Bending tests were performed on concrete beams reinforced with large-sized deformed bars, designated as D64, having nominal diameter of 64mm and screw-type rolled deformation. Crack-control reinforcement D29 were arranged near the concrete surface for D64 in order to control crack widths. It was shown that the crack-control reinforcement near the concrete surface was effective for crack control of the beams. At the tensile stress of 1800kgf/cm² of main tension reinforcement, the number of crack in the bottom surfaces of the beams increased by 1.6-1.8 times and the maximum bottom-surface crack widths of beams decreased by about 0.40 times those of the beams without crack control reinforcement. These maximum surface crack widths can be estimated by the calculation equation given in J S C E Standard Specification for Concrete Structures.

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A new stress function for an interface crack between two dissimilar elastic half planes which are subject to uniform tension is proposed in this paper. Figures and tables are used to show the relation of the elastic characteristics of the both materials and the maximum stress concentration ratio, or the relation of the J-integral value that was given by a conventional solution and that obtained by this study. The character of this function consists of finite stress concentration with no oscillations at the crack tips, although the elastic solution is used. It is introduced that the behavior of the J-integral values obtained by proposed function are stable for the crack extension, so that this function is suitable for using in numerical simulation of fracture phenomena.

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It is considered that concrete gravity dams constructed by the rationalized construction methods such as the RCD method or the ELCM (Extended Layer Construction Method) are more advantageous to thermal stress than the conventional construction method, for the concrete has a little content of cement and is placed rapidly and continuously. With regard that, the authors carried out thermal stress analysis by the Restraint Matrix Method in order to study on thermal strain in the dam body. As a result, the proposal for placing speed in the rationalized construction method is to be attempted introducing the relative placing speed which is placing speed divided by dam height.

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Effect of cement, admixture, water-binder ratio and volume concentration of aggregate, on autogenous shrinkage of cement based materials was experimentally investigated. Large amount of autogenous shrinkage was observed in cement paste and concrete with very low water-binder ratio. Autogenous shrinkage was increased with increase in C₃A content of cement. It was increased by blast-furnace slag with higher fineness. Effect of volume concentration of aggregate was able to be estimated by an existing composite low. Some kind of admixtures could decrease autogenous shrinkage.

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This paper describes a practical evaluation method of structural safety and its change in service of concrete bridges based on only brief material tests, using statistical factor analysis of structural safety for actual bridges evaluated by non-destructive loading tests and material tests. Furthermore, the remaining life based on current maintenance criteria for repair, rehabilitation and renewal, is discussed by linking predicted results by presented method and the diagnosis by the bridge engineers through visual inspection. Finally, application example to an actual bridge is presented so as to demonstrate the suitability of the presented method.

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To establish a method for evaluating the long-term water-tightness durability of underground concrete structures, the authors firstly studied a deterioration evaluation model to express the deterioration condition of concrete structures and constructed, on the basis of this model, a function evaluation model to estimate the lowering of functions due to deterioration, consequentlly indicating a “concept for evaluating the deterioration and functions of concrete structures” which will make it possible to perform the functional evaluation of concrete structures.
Based on tihs concept, the authors then discusses a technique for evaluatinig the long-term water-tighthess durability of underground concrete structures, specifically indicating the tectnique by means of illustrations.

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Many concrete construction joint interfaces are expected to transfer shear forces In this study, three types of joint were examined for shear strength; concrete placed onto previously hardened concrete with an intentionally toughened surface (to 5-10mm); concrete placed onto smooth concrete or steel plate; and concrete placed onto steel formwork offering concrete shear key joints. The results of push-off shear tests form the basis for a discussion of the shear transfer mechanism, and a method of calculating shear transfer capacity is introduced based on limit analysis of lines of discontinuity for displacement. A design shear transfer strength equation, incorporating a certain safety factor, is then proposed and its propriety demonstrated.

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The fracture toughness for the interfacial zone between a steel fiber and cementitious matrix was experimentally obtained by applying a compliance method to the single fiber pull-out test. Effects of the addition of silica fume and sand grains, and water: cement ratio on the fracture toughness were discussed relating them to characteristics of the fracture process revealed by the fluorescence microscope. Interfacial fractures under the pull-out loading were not a simple shear failure along the real interface. Local failures of the extended regions around a steel fiber were accompanied in the fracture process. The decrease in fracture toughness due to the addition of silica fume can be related to less microcracking in the interfacial zone and less tortuous extension of the interfacial cracks. In order to increase the fracture toughness for the interfacial zone, a small amount of carbon fiber was incorporated into the matrix. The addition of short carbon fibers was effective to improve the fracture toughness and the frictional stress in the interfacial zone. Steel fiber reinforced mortar with the matrix containing silica fume and short carbon fibers exhibited greater M. O. R. and toughness.

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This study aims at revealing the mechanisms of the influence of NaCl externally supplied on the expansion of mortars due to the alkali-silica reaction. In a reactive aggregate-bearing mortars with relatively low alkali contents, the promotion of their expansions in 1N NaCl solution at 38°C was caused by a rise of OH^- ion concentration in the pore solution. The increase in OH^- ion concentration in the pore solution in mortars was responsible for the intrusion of NaCl into mortars containing a reactive aggregate. In a reactive aggregate-bearing mortars with a relatively large amount of added NaOH, a high possibility that a part of the unusual expansions of mortars was caused by the formation of ettringite during the immersion in NaCl solution.

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3-D solid linear FEM analysis is now becoming a common method in design of large scale RC structures, however, there is no widely accepted design method available so far, in which 3-D solid linear FEM analysis is applied especially to determine appropriate amount of reinforcement. This paper proposes a new method to calculate the required amount of reinforcement using element stresses obtained in a 3-D solid linear FEM analysis. Several examples demonstrate a practical application of the method to a design. An investigation on a recently proposed design method for shearing force is also presented along with some other methods.

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An analytical method of stresses in prestressed concrete cylindrical tanks is proposed, in case that they are subjected to anti-symmetric loadings such as hydrodynamic pressures and inertia forces. Ordinary differetial equation of 4th order with respect to the radial displacement of cylindrical tanks is deduced from replacing one of the fundamental equilibrium equations on circular cylindrical shell by a global equilibrium equation of bending moment of the tank wall. It is shown that this ordinary differential equation is equivalent to the differential equation which governs deformation of a beam supported by vertical and rotational springs. The differential equation on the beam deduced above is easily analyzed by using general computer program for frame works. It is clarified that the stress in cylindrical tank walls subjected to anti-symmetric loadings can be approximately treated as that of axi-symmetric loadings by neglecting minor terms in the differential equation on the beam supported by springs.

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Untill now, the agitating efficiency of the truck agitator has been estimated by quality of discharged concrete after agitating. Because directly we can't observe the flow of concrete in the agitator. In order to study about the agitating efficiency of fresh concrete, a new technique was discussed in this report. With help of visualization technique, it became possible to obtain the information about movements of coarse aggregates and mortar in fresh concrete model. As a result, it was cleared that there were three types of flow, which consist of surface layer flow, overflow and confined flow, of fresh concrete model mixed in it. In addition, the study also shows that the segregation of the fresh concrete consisting of coarse aggregate and mortar occurred at the interior in a truck agitator when amount of concrete was increasing.

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It is well known that by confining a concrete element in two out of three mutually perpendicular directions the ultimate compressive strength of the element in the third direction increases considerably. In practice, confinement is usually passive, and provided by steel which induces compressive stresses in the element.
The present paper has investigated experimentally the deformational behaviour of concrete under passive confinement. In the experiment, concrete cast into a steel tube was subjected to axial compression. The parameters investigated were the strength of the concrete and the thickness of the steel tube. The experiment has clarified some of the most important characteristic features of concrete behaviour under passive confinement; these include elastic properties, ultimatestrength envelope, plastic strain, ductility and volumetric change.

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When a concrete cylinder is confined laterally by a steel tube, or it is strongly reinforced with closely-spaced hoop reinforcement bars, the axial strength and ductility of concrete are improved considerably. In such structures, large confining pressures are passively induced by steel due to the lateral expansion of concrete.
The present paper proposes a constitutive model for describing the multiaxial deformational behaviour of concrete under passive confinement by using the work-hardening elasto-plasticity theory. The derivation of the proposed model is based on the use of experimental information obtained from tests in which concrete has been subjected to passive confinement. A computer program for finite-element (FE) analysis based on the use of the proposed model has been developed. The FE analysis successfully predicted the load-carrying capacities and deformational responses of concrete-filled composite columns subjected to eccentric loading.

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Investigation of the behavior of embedded box-type reinforced concrete (RC) structures for nuclear power stations subjected to lateral earthquake earth pressure, concerning shear rigidity and its reduction, has been conducted analytically in this study. A nonlinear finite element approach based on smeared crack model of RC plate element was utilized. From the parametric study of a real RC duct for accommodating emergency cooling water pipes in nuclear power stations, it was found that lower reduced shear rigidity factor, which was defined as the ratio of reduced and initial shear rigidity, could be attained by arranging lower concrete compressive strength, higher yield strength of reinforcing bar, higher reinforcement ratio and thinner wall thickness of the RC duct. Finally, a formula to predict the reduced shear rigidity factor has been proposed based on the parametric study.

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The determination of the optimal cover thickness of concrete slab provided with the limit state as the corrosion of reinforcement is affected by the carbonation formulae. In this paper, typical two formulae are employed to investigate the differences of the results between them. It shows that the differences don't affect the results, greatly.

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It is necessary to analyze the life cycle cost in the case of designing asphalt pavement. In this paper, we developed a project level pavement management system based on dynamic programming and propose the optimal design method of asphalt pavement in consideration of the life cycle cost by using this system.

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