Each community has a special identity-be it a tie to a historic establishment, an industry, an area attraction or the local environment. It is an image that creates a sense of place and reflects a quality of life. Identifying this "theme" or "identity" is often part of the community participation for a new major bridge design, developed during a FIGG Bridge Design Charette. This specialized process involves the public in selecting elements of their bridge design to reflect the community's image, while building consensus. The design process itself is unique as members of the public learn about the options available to them, speak their minds, discuss, question and suggest, then vote for those options that they believe best represents their community. This process is often an asset to the development of engineering innovations in technology and aesthetics.
Examples of bridge innovations in technology that were inspired by the public are featured on two major cable-stayed bridges currently in construction, the Veterans' Glass City Skyway in Toledo, Ohio, (for the Ohio Department of Transportation) and the Penobscot Narrows Bridge & Observatory (for the Maine Department of Transportation) over the Penobscot River along the coast of Maine. Innovations in aesthetics also are found on such bridges as Daytona Beach's Broadway Bridge (for the Florida Department of Transportation).
Cradle and all
Toledo, Ohio, is known as the Glass City because of its long history of innovation in all aspects of the glass industry: windows, bottles, windshields and construction materials. The new high-level fixed bridge will carry I-280 over the Maumee River in the heart of Toledo, replacing a moveable bridge.
Through the community involvement process, the people chose a theme of glass in tribute to their industrial heritage. Through the design process, several ways to use glass on a bridge were explored to find a solution that provided maximum effectiveness and the least construction cost. The single pylon became the focal point for the glass. The pylon needed to be slender to reduce the amount of glass, yet still have the proper concrete structural capacity needed for a cable-stayed system.
To find the best solution required innovation. FIGG solved this challenge with the invention of a new cable-stayed cradle system, allowing the top 190 ft of the slender single pylon to be faced on four sides with layered glass that will reflect the sky during the day and shine in an endless array of colors provided by the LED fixtures mounted behind the glass at night.
FIGG's cable-stayed cradle system eliminated the need for anchorages in the pylon, allowing for the slender, sculpted pylon shape. The cradle permits the load transfer to the concrete pylon to occur in a natural compressive state applied vertically to the pylon. This is a more desirable structural condition and reduces construction costs since no additional reinforcing or concrete is required in the pylon to control the high splitting forces that would be introduced by the use of anchorages in the pylon.
The invention of the cradle system (U.S. Patent 6,880,193) provides additional benefits, including an increase in the service life of the bridge. Because the individual strands within each stay are unbonded, it is possible to selectively remove, inspect and then replace individual strands. Each stay includes a reference, or extra strand, that can be removed at any point in the future and physically inspected to determine the condition of strands in the stay. Equally, with all stay stressing at deck level, cable-stayed strands can simply be replaced with new strands of the same material or newly developed strand materials, further extending the service life of the bridge beyond the projected 150 years. This innovation allows for the serviceability of the strands out of view from traffic and keeps the bridge in full operations at all times.
Extensive testing, including axial, ultimate static and corrosion protection, verified that stays as large as 156 strands (the largest in the world for a cable-stayed bridge) could be used with the new cradle system. With larger stays and the streamlined cradle system, there could be fewer stays and fewer construction operations for stay installation. The single plane of stays accommodates the structural needs and creates the space necessary to incorporate the pylon glass system.
When the new Veterans' Glass City Skyway bridge is completed in Toledo, it will capture the community's vision, while advancing bridge technology for a longer life structure.
Picking pylons
During the FIGG Bridge Design Charette process, the coastal Maine communities in Waldo and Hancock Counties chose a theme of "Granite-Simple & Elegant" for their new cable-stayed bridge. The emergency replacement of the Waldo-Hancock Bridge carrying U.S. Rte. 1, an economically important highway, began in community workshops while the new Penobscot Narrows Bridge foundations were in design. The public understood that the new bridge would have to last much longer than the 75-year-old existing Waldo Hancock Bridge. As the public became engaged in the idea of a new bridge, the pylon heights necessary to carry the 1,161-ft cable-stayed main span were discussed. The pylons would need to be almost twice as tall as the older bridge suspension towers.
With the bridge adjacent to historic Fort Knox (made from granite quarried from the adjacent hillside), the public liked the idea of pylons with an obelisk shape. From this concept, the idea of placing an observatory at the top of the pylon evolved to turn the new pylon height into an advantage. The new bridge will provide both transportation and economic development with the multilevel glass observatory attracting tourists to both the bridge observatory and Fort Knox.
This community involvement recently earned Maine DOT first place in the 2006 American Roads & Transportation Builders Association PRIDE awards program for Community Relations. Using the cable-stayed cradle system in the pylon provided space in the core of the pylon for an elevator to reach the observatory.
Additionally, innovations were created in the stay system to advance the state of the art with an inert gas system inside the stay sheathing, a stay force monitoring system (See Good, Great, Wicked!, p 32, November 2005) and the inclusion of carbon fiber strands for the extra strands. Once stressing operations are complete, one traditional steel strand will be replaced in each of a short, medium and long stay with a carbon fiber strand. The performance of the strands will be monitored closely, allowing engineers to evaluate the advantages offered by carbon fiber. The new Penobscot Narrows Bridge & Observatory captures the communities' vision, while inspiring new technology.
The significant benefits provided by the cradle system, utilized in both the Veterans' Glass City Skyway and the Penobscot Narrows Bridge & Observatory, and the technology that was inspired through the public involvement has been recognized with two national awards. The National Society of Professional Engineers has selected the cable-stayed cradle system to receive the 2006 NSPE New Product Award. In early 2006, The History Channel's Modern Marvels Invent Now Challenge received more than 4,300 entries for new inventions. The cradle system was one of 25 winners and is included in a national exhibit currently touring the country and concluding at the National Inventors Hall of Fame in Akron, Ohio.
Priceless feedback
Bridge innovations in aesthetics have been inspired by the public in projects like the Broadway Bridge in Daytona Beach, Fla. In 1994, to move forward with the public involvement process for the replacement for the Broadway Bridge in Daytona Beach, FIGG provided the Florida Department of Transportation and the citizens of Daytona Beach with community design charettes.
During the charettes, various options were presented to the participants on 30 topics, including pier shape, colors, textures, sidewalk elements and such. Participants used a consensus voting method (1-less favorable to 10-highly desirable) to rank the options offered on each topic, then the votes were compiled to create a composite score. The immediate outcome was that the project moved forward with community support. The long-term outcome is a bridge that was dedicated on July 21, 2001, in a community-wide celebration.
To illustrate the community-selected theme, "Timeless Ecology," the design team, led by FIGG, developed a plan for 10-ft-tall mosaics of dolphins, manatees and other water life that encircle each of the bridge piers above the water line. The image is common from pier to pier, but shifted slightly to impart a sense of motion, providing a special experience for boaters along the Intracoastal Waterway.
Pedestrians and cyclists along International Speedway Boulevard use the bridge to reach the city's famous beaches and are treated to 18 wildlife mosaics on each of the twin structures 7 ft in height and housed in a concrete shell design. The mosaics near the bridge landings feature waterlife, such as turtles, then progress to wildlife of the land, then birds, as the bridge climbs in height over the Intracoastal Waterway. The mosaic at the apex of the bridge is home to a pair of bald eagles. Each sidewalk mosaic is signed by the installer with a star-shaped mosaic, leading children who love the bridge to run from mosaic to mosaic in a contest to find all the "Stars on Broadway."
The bridge has become an attraction to those living and visiting Daytona Beach-out of a community-voiced desire to showcase the ecology native to their area, an important element to local residents. The new bridge has encouraged economic development in Daytona Beach, while winning eight awards for engineering excellence and unique aesthetics, including the Gustav Lindenthal Medal from the International Bridge Conference in 2001 demonstrating "technical and material innovation, aesthetic merit, harmony with the environment or successful community participation." Broadway Bridge also was selected to receive first place in the 2001 Spectrum International Ceramic Tile Design Competition for the creative use of tiles, earning the bridge recognition in the Orlando Sentinel as "Daytona beach's newest permanent art exhibit." People often say that "necessity is the mother of invention." But perhaps in the design of bridges that truly fit a community, we can say that invention and technology become a necessity in order to find the best solution. In any case, the public can be an inspiration through their vision, and when this is matched with a passion for bridges, the result is form, function, economy and innovation that create bridge landmarks.
