| Summary: | 碩士 === 國立海洋大學 === 河海工程學系 === 88 === At present, many infrastructure constructions in Taiwan are approaching the middle or the end of the service life. There is an urgent need to establish a method for predicting the useful life and durability for these structures. This study concentrated on evaluating the carbonation damage and service life of concrete bridges using a grey-forecasting model. In order to provide a basis for structural repair, reinforcement or demolition. Some conclusions of this study are given below:
1. GM (1, 1) is a method of evaluating the regularity with exponential variation of original data sequence. Using the improved GM (1, 1) model we evaluated the carbonation depth of some concrete bridges in Taipei. These results are compared with those obtained from empirical formulas of natural and accelerated carbonation tests. It is found that the improved model arises the predicted accuracy at a certain degree.
2. Based on grey theory, the carbonation law of concrete can be expressed as a bounded region. Every point in the bounded region is all of corresponding of weight. This implies that the durable life of concrete structures with carbonation has a large range and means that the service life of concrete structures due to carbonation damage is of larger scattering.
3. Both the Huey-tong and Jzyh-chyang bridges in Taipei were used to illustrate the prediction or remaining service life. The results of this investigation indicate that the grey model predicted the remaining service life 8 years and 18 years of the Huey-tong and Jzyh-chyang bridges, respectively. The improved grey model predicted the remaining service life 6 years and 16 years of the Huey-tone and Jzyh-chyang bridges, respectively. The regression analysis model predicted the remaining service life 12 years and 22 years of the Huey-tong and Jzyh-chyang bridges, respectively.
4. The probabilistic or statistical method adopted to analyze the law of carbonation damage of concrete with less observed data seems unsuitable. Use the grey method can remedy statistical method’s blemish.
This investigation proved that use grey analysis is not only serviceable but also reliable. The order of reliability of these models is the improved grey model, grey model and regression model.
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