As one of strengthening methods for damaged reinforced concrete bridge slabs, this study has been carried out to develop an alternative method by using methyl meta acrilate (MMA) resin concrete with carbon fiber sheets (CFS), in which strengthening and waterproof properties are expected. The test results both in static and fatigue loadings using the full-scale beam specimen that have been carried out under the loading of negative moment are reported and discussed. Main results from this study are as follows: 1) The MMA resin concrete has an excellent bonding property up to the failure like as the epoxy resin one. 2) the bonding length for CFS is required at least the length between the bent-up bars. 3) for the fatigue design of the strengthened slab, the S-N relationship was obtained.

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The tensile strength tests using reinforcing bars with buried straingages have been carried out, and effects of the parameters, which influence ultimate strength and crack width of the loop splice joint, were discussed. Through the investigations, the relationship between bearing force and crack width at the loop splice joint has been revealed. Moreover, the new design method of the loop splice joint considering bearing force has been proposed.

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In order to study the application of a new type of aggregates made from fly ash for prestressed concrete structures, the authors prepared prestressed concrete beam specimens and carried out 1) bending tests, 2) shear tests and 3) stress measurement of prestressing strands. The results show that prestressed concrete beams used the aggregates have few structural problems and the aggregates can be applied to prestressed concrete structures. Moreover, the material properties of concrete used the aggregates made from fly ash were also investigated.

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This study attempted to enhance conventional lattice model that can express the shear resisting mechanism of RC members to the 3D analytical method. Analytical studies of the biaxial and torsional response of RC members based on the 3D lattice model are presented. Results obtained by using the 3D lattice model are compared with several sets of experimental results for RC columns subjected to pure torsion or combined loads of torsion and bending. Based on these comparisons, the applicability of 3D lattice model to the prediction of the behavior of RC columns is demonstrated. In addition, the influence of characteristics of the earthquake ground motion on the seismic performance of RC columns is estimated from the simulation using several kinds of 3D ground motions.

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In UBRC piers, the additional high strength bars are installed to add and control the post-yield stiffness of the skeleton curve. The original concept is to use perfectly unbonded bars, but in terms of the construction works and cost, it is desirable to use the round conventional bars without unbonding treatment. In this study, in order to clarify the influence of bond characteristics of bars, cyclic loading is carried out. Also, by analysis for experimental specimen, the behavior of splitting the bonding between the bars and the concrete is analyzed. As the results, it is found that it is possible to realize the UBRC structure with the conventional round bars, if the bond splitting can be controlled.

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The deterioration of concrete structures due to acid rain is regarded as a long termed phenomenon. Therefore, it is considered that there are many unclear points still on phenomenon and mechanism of it. In this study, it was tried to clarify that the deterioration mechanism on concrete structure due to acid rain. The results are shown as follows; 1) Discoloration of the concrete surface is caused by the formation of ferric sulfate. 2) Elution of alkali metal ions and alkali earth metal ions from the inside of concrete accelerates under the acid rain condition. 3) The neutralization area would extend further depth in concrete due to the diffusion of H₂CO₃, that is formed by the reaction between the acid rain and CaCO₃ existing in the neutralization area in concrete. 4) The corrosion of steel in concrete would be accelerated by not only extension of neutralization area but also the concentration of SO₄^2- and Cl^- from the acid rain at the interface between the neutralization area and the high alkali area of concrete.

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It is known that the tensile strength of FRP rod is influenced by the loading direction and diagonal tensile strength is less than uniaxial tensile strength. Therefore the FRP rod would fracture under a tensile stress which is less than the uniaxial tensile strength due to the secondary stress at a crack intersection in concrete. This paper shows that finite element analysis with consideration of the geometrical nonlinearity is applicable to predict the relationship between the deformation and applied force of FRP rod under the combined tensile and shear stress at the crack intersection of concrete. Furthermore, the fracturing stresses of FRP rod are predicted by using the experimental and analytical results.

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Investigations of comprehensive maintenance targeting 100-year-design life about a RC hollow slab bridge, which was damaged by salt contamination with use of initial chloride from sea sand and deicing salt, were conducted. The bridge was deteriorated seriously by reinforcement bars corrosion, cracks on concrete surface and exfoliations, and needed immediate repairing. It was clarified that removing of concrete 30mm deeper than rebar position and repair of cross section 55mm over thickness were necessary to the bridge by present conditions and prediction using neural network method.

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Although drainage pavement is highly evaluated for high driving safety and low traffic noise, air voids in its porous structure are easily clogged with dust generated during normal service, preventing the pavement from functioning as expected. The authors have been studying drainage pavement of a dual structure consisting of a top layer of conventional porous asphalt concrete and a bottom bed equipped with rail-shaped bars, so that the performance is improved and maintained over time. The study results revealed that the dual drainage pavement is applicable to existing roads.

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This paper describes experimental results of shear capacity of concrete beams reinforced by PVA short fiber. Loading test was carried out on reinforced concrete beams with PVA short fiber by changing fiber type, fiber content, shear reinforcement ratio, effective depth, and shear span-to-effective depth ratio. As a result, it was confirmed that shear capacity is improved by mixing PVA short fiber and that the increase in shear capacity is influenced by fiber content and specimen size.
The fiber was confirmed to effectively act in tied-arch beams. Therefore, an equation to estimate shear capacity for reinforced concrete beams with small shear span-to-effective depth ratio was modified by using the breaking point stress of tension softening curve and the effective depth of beam to express the capacity of the beams reinforced by PVA short fiber.

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An equation was formulated for estimating the plastic viscosity of cement paste containing an air-entraining admixture, which is a commonly used chemical admixture for concrete. Air entraining admixtures slightly increase the plastic viscosity of neat cement paste. The viscosity equation was derived by incorporating this effect to minimize the difference between the estimation and measurement. The sample temperature and time-related changes were also considered. The ratio of the plastic viscosity estimated from the proposed viscosity equation to the measured plastic viscosity was found to be approximately 1, the anticipated value. Viscosity equations for mortar and concrete were also formulated based on an existing viscosity equation and found to be valid even when the plastic viscosity of the matrix changed.

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In order to clarify the deterioration mechanisms of concrete caused by alkali-silica reaction (ASR) and sea water attack in marine environment, both the in-situ survey and the laboratory test using cores were carried out. As a experimental result, the influence of the petrographic feature of reactive andesite aggregates used, the mix proportion of concrete and the structural type, and the environmental condition around the structure on the degree of damages in ASR affected structures was investigated especially in relation to the amount of ASR gel and other reaction products. Furthermore, a new test method to evaluate the residual expansion capacity of cores in marine environment was proposed.

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