Estimating Load Impacts on Highway Structures Using the National Bridge Inventory Database

by Jos? Weissmann, Univ of Texas, Austin, United States,
Rob Harrison, Univ of Texas, Austin, United States,
Leonard Joanes, Univ of Texas, Austin, United States,

Document Type: Proceeding Paper

Part of: Microcomputers in Transportation


The issuance of single and multiple permits to operate vehicles exceeding legal weight limits, along with the policy-level analysis of bridge impacts induced by changes in vehicle size and weight legislation, involves tedious and massive calculations. This paper describes a computerized routine - termed LOAD - that uses the National Bridge Inventory (NBI) database prepared annually by each state for the Federal Highway Authority (FHWA). This routine allows each bridge on a specific route, or parts of a state bridge network (e.g., the interstate system), to be evaluated for non-standard vehicle operation. LOAD performs live load bending moment calculations, allowing comparisons between the effects of the rating vehicle (recorded in the NBI database for each bridge) and the non-standard vehicles. Designed to serve as a database and statistical analysis software package subroutine, LOAD reports the impacts of the rating and non-standard vehicles in terms of bending moments. The resulting bending moments are then used exogenously to determine bridge deficiencies and associated costs. For single and multiple trip permits, along with the supporting computer code from a database-oriented language, the routine generates reports of bridges rendered deficient by the non-standard vehicle along a specific route. These reports could then be submitted to a more detailed analysis by bridge engineers. At a policy level, the routine has been used to report the costs, bridge deck areas, and the associated average daily traffic (ADT) of bridges rendered deficient by the operation of various longer combination vehicles (LCVs). In this paper, deficient deck area and associated ADT reports have been used to asses LCV bridge impacts for the Texas interstate bridge network. Such impacts include both the costs to upgrade deficient bridges, and the associated user costs incurred from traffic impeded by bridge reconstruction.

Subject Headings: Highway bridges | Bridge-vehicle interaction | Vehicle loads | Load factors | Highway engineering | Bridge tests | Bridge engineering | Texas | United States

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