Up to now, the existing constitutive models of concrete are composite more than one criterion corresponding to the different stress states. In this paper, a unified plastic model for concrete, in which only one criterion is used to describe the behavior of concrete under different stress states, is proposed. This model can treat the major nonlinear phenomenon of concrete such as cracking, shear transfer degradation, tension stiffening and compressive strength reduction. By use of this model, the cumbersome considreation in an analysis the concrete structures by using other models can be eliminated.

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Assessment was made of the strength of the various grouted sands as a function of age. The physical and chemical stability of pure grout with age was also examined. By curing pure grout in water for 2000 days, the cause of SiO₂ leaching related to chemical stability, was shown to be unreacted SiO₂. Change in grouted sand strength with age was of the following three types. Grouted sand strength in organic grouts decreases slowly with age. Grouted sand used in non-alkaline silica sol grout shows peak strength at a certain age. Colloidal sol grout increases with age. The strength of grouted sand was shown to be affected by change in pure grout and the modulus elasticity of grouted sand.

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Concrete structures have been long expected as permanent structures, and then they have been constructed without priory considering their maintenance. Recent year, however, they are suffered from severe damage. An artificial neural network is applied to assess deteriorating reinforced concrete structures using periodical inspection data for thermal power plants along the coast of Tokyo Bay. Using a completed training neural networks, a sensitivity analysis to determine the influence of a change in each variable such as maximum crack width, are of peeling-off of concrete surface, exposure of reinforcement, etc., on the damage level.

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Generally speaking, lightweight concrete, using artificial lightweight aggregate, has lower resistance to freezing and thawing, and this presents a serious problem. This study reported here was carried out on the frost resistance of high-strength lightweight concrete. We proposed five methods of manufacturing high-strength lightweight concrete possessing superior durability. They are to use lightweight aggregate with low initial moisture content, to decrease a degree of saturation of concrete due to drying, to use coated aggregate or aggregate absorbed with non-freezing agent, and to cast concrete into a steel enclosure. Evaluating synthetically these improving techniques, the best one is so far to use lightweight aggregate with low initial moisture content.

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The effects of mechanical degree of prestress, volumetric ratio of lateral confinement, compresssive strength of concrete, steel index and shear span effective depth ratio on the energy dissipation properties of partially prestressed concrete beams were investigated under different loading histories. Relationships between these test variables and nondimensional dissipated energy were derived based on the test results. It was also indicated that seismic damage of partially prestressed concrete beams could be evaluated quantitatively by the proposed damage index based on hysteretic dissipated energy.

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An analytical procedure which deals influencing factors affecting to temperatures in the structure is herein proposed. Factor analyses were conducted against the thermal characteristics affecting to thermal analytical results by means of the method of sensitive analysis. The variances of temperature in the structure having variable thermal characteristics of concrete and environment were evaluated from the sensitivity obtained by the sensitive analysis and the approximated theory using Taylor's expansion.

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Precast concrete pavements (PCCP) are constructed by placing small size precast concrete plates on the subbase. In this paper, the mechanistic characteristics of PCCP is discussed based on the experiment and FEM analysis. The nonlinearity due to lifting up of the plates is considered in the FEM analysis. From the results of the analysis, it was found that stresses in the plate are large in the case of large size of the plate. Therefore, in this case, the plate should have enough thickness to prevent cracks due to wheel load. Whereas, in the case of small size of the plate, deflections are large, therefore, strong subbase should be used.

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A high-performance artificial lightweight aggregate has been developed through application of a new manufacturing method. This aggregate is principally characterized by aggregate particles having no cracks or large voids, and most of the pores being closed and uniformly small. The aggregate water absorption is so extremely low that, even if dry aggregate is used, the concrete can be cast by pump without changing its workability. The strength of the aggregate is improved permitting a higher strength concrete to be obtained. Furthermore, high resistance to freezing and thawing action can be assured.

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Performance forecasting model is indispensable to any pavement management system. Generally, pavement performance model is obtained by multivariate nonlinear regression. In this study, neural network approach is evaluated for developing pavement performance model.

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