Bridge preservation activities have focused on the service life extension of bridge components or protection systems that extend the useful life of bridges. National efforts are underway to look at materials, design and construction practices to extend the useful life of 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 may not be driven by the condition of the bridge. 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 service life.
The objective of this research project is to determine the driving causes of bridge decommissioning in the United States.
Task 1. Perform a synthesis of similar and related research on the topic of causes of decommissioning of bridges.
Task 2. Conduct a survey of State DOT’s to capture the policies and justifications for replacement of bridges. This survey should relate condition, performance, vulnerabilities and functional replacement justifications to associated NBI data.
Task 3. Utilize nationwide 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.
Note: Submit a draft letter report for Tasks 1 through 3 no later than 4 months after contract award. NCHRP approval will be required before proceeding with the remaining tasks.
Task 4. 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.
Task 5. Present the research findings to the AASHTO Subcommittee on Bridges and Structures, Technical Committees: T-9 Preservation.
Task 6. Summarize the findings from both national and state level reviews and recommend needed research areas to help achieve extended bridge service lives.
Task 7. Submit the final report describing the entire research. Following receipt of the draft final report, the remaining 2 months shall be for NCHRP review and comment and for research agency preparation of the revised final report.
STATUS: Project in progress