ASPIRE is a quarterly magazine published by PCI in cooperation with the associations of the National Concrete Bridge Council. The editorial content focuses on the latest technology and key issues in the Concrete Bridge Industry.
Issue link: http://www.aspiremagazinebyengineers.com/i/306162
S A F E T Y A N D S E R V I C E A B I L I T Y In 2008, the Federal Highway Administration launched the Long-Term Bridge Performance (LTBP) program, a 20-year-long research program to collect, maintain, and study high- quality, quantitative performance data on bridges. These data will support a better understanding of how and why bridges deteriorate, how to best prevent or mitigate deterioration, how to advance the design and construction of the next generation of bridges, and how to focus the next generation of bridge management tools. The LTBP program is an undertaking of immense complexity. There are dozens of factors and thousands of combinations of those factors that characterize the bridge population and influence the condition and performance of bridges. Bridges differ greatly by span type, design features, construction materials, dimensions, live load histories, environmental and climatic factors, physical changes that occur on the bridge, and history of maintenance, preservation, and rehabilitation. Each and every bridge represents a unique combination of these factors. the LtBP Program roadmap These differences illustrate the challenges that the LTBP program must address. Because of these complexities and the intended 20-year duration of the program, a well-designed research plan is essential. The roadmap steps include the following: 1. Defining bridge performance in terms of the specific important issues 2. Identifying critical gaps in knowledge and data 3. Creating a data infrastructure for bridge data from a variety of sources and with different formats 4. Designing experimental studies to answer key performance questions 5. Collecting data on representative samples of bridges, analyzing data, and creating performance models starting with What is Known T h e N a t i o n a l B r i d g e I n v e n t o r y ( N B I ) contains records on every bridge on all public highways in the United States. The NBI provides information on location, age, type of construction and geometry, functional class of the route carried, and up-to-date data on the condition and adequacy of the structure. The NBI is an invaluable resource for matching bridge types and bridge conditions with factors such as age, average daily truck traffic, and environment, and revealing performance relationships and trends that should be studied further. When culverts and tunnels, which will not be studied under the LTBP program, are excluded, over 80% of the bridges in the United States are simple or continuous spans of steel or concrete I-beams, boxes, or slabs. These are the bridge types that will be the initial focus of the LTBP program. A s a par t of the development phase, the LTBP program has identified 20 high-priority bridge performance issues in collaboration with 15 state Department of Transportation (DOT) bridge offices. Experts from the DOT offices included those responsible for the design, construction, inspection, management, and maintenance of bridges. These states were selected on the basis of size, geographic location, and climatic conditions to ensure broad national representation. The high- priority performance issues that have been identified are the most common concerns and the most costly activities that the states face in maintaining, repairing, and rehabilitating bridges. These state DOTs also helped identify what data they currently collect and use for their decision-making processes and what gaps they see in their currently availa ble d a t a . T h e s e p e r fo r m a n c e i s s u e s i n c l u d e performance of cast-in-place (CIP) concrete decks with various protective measures, joints and bearings, coated steel and weathering s t e e l g i r d e r s , c o n c r e t e a n d p r e s t r e s s e d concrete girders, substructure members, and mechanically sta bilized ear th walls, plus foundation elements vulnerable to scour. the FHWA Long-term Bridge Performance Program by John M. Hooks, J. M. Hooks & Associates One of seven pilot bridges is located near Perry, Utah. Photos and graphic: Federal Highway Administration. Book_Win11.indb 44 1/4/11 2:34 PM