The nation’s transportation system includes not only the extensive National Highway System but also the local highway systems that provide important links in the transportation network. Bridges are an essential component of these local systems. The primary focus of this synthesis is on local or off-system bridge design, construction, maintenance, financing, rehabilitation, and replacement. The definition of “off-system” can vary from place to place. Off-system bridges in this report will refer to those bridges typically owned and maintained by local agencies (i.e., cities and counties) and by state agencies on rural and other lowvolume roads. Information was gathered from several sources, including a project survey, published literature, electronic media, personal contacts, and manufacturers of bridges or bridge-related products. Several current practice areas that need improvement (e.g., design standards, replacement strategies, and maintenance) were also identified. Several hundred surveys were disseminated electronically to state and local agencies. Twenty states and 70 local agencies responded, with many of the local agency responses from a small group of states. Survey results indicated a general agreement between state and local agencies on a variety of issues. Survey responses provided some interesting data. The preferred type of bridge for new construction is a concrete box culvert because of its ease of construction, design, and being essentially maintenance free. Bridge decks were identified as requiring the most maintenance. Survey respondents noted that because of legislative restrictions on the work that can be done in-house and staff size limitations, design and construction of off-system bridges are usually completed by consulting engineers and contractors, respectively. Numerous survey responses indicated the need for improved design standards for off-system bridges and the desire for more flexibility in project funding. Of the hundreds of deficient, deteriorated bridges in this country, a very large number are locally owned or on “other” low-volume roads. Approximately 30% of the National Bridge Inventory bridges are considered structurally deficient or functionally obsolete. Because bridges less than 6.1 m (20 ft) long are not included in the National Bridge Inventory data, it seems reasonable to assume that the percentage of problematic bridges is even higher. Recent helpful changes in the Highway Bridge Replacement and Rehabilitation Program now permit the use of these funds for preventative maintenance activities that extend the useful life of a given bridge. More appropriate decisions are required in all areas of bridge maintenance, rehabilitation, and replacement. “Data-based” decisions derived from asset/bridge management, as well as construction techniques, maintenance procedures, materials, etc., to promote extended life, are required. New high-performance materials as well as fiber-reinforced polymer products are currently being researched. Several of these materials show promise for use in off2 system bridges because they have excellent durability, require minimal maintenance, and appear http://www.trb.org/publications/nchrp/nchrp_syn_327.pdfto have long life. One of the more comprehensive reviews in this synthesis is the coverage provided on bridge strengthening and rehabilitation. In addition to the numerous traditional procedures, several articles on the use of fiber-reinforced polymers in the strengthening of various bridge components are reviewed. Various aspects of bridge replacement structures are also given comprehensive coverage. Numerous options for off-system bridge replacements including pre-engineered bridges are presented. Bridge design aids, design software, and numerous websites, which can be used to expedite the replacement engineering process, are referenced. Various administrative issues were reviewed in this synthesis. Bridge management systems for off-system bridges are reviewed. Because asset management systems rely on historic cost data, the degree a given agency can use such a system is a function of the availability of such data. Several examples of bridge and asset management concepts for areas with small populations are presented as are some alternate strategies, such as road abandonment or total road closure. Various sources of funding (and potential new funding) for off-system bridges are discussed. In addition to traditional funding, additional federal programs such as the Surface Transportation Program and the Innovative Bridge Research and Construction Program are discussed. Information on the environmental process and some of the associated requirements are presented. Sufficient information and references are included to provide bridge owners with assistance in these areas. This synthesis has identified numerous existing deficiencies, and repair, rehabilitation, and strengthening procedures, as well as replacement options that owners of off-system bridges can employ. The suitability and cost-effectiveness of the many options and procedures identified are likely to vary in different regions of the country. This publication can be considered as a “user manual” or “tool box” of information, procedures, and choices for use by owners of off-system bridges in the management of their bridge inventory. (Author/publisher) This report may be accessed by Internet users at
Samenvatting