Bridges
Mn/DOT Research and Innovation Roadmap
Product 1 – Bridge Decks - Assessments
Implementation Plan
Overview
Bridge decks serve multiple functions. They are primary load carrying members for
bridges supported on longitudinal beams. They also are the structural element used to
anchor safety railings and other appurtenances. In addition to structural functions, decks
are the primary element used to convey roadway drainage to drainage features or off of
bridges. The service life of a reinforced concrete bridge deck is highly dependent on the
amount of cracking present, the presence of de-icing chemicals, and the durability of
embedded items.
Other states have had success constructing reinforced concrete bridge decks with very
little cracking. Mn/DOT has tried constructing a handful of such “Darwin” bridges with
poor results (E.g., Diamond Lake Road). To increase the service life of Minnesota bridge
decks it is desirable to minimize deck cracking. It is important to understand what caused
Mn/DOT’s “Darwin” decks to crack. Knowledge gained from such an investigation
could potentially be applied to all conventional bridge decks to reduce the cracking in
them as well.
There is anecdotal evidence that alternative de-icing chemicals such as potassium acetate
may significantly reduce the service life of galvanized components and other bridge
elements. It is believed that Michigan Tech has performed research on the impact of
alternative de-icing chemicals on bridge components.
Objectives
1.
Confirm and document that alternative de-icing chemicals are not
significantly reducing the service life of bridges or bridge components
2.
Identify the causes for less than ideal performance of Minnesota’s “Darwin”
deck bridges constructed thus far.
Anticipated Sequence of Tasks
1.
Identify appropriate Mn/DOT project champions for both research projects
(H08 – Impact of Alternative De-icing Chemicals, and H19 – Assessing
Mn/DOT Experience Constructing “Darwin” Decks
2.
Refine the work plans for both projects
a. Identify technical resources inside (and if necessary outside of) Mn/DOT
to lead the studies.
b. Search the literature to identify past research completed on either topic.
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c. Obtain detailed information on Mn/DOT’s use of alternative de-icing
chemicals (what chemicals have been used and when, where various
chemicals have been used). Obtain detailed construction records for the
“Darwin” deck bridges constructed by Mn/DOT.
d. Compare and contrast Mn/DOT’s practices related to these topics to the
practices of other states.
e. Locate or prepare anticipated deterioration curves for various de-icing
chemicals on various decks, railing components, and appurtenances.
Identify the variances in Mn/DOT’s “Darwin” deck construction
procedures most likely to be causing cracking.
f. Hypothesize the condition of bridge components subjected to alternative
de-icing chemicals. Hypothesize the primary reason for deck cracking.
g. Conduct fieldwork to assess the performance of Mn/DOT’s bridges related
to alternative de-icing chemicals and “Darwin” decks.
h. Prepare reports summarizing the findings of the assessment studies.
i. Propose future research to confirm the findings in the assessment studies.
3.
Execute the Research Projects
4.
Modify the Bridge Special Provisions and the Standard Specifications based
on the findings of the research projects
5.
Communicate the findings of the projects through multiple outlets. Update
content in the Bridge Design Manual related to concrete mixes. Highlight the
new material at LRFD Bridge Design Manual Workshops conducted by the
Bridge Office. Present the findings of the studies at the annual CTS Research
Conference and potentially at the annual Minnesota Concrete Conference.
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