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Ito Y.,Japan Testing Center for Construction Materials | Makitani E.,Kanto Gakuin University | Mogi J.,Maeda Technology
Journal of Structural and Construction Engineering

The structural characteristics of new seismic retrofitting methods for existing RC columns which were wrapped with the divided thin steel plates and continuous fiber sheets was discussed in the previous papers It was confirmed that the flexural resistance was significantly improved. Therefore the proposed methods in our previous paper is expected as an useful repairing and strengthening methods for the columns damaged by earthquakes. In this research to examine the ultimate flexural strength of RC columns wrapped by the same means repairing and re-retrofitting specimens were tested again. The test results indicated that the calculated value by current ultimate flexural capacity formula was underestimate these results because the lateral confinement caused by steel plates and fiber sheets effect on the design of a column was generally unconsidered. Then authors obtained a one solution of increasing effect of flexural strength based on the arch mechanism model by plane stress fields theory. Source

Ryuuda Y.,Japan Testing Center for Construction Materials | Ohkubo T.,Hiroshima University | Takase Y.,Hiroshima University | Yonei T.,Hiroshima University
Journal of Structural and Construction Engineering

This basic research is that focused on that not only repair effect immediately after the repair (initial performance) but also necessity of valuate its persistence in the environment of various weather in order to select a reasonable crack repair materials. In this report, we simulated the temperature of weather in japan at the laboratory level to perform bending tests, environment under -10°C, 5°C, 23°C, 40°C and 60C, for mortar specimens that were subjected to single repair material and repair cracks, so we extracted four types of materials, three types of epoxy resins repair materials and one type of acrylic resin repair material, that are widely used as a crack repair materials. The results shows importance that to clarify the effect that the decline of repair materials or change of a single repair materials are quite different for each repair materials and to evaluate the persistence of the effect repair. Source

Koshiishi N.,Waseda University | Shoji T.,Tajima Roofing Inc. | Shimizu I.,Japan Testing Center for Construction Materials | Tanaka K.,Tokyo Institute of Technology
Journal of Structural and Construction Engineering

The development of energy-efficient roofing systems has been of intense interest in numerous countries in recent years, as a measure for reducing the energy consumption of air conditioning during hot weather. In this study, fifteen kinds of membrane waterproofing materials with high solar reflectance were exposed respectively to varying atmospheric environments at six locations within Japan in order to investigate the range of reflectance reduction. In addition, the relationship between the retention rate of reflectance after exposure and the mass of the ingredients and their composition adhered to the surface of waterproofing materials exposed. Source

Kitsutaka Y.,Tokyo Metroplitan University | Uchida Y.,Japan Testing Center for Construction Materials | Matsuzawa K.,Tokyo Metroplitan University
Concrete Solutions - Proceedings of Concrete Solutions, 5th International Conference on Concrete Repair

In this paper, the mechanical properties of corroded rebars in deteriorated reinforced concrete structures were investigated. Since reinforcing bars in concrete members bear tensile forces, their corrosion greatly damages the load-bearing capacity of reinforced concrete members. This study aims to investigate changes in the mechanical properties of deformed reinforcing bars of different types and sizes when they were subjected to salt spray testing. As a reinforcing bar is corroded and the cross-sectional area is reduced, the yield point linearly decreases. The rate of such reduction is common to all types, being independent of the strength and diameter of the bar. The apparentYoung's modulus linearly decreases as corrosion proceeds. The rate of such reduction is common to all types, being independent of the strength and diameter of the bar. © 2014 Taylor & Francis Group. Source

Nakamura N.,Japan Testing Center for Construction Materials | Abe M.,Kogakuin University
AIJ Journal of Technology and Design

In this investigation the trend of research on accelerated carbonation of concrete and the changes in the conditions of experiment were followed in Japan. A survey on the history of the standards of test for concrete was conducted in time series, a flow of enactment and revision of the standards was followed. In addition the test condition of JIS was compared with those of European methods and on the application of the standard of accelerated carbonation test for concrete, a statistical survey of the requested tests was conducted. Source

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