Load and Resistance Factor Rating Using Site-Specific Data

Abstract

Traditional techniques for bridge evaluation are founded on design-based deterministic equations that use limited site-specific data; they do not necessarily conform to a quantifiable standard of safety and often are quite conservative. The newly emerging method of load and resistance factor rating (LRFR) addresses some of these shortcomings and allows bridge rating in a manner consistent with load and resistance factor design but is not based on site-specific information. A probability-based method for load rating of bridges using site-specific in-service structural response data in an LRFR format is presented. The use of site-specific structural response data eliminates a substantial portion of modeling uncertainty in live load characterization (involving dynamic impact and girder distribution) and yields more accurate bridge ratings. Rating at two limit states—yield and plastic collapse—is proposed for specified service lives and target reliabilities. This method considers a conditional Poisson occurre...