United States Department of Transportation
i
Quantifying the Impact of Cover Deficiencies on Bridge Deck Service Life: Recommendations for Contracting
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2020-09-01
[PDF-14.74 MB]
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Edition:Final; August 2017 – September 2020
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Abstract:Construction of reinforced concrete bridge decks with shallower or deeper-than-specified concrete cover remains an ongoing challenge for the Georgia Department of Transportation (GDOT) because it has the potential to lead to reductions in service life. This reduction in service life can result in negative consequences on traffic (and create an associated economic impact), in addition to reducing ride quality and bridge safety. To mitigate these factors, the overarching goal of this research project was to explore the use of scientifically-based contracting mechanisms as a means to prolong bridge deck service life. Specifically, the research objectives were (1) to understand the extent of cover depth variability in Georgia through interviews with construction and maintenance engineers at GDOT, (2) to use that data to model service life for various cover depths, concrete mixtures, reinforcement types, extent of cracking, and environmental conditions, considering the range in materials and exposure conditions in the state, (3) to examine contracting arrangements used in other states, (4) to assess what portion of construction costs are reasonably associated with service life, making recommendations for an appropriate liquidated damage for time delays or other performance penalty structures for less-than-specification cover depths, including a lower bound where reconstruction or immediate amelioration should be undertaken; incentives for contractor performance were also to be considered, and (5) to draft recommended practices for GDOT for contracts for bridge deck construction based upon performance. Through interviews and an analysis of historical records, this project examined concrete cover practices and variability. The observed cover ranges were then related to the long-term durability of the bridge deck through corrosion-based service life modeling. The results of the modeling, in combination with current GDOT specifications, were then used to explore alternative contracting methods that could be adopted such as adjustable payment plans, for the purpose of incentivizing better cover control in new construction.
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