 40 ft (12 m)[3] |
| History | |
| Opened | March 30, 2003 (NB) December 20, 2003 (SB)[3] |
| Location | |
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The Leonard P. Zakim Bunker Hill Memorial Bridge, commonly known as The Zakim Bridge, crosses the Charles River connecting Boston, Massachusetts to Charlestown. This is the world's widest cable-stayed bridge, consisting of 10 lanes for traffic. On December 20, 2003, the bridge was opened to traffic in both the north and southbound directions replacing the old Charles River Bridge. The Central Artery/Tunnel Project (CA/T), known as the Big Dig, was a megaproject in Boston that rerouted the Central Artery in the city. The total cost of the project was close to $22 billion which made it the most expensive highway project undertaken by the United States. The Zakim Bridge was just part of this massive project and because the cost of the Big Dig vastly exceeded the budget (by almost four times the original budget) there was less money to build the bridge. Overall, the total cost of construction was $115,000,000. The intelligent design, use of minimal material to support all loads, and contemporary beauty make this bridge an efficient, economical and elegant structure.
Design
[edit]Due to the length of the spans, the best choice for the design of the Zakim Bridge was a cable-stayed bridge. This style consists of one or more columns with cables supporting the bridge deck. Specifically, the Zakim Bridge is in a fan design, which is where the cables all connect to or pass over the top of the tower.
Despite its elegant, streamlined appearance, the new bridge was designed to be exceptionally strong. It was built to withstand winds of over 400 miles per hour, as well as hold up against a magnitude 7.9 earthquake. [4]. In addition, the Zakim is world's widest cable-stayed bridge with a width of 56m and 10 lanes across. In addition, the upside down Y shaped towers spread out further at the bottom to all for additional stability and strength. When structural loads are applied to the bridge deck, the forces travel up through the cables in tension until reaching the columns where it travels down to the ground.
The bridge was designed by Christian Menn along with architect Miguel Rosales. The lead civil engineer involved with the construction of the project was David Goodyear. The materials used to build thi bridge were steel and reinforced concrete. The bridge deck and cables are made of steel, and the bridge towers are composed of steel reinforced concrete.[5]. Steel is an extremely effective and relatively cheap material to use and was the wisest choice in constructing the Zakim Bridge. With such a wide deck, and so many lanes of traffic, the live load of the cars travelling across the deck at any given time is going to be extremely large. In a relatively windy city, wind loads also have to be taken into consideration in addition to the live and dead loads. To account for all of this, the use of material was vital to the permanence of the structure. The towers were constructed of hollow concrete and are merely one to four inches thick. The 116 cable stays that support the roadways were drilled into the spires to attach them to these 322 ft. and 295 ft. tall towers.
Structural Art
[edit]To classify the Leonard P. Zakim Bridge as structural art it must attain excellence in efficiency, economy, and elegance. This Bridge is a beautiful landmark for the city of Boston and is one of the first standout structures you see when entering the city from the North.
These 'Three E's' as they are called can be defined as follows:
- Efficiency: The use of the minimum amount of material needed to ensure that the structure safely performs its function.
- Economy: Avoidance of excessive monetary cost in the design, construction, operating and decommissioning costs of a structure. Economy should be evaluated in terms of the life-cycle cost of the structure whenever possible.
- Elegance: The structural form should be aesthetically pleasing, but should be defined and driven by engineering considerations. Thus, an elegant design is not simply one that is pleasing, but one that arises from engineering creativity, satisfies the requirements of efficiency and economy, and is also pleasing.
In regards to the Zakim Bridge, the 'Three E's' can be assessed as:
- Efficiency: This bridge used steel and reinforced concrete in a resourceful way. The strength and stiffness of the bridge was achieved with little material and because of the ensured safety it provides, the Zakim Bridge can be considered an extremely efficient bridge.
- Economy: Because the cost of the entire Big Dig project was so extreme, the budget of the bridge had to be lessened.The cost of steel is less than most other materials so this was a wise choice to use in construction. The cost of the material is also important because the permanence of the bridge should be an extensive time period so it will save money in the future with less repairs and maintenance needed.
- Elegance: The creativity in the design of this bridge gives it a pleasing appearance along the skyline of the city of Boston. The spires of the towers were designed to be somewhat evocative of the Bunker Hill Monument seen in the distance. The Symmetrical design of the bridge in its entirety gives it a simplistic look but then the cables extending down to the deck add some complexity. At night, the bridge is lit up and the light illuminates the picturesque structure.
In an already beautiful city, filled with a busy skyline and remarkable skyscrapers, the Leonard P. Zakim Bridge only adds to the charming depiction. A vital roadway crossing the Charles River, the Zakim serves as an important means of transportation for the large population and commuters coming in and out of the city. This efficient, economical and elegant structure, while still relatively new, is a signature landmark and a brilliant addition to the city of Boston, Massachusetts.
References
[edit]- ^ Massachusetts Turnpike Authority. "MTA - The Charles River Bridges". Retrieved 2006-10-19.
- ^ "MTA - The Charles River Bridges".
- ^ a b Eastern Roads. "Leonard P Zakim-Bunker Hill Memorial Bridge (I-93 and US 1)". Retrieved 2006-10-19.
- ^ "Boston Area Roads, Crossings and Exits". Retrieved 3/4/12.
{{cite web}}: Check date values in:|accessdate=(help) - ^ Janberg, Nicolas. "Leonard P. Zakim Bunker Hill Bridge". Structurae. Retrieved 3/4/12.
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