Load Rating

See AASHTO, Manual for Bridge Evaluation. The capacity is commonly evaluated for the following load assumptions:

a. Inventory Rating. Represents the safe loading for application on a vehicle bridge on a day-to-day basis. It is the largest sustained live load that an existing structure can safely carry for an indefinite period of time without undergoing damage from repeated maximum loads. The rating is based on AASHTO design specifications and takes into account the current condition or deterioration of the bridge elements due to age and service. Applicable to vehicle bridges.

b. Legal Load Rating. Represents the maximum size or weight limits permissible on a specified portion of road by law for the State in which the bridge is located. The legal dimensions and weights vary between states. Applicable to vehicle bridges.

c. Maximum Rating. Represents the load level that can be supported on a railroad bridge at infrequent intervals with applicable speed restrictions. Applicable to railroad bridges.

d. Normal Rating. Represents that load which can be operated on a railroad bridge indefinitely without inducing damage. Normal ratings will be determined in accordance with the American Railway Engineering and Maintenance-of-Way Association with and without fatigue considerations. Applicable to railroad bridges.

e. Operating Rating. Represents the maximum permissible live load that can be placed on the vehicle bridge. Unlimited use by vehicles that subject the bridge to operating levels may shorten the useful life of the bridge. This rating also includes the same load in multiple lanes. Applicable to vehicle bridges.