Investigation of Load-Path Redundancy in Aging Steel Bridges.

摘要

National statistics on numbers of structurally-deficient bridges and the associated limited financial resources for infrastructure renewal require ever more thoughtful approaches to bridge management. One significant opportunity for better prioritizing the limited funding available for this purpose is through better quantification of the existing strength of aging structures. Specifically, one promising means for achieving this goal is leverage the load-path redundancy inherent to steel girder bridges to calculate a so-called system capacity of the structure, in contrast to the present approach of calculating a strength that is governed by the weakest or mostheavily loaded member. When this more realistic approach is utilized, bridges have significant reserve capacity above what is predicted from modern analysis and design methods predicated on the analysis of individual members. The present research was motivated by this promising concept of system capacity and the identification of information needed to transition this concept to practice. These needs include both knowledge needed with respect to structural mechanics (which was the subject of Phase 1 of this project) as well as practical needs to synthesize the research result into a format that is synergistic with existing evaluation methods used by bridge engineers (which was the subject of Phase 2 of this work). The structural mechanics that must be assessed and quantified relates to the fact that in system level analysis the transverse load distribution mechanisms become more influential than in current methods, so further understanding of this phenomena are needed. Furthermore, the reliability of these transverse load distribution mechanisms, particularly those achieved through reinforced concrete bridge decks, in aging structures with various states of deterioration was unknown. For the results of these efforts to be most beneficial, they must be translated into a rating approach consistent with American Association of State Highway and Transportation Officials (AASHTO) Load and Resistance Factor Rating (LRFR) procedures for highway bridges. In addition, a means to incorporate the actual condition of the deck as quantified by the inspection report specific to each structure would further improve the applicability of the research.