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Miami bascule 'bridges' city's past, present, future

Bridges Article December 28, 2000
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The New Brickell Bridge is a reflection of Miami, a city long in history that has transformed itself into a cultural center and the modern financial capital of Latin America. Like the city, the designers of the bascule bridge, which opened late last year, remained true to artistic and aesthetic elements of the bridge's past while incorporating a modern, technologically advanced design into its structure.


Located in the heart of the city on Brickell Avenue, the New Brickell replaces a worn bascule bridge built in 1929. The old two-leaf bridge had become too narrow to adequately carry the 32,000 vehicles per day that crossed it. The time it took to raise and lower the bridge for the passage of 3,000-ton vessels on the Miami River in the center of the city's financial district also was a factor in its replacement.


In making way for the new, respect for old and ancient structures and cultures was upheld. The bridge's designers and builders were especially cognizant of the site's tightly constrained right of way. The added emphasis was due to the discovery of a Native American burial ground near the site prior to the beginning of construction.


Perhaps more than the typical replacement bridge, the New Brickell became a focus for community involvement-rather late in the game. Even though the bridge's designer, Kunde, Sprecher & Associates Inc. (KSA), Miami, had completed a design for the new bridge, community and political leaders called for the bridge to incorporate architectural and artistic elements. Toward this end, the Brickell Bridge Gateway Design Competition, an international architectural open-design competition, which garnered more than 150 entries, was sponsored. The firm of Portuondo Perotti Architects, Coral Gables, Fla., was selected by a committee, which included a Florida DOT representative, to perform what was termed an "architectural design intervention" on the project.


William Junkin, P.E., vice president of KSA, attributes the amount of public involvement and importance placed on the architecture and aesthetics of the bridge to Miami being a community of artists with deep interests. "Also, everybody wants something in their community that looks a little better than the one down the road," he said.


KSA scrapped its first design and began anew-this time with Portuondo Perotti working as a subconsultant on the redesign. "They were realistic," said Junkin of Perotti. "They had reality on their minds." A notable artistic point featured on the bridge is a towering statue by artist Manuel Carbonel. The bronze sculpture, a modern version of a totem pole, traces the history of the city, which is celebrating its centennial. The sculpture is topped off by a native aiming his drawn bow and arrow toward the sky.


While the aesthetics of the bridge are admirable, it is its engineering elements that truly set it apart from other bascule bridges. For the company, which designed its first bascule bridge in 1960, the bridge stands apart from those it has designed in the past, from its piers to its high-tech method of actuation.


Although the bridge's two piers are more decorative than most-angles have been used to complement the bridge and niches have been inset into the sides of the piers to accommodate additional art pieces-they are designed to withstand impacts of ships of over 3 million lb.


While the previous bridge featured two leaves and narrow lanes, the New Brickell is much larger, boasting four leaves made of structural steel and concrete, which carry six lanes of traffic. The bridge piers house four bascule leaves, each weighing nearly 1 million lb and supported by four spherical roller bearings erected to an exacting tolerance of less than 0.010 in.


"The bridge is the first bascule bridge in Florida to use spherical roller bearings," Junkin told ROADS & BRIDGES. According to Junkin, the Florida DOT required the use of the bearings because of their precision and quality. A millwright was given the responsibility for setting the alignment of the roller bearings. Without an accurate alignment, the bridge would not perform as designed.


The bridge was designed with painstaking attention given to providing more-than-adequate room in the internal spaces of the bridge piers. "Nearly the entire bridge is accessible by way of stairs," said Junkin. Remote rooms in the piers house the hydraulic machinery that enables the bridge to raise and lower. In-lock access areas, which are entered from atop the bridge deck, also enable maintenance workers to reach the interlocking mechanisms where the leaves of the bridges come together.


By providing these spaces for the bridge's circulation and maintenance layouts, the designers were able to improve the bridge's functionality and accessibility for maintenance. According to KSA, this has translated into improved operational reliability.


The first movable bridge that KSA designed operated via the use of motors and gears, according to Junkin. The design of bascule bridges has come a long way since the early '60s. "The New Brickell uses hydraulics to open and close each of the four 1-million-lb leaves in less than 75 seconds," he said. To actuate the bridge, a state-of-the-art computerized control system was installed in the bridge's control tower. The system activates the bridge's hydraulic pumping systems and hydraulic cylinders to raise and lower the leaves. The hydraulic cylinders use newly developed corrosion-resistant ceramic coatings to enhance the bridge's durability.


KSA was one of the first firms to design bascule bridges using hydraulics, having designed its first in Broward County, Fla., more than 10 years ago, according to Junkin. "To introduce hydraulics into bascule bridges was a huge undertaking," said Junkin, who acknowledges the bridge design's connection to the past. "Movable bridges probably have one of the greatest links to the past, but their technology continues to improve with each project."

About the author: 
Flynn is editor of Roads & Bridges
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