Project Overview
By the mid-2010s, it was apparent that the original Harry W. Nice Memorial/Senator Thomas “Mac” Middleton Bridge (Nice-Middleton Bridge), which was built in 1940 as a key gateway connecting Virginia and Maryland, did not meet the needs of modern motorists. Therefore, the decision was made to replace the existing 1.9-mile, two-lane undivided bridge with a new, 61-ft-wide bridge featuring 12-ft-wide lanes along with a center median and shoulders to increase traffic capacity, improve safety, and facilitate access for maintenance and wide-load vehicles. When designing and erecting the new structure, the talented project team used many precast concrete components as part of the strategy for success.
A Cost-Effective and State-of-the-Art Design
In addition to increased capacity for vehicular traffic, the $463 million new bridge features a navigational vertical clearance of 135 ft, enabling large ships traveling the Potomac River to pass under the structure. Additionally, according to Kenneth V. Butler, PE, senior vice president and director of complex bridge practice with project engineer of record AECOM, more gradual vertical grades on the new Nice-Middleton Bridge allow vehicles to maintain a safe, consistent speed—and offers several other advantages.
“The innovative bridge design incorporated efficient and cost-effective span lengths, structural performance, constructability, and maintainability considerations that saved on project costs for the Maryland Transportation Authority while improving aesthetics and lowering long-term maintenance costs,” he said.
This design cost-effectively balanced the number of spans used against the number of supporting piers and leveraged a combination of prestressed concrete girders in the low- and high-level approach spans with long-span, haunched steel girders over the main channel. Coastal Precast of Wilmington, N.C., manufactured the project’s various precast concrete products, which included girders, massive piles, and more. The bridge’s substructure and foundations vary from pile bents to concrete columns and caps on waterline footings. Deep foundations were made possible using 36- and 66-in. prestressed concrete piles with lengths up to 190 ft. All the precast concrete elements specified for the project were designed to provide a simple and repetitive structure, which increased construction efficiency so that the design and construction to be completed within two years from notice of award.
The project featured many innovative uses of precast concrete. Coastal Precast manufactured the 66-in. cylinder piles with carbon-fiber prestressing strands, precast concrete drainage troughs that were installed beneath modular expansion joints, and precast concrete foundation frames dubbed “bathtubs.” Building information modeling (BIM) also played a significant part in the effort, with the team leveraging BIM approaches and technology to identify elements of the bridge that could be designed as precast concrete pieces. Ultimately, the use of precast concrete enhanced the project’s safety, as many of the components could be produced in a controlled, off-site environment and then delivered to the site, where workers could complete repetitive installation tasks on the ground. Alternatively, cast-in-place concrete construction would have situated workers at varying heights over water, resulting in a more complex installation process, greater safety risks for workers, and likely a longer timeline that would have further inconvenienced the public.
“The new Nice-Middleton Bridge offers a 100-year service life and is a benchmark to the start of a new era for the southern Potomac area of Maryland and Virginia,” Butler said. “The bridge reduces life-cycle costs through state-of-the-art design details and durable material selection while providing a structure that is easily accessible for future inspections and maintenance.”
Mason Nichols is a Grand Rapids, Mich.-based writer and editor who has covered the precast concrete industry since 2013. |