A landmark cable-stayed bridge over the Charles River, Boston, Massachusetts

Abstract

Boston, in the forefront of the American Revolution over two centuries ago, is now in the forefront of another revolution—in the field of cable-stayed bridge technology. A highly complicated structure, unique in the world, is complete. New technologies and innovations have become hallmarks of the Leonard P. Zakim Bunker Hill Bridge. This crossing of the Charles River at the north end of Boston was a challenging assignment from the start. It brought the community, engineers, and architects together to create a ‘signature bridge’ and a ‘gateway’ to the city. Located at a pre-eminent point where Paul Revere crossed in 1775, warning colonists that the British were coming, the bridge took on special meaning from a historical perspective. Numerous alternatives were studied for the crossing and the interchange configurations on both sides of the river. Eventually, the option known as the ‘non-river tunnel’ alternative was chosen, which required a ten-lane crossing of the Charles River. The ten lanes include four lanes each for Interstate 93 (I-93) northbound and southbound, as well as a two-lane ramp on the east side. Some impediments the bridge had to contend with included the Orange Line subway adjacent to and below the bridge; the close proximity of the Charles River lock and dam, and the need to maintain navigation; a major water main in the area of the south tower footing; a cantilevered two-lane ramp on only one side of the structure; the existing Storrow Drive ramps at the south end, dictating the arrangement of the stay cables in the back spans; and a new tunnel at the south end of the structure.