United States Department of Transportation
i
Temperature Effects in Match-Cast Segmental Bridge Construction
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2023-02-01
[PDF-7.29 MB]
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Edition:Final Report May 2020-February 2023
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Abstract:Precast segmental bridge construction has provided a versatile, efficient, and cost-effective method for constructing bridges. Bowing distortion issues can however occur during segment fabrication, causing segments to have slightly different lengths in the center than outside edges. This occurs when the match-cast segment bows as a result of the heating of the face in contact with the hydrating concrete of the newly cast segment. A simulation matrix of 157 member geometry, materials, and construction factor combinations that explored the variables believed to be the most influential on bowing distortion was developed. The ability of the finite element software used for modeling, b4cast (ConTech Analysis ApS), the finite element software used for modeling in this project, to predict temperatures of hydrating concrete members was confirmed by comparison with a concrete physical model instrumented for temperature. The ability of an analytical expression to predict the bowing distortion of the concrete members studied from the thermal gradient developed in the match-cast segment was confirmed; however, the utility of this method is limited because it requires the temperature development to be known. A decision tree was developed to classify risk of bowing distortion in the construction process. A regression model was also developed that relates the member geometry, materials, and construction variables to the bowing distortion calculated. Analysis of the simulation results showed that segments with a width-to-length ratio lower than six had a low risk of excessive bowing distortion. They also showed that use of low heat of hydration mixes and low coefficient of thermal expansion aggregates can reduce the bowing distortion generated in the match-cast segments. Recommendations on methods to mitigate bowing distortion in match-cast segmental construction are given.
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