Page 8 - SeptOct2021Vol33No3

STATEWIDE By Adam Davidson, P.E.
Maintaining Links: ABC Techniques

Benefit Urban, Rural Agencies

The collapse of the Silver Bridge over partial road closures for months or even be standardized so that the contractor
the Ohio River in 1967 cost the lives of years from traditional construction can fabricate replacement items
67 people and brought national attention processes, ABC can limit motorists’ identically. This reduces cost and
to the issue of bridge safety and the need disruption to a few weekends or non-peak makes installation more seamless.
for maintaining safe structures. This hours.
prompted the United States Congress Robertson County Bridges: Miller Creek
to enact the National Bridge Inspection and Calebs Creek
Standards (NBIS), nationwide legislation
for bridge inspection, load rating and In the case of the Tennessee State
inventory. Route 49 bridge project, a Tennessee
The NBIS establishes the minimum Department of Transportation (TDOT)
qualifications required for the country’s rehabilitation project was needed on
bridges, ensuring that routine, proper two rural Robertson County bridges
safety inspections regularly evaluate originally built in 1929 and rehabilitated
in 1964. Using ABC techniques, both
the loading demands of a constantly the Millers Creek Bridge and the Calebs
changing freight logistics industry, Creek Bridge were converted from two
which is necessary in preserving bridge
service life. span to single span structures with
With proper maintenance, the lifespan most of the work completed during a
of new bridges can be around 75 single weekend closure, limiting traffic
years. However, older bridges were not disruptions to just 56 hours.
The following checklist can help an
designed for that length of time, thus an agency determine if ABC is the right
increasing number are in need of repairs solution for repairing or replacing a
or replacement.
bridge:
Accelerated Bridge Construction (ABC) • Minimized Impacts on Drivers: A
Accelerated bridge construction (ABC) major benefit to using ABC is the
may be the solution for local urban or minimization of risk and improvement
rural agencies who are looking at their of safety for the immediate area.
own bridge infrastructure. Growing Bridge and roadway closures have an
municipalities and rural counties can immediate impact on society and the
greatly benefit from a number of advances daily users. The length of time and
made in recent years as it relates to traffic congestion for the relocation of
ABC, since much of the fabrication and traffic onto a detour also are important
assembly can be completed long before factors. How will this affect emergency
any road closures are announced. routes? Business and school access?
When addressing unsafe conditions in What about the local environment?
bridge evaluations, the most economical • Factored In Site Conditions: To save
solution often is to repair or rehabilitate time and headaches, prefabrication of
a structure to extend its functional certain bridge units can be constructed
life. According to the Federal Highway offsite by the contractor, then
Administration, approximately 25% installed and joined together during
of the nation’s 600,000 bridges are in a weekend road closure. Geometrics,
need of repairs, rehabilitation or total and conditions such as condition of
replacement. the bridge, all impact the feasibility of
Depending on the project, location and ABC.
a variety of other factors, ABC proves to • Standardized Plans: When dealing
be beneficial when taking into account with multiple bridges along a
the reduced disruption to community roadway, the contractor will need a
residents, as well as user, economic and bridge-specific removal plan for each
societal impacts. Instead of dealing with structure, but the repair details can

8 TPW September/October 2021