Nearly half of the 587,000 bridges in excess of 6.1 m (20 ft) long on public roads in the United States are located off the Federal Aid System, are on local rural and urban roads or rural minor collectors, and are classified as off-system bridges. Approximately one-third of the off-system bridges are structurally deficient or functionally obsolete. The majority of states with large bridge populations are rural states with large percentages of structures owned by counties and other local agencies. Many of these bridges are on low-volume roads. Given the size of the deficient bridge population and the concentration of these bridges largely on locally owned networks, a recent NCHRP synthesis (NCHRP 32-08, "Cost Effective Structures for Off-System Bridges") has explored the current practices regarding the maintenance, rehabilitation, and replacement of off-system bridges. The administrative aspects of off-system bridge ownership and management were explored, including sources and problems of funding, bridge asset management, design policies for off-system bridges, exploration of the environmental process, and discussions of interagency partnering and coordination problems. A significant body of work exists on effective bridge maintenance and rehabilitation. A significant discussion of bridge strengthening, including specific techniques used on low-volume-road bridges, was also examined. Concerning bridge replacements, the literature and owner survey were used to provide information on successful concepts currently being used. In addition to successful bridge replacement options, discussion of the use of standard plans, design aids, and software is promoted as leading to standard and efficient low-volume-road bridge replacements. This paper is also available on CD-ROM (see C 30152 CD-ROM).
Samenvatting