This report presents the derivations of the live load factors and associated checking criteria incorporated in the proposed Manual for Condition Evaluation and Load and Resistance http://gulliver.trb.org/publications/nchrp/nchrp_rpt_454.pdfFactor Rating of Highway Bridges prepared for NCHRP Project 12- 46 (hereafter referred to as the Evaluation Manual). A final draft of this Evaluation Manual was submitted early in This report may be accessed by Internet users at 2000 to the project panel and to appropriate AASHTO committees. In addition, there is a companion project report (prepared by Lichtenstein Consulting Engineers, Inc.), which contains trial ratings, numerous bridge examples, and comparisons of proposed and existing rating results. The evaluation criteria, along with corresponding live load factors developed herein, are recommended for the legal load rating analysis and the evaluation of permit loadings and postings, including the use of available site-specific data input. The material herein supplements the text and commen-tary in the proposed Evaluation Manual related to the Load and Resistance Factor Design (LRFD) factors. A major goal in this report is to unify the reliability analyses and corresponding database used in the load and resistance factor rating (LRFR) and the recommendations for the Evaluation Manual compatible with the AASHTO LRFD bridge design specifications. In addition, the following topics, unique to the development of the evaluation criteria, are also presented in this report : the derivations of the proposed live load factors using reliability methodology for the various categories of bridge ratings described in the proposed Evaluation Manual. (These derivations included the extension of the reliability methods utilized in the AASHTO LRFD Bridge Design Specifications [AASHTO, 1994] to the requirements for evaluation and rating of bridges) ; the traffic models and database used for calibrating the recommended live load factors in legal load rating for site-specific input of annual daily truck traffic (ADTT) ; an extension of the modeling of live load factors for the specific cases of checking of random traffic, routine per-mits, and special permit evaluation for heavy vehicles ; the derivations and the implied safety criteria contained within the proposed allowable truck weight posting curve ; how site weigh-in-motion (WIM) data, if available, can be incorporated in adjusting the load factors and ratings of specific bridge sites ; an alternative rating procedure to the LRFD checking equations that directly uses the target safety indexes in calculating bridge ratings ; methods for extending the recommended live load factors to special cases that are not covered in the Evaluation Manual; and areas for research and further data gathering. (A)
Samenvatting