Long-Term Bridge Performance Program

Need | Objective | Data Collection Goals | Approach | Oversight

Long-Term Bridge Performance (LTBP) Program Overview

Need

Federal Highway Administration's (FHWA's) National Bridge Inspection Standards (NBIS) facilitated the creation of one of the most comprehensive sources of bridge information in the world, the National Bridge Inventory (NBI). The NBI contains information on the conditions of more than 590,000 bridges, tunnels, and culverts located on public roads. In 2007, according to the NBI, there were approximately 152,136 structurally deficient or functionally obsolete bridges. This number is likely to increase in coming years due, in large part, to increased traffic demand, continued bridge aging and deterioration, and limited funds for rehabilitation and maintenance.

A number of States have adopted and implemented the American Association of State Highway and Transportation Officials' (AASHTO) AASHTOWare^® Pontis^® bridge management system or a similar system with advanced asset management decisionmaking capabilities. Some States augment the NBI data used in advanced bridge management systems by also collecting element level bridge data. Even with these bridge management tools and data, however, there remain many unknowns about the performance and degradation of structures and materials over time, and the effectiveness of maintenance, repair, and rehabilitation strategies for a given component or a complete bridge system. In addition, with the recent move to higher performance materials and advanced structural systems, high-level, long-term performance and durability are assumed, but not demonstrated at this time.

For the Nation's bridge network to meet these increasing demands without similar increases in funding, future bridge management systems will require improved life cycle cost and performance models, and information on the effectiveness of maintenance and repair strategies. Such improvements will require high-quality quantitative data on which to base the development of new models and decision making algorithms.

Objective of the LTBP Program

The objective of the LTBP program is to compile a comprehensive database of quantitative information from a representative sample of bridges nationwide, looking at every element of a bridge. By taking a holistic approach and analyzing all of the physical and functional variables that affect bridge performance, the study will provide a more detailed and timely picture of bridge health and better bridge management tools.

LTBP researchers will conduct detailed periodic inspections, monitoring, and evaluation of the population of bridges representing the national bridge inventory by taking advantage of nondestructive evaluation (NDE) techniques and visual inspections. NDE techniques may include ground-penetrating radar to detect flaws and corrosion inside the structures-and sensor technologies that monitor traffic loading, cracks due to fatigue and corrosion, overloads, environmental conditions, etc. For selected bridges in the study, researchers will conduct recurrent, periodic evaluations throughout the life of the program and may perform forensic autopsies of decommissioned bridges to learn more about their capacities, reliabilities, and failure modes.

Data Collection Goals

The wealth of data collected through the LTBP program, and the subsequent data analysis, will lead to:

• Improved knowledge of bridge performance
• Advances in deterioration and predictive models
• Deterioration models that can simulate interactions between pavement, bridges, and traffic
• Effective use of life cycle cost analysis
• Improved inspection/condition information through NDE and structural health monitoring; and the fostering of technology for assessment of critical but invisible bridge elements and components
• Support for development of improved design methods and maintenance/bridge preservation practices
• Quantification of the effectiveness of various maintenance, repair, and rehabilitation strategies
• Improvement of the operational performance of bridges with the potential to reduce congestion, delay, and crashes
• The fostering of the next generation of bridge and bridge management systems
• Contributions for setting national policy

Ultimately, improved understanding of bridge performance will promote safety, mobility, longevity, and reliability of the Nation's highway transportation assets.

Approach

The research team will conduct the work in two phases for achieving the objectives of the FHWA LTBP program. These phases are the following: 1) Developmental Phase, and 2) Execution Phase. The current activities of the program are related to the Developmental Phase, which includes identifying specific data to be collected that are most relevant to the objectives of the program; establishing an open, scalable, and extensible data management and data analysis infrastructure; developing protocols for data sampling and collection, and quality assurance; and developing a methodology and rational for sampling bridges from the National Bridge Inventory database to determine the types, numbers, and locations of bridges to be inspected, monitored, evaluated, and instrumented in the pilot phase of the program. This table shows task descriptions for the Developmental Phase and associated responsibilities by the research team.

Task Number	Task Description	CAIT	PB	UTC	VTRC	Siemens	Advitam	BDI
1.1	Road Map		X
1.2	Specific data to be collected				X
1.3	Development of Data Infrastructure					X
1.4	Protocols for data sampling, collection and Q/A						X
1.5	Bridge Sampling Methodology	X
1.6	Synthesis of bridge monitoring and autopsy methods			X
1.7	Protocols for Bridge Monitoring Autopsy			X
1.8	Communication/Marketing Plan and Products	X
2.1	Project Coordination (for fieldwork)		X
2.2.1	Draft Pilot Study Plan		X
2.2.2	Pilot Study Execution	X	X
X	Indicates team member with primary responsibility
	Indicates team member that will provide significant contributions to the task

In the pilot portion of the program (which is part of the Execution Phase), researchers will validate protocols for data collection and management and ensure that all of the components needed to achieve the long-term objectives of the LTBP program are specified before initiating work on the large population of bridges nationwide. Both phases require an active engagement between the research team, FHWA, bridge owners, industry, other government agencies, and the international community. It is also essential to coordinate with other long-term strategic research programs undertaken by the FHWA, AASHTO, Transportation Research Board, American Society of Civil Engineers, National Cooperative Highway Research Program, Strategic Highway Research Program 2 (SHRP2), National Institute of Standards and Technology, National Science Foundation, and the U.S. Army Corps of Engineers.

Oversight

External and internal Expert Task Groups (ETGs) were established to provide a rigorous oversight and quality control to the FHWA and the research team on matters relating to LTBP program activities. The members of these two groups were appointed by FHWA, based on their technical expertise in bridge design, inspection, maintenance and preservation, management, NDE/nondestructive techniques and structural health monitoring of bridges.