Revised load and resistance factors for the AASHTO LRFD Bridge Design Specifications

[摘要] There has been considerable progress in reliability-based code development procedures. The load and resistance factors in the 2014 edition of the American Association of State Highway and Transportation Officials’ AASHTO LRFD Bridge Design Specifications were determined using statistical parameters from the 1970s and early 1980s. Load and resistance factors were determined by first fixing the load factors and then calculating resistance factors. Load factors were selected so that the factored load corresponded to two standard deviations from the mean value, and the resistance factors were calculated so that the reliability index was close to the target value. However, from a theoretical point of view, the load and resistance factors should be determined as coordinates of the design point that corresponds to less than two standard deviations from the mean. Therefore, the optimum load and resistance factors are about 10% lower than those specified in the AASHTO LRFD specifications. The objective of this paper is to revisit the original calibration and recalculate the load and resistance factors as coordinates of the design point for the Strength I limit state. The analysis was performed for the same types of girder bridges—reinforced concrete T beams, prestressed concrete girders, and steel girders—as in the original calibration presented in the 1999 National Cooperative Highway Research report 368, Calibration of LRFD Bridge Design Code. The recommended new load and resistance factors provide consistent reliability and a rational safety margin.

[学科分类] 建筑学

[关键词] 2017;201705;Year;Publications;J2017;Journal;Pubs