부산대학교 도서관

The work required to keep a bridge in its present condition and to control potential future deterioration. Bridge maintenance usually involves inspection, evaluation and rating, repair, rehabilitation, strengthening, and retrofitting. As a vital part of transportation systems, bridges must be properly maintained to perform their designed functions. There are approximately 600,000 highway bridges in the United States. About 50% of them were built before 1940, and many have not been adequately maintained. Most of these bridges were designed for lower traffic volumes, smaller vehicles, slower speeds, and lighter loads than are common today. Over time, bridges rust, decay, crumble, fail, grow obsolete, and become functionally inadequate. In addition, deterioration caused by environmental factors is a growing problem. According to the U.S. Federal Highway Administration (FHWA), almost 40% of the nation's bridges are classified as deficient and in need of rehabilitation or replacement. Many of these bridges are deficient because their load-carrying capacity is inadequate for today's traffic. Strengthening can often be used as a cost-effective alternative to replacement or posting.