Bridge Engineering Handbook, Second Edition

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Transportation Research Board 94th Annual Meeting (TRB) Compendium of Papers

As of 2013, 14% of highway bridges were classified as functionally obsolete. This classification is given to bridges that have capacity and geometric conditions that do not satisfy modern requirements and thereby limit usage. The first part of this paper is a general discussion of obsolescence and sustainability of highway bridges, and describes the impact of obsolete bridges on economic, social, and environmental sustainability. The second part of the paper proposes a theoretical model for quantifying obsolescence due to load carrying capacity, a subcategory of functional obsolescence. The model includes features to account for increasing load demand and decreasing structural capacity over time. Historic trends for bridge design loads are discussed as they relate to the model, as are methods for calculating degradation of structural capacity. Limitations, applications, and possible extensions of the model are discussed. The third part of the paper applies the capacity obsolescence model to an example problem involving a simple span reinforced concrete bridge. The example demonstrates a methodology for simultaneously evaluating capacity obsolescence and environmental impact using multi-criteria decision analysis (MCDA). The paper concludes by suggesting future research to advance the proposed methodology. The overall objectives of the paper are to propose a model for quantifying obsolescence and to demonstrate how obsolescence can be jointly considered with other bridge design criteria.

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