Rehabilitating Our Nation's Bridges

摘要

According to the Federal Highway Administration's (FHWA) National Bridge Inventory (NBI), 591,061 bridges in the United States are more than 20 feet long. Of this total, 360,446 (61 percent) are constructed of concrete and 194,827 are structural steel (33 percent). The rest are wood, masonry, aluminum, or other materials. Currently 29 percent of the concrete bridges and 55 percent of the steel bridges need repair, and 81,543 bridges are obsolete and need to be replaced. The average age of bridges in the Jnited States is 40 years. Paul Kivisto, the metropolitan region bridge engineer for the Minnesota Department of Transportation (MinDOT) says, "The average life of a bridge is approximately the same as for a person-about 70 years." Whether a bridge makes it that long or exceeds its life expectancy depends on how well it's maintained over its life span- the same as for people.