United States Department of Transportation
i
Increasing bridge deck service life, volume II -- economic evaluation.
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2014-12-01
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[PDF-5.53 MB]
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Abstract:Deterioration of bridge decks is a primary factor limiting the lifespan of bridges especially in cold climates where deicing salts are commonly used.
While controlling deck cracking or decreasing the permeability and porosity of concrete can improve performance and service life, chloride and
moisture ingress as well as cracking cannot be eliminated. Full‐depth cracks which are caused by restrained shrinkage allow for corrosive
conditions at early ages for both the top and bottom reinforcement mats. Therefore, the use of corrosion‐resistant reinforcement is essential to
mitigate deterioration of bridge decks. The objective of this research program to examine the efficacy of using alternative materials in a bridge
deck from both technical and economic perspectives. For the technical evaluation (Volume 1), a three phase experimental investigation was
conducted considering a wide range of corrosion‐resistant reinforcing materials. These materials included stainless steels, microcomposite steel,
and coated steels considering a variety of metallic and nonmetallic coatings. The first phase evaluated the bond between corrosion‐resistant
reinforcement and concrete using lap splice tests. The second phase evaluated the cracking behavior of slabs reinforced with corrosion‐resistant
reinforcement. Finally, the third phase evaluated corrosion resistance under uncracked and cracked conditions using macrocell test specimens.
Transverse steel was also tied to the longitudinal steel to simulate actual bridge deck conditions. Recommendations are provided on
development and splice lengths for both conventional black and corrosion‐resistant reinforcing steel, control of cracks widths, as well as the
selection, design, and construction of corrosion‐resistant reinforcement. For the economic evaluation (Volume 2), a decision support
methodology and associated spreadsheet tool for robust analysis of the cost‐effectiveness of alternative material types for bridge deck
reinforcement was developed. The two evaluation criteria are agency and user costs, and the input data that influence this criteria include the
deck service life, material process, discount rate, detour length, and bridge size. The methodology incorporates analytical techniques that include
life cycle analyses to evaluate the long‐term cost and benefits of each material over the bridge life; Monte Carlo simulation to account for the
probabilistic nature of the input variables; stochastic dominance to ascertain the probability distribution of the outcome that a specific
reinforcement material is superior to others; and analytical hierarchical process to establish appropriate weights for the agency and user costs.
The study methodology is demonstrated using a case study involving three reinforcement material alternatives: traditional (epoxy‐coated) steel,
zinc‐clad steel, and stainless steel. Through this study, it is demonstrated that the use of corrosion‐resistant reinforcing materials can significantly
increase bridge deck life, reduce agency and user costs associated with bridge deck rehabilitation and maintenance, and thus lower the financial
needs for long‐term preservation of bridges
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