User:BLeahy20/Zakim Bridge

The Zakim Bridge, part of the major Big Dig project, was constructed in 2003 to replace an old trussed bridge that spanned the Charles River. Construction started in 1997 and was completed 6 years later. The bridge carries 4 lanes each way of Interstate 93; northbound and southbound. The Zakim Bridge is a cable-stayed bridge; two concrete towers with steel cables hold the loads. The Zakim Bridge exemplifies social importance, scientific qualities and a symbolic structure; all qualities of structural art

Social
The Zakim Bridge had a social impact on the city. The engineers had to make sure they did not interfere with other public transportation because it would cause more delays for people. The MBTA orange line was in the path of the supports so engineers had to design the supports to avoid messing with the tracks. The final design was for the steel shafts to be encased in tubing, and the legs of the towers were inverted at a 55-degree angle to straddle the MBTA tracks below. The bridge cost just over $100,000,000 dollars which was expensive for the city, yet in comparison to The Big Dig project, the expense was a small portion. However, there were some costly mistakes that delayed the completion; the concrete on the bridge deck had not adhered correctly to the steel rebar on the inside. Workers had to tear up the large section which was a setback in time and a waste of money. The bridge is a gateway in a certain aspect because it is the entrance into Boston.

Scientific
The scientific qualities of the Zakim Bridge are intriguing. At 183 feet in width, the Zakim Bridge is the widest cable-stayed bridge in the world. The bridge consists of ten lanes, two of which are cantilevered. The cables in the tower had to be moved three inches of center to accommodate the loads of the cantilevered lanes. There are 3 main loads acting on the bridge; dead load, wind load and live loads. The live loads consist of the traffic on the 10 lanes on the bridge deck. The loads are carried by 2 hollow concrete towers and a total of 116 cable stays that are anchored into the towers and bridge deck. The cables carry tension loads which transfer to compression in the towers and then exits to the ground. From all these parameters, the bridge shows scientific qualities. Boasting the wide cabe-stayed bridge in the world is a wonderful feat and uses a hybrid system of cocnrete and steel which is an efficient use of materials.

Symbolic
The Zakim Bridge is symbolic to the city of Boston in many ways. The bridge is named after a civil rights activist Leonard P. Zakim who lived in Boston most of his life and helped to bring people together and diversity in Boston. The Bridge is also named after the Bunker Hill memorial which was to remember those who fought in the Revolutionary War at the Bunker Hill site that kick-started the war. The concrete towers of the Zakim Bridge are designed to resemble the Bunker Hill monument while the white steel cables are designed to resemble the rigging of the USS Constitution. The elegance of these two combined design features makes the bridge symbolic on its own. The bridge became an instant symbol of Boston and became part of the sky line because of its elegance and scale. The media often use the bridge as a back drop to give away the location of where they are reporting from. Blue and white lights illuminate the tower and cables subtly so that the bridge blends in with the skyline at night. Engineers cut 70 small diamond shaped holes into the bridge's deck to allow light to reach the river below. Entering the city with the Zakim Bridge being the first spectacular view one might see is another reason the bridge is a landmark of Boston; when you think of Boston you think of the Zakim Bridge.

Almost instantly after construction, the Zakim Bridge became a major part of Boston’s skyline, scientific innovations and social life. The bridge that was there before had little importance to the city except to carry traffic over the Charles River. As soon as the Zakim Bridge was erected the city embraced the elegance and the symbolic icon it has become.