Characteristics of Decommissioned Bridges
Bridge preservation activities have
focused on the service life extension of bridge components or protection
systems that extend the life of bridge as a whole. National efforts are underway to look at
materials, design and construction practices to extend the useful life bridges
toward an elusive 100 year mark.
Informal research done by the Transportation Research Board Bridge
Preservation Committee (AHD037) using 20 years of National Bridge Inventory
data for all states in the United States indicates that the majority of bridge
replacements are not driven by the condition of the bridge. Additional evaluation of the causes of bridge
replacements in California has found similar results to the national
If the majority of bridges are not
being replaced due to condition, then what is driving bridges to be taken out
of service? Are bridge preservation
efforts appropriately focused on the true factors that are leading to the
premature replacement of bridges?
Understanding what is causing bridges to be decommissioned will allow
bridge managers to better adapt practices to achieve the maximum possible
initial research activity will mine many years of National Bridge Inventory
(NBI) data to characterize various attributes of bridges in their last year of
NBI reporting prior to being decommissioned.
The study seeks indicators of causes of decommissioning. The causes can
indicated by general condition ratings
to mobility, indicated by number of lanes on/under structure, and load ratings
indicated by ratings for scour critical bridge item, and critical feature items
constraints, indicated by deck width, and vertical clearances
to replace/retain bridges may be found to depend on relations of NBI items to
route functional class, ADT, and ADTT.
For decommissioned bridges, the study will examine the importance of
individual NBI items and cross-correlations among NBI items. Quantification of
the average life span of bridges by material, design type, geographic area and
environment will be determined. Armed
with the results of the national analysis, the research will evaluate more
definitively the cause of replacements for three or four selected States using
Department of Transportation project information.
management of the aging bridge population in the United States is a
multi-billion dollar public liability.
National focus in the areas of bridge preservation has been geared
toward condition extension methods.
These conditioned focused efforts are important, but if bridges are
found to be replaced for reasons other than condition, then bridge managers
should focus additional research, practice, and policy on addressing these
issues. Research that clearly identifies what drivers we are trying to preserve
for holds the potential to extend the service lives of bridges and save
billions of taxpayer dollars.
previous published research could be found evaluating the causes of
decommissioned bridges. Published
research is available that investigates the causes of bridge collapses may
inform this effort, but is not focused on bridges removed from service in non-catastrophic
research report titled, “The Need for Conducting Forensic Analysis of
recognizes the need for a broad study similar to the one proposed in this needs
statement. This research found that over
30% of decommissioned bridges had no condition deficiencies support the premise
of this proposed research.
unpublished study examined NBI data of bridges that were replaced. Additionally, The California Department of
Transportation has evaluated the cause of bridge replacements over a 10 year
period has been published in presentation form only.
 Chase,S.B.(2012). The Need for Conducting
Forensic Analysis of Decommissioned Bridges. UVA-2012-05, 36p.
 Hooks,J.M (2011). Structural and
Functional Characteristics of Decommissioned Bridges. Proc. National Bridge
and Preservation Conference, Proctor, Varma, Hooks, eds.
research consists of a number of related tasks to help ascertain the driving
causes of bridge decommissioning in the United States. Specific tasks include:
Perform a synthesis of
similar and related research on the topic of causes of decommissioning of
Conduct a survey of
State DOT’s to capture the policies and justifications for replacement of
bridges. This survey should related
condition, performance, vulnerabilities and functional replacement
justifications to associated NBI data.
National Bridge Inventory databases to analyze the characteristics of bridges
in their last year in the inventory prior to decommissioning. Determine the expected service life of
bridges based on material, design types, traffic volumes, truck volumes, geography,
environmental conditions, functional classifications, and others. For bridges that are not structurally
deficient at the time of decommissioning, determine the probable cause of the
replacement by looking at alternative drivers, including by not limited to
scour vulnerabilities, load capacities, vertical and horizontal clearances, and
adequacy of service (level of service) of the roadway carried on the bridge.
Utilize the results from
task 2 to select three to four State Departments of Transportation where
project level records exist to positively confirm the characteristic drivers
for bridge replacement. This task will
involve a review of agencies replacements and project records to determine the
causes of replacements. The state level
results should be correlated to the national level results.
Summarize the findings
from both national and state level reviews and recommend needed research areas
to help achieve extended bridge service lives.
The results from this
research will be of immediate use for the determination of realistic service
lives of bridges to be used in life cycle cost analysis. Causes of replacement other than condition
related may justify additional research in those areas to help achieve a
greater bridge service life. Strategies
to design and construct bridges that are adaptable to changing functional needs
over time may result in improved practices.
The American association of State Highway and Transportation Officials
is in the process of developing a “Bridge Preservation Best Practices Manual”
that would provide an avenue for findings to immediately impact bridge
Having a clear understanding of what is really driving bridge replacements will guide bridge preservation efforts to include methods to extend the life span of bridges that are not entirely focused on condition. If bridge preservation efforts are targeted towards replacement drivers beyond condition, a hundred-year service life for bridges may become a commonplace.
|Sponsoring Committee:||AHD37, Bridge Preservation
|Research Period:||24 - 36 months|
|RNS Developer:||Michael B. Johnson, Jeff Weidner, Reed Ellis|
|Source Info:|| Chase,S.B.(2012). _The Need for Conducting Forensic Analysis of Decommissioned Bridges_. UVA-2012-05, 36p.|
 Hooks,J.M (2011). _Structural and Functional Characteristics of Decommissioned Bridges_. Proc. National Bridge Management, Inspection and Preservation Conference, Proctor, Varma, Hooks, eds.
|Index Terms:||Maintenance practices, Preservation, Service life, Bridge construction, Bridge design, National Bridge Inventory, California, Replacement (Bridges), |
Maintenance and Preservation
Bridges and other structures