Using Diagnostic Load Tests for Accurate Load Rating of Typical Bridges

Historically, bridge load ratings based solely on theoretical calculations tend to be overly conservative, due to the many assumptions made in modeling of the bridge. A controlled load test can be used to determine a more accurate load rating of the bridge. Presented in the paper is an overview of a typical controlled load test. Specific attention is given to determining the actual load distribution in the bridge, assessing support fixity, unintended composite action, and contributions from nonstructural components. The manner in which these factors are adjusted and applied to a simple beam model of the bridge for load rating is also discussed.