RC columns made of concrete and steel from normal-strength up to high-strength were tested under concentric loading. The following variables were evaluated for their effects on the compressive fracture zone length and load-displacement relationship: tie arrangements, column length, concrete compressive strength, tie yield strength, and tie volumetric ratio. A formalized stress-strain model for confined concrete was developed, based on the test results in this study and our previous studies. Regardless of the gage length, tie arrangement and material strengths, it can be used more extensively than the previous models. The RC columns with high-strength materials subjected to cyclic loading were evaluated based on fiber analysis using the confinement model. The analytical results were in good agreement to the experimental results.

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Properties of bound chloride ion in concrete are examined for the exsistent structure constructed under a marine environment. The adsorption equilibrium relation varies with higher or lower than the threshold concentration to assume a certain concentration of free chloride ion as a threshold concentration. Moreover, since the chloride adsorption isotherm is changed by carbonation of concrete, the amount of the fixed chloride ion in carbonated concrete decreases and also the amount of the free chloride ion in carbonated concrete increases.

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Present paper shows effects that bar arrangement in concrete have on gas permeability through crack. Experimental set-up enables simultaneous gas flow through crack during which concrete cylinder with bar arrangement is loaded by the split tensile strength test configuration. Crack openings were measured at both ends of the concrete cylinder and gas pressure difference and volumetric gas flow rate were monitored. It was found that gas permeability was different despite an equal crack opening and was depended on the bar arrangement. Steel ratio and the projected surface area of steel that was in the way for the flow of gas in the crack were used to explain the effect of the bar arrangement

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This paper studied about the influence of corrosion of reinforcing bars on bending performance of reinforced concrete (RC) members in order to serve for maintenance of RC strucutures. Bending tests on corroded RC members and 3 dimensional shape scanning of the corroded reinforcing bars were carried out. It was proved that tensile strength of reinforcing bars and ultimate strength of RC members were decreased by not only the weight loss (which means the averaged reduction of cross section) of the reinforcing bar but also the localized corrosion. It was also clarified that the localized corrosion of reinforcing bars had effect on the stress-strain relationships of reinforcing bars around the yield point.

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The detailed modeling dependent on alkali ion density of pH transition in pore solution, carbonation mechanism and changing of pore volume due to carbonation reaction in concrete are developed based on a law of electric charge balance in analytical chemistry. While calcium hydroxide on solid phase, it is noted that pore solution pH will be constant value. On the other hand, after disappearance of calcium hydroxide existing on solid phase, it is noted that the gradual drop of pore solution pH will be occur and the drop rate becomes higher according to high alkali ion density in concrete. Moreover, it seems that the changing of pore volume due to carbonation will be determined by CaO/SiO₂ ratio mainly and in the region of high CaO/SiO₂ ratio the pore volume increases, on the other hand in the low CaO/SiO₂ ratio the pore decreases.

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In this paper, the applicability of Impact Elastic Wave Method for evaluation of grouted condition in tendon ducts was investigated thorough two methods for each objective structure. One is applied to lateral prestressing steel bars to connect Prestressed Concrete beams, where wave velocity was measured for the evaluation of grouted conditions in tendon ducts. The other is the measurement at cross-section of steel strands in PC beams, where frequency spectrum was applied for the evaluation. In both cases, actual conditions in tendon ducts were confirmed by visual observation after drilling. Results show the applicability of the both methods to evaluate grouted conditions in existing PC structures.

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In conventional accelerated tests all sides of specimen are exposed to Freeze and Thaw, whereas in actual concrete structures only one side would be exposed. This paper reports the experimental results by limiting the exposure to one side only, which is more similar to the actual condition. We took plain concrete without AE agent as an object of this study. In this paper, we reveal that 1) there is some discrepancy between the measured deterioration depth of one side test and the prediction results by conventional tests at the same lowest temperature; and 2) whereas the result of the conventional tests overestimates Freeze and Thaw durability in the inside, underestimates the durability of the surface on the tested side. This discrepancy is almost likely caused by the strain gradient along the specimen which induces a self-equilibrating set of forces.

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The structural fire behavior of shield segment and tunnel under RABT fire is analytically investigated. The applicability of numerical simulation methods for segment temperatures and structural behavior are confirmed by the comparison with fire test results. As the result of numerical analyses on structural fire behavior of tunnel lining, the tunnel structure does not collapse even if the section of reinforced concrete segments at spring line are reduced by spalling of concrete. Fire damages to the tunnel structure can be mitigated not only by covering the inner surface with fire proofing material, but also by the application of concrete mixed with synthetic fibers to the tunnel structure.

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This paper reports on the effects of differences in asphalt mixtures and asphalt layer thickness on the long-term performance and durability of pavements, based on long-term observation at a road in service.
The observation was performed at Bibi New Test Road, which consists of eight sections of differing pavement structure design. Traffic conditions, cracking, rutting, and surface smoothness have been measured each year for the 14 years.
The long-term road surface characteristics was found to differ by the type of asphalt materials and its thickness. The layers in which rutting deformation occurs (e.g., asphalt mixture layer, base course, subgrade) was found to differ according to the pavement configuration. Fatigue cracking, which is caused by vehicle loading, was also found to have occurred in the asphalt layers, and the time of occurrence was shown to differ according to asphalt type and thickness.

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This paper reveals that the length dependent friction coefficient λ is practically negligible and presents the actual values of angle dependent friction coefficient μ through a statistical analysis that is different from commonly employed methods.

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