Page 95 - Bridge and Highway Structure Rehabilitation and Repair

70 SECTION 1 ADMINISTRATIVE ISSUES

• Design a special railing matching the appearance of the existing railing with higher strength
material to meet the crash test requirements.
It may not be necessary to crash test the new railing if the geometry and calculated strength
equals or exceeds a crash tested traffi c railing.
4. Historic Shelby Street Bridge in Nashville, Tennessee has been retained as a footbridge. One
hundred year old Shelby Street Bridge originally was built in 1909. Problems with concrete
used in its construction led to repairs in the 1920s and again in 1960. In 1998, the bridge
was declared unfit for traffic and was slated for demolition. However, because of its historic

nature, the bridge was not torn down, but was converted into a pedestrian bridge linking
entertainment venues and the coliseum on either side of the Cumberland River.
The bridge was repainted in 2003 with an inorganic, zinc-rich primer, a cycloaliphatic
amine cured epoxy middle coat, and a fl uorourethane topcoat. The bridge often is lit with
lights of various colors, often reflecting the season. A gray topcoat was selected because it

shows the color of the lights better. At 3150 feet, it is one of the longest pedestrian bridges
in the world.

2.6.6 Restoring Historic Masonry Arch Bridges
1. A two lane precast concrete arch bridge in Lancaster County, PA replaced a masonry bridge
built in 1917, but retained the original structure’s character.
A safety inspection of the original 1917 bridge revealed deterioration and structural
defi ciencies too extensive for repair. Design was sensitive to surrounding rural landscape.
The county was able to quickly secure the Pennsylvania Historic Museum Commission’s
(PHMC) approval for the bridge replacement. The new concrete bridge mimics the features
of the original historic structure and matches the stone-masonry-like façade of a nearby
farmhouse.
2. Restoration of the Wisconsin Avenue Bridge in Washington, D.C.
The new arch bridge needed to be simulated. Based on the analysis of a three dimensional

simulation model, reinforcement configurations to resist the stresses were finalized. It was
successfully restored by using a proprietary system.
The method allowed 2.5-inch diameter holes to be drilled in the arch. Stainless steel 1-inch
diameter anchor bars were embedded into a polyester sock material. Cementitious grout
was pumped into the sock causing it to inflate and encase the steel in 6000 psi compression

grout.
3. The historic 19th Century bridge located in Valley Forge National Park in Pennsylvania is
a wrought-iron through truss built in 1886 and was rehabilitated using advanced composite
materials. It spans19 meters and carries one lane of vehicular traffic. Based on the deterio-

ration of stringers that supported a timber deck, a rehabilitation project was initiated. The
solution chosen was to remove the stringers andin their place install a glass fi ber-reinforced
polymer (GFRP) slab. The weight of the slab was roughly half the weight of the existing
stringers, thereby reducing the dead load effects onthe remaining structure. A wood wearing
surface was installed on top of the GFRP slab to restore the deck to its initial condition. In
1998, a diagnostic load test wasperformed on the bridge using a pre-weighed truck. Strains

and deflections of the GFRP slab and truss elements were recorded for two different truck
weights and for variousload passes.
4. Evaluation of historic bridges constructed in the first half of the 20 Century: Construction
th

Technology Laboratories, Skokie, IL used advanced NDT methods to provide vital structural
and material information necessary for successful rehabilitation. Laboratory testing ad-
dressed such topics asthe extent of deterioration and chloride concentration in the concrete,
as well as identification of aggregates and cement constituents, sorepair concrete could be