Crews working on Phase 2 of the Dulles Corridor Metrorail Project have successfully completed a significant construction operation, by pouring 473 cubic yards of concrete needed to construct a large “straddle bent” over the Dulles International Airport Access Highway.
A straddle bent supports a structure that spans a particularly wide area where piers cannot be used directly beneath the span.
Massive concrete operations require significant coordination between project crews and the airport.
The work on January 8 required 49 truckloads of concrete, and caused minimal interruptions to eastbound traffic along the Access Highway. The concrete pour took about 6.5 hours to complete, including preparation time.
Dulles Corridor Metrorail Project Phase 2 crews place 473 cubic yards of concrete overnight to construct a straddle bent over the eastbound Dulles International Airport Access Highway
Photos by: Jennifer Alcott
“Completion of the straddle bent signals a major step forward,” according to Charles Stark, executive director of the rail project.
To ensure structural integrity, several tests are conducted prior to pouring the concrete. Test cylinders are poured and post-tensioning cables are tested to confirm compliance.
As the project continues, it will require seven additional large straddle bents on or near airport property, including two more over the eastbound Access Highway lanes and one over the westbound lanes. This work is scheduled to be completed by the third quarter of 2016. Work on the four remaining straddle bents over the eastbound lanes of the Dulles Greenway is projected to begin in late 2016.
“The use of straddle bents enables(?) us to span significant roadways or environmental features,” said Keith Couch, project director for Capital Rail Constructors, the joint venture of Clark Construction and Kiewit Infrastructures South, the contractor executing the design-build contract for the second phase of the Silver Line.
Phase 2 runs from Wiehle avenue in Reston west through Herndon, Dulles Airport and to Ashburn in eastern Loudoun County.
