AMERICAN LEGION BRIDGE CONCEPT DESIGN
The American Legion Bridge is part of the vital transportation highway I-495 in the Washington, D.C. region and spans the Potomac River between Maryland and Virginia (for those who have heard the term, “the Beltway,” this is it). It is in extreme need of expansion to handle choking traffic volume. Virginia added four lanes of dedicated HOV roadway on its side of the beltway in the last decade, but Maryland’s side of the Beltway has been unchanged for almost 30 years. Miles of traffic backups occur on each side of the bridge during extended daily rush hours and the most minor of accidents on the span can bring regional traffic to a halt. For those who have flown into Washington, D.C., this is also the point on the river where planes begin their descent, offering a stunning picturesque glide-path to Reagan National Airport.
Over the centuries, there have typically been two strategies employed for replacing or expanding bridges: (1) tear down the existing bridge and build a new, wider one in its place; and (2) construct a new and better bridge beside the existing one and remove the old bridge when the new one is completed. In the case of the American Legion Bridge, neither is an option.
As a vital transportation artery, it would be impossible to take the existing bridge out of service for a new span to be built in its place. For the second strategy, difficult topography, environmental concerns and dense development on both sides of the river prevent creating a new span beside the existing one.
So, what to do at the bridge when Maryland expands its side of the Beltway in the next decade and adds its own four lanes of dedicated HOV to meet up with those in Virginia? The Skunk Works Design Lab at STUDIO FINDLEY DESIGN took on the challenge.
The solution? A new dedicated, four-lane HOV roadway suspended from a single bowstring arch above an expanded existing bridge. Construction would occur in two phases (continued below).
EXISTING BRIDGE SPAN NEW BRIDGE SPAN WITH HOV
Composite sketch showing portions of the existing and new bridge design.
The existing bridge would be expanded by one traffic lane and one pedestrian walkway on each side in each direction (the walkways would tie into Potomac River hiking trails). The additional lanes on each side are required to replace two lanes in the middle of the bridge that would be removed from service to provide a structural zone for the insertion of the bowstring arch supports at each end of the span. The added lanes and walkways would be supported from below in the same conventional way the existing bridge is supported. Traffic flow remains minimally impacted during this phase. The number regular traffic lanes on the main deck of the bridge remain the same but with improved roadway access on each side.
Construction of a dedicated, four-lane HOV roadway suspended from a cable-stay bowstring arch. Traffic flow also remains minimally impacted during this phase.
The bridge design solves a multitude of logistical, engineering and technical problems as it solves the biggest problem of all – how to increase the capacity of the bridge without taking it out of service and without requiring the acquisition of large amounts of land on each side for a new bridge.
A stunning visual landmark – both by day and by dramatic illumination at night – would be created on one of the most important transportation routes in the region, and a new, instantly recognizable landmark from the sky would be established for arriving airline passengers from around the nation.