The thesis started from the nostalgia for the historic district and the life within it. I don't agree with the radical method of reforming the historic district at the moment, which is rebuilding the whole district or demolishing it. I tried to find a new way to reform the historic district, so that the new project can blend into the habitats' lifestyle, in which way people can reconnect to their home land. During the design process, there is movie scenes, kungfu novels, and the living moment from my childhood came to my mind. And I translate those scenes into the spaces in the project through an architectural language. / Master of Architecture / I tried to find a new way to reform the historic district, so that the new project can blend into the habitats' lifestyle, in which way people can reconnect to their home land. During the design process, there is movie scenes, kungfu novels, and the living moment from my childhood came to my mind. And I translate those scenes into the spaces in the project through an architectural language.

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Weathering steel is a high-strength, low-alloy steel which has been proven to provide a significantly higher corrosion resistance than regular carbon steel. This corrosion resistance is a product of the small amounts of alloying elements added to the steel, which enable it to form a protective oxide layer when exposed to the environment. The main advantage of its use in bridges is that, under normal conditions, it may be left unpainted, leading to significantly reduced maintenance and environmental costs. Weathering steel has been a material of choice for highway structures for almost half a century, and a very large number of structures have been constructed with it. Although its use has for the most part been successful, it has also become evident that, in circumstances where there is the presence of salt and sulphur oxides, its performance is deficient. In these situations the corrosion penetration rate is much higher than expected, and the oxide layer forms in thick layers. This presents an added risk, since these layers flake off and fall onto the roadway. The degree of corrosion on structures can be very different, even if the structural type, location, and climate are similar. Therefore the focus of the thesis is on the lifespan of weathering steel highway structures. Primarily this research is concerned with the effect of corrosion on the integrity of these structures, as well as ways of quantifying corrosion loss and protecting the structure from further corrosion. In order to determine the lifespan of weathering steel highway structures subject to different rates of corrosion, a probabilistic structural analysis program has been developed to assess the time-dependent reliability of the structure. This program used iterative Monte Carlo simulation and a series of statistical variables relating to the material, loading, and corrosion properties of the structure. A corrosion penetration equation is used to estimate thickness loss at a selected interval, and the structural properties of the bridge are modified accordingly. The ultimate limit states of shear, moment, and bearing, and the fatigue limit state of web breathing, are taken into account. Three types of structures are examined: simply-supported box and I-girder composite bridges, and a two-span box girder bridge. Based on the structural analysis of the corroding bridge structures presented herein, it can be seen that corrosion to the weathering steel girders can cause reduced service lives of the structures. I-girder bridges are shown to be more susceptible to corrosion than box girder bridges, with continuous box girder bridges showing the best performance. The amount of truck traffic does not affect the reliability of the bridge. The short-span and high strength steel bridges are more susceptible to corrosion loss, primarily because their girders have thinner sections. A two-lane bridge also has better performance than the wider bridges because the weight of the barriers and sidewalks is carried by fewer girders, so these girders are stockier. The web breathing limit state is less significant than the combined ultimate limit states. Lastly, and most importantly, inspection data from a highway bridge is used to demonstrate the benefit that can be derived from using field data to update the time-dependent reliability. The ultrasonic thickness gauge (UTG) is a common tool for thickness measurement of steel sections. When used to measure weathering steel, this instrument provides accurate data about the depth of corrosion pits, but not their lateral dimensions. The measurement does not include the corrosion layer on the opposite side of the plate from the one being measured; however, if the corrosion layer is on the measured face, a disproportionate increase in the measured thickness can be seen. In order to prevent or minimize corrosion loss, the steel is currently painted, a process with several environmental and financial disadvantages. Therefore, three novel protection methods have been assessed in a cyclic corrosion test: a zinc metallizing, an aluminum-zinc-indium alloy metallizing, and a zinc tape with a PVC topcoat. All these coatings are designed to act not just as barriers, but also as sacrificial anodes. The test was run for 212 24-hr cycles, over the course of which the all the coatings were proven effective at protecting the steel substrate, regardless of steel type and surface roughness and pretreatment. In conclusion, the threat to all types of weathering steel highway structures by contaminant-induced corrosion is significant, but inspection data permits a more accurate prediction of time-dependent reliability for a structure, and protective coatings are a promising method of slowing the advance of corrosion.

Weathering steel is a high-strength, low-alloy steel which has been proven to provide a significantly higher corrosion resistance than regular carbon steel. This corrosion resistance is a product of the small amounts of alloying elements added to the steel, which enable it to form a protective oxide layer when exposed to the environment. The main advantage of its use in bridges is that, under normal conditions, it may be left unpainted, leading to significantly reduced maintenance and environmental costs. Weathering steel has been a material of choice for highway structures for almost half a century, and a very large number of structures have been constructed with it. Although its use has for the most part been successful, it has also become evident that, in circumstances where there is the presence of salt and sulphur oxides, its performance is deficient. In these situations the corrosion penetration rate is much higher than expected, and the oxide layer forms in thick layers. This presents an added risk, since these layers flake off and fall onto the roadway. The degree of corrosion on structures can be very different, even if the structural type, location, and climate are similar. Therefore the focus of the thesis is on the lifespan of weathering steel highway structures. Primarily this research is concerned with the effect of corrosion on the integrity of these structures, as well as ways of quantifying corrosion loss and protecting the structure from further corrosion. In order to determine the lifespan of weathering steel highway structures subject to different rates of corrosion, a probabilistic structural analysis program has been developed to assess the time-dependent reliability of the structure. This program used iterative Monte Carlo simulation and a series of statistical variables relating to the material, loading, and corrosion properties of the structure. A corrosion penetration equation is used to estimate thickness loss at a selected interval, and the structural properties of the bridge are modified accordingly. The ultimate limit states of shear, moment, and bearing, and the fatigue limit state of web breathing, are taken into account. Three types of structures are examined: simply-supported box and I-girder composite bridges, and a two-span box girder bridge. Based on the structural analysis of the corroding bridge structures presented herein, it can be seen that corrosion to the weathering steel girders can cause reduced service lives of the structures. I-girder bridges are shown to be more susceptible to corrosion than box girder bridges, with continuous box girder bridges showing the best performance. The amount of truck traffic does not affect the reliability of the bridge. The short-span and high strength steel bridges are more susceptible to corrosion loss, primarily because their girders have thinner sections. A two-lane bridge also has better performance than the wider bridges because the weight of the barriers and sidewalks is carried by fewer girders, so these girders are stockier. The web breathing limit state is less significant than the combined ultimate limit states. Lastly, and most importantly, inspection data from a highway bridge is used to demonstrate the benefit that can be derived from using field data to update the time-dependent reliability. The ultrasonic thickness gauge (UTG) is a common tool for thickness measurement of steel sections. When used to measure weathering steel, this instrument provides accurate data about the depth of corrosion pits, but not their lateral dimensions. The measurement does not include the corrosion layer on the opposite side of the plate from the one being measured; however, if the corrosion layer is on the measured face, a disproportionate increase in the measured thickness can be seen. In order to prevent or minimize corrosion loss, the steel is currently painted, a process with several environmental and financial disadvantages. Therefore, three novel protection methods have been assessed in a cyclic corrosion test: a zinc metallizing, an aluminum-zinc-indium alloy metallizing, and a zinc tape with a PVC topcoat. All these coatings are designed to act not just as barriers, but also as sacrificial anodes. The test was run for 212 24-hr cycles, over the course of which the all the coatings were proven effective at protecting the steel substrate, regardless of steel type and surface roughness and pretreatment. In conclusion, the threat to all types of weathering steel highway structures by contaminant-induced corrosion is significant, but inspection data permits a more accurate prediction of time-dependent reliability for a structure, and protective coatings are a promising method of slowing the advance of corrosion.

Content of Doctoral thesis is a methodology for juridical experts on the assessment of structures manufactured of weathering steel, with special attention to evaluation of the protective corrosion layer.

京都大学 / 新制・課程博士 / 博士(工学) / 甲第23483号 / 工博第4895号 / 新制||工||1765(附属図書館) / 京都大学大学院工学研究科社会基盤工学専攻 / (主査)教授 杉浦 邦征, 教授 清野 純史, 教授 八木 知己 / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DFAM

This work deals with the influence of atmospheric corrosion on high-cycle fatigue properties of a weathering steel ATMOFIX B. New experimental data on fatigue strength of a steel exposed for 20 years to an atmospheric corrosion were compared to those characterizing the base material. Reduction of the fatigue lifetime of the exposed material compared with the base material was predicted on the basic of fractographic examination of fracture surfaces and the influence of surface notches on fatigue strength. The predicted results agree well with the experimental results.

This work deals with the influence of atmospheric corrosion on high-cycle fatigue properties of a weathering steel ATMOFIX B. New experimental data on fatigue strength of a steel exposed for 20 years to an atmospheric corrosion were compared to those characterizing the base material. Reduction of the fatigue lifetime of the exposed material compared with the base material was predicted on the basic of fractographic examination of fracture surfaces and the influence of surface notches on fatigue strength. The predicted results agree well with the experimental results.