When designing anything related to traffic in the Washington, D.C., metro area, the utmost respect must be paid to drivers, who already face some of the worst congestion and commute times in the country. When first faced with the challenge of designing the reconstruction of the Eastern Avenue Bridge over Kenilworth Avenue, N.E. for the District Department of Transportation (DDOT), the staff at Greenhorne & O’Mara knew that design decisions needed to ensure that the contractor could build it while keeping traffic moving as much as possible.
Prior to reconstruction, the minimum vertical clearance between the bridge and Kenilworth Avenue was only 14 feet. Because of this minimal clearance, the bridge was vulnerable to being struck by vehicles exceeding the clearance limits such as oversized tractor trailers and construction equipment on trailers. Over time, the safety of the structure had been compromised. Visible damage was apparent at the bottom flanges and several of the prestressed girders. Consequently, DDOT determined that the bridge would need to be reconstructed, with the primary objective of increasing the minimum vertical clearance over Kenilworth Avenue to 16 feet, 6 inches and improving vehicle and pedestrian movements across the bridge.
Built in 1956, the Eastern Avenue Bridge over Kenilworth Avenue (I-295) is a vital link for pedestrians and vehicles between the communities of northeast Washington, D.C. that are divided by Kenilworth Avenue. While there are pedestrian bridges at approximately 1/4-mile intervals to the south, the closest vehicle access across Kenilworth Avenue is approximately 3/4 mile away. The bridge also is an important truck turn-around for the industrial sites in the area. Kenilworth Avenue is a major north-south corridor between Maryland and Virginia and is a commuter route into Washington, D.C., from the north, south, and east.
In addition, Kenilworth Avenue is a Homeland Security Evacuation Route to evacuate Washington, D.C., in the event of an emergency. An average of 155,000 vehicles per day use the bridge and Kenilworth Avenue underneath the bridge. All of these factors meant that the bridge had to be reconstructed in the shortest duration possible to minimize the impacts to commuters, residents, businesses, and public safety. In addition, DDOT required that all three lanes in each direction of Kenilworth Avenue be maintained during peak times. Rerouting traffic during heavy construction during off-peak times would also be difficult. The plan would need to address the volume of traffic on Kenilworth as well as capacity of the surrounding streets to handle diverted traffic.
Faced with those challenges, Greenhorne & O’Mara researched numerous options to meet the needs of DDOT, drivers, and pedestrians. Through that investigation, the use of prefabricated superstructure and pier elements emerged as the best method to minimize onsite construction duration and traffic impacts. Prefabricated superstructure and pier elements similar to those chosen for this project have been used successfully by several states including Virginia, New York, Vermont, Texas, and Washington. For the Eastern Avenue bridge reconstruction, prefabrication significantly shortened the construction time when compared with traditional cast-in-place construction. And since the elements were transportable, a nearby fabrication site was not required. A maintenance-of-traffic scheme was developed that allowed full closure of the bridge during construction, yet maintained all lanes of Kenilworth Avenue through the work zone during peak traffic hours.
Since the profile of Kenilworth Avenue below the bridge could not be lowered and the adjacent service roads could not be raised significantly, Greenhorne & O’Mara proposed that the existing bridge be replaced by a two-span structure to minimize superstructure depth and increase the vertical clearance under the bridge. The traffic crossing the bridge would be divided by concrete medians to reduce center lane accidents and dedicated truck turn-around lanes would be added. Sidewalks on the bridge were positioned with pedestrian safety in mind and planters were added along the sides of the bridge to create a green space and enhance the surrounding community.
A pier footing and median barrier were cast in place along the median of Kenilworth Avenue and prefabricated pier elements were installed during nighttime operations. The prefabricated pier elements were tied to the median barrier with mechanical rebar couplers and closure pours. A total of 16 prefabricated pier elements were installed in less than a week. To speed construction and simplify prefabrication, the top of the median barrier was cast level so that all of the pier elements were the same height. Once the pier and abutment reconstruction was complete, 14 prefabricated superstructure units were installed during nighttime operations. These required less than two weeks to erect. After that, reinforced keys were cast between the prefabricated superstructure units along with the construction of the median, barriers, and planters. To complete the superstructure, a waterproof membrane was placed over the prefabricated superstructure units with a 3-inch asphalt overlay. With the bridge closed and prefabricated superstructure units protecting traffic below, the remaining superstructure construction did not require nighttime work.
In addition to design and construction challenges, there were also social, economic, and sustainable design considerations that had to be reflected. The precast technology reduced a two-year project to less than a one-year timeframe, and the bridge was opened for traffic on Oct. 27, 2010. Fort Myer Construction Corp. was the general contractor and Fort Miller Co. Inc. fabricated the pier elements and superstructure units. The actual construction cost was $1 million less than the engineer’s estimate of $9.7 million without contingency. This shows that even though extensive prefabrication is not frequently used in the region, accelerated construction methods will still lead to completive bidding among contractors and provide value to the client.
The value extends to the community and commuters. By using prefabrication techniques, Greenhorne & O’Mara was able to apply for and receive a $1 million construction grant for DDOT from the Federal Highway Administration’s Highways for Life program, which encourages state transportation departments to use accelerated construction methods in their projects. The project achieved the Highways for LIFE performance goal of a 50-percent reduction in the time highway users are affected by construction. The total budgeted cost for the project was $11,068,605.
The reconstruction of the Eastern Avenue Bridge over Kenilworth Avenue project also was selected for an American Council of Engineering Companies National Recognition Award.
Michael Chamberland, P.E., is transportation project manager, and Bimal Patel, P.E., is transportation department head, for Greenhorne & O’Mara Inc.
Get the latest from the RAI NewsBlog in your inbox!