Methodologies for the analysis and load rating of prestressed and preflex bridge superstructures.

摘要

Bridge superstructures consisting of prestressed, post-tensioned, and preflex systems are evaluated with load rating methodologies adopted by private and government entities, establishing possible restrictions.Based on the importance bestowed in these structures to properly withstand service loads, this study considers the following tasks: (i) description of the analysis and load rating methods of prestressed beams based on AASHTO requirements (ii) develops a methodology for the analysis and load rating of preflex beams and (iii) present a parametric study of prestressed and preflex bridges with four different span lengths.The results show that AASHTO distribution factors are conservative in comparison to the values obtained from three-dimensional finite element models. In terms of the comparison between both systems (pre-tensioned and preflex), the preflex systems provide more slender sections (in the order of 62%) than prestressed concrete AASHTO I-type sections. Contrarily, live load deflections in the pre-tensioned systems were smaller (in the order of 8%), but for no case AASHTO limits were exceeded. The load rating values obtained from the methodologies considered in this study show that for both systems, the LRFR philosophy results are more critical to determine special conditions.