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LOCATION

Montgomery & Prince George's Counties, MD

STATUS

Design Completed 2012, Construction Ongoing

CLIENT

Maryland Transportation Authority MTA

TYPOLOGY

BRIDGES

ROLE

Architecture Bridge Designer

The Purple Line light rail project is the 1st circumferential transit line passing around the city through may communities and over varier terrains requiring numerous bridges to keep the tracks as level as possible.  There are at least six major bridges that were designed by KGP as part of the project.  Each has conditions that create a specific bridge type related to the surrounding environment and technical constraints.

Signifying the arrival of the Purple Line into the Chevy Chase Neighborhood, this pair of pedestrian and LRT bridges serve as a landmark for the directly adjacent Connecticut Avenue Station. KGP design studio studied several bridge types and alignments with track, station, and trail support structures. Due to geotechnical challenges, continuous aerial structures were determined cost-prohibitive for the location, and an MSE solution was selected, thereby creating simple abutments and a singular span. The pedestrian and LRT bridges were to remain separate for purposes of ownership and maintenance.

After examination of alternatives of the same type for each span, a contrasting composition of heavy and light bridge types, expressive of their distinct spans and loading, was selected. The pedestrian crossing is a lightweight, open-basket handle arch spanning 170 feet. The sidewalls of the arch are sheathed in an architectural fabric, serving as a throw barrier over the roadway. Monolithic and massive in form, two steel trapezoidal box girders support the trackway. Similar to the bowstring, the bellied structure of the girders is expressive of the released spans, visually displaying a maximum moment and depth at mid-span.

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