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Route 360 Over Rappahannock River (Downing Bridge) Fender Replacement Study. Virginia Department of Transportation, Virginia.
The existing fender system protecting the channel-span piers of the Route 360 over the Rappahannock River, original to the 1963 construction, are in need of significant repairs.
In 2009, the Fredericksburg District of the Virginia Department of Transportation (VDOT) approached WRA to perform a study to replace the failing existing timber fenders around the channel-span piers of Route. 360 over the Rappahannock River with a low-maintenance fender. WRA prepared a study beginning with generating a record of river traffic and calculating vessel collision energies and forces required to be resisted by the fender system in accordance with the AASHTO Vessel Collision Specification. The river geometry at the bridge location combined with fast moving, heavily laden barge traffic necessitated a robust fendering system. WRA then prepared multiple viable fendering design concepts, performed a probabilistic cost-benefit analysis to determine the optimal level of fendering protection for the bridge piers, and then provided a system recommendation and cost estimate.
WRA engineers generated a record of river traffic traversing under the bridge. Based on the recorded vessels and velocities, WRA calculating vessel collision energies and forces required to be resisted by the fender system in accordance with the AASHTO Vessel Collision Specification.
WRA performed preliminary structural design and analysis for the fendering concepts. For each fender system, WRA calculated the approximate strength, stiffness, and energy absorption capability