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Abstract

The main purpose of this investigation was to study the durability evaluations of existing concrete bridges due to carbonation contamination. The linearly unbiased estimation method associated with the JC method developed by the Joint Committee on Structural Safety was adopted to predict the mean value and standard deviation of the normal distribution for the carbonation depths and cover thickness of concrete bridges. The reliability index (β) and failure probability (Pf) of concrete bridges were also evaluated. Since the linearly unbiased estimation method is very suitable for analyzing a small number of specimens obtained from practical engineering problems, the unknown parameters can be conveniently and actually determined. In order to verify this proposed method, ten concrete bridges in Taipei were used to predict the mean value, standard deviation, reliability index and failure probability. In this paper, the results of this investigation indicate that both the Beei-men viaduct (β = 0.23) and the Jzyh-chyang bridge (β = 0.39) require extensive repair. Both the Ay-gwo west road viaduct (β = 0.92) and the Shiyuan bridge (β = 0.88) require relatively light repairs. The other bridges (β = 1~2.0) are safe and serviceable. The linearly unbiased estimation combined with JC method is useful to evaluate the durability of existing concrete bridges with carbonation contamination.

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