In this paper, a stress-strain relationship of concrete which takes account of confinement effectiveness is proposed based on a series of loading tests for reinforced concrete column specimens. Reinforced concrete column specimens, with circular and square cross section, including various hoop reinforcement, were loaded. Predominant factors for controlling the stress-strain relation of the concrete columns were examined, and stress-strain model consisiting of exponential function and straight line is proposed. The predicted relation agreed quite well with the test results.

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An application of acoustic emission (AE) to the evaluation of deterioration in concrete is studied. AE activity of concrete samples under uniaxial compression is analyzed to estimate the deterioration degree quantitatively. For this purpose, a stochastic analysis of AE activity is introduced. The analysis is performed on concrete newly cast, concrete expanded due to alkali-aggregate reaction, and concrete subjected to freezing-thawing process.
A probability function of AE generating behavior at stress level, V, between 0% and 50% to the compressive strength is represented by an exponential function bV^a. It is found that the values a and b distribute in the characteristic zones depending on the deterioration. The variation from the sound concrete is denoted by the deterioration coefficient and the classification of concrete based on the coefficient is proposed.

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An one dimentional nonlinear constitutive equation for describing both long period viscuos effect and short period elastic effect is presented in this paper. The parameters of the constitutive equation are determined by means of curvilinear regression of experimental data in the flexural creep tests for a sort of asphalt concrete.
The results indicate that the constitutive equation is valid for the strain response with different histories of stresses.

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A mathematical model for drying shrinkage of concrete is presented in this paper. The proposed model originates from some simple hypotheses which are concerned to the configuration of the pore structure of concrete and micromechanical behavior of water in pore. The characteristic of pore structure of hardened cement paste in concrete is expressed by the distribution function of pore size. Micromechanical phenomena in concrete, which are thermodynamic equilibrium and transport process of vapor and liquid water and associated volumetric change of concrete, are incorporated based on the unified concept of micro pore. Drying shrinkage behavior of concrete specimen, which are both weight loss and volumetric change, can be numerically simulated taking their pore structure into consideration.

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This paper concerns the development of the pavement structural design in the railway container yards where the heavy weight machines for loading works (forklift, reach stacker and so on). The wheel load of the loading machine is far much more heavier than that of the commonn car or truck. It is difficult to design the asplalt pavement thickness for such the heavy weight machine by using the common standards.
In this study the multi-elastic layer theory and the design criteria developed by Asphalt Institute in USA were introduced to develope the thickness design for such heavy weight machines. Then it has been able to design the thickness for the machines having from the common weight wheel load to the heavy one as much as about 40 tonne.
The good result has been got in the application of this study on some yard pavements by using opengraded large stone and asphalt emulsoin stabilized base.

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An accurate assessment of the decreasing ultimate strength of degrading structures is one of the important techniques to maintain the present infrastructures.
This paper deals with the residual strength of reinforced concrete members subjected to constant fatigue loads.
We first make an attempt to model the accumulated strain of fatigue damage and the residual compressive strength of concrete under constant cyclic loads, in comparison of experimental observation. The proporsed model is applied to reinforced concrete columns subject to cyclic axial force and bending moment. The probabilistic prediction for compressive failure of the columns is then presented as a function of number of cyclic load based on the first-order and second-moments method.

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For the purposes of desalination and re-alkalization, electoric controlling of migration of ions in concrete is considered. However, the mechanisms of migration of ions and the effects of this method are still unclear. So, in this paper, effects and serviceability of electric controlling method were experimentally investigated. Two controlling systems, inter-electrode system (reinforcement was used as cathode) and outer-electrode system (both electorodes were placed out of specimen), were prepared in this test. To evaluated these systems, contents of chloride ion and alkali ion were measured. Through these investigations, some useful information of the effects of these two systems were found out.

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Recently, electric controlling of ions' migration is expected to repair of concrete structures, or to evaluate the migration resistance of concrete. However, the mechanisms of electric migration is still unclear. So, in this paper, the authors experimented to find out the mechanisms of electric migration of ions, such as Na⁺, K⁺, Cl^-, and OH^- through hardened mortar and concrete by using original diffusion cells. In this study, (1) current density, (2) kind of solution in cells, and (3) mix proportion of mortar and concrete were mainly selected as influencing factors for migration of ions. Moreover, the differences between electric migration and natural diffusion were experimentally investigated.

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Most of silica fume used in Japan are imported silica fume. As very small amount of silica fume is produced in Japan, it is expected silica fume concrete to be high (or very high) performance concrete in Japan. It means that slica fume concrete should have many good properties such as high strength, high durability and high workability. So, it is necessary to know which characteristics of silica fume relates to the properties of concrete. The purpose of this paper is to find out the influence of the characteristics of 13 kinds of silica fumes, which are now on the market in Japan, as concrete admixtures considering.

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The durability of surface coatings is evaluated through the accelerated tests and the examination of a existing concrete structure. In the accelerated tests, weatherability, elasticity, and permeability of chloride, oxygen and vapor were tested.
The selected surface coatings through the accelerated test are painted on the existing concrete structure and have been exposed to the marine environment for 8 years. The surface coatings were sampled from the structure and external appearance, crack-bridging ability and bond strength of coatings were examined.

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In this study the effects of surface coatings of concrete for protection of chloride attack is studied through the chloride diffusion process in concrete.
The diffusion process of chloride is evaluated by the changes of chloride distributions in existing concrete structure which has been repaired with surface coatings 8 years before the examination.
The effects of surface coatings is examined through the simulated chloride concentration at the position of rebras in concrete and the corrosion rate of rebars.
As the results, the effects of surface coatings are estimated only when the chloride concentration at rebars is smaller than the critical value.

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A mathematical model of early age concrete is presented to investigate the time dependent behaviour taking into account the rapid change of the properties. The study concentrates on the role of pore water in creep and relaxation of early age concrete. Several experimental results are analyzed with the model and pore water effect on early age concrete is discussed.

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The townscapes of colored pavement can be evaluated for the qualities of their colors and shapes by fractal. While the fractal dimensions for shapes are calculated with box-counting method, the fractal dimensions for colors are computed with the semivariograms constructed by color vectors in CIE chromatograph and space vectors. Both the fractal dimensions of townscapes are greater than ones of natural landscapes. However, the fractality of colors for the former is less than for the latter. In landscape design, fractal dimensions and fractality can be the indicators for evaluating comformity of landscapes and urban construction.

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The purpose of this investigation was to study the condition and mechanism of microcrack formation on the surface of concrete at steam curing period. A new X-ray technique using a cntrast medium was development for this study. Influences of steam curing conditions on the formation of microcracks were studied through experiments with reinforced concrete specimens. As a result, successful detection of three different types of microcracks was possible. Influences of various factors on the formation of microcracks were also studied and the results were compared with the specification regulations of JSCF, JASS, ACI from the viewpoint of cracks prevention.

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In this study a shear resisting model for concrete beams reinforced with non-yielding reinforcement, such as FRP rods was developed based on a non-linear finite element analysis. In the model a shear resisting force of a beam is defined as a summation of shear resisting forces by concrete in a compression zone, by shear reinforcement and other than shear reinforcement, such as aggregate interlocking, in a shear cracking zone and by concrete in a horizontal zone which links the compression zone with the shear cracking zone. It was confirmed that the shear resisting model can predict strengths for shear compression failure with reasonable accuracy.

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Recently, fiber reinforced plastic is applied as reinforcement for concrete. However, few reports have been published concerning its durability. This paper describes the alkali resistance of some kinds of fiber reinforced plastics. The influences of type of fiber, alkali solution, prestressing level and ambient temperature on mechanical behavior are discussed.

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A composite bridge column with steel tubes combined with reinforced concrete, has been developed aiming at not only high speed construction but also skilled labor savings especially for high colums with 40 to 100m height. This bridge column has some significant structural features, i. e. 1) several steel tubes are placed in the reinforced concrete section, 2) steel tubes with external spiral ribs are utilized for anchorage and 3) PC strands are wound instead of lateral rebar. The present study has indicated effectiveness of the new type bridge colum by conducting a bond test of steel tubes with external spiral ribs and a cyclic horizontal loading test with a colum model designed on the basis of an actual bridge colum to be constructed. Followings are concluded: 1) bond strength of 68kgf/cm² which is around three times the allowable stress was obtained in the bond test, 2) flexural loading capacity of 84tf which is further larger than 64tf, calcurated value by the superposed equation, was provided in good agreement with a predicted value based on the beam theory in assumption of perfect bond action between concrete and steel tubes, 3) superior displacement ductility and absorbed energy characteristic were obtained in comparison with the RC specimen.

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A neuro-computing pavement performance model equiped with 4 input units of MCI, T_A, volume of large vehicles, design CBR and surface course material and an output unit of MCI was developed. The model was applied to a project level pavement management system. Since the neuro computing performance model can be reformed easily by measured data, it is suitable for pavement management system.

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The model proposed in this study deals with the change of pore structure of hardened Portland cement during hydration. This model combines the aggregation model considering quantitatively the effect of water cement ratio and the pore structure model considering the position where hydrate precipitate during hydration, and it can estimate the development of the pore structure as a function of curing time. It is found that a pore size distribution measured by mercury porosimeter is similar to that obtained from this model. As the results obtained confirms the validity the proposed model, the assumptions made on aggregation of cement particles and hydrate precipitating position can be considered as valid.

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The shear resisting model for concrete beams reinforced with FRP rod which was proposed by the authors is expanded to predict the shear strength of prestressed concrete beams with FRP tendon. The shear resisting model consists of four shear resisting forces which are defined as functions of prestressing force, concrete strength, shear span to effective depth ratio, stiffness of tendon and shear reinforcement. The applicability of the model is confirmed by comparing with experimental results.

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In this paper the influence of the reinforcing ratio on the shear strength of the reinforced concrete beams subjected axial tension and bending is studied. From experimental results and numerical analyses, it is observed clearly that the reinforcing ratio influences the shear capacity of the beam. Considering the influence of reinforcing ratio the adequate regressive equations are defined based on the experimental and numerical results. Our previous experimental results of rectangular beams and T-shaped beams as well as the results by Mattock et al. verify the accuracy of the equations proposed herein.

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The hydration of cement and strength development of concrete are dependent on the temperature. The present study proposes the analytical procedure for the thermal stresses induced in the mass concrete structures in order to obtain more accurate estimation of cracking, when the properties dependent on the temperature are included. The present analytical results are compared with the conventional analytical results for the wall structures and slabs having a water cooling system.

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In this paper, comparing with the results of numerical step-by-step method, we examined whether the formula shown in “Specification for Highway Bridges” could evaluate exactly the influence of internal restraints by steel and delayed elasticity factor of concrete in the calculation of prestress decrement and indeterminate force due to creep and shrinkage of concrete. We discussed a formula to evaluate collectively those influence on the prestressed concrete structure which is subjected to the change of restraint conditions. And we illustrated the validity of the formula by some numerical results on the prestressed concrete continuous beams.

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It has been acknowledged that fatigue lives of concrete exhibit wide scattering, which should be properly taken into consideration in the limit state design. This paper proposes a generalized Miner's number for concrete under varaible cyclic loads, assuming the total number of repeated loads and fatigue strength of concrete are random variables. The Monte Calro simulation is carried out to obtain the probability of fatigue failure in relation of the generalized Miner's number. Median, expectation and standard variation of generalized Miner's number at failure are examined through numerical simulation and analytical formulation with experimental results.

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Deterioration of reinforced concrete under chloride ion atomosophere is peresented by penetration of chloride ion. Penetration of chloride ion is explained by Fick's diffusion equation. The constant parameters on Fick's diffusion equation are diffusion coefficient D₀ and surface chloride ion density C₀.
The parameters on Fick's equation are estimated by structural identification techniques based on Gauss-Newton method by using the recorded chloride ion density of existing structures.

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The nonlinear finite element analysis program for reinforced concrete planar member subjected to reversed cyclic loading is expanded to analyze reinforced and prestressed concrete linear members with shear reinforcement subjected to one-sided cyclic loading. It is found that the predicted strains of shear reinforcement can be made much closer to the experimental ones by considering reduction of concrete tension stiffness due to slip of shear reinforcement at its lower bent. The ultimate strengths of beams are also predicted reasonably. Based on the analysis, a new truss model is presented to explain shear resisting mechanism of beams with shear reinforcement.

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Because of low W/C of high strength concrete, heavy dosage of superplasticizer is needed for high workability of concrete. The concentration of superplasticizer is so high that it may effect the hydration and strength of the cement. In this paper three types of superplasticizer in a large range of dosage were used, and the effects of superplasticizer on the hydration and strength of cement were investigated. According to the test's results, it is concluded that the adsorption of superplasticizer on cement and effect of superplasticizer on concentration of Ca²⁺ in solution of paste influence the hydration of cement and strength of the mortar.

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Behavior of concrete confined by lateral reinforcement is addressed through experimental approach. The primary objectives of the experimental study are to mechanically define the confinement effectiveness of lateral reinforcement layouts and to obtain reliable data for verification of non-linear, three dimensional concrete constitutive law under non-uniform stress field produced in confined concrete cores of column members. Further, identification of the influence of detailing parameters on the confinement phenomena was aimed for the purpose of developing and examining a behavior oriented macro-model.

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Three-dimensional elasto-plastic and continuum fracture model for concrete, which had been originally developed with reference to uniform stress field, is verified on structural member level of non-uniformity. This study adopts idealized square concrete cores purely confined by closed square lateral steel ties. The constitutive model is examined in view of confining stress induced from lateral steel to core concrete and enhanced strength and ductility of core concrete at the axial capacity of columns. The verified applicable range of the constitutive model is clarified under practical stress conditions and paths arising in RC column members. The effect of loading rate on the plasticity evolution is also discussed.

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