Location: Virginia, Maryland and District of Columbia
Client: Maryland Department of Transportation
The new Woodrow Wilson Bridge (WWB), is a signature crossing over the Potomac River just south of Washington, DC which links Maryland to Virginia. It carries twelve lanes of Interstate I-95/495 traffic. The bridge has been designed to accommodate plans for a commuter rail system. Its construction is part of the 7.5 miles, $2.5 billion Capital Beltway Interchange Project that connects Maryland and Virginia.
The new bridge WWB is 6,000 ft and has four, side-by-side, 222 ft double-leaf bascule spans that provide navigational clearances of 175 ft horizontally and 70 ft minimum of vertical clearance in the span-down position, and completely unrestricted with the span raised. The bridge’s parallel double-leaf spans have 270 ft center-to-center trunnion spacing and an overall bridge width of 249 ft. The bascule span is supported on V-shaped concrete bascule piers. The new bascule spans weighing approximately 2000 tons each comprise the world’s largest movable bridge.
(The bascule spans of the new bridge are the heaviest movable load of any bridge in the United States, as 34 million pounds of structure move to clear a ship through the channel.)
Features of the span include a composite lightweight reinforced concrete deck, sixteen moment-transferring span locks, sixteen tail locks, interlocking spans, redundant electrical power and control systems, eight warning gates, four barrier gates, four pedestrian gates, thirty two submarine cables, sixteen motor drives, twelve control cabinets, eight motor control centers, thirty brake assemblies and a single control console fabricated from eleven individual control stations.
The bascule span and all ancillary devices are capable of operating in group mode, all eight leafs together, or individually. The redundant electrical control systems allow for seamless transition and operation in the even of a fault or malfunction from one control system to another.
Multiple levels of power redundancy also are provided through medium and low voltage switchgear substations in conjunction with two stand-by generators. Normal power is achieved through two separate substation and are interconnected to transfer power to the alternate power source should the primary source fail. In the event both normal power sources fail two generators are provided capable of supply power for bridge operation.
Hardesty & Hanover’s responsibilities included the complete design of the movable span superstructure, the trunnion towers, and the mechanical and electrical systems. Hardesty & Hanover also construction support service engineering through project completion and construction inspection services for the entire electrical system for the duration of construction. Hardesty & Hanover is currently performing bridge operation services for the bascule span for maintenance and marine vessel openings.