Highway Bridge Type and Performance Patterns

Abstract

National Bridge Inventory (NBI) data for bridges built from 1950 to 1987 were used to identify the 12 most common bridge types. Three of these types account for almost half of the bridges built in the United States during that period but have the highest percentages of structural deficiency as classified by Federal Highway Administration (FHWA) criteria. Many timber stringer and steel stringer bridges built during the 1980s already are classified as structurally deficient in the 1987 NBI. The most common deficiency on interstate bridges is the deck, whereas the most common deficiency on county bridges is the substructure. On the average, in a given state, the three most common bridge types account for two‐thirds of all bridges built within that state during the period 1950–1987. Data for six selected states show considerable variety in types of bridges built, percentages classified structurally deficient, and the most common deficiencies. Data for two adjacent states indicate differences in bridge performance, apparently influenced more by state policies than by climate and load capacity. The study raises questions regarding the effects of local practices on long‐term highway bridge performance.