Transportation infrastructure is fundamental to the health of a country’s economy. It enhances business, productivity, security, and public health and welfare for its citizens. With that in mind, the editors of Rebuilding America’s Infrastructure salute the ingenuity and foresight of project owners, engineers, contractors, subconsultants, software providers, and the many others that have contributed to the strength of America’s infrastructure by highlighting some of the projects that have earned top awards in our industry during the last few years.
I-35W Bridge, Minneapolis
Following the tragic collapse of the I-35W Bridge in Minneapolis in August 2007, the Flatiron-Manson joint venture design-build team mobilized quickly to begin work on the replacement structure over the Mississippi River. The replacement structure was designed for a 100-year life span and was constructed on an accelerated schedule. On Oct. 8, 2007, the Minnesota Department of Transportation (Mn/DOT) awarded the contract to build the replacement bridge for $234 million, and on Sept. 18, 2008, the new bridge was opened to the public, three months ahead of schedule.
The new bridge, a 1,216-foot-long, 10-lane concrete structure, has a 504-foot-long precast segmental main span. The three land-based supporting piers host four columns each and stand 70 feet tall. Segments were cast on the south bank of the river on an existing closed section of I-35. There are 120 precast segments ranging in weight from 170 to 210 tons each. High-performance concrete was used for superior durability. A state-of-the-art sensor and monitoring system was built into the bridge to allow for easier and more comprehensive monitoring and implementation of a comprehensive safety program for all aspects of the design and construction process.
Major software used
David Kreitzer Lake Hodges Bicycle Pedestrian Bridge, San Diego
The San Dieguito River Park Joint Powers Authority was formed in 1989 to develop a park along the San Dieguito River Valley, which runs 55 miles between the Volcan Mountain foothills and the Pacific Ocean. The David Kreitzer Lake Hodges Bicycle Pedestrian Bridge in San Diego was one of the remaining components of the Coast to Crest Trail. The 1,000-foot-long ribbon-thin bridge holds the title as the world’s longest stress ribbon bridge. The structure exploits a 16-inch-thick concrete deck and extends more than 330 feet between supports for a depth-to-span ratio of 1:248. The stress ribbon design was selected to blend into its surroundings. It incorporates steel cables stretched end to end to support the structure. The exceptionally thin bridge requires only two piers, which resulted in minimal impact to the lake.
Sound Transit Central Link Light Rail Beacon Hill Station & Tunnels, Seattle
The Sound Transit Central Link Light Rail Beacon Hill Station & Tunnels provide a previously isolated urban neighborhood with fast, efficient access to downtown Seattle and SeaTac airport. An access shaft using an adaptation of slurry wall construction, below-ground tunnels using a dual side wall drift technique, and platform tunnels using a single side wall drift method were built to withstand conditions at depths and dimensions far exceeding anything previously attempted in soft ground in the United States. Twin mile-long transit tunnels were built to withstand unstable conditions 200 feet below the earth’s surface.
The engineering team designed the complete excavation including the initial and final support systems for the large-diameter shafts and deep tunnels, which were constructed using the sequential excavation method. A 3D finite element analysis of tunnel excavation and of the initial support required for it was completed to provide confidence in final decisions regarding shaft and tunnel design and construction methods.
Bob Kerrey Pedestrian Bridge, Omaha, Neb.
The $22 million Bob Kerrey Pedestrian Bridge, which connects Omaha, Neb., to Council Bluffs, Iowa, was opened to the public in September 2008. The design-build project is a unique cable-stayed, steel superstructure that features two pylons rising 203 feet in the air.
The curvilinear shape symbolizes the flowing waters of the Missouri River below it. While the river is only 800 feet wide where the bridge crosses, the slithering structure stretches more than 2,300 feet, making it one of the longest pedestrian bridges in the country.
Marquette Interchange Reconstruction, Milwaukee
The vintage 1960s Marquette interchange on average experienced three accidents per day, carried more than twice the traffic for which it was designed, and had functionally obsolete left-side ramps and short merge distances. In addition, having withstood four decades of Midwest winters, the old interchange was literally crumbling. A four-year, $810 million reconstruction replaced and modernized the existing four-level system downtown interchange with a five-level interchange at the junction of I-94, I-43, and I-794.
Two lanes of traffic in each direction remained open during the entire project. The design team saved millions of dollars on the west leg project by using a significant portion of the existing freeway alignment and by reconfiguring the 25th Street interchange. An aggressive outreach campaign was crucial in keeping the public aware of ramp closings and offering alternate routes.
Other notable, award-winning projects
Theresa M. Casey, FSMPS, CPSM, is founding principal of On Target Marketing & Communications, LLC, based in Columbia, Conn. The firm specializes in the engineering, architecture, construction, accounting, and legal industries. She can be contacted at firstname.lastname@example.org or 860-228-0163.
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