Francis Scott Key Bridge Rehabilitation over the Potomac River
Location: Washington, D.C.
Client: District Department of Transportation
Accessing and inspecting post-tension rods using specially designed equipment operated from sidewalk
JMT performed field inspection, concrete and steel testing and
evaluation for a historic bridge.
JMT performed the 100% hands-on field inspection, concrete and
steel testing and evaluation for the historic Francis Scott Key
Bridge which was built in 1929. This 1,781-foot long
reinforced concrete, open-spandrel arch bridge consists of
eight spans over the George Washington Parkway, Potomac River,
Whitehurst Freeway and C&O Canal. The bridge not only served as
a major commuter route into Washington, DC, but it also was listed
on the National Register of Historic Place, which required
coordination with the National Park Service since it spanned the
C&O Canal and George Washington Parkway. The inspection also
involved several utilities including water and gas lines on the
bridge, one of which was under the jurisdiction of the US Army
Corps of Engineers. Since the bridge was over navigable
waters, coordination was also required with the US Coast Guard both
during inspection as well as construction.
The inspection required free climbing the arch structure as well
as using specialized access equipment including articulating
snoopers and boats with bucket lifts. JMT worked with a bridge
access company to develop a new and innovative piece of equipment
to access and inspect post-tension rods which had failed and were
jutting out of the deck. This equipment operated from the sidewalk,
thereby eliminating any lane closures during this phase of the
work. Whenever possible, equipment and inspection methods were
selected to minimize maintenance of traffic issues.
The problem areas identified included a failing post-tensioned
deck slab which was installed in 1985 and significant concrete
deterioration to the portions of the concrete structure below the
deck slab. Testing was performed on concrete samples to determine
chloride content and compressive strength. Concrete cores were also
taken for petrographic analysis to determine evidence of alkali
silica reactivity (ASR), carbonation and delayed ettringite
formation (DEF). Echo impulse, a non-destructive test method, was
employed for locating voided post-tensioned ducts within the deck
slab. Samples of the post-tensioned bars were retrieved for testing
and determination of failure mode.
JMT helped to restore the deteriorated portions of the
structure, improving its structural integrity while maintaining
those architectural features which contribute to its historical
significance. A repair design for a 30 year additional life span
was requested by the District Department of Transportation (DDOT).
Preliminary repair plans were prepared which include conventional
concrete patching repairs as well as strengthening with carbon
fiber reinforced polymer reinforcing bars and sheeting materials.
Final contract documents for the structure repairs are being
developed. The construction cost is estimated to be approximately
« Go Back