NCHRP project 20-07/task 122: Load rating by load andresistance factor evaluation method

摘要

The Draft Manual for the Condition Evaluation and Load and Resistance Factor Rating of Highway Bridges was developed under NCHRP Project 12-46. The manual has been extensively reviewed, and changes have been made to Section 6, Load and Resistance Factor Rating (LRFR). The revised version was adopted as a Guide Manual at the May 2002 Meeting of the AASHTO Subcommittee on Bridges and Structures. The LRFR methodology is based upon calibrated load factors using the principles of structural reliability. Further, the LRFR procedures were subjected to trial analyses as part of the development. Nonetheless, there exists a need to further demonstrate that the method gives valid, consistent results for all major bridge types and span ranges, and to document and explain differences between LRFR and current load factor ratings (LFR) results. The objective of this project is to provide explicit comparisons between the ratings produced by the LRFR methods of the Guide Manual and LFR ratings from the latest edition of the AASHTO Manual for Condition Evaluation of Bridges. Based upon the results of this limited investigation, in general, LRFR rating factors are equal to or greater than LFR ratings factors except for reinforced-concrete slab bridges.