Approach to Setting Bridge Crossing Rating Criteria

摘要

Document describes a methodology for rating bridges for non-normal crossing conditions. This methodology is based on probability of failure calculations, for normal crossings, for the recommended caution crossing rating the bridge will have the same probability of failure as for the normal crossing. Risk crossing ratings are to be set allowing higher probability of failure and considering only the modes of failure which prevent completion of the crossing, Example calculations were performed which illustrated the caution and risk crossing bridge rating that could be obtained, e.g., for caution crossings, 20% increase in vehicle weight over normal crossing allowable. Changes to the Trilateral Design and Test Code to include bridge rating procedures for caution and risk crossings have been recommended. These include: Design Calculations, and Verification Test Requirements. Rating of bridging for use under non normal conditions enables the commander to make rationale usage decisions in the field.