In this paper two singular stress functions suited to analyze crack problems of plates are presented. One of them is a stress function of two-dimensional problems which creates a crack opening displacement due to normal loads applied along the crack (mode 1) in an infinite plate. The other is the same function as that but due to shear loads along the crack (mode 2). The Authors define these two functions as elementary crack function with opening of unit length. Super-posing these functions with different length of elementary crack opening, the stress concentrations due to many cracks contained in the infinite plate can be analyzed numerically with good accuracy. The characteristics of this method is that the stress softening zones at both end of the crack can be constructed where either crack opening displacements or stress concentrations with finite magnitude appear.

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The pipe cooling method is of use for control of thermal cracks in various massive concrete structures. This paper presents a new theoretical technique for solving the pipe cooling problems. The numerical computation is made by means of the modified Fluid in Cell (MFLIC) method which was developed for simulating energy equation with a large Peclet number. The experiment is done by using a large-sized rectangular concrete prism. Comparing theoretical results with experimental ones, the application technique of MFLIC method is confirmed. In addition, some characteristics of heat transfer at cooling pipe surface are theoretically clarified by the aid of computed results.

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This paper presents adiabatic temperature rise of portland cement concrete incorporating ground granulated blast furnace slag. The ground granulated blast furnace slag is intended to use as concrete admixture, but the temperature rise of concrete with slag and the hydration mechanism of slag and portland cement are not clear perfectly, Therefore adiabatic temperature rise of concrete effected by slag content in mixtures, concrete temperature at mixing, fineness, gypsum content and different blands of slags are tested. And hydration of slag depending on curing temperature are discussed through conduction micro calorie meter and other some chemical mesures.

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There are many methods ranging over design and construction to control thermal cracking in mass concrete structures. However, it is necessary to evaluate the effect of each method quantitively in order to control thermal cracking effectively.
In this study the equations to express the effect of the methods, for example, concreting temperature, curing method, and lift separation, to control thermal cracking in mass concrete slab are obtained in the result of thermal stress analysis. The most effective method according to the size of the structure and the external restraining level can be selected easily using these equations.

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Stress relaxation of concrete, especialy in early ages, is one of an important property for thermal stress analysis in concrete structure. But, the information on the relaxation is very small because of an experimental difficulty in maintaining a specimen at a constant deformation. This paper describes the results of compression and tension relaxation tests on concrete in early ages. Test were performed by electro-hydraulic closed-loop testing machine system for compression and by loading frame with high rigidity for tention. Based on the test results, the influences of the age of loading and stress level upon the compression and tension relaxations are fully discussed and estimating equations for the relaxations at various ages are proposed.

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The foreknowledge of deformation of very early aging concrete subject to sustained load has become very important to introduce the systematization of concreting practice.
The present study has been carried out to enable foreknowledge of deformation of very early aging concrete for sustained load by means of finite element analysis of visco-elasticity. Further, the comparison between calculated results by finite element analysis and measured results by test was carried out on a problem of deformation resulted from dead load of column.

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The objective of this study is to investigate the behavior of air flow through concrete due to a pressure difference, and to evaluate the air permeability of concrete quantitatively. Different mix proportions and curing conditions are used so as to detect the dominant factors affecting air permeability. It is found that the coefficient of air permeability can be used as an index of air permeability of concrete, and it can be quantitatively estimated by mean pore radius and porosity based on the volume of evaporated water. In addition, air permeability of concrete is found independent of the total capillary pores in concrete, but dependent on the dried capillary pores without moisture.

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The finite element analysis is developed in order to estimate the hysteretic behavior of prestressed concrete structures in partially bonded condition under cyclic loading considering non-linear stress-strain relation of concrete and steel. The method is applied to the bonded and unbonded prestressed concrete beams and rigid framed structures composed of precast concrete members and connected by prestressing steel, and the deformations and the angle of rotation observed in the experiment are compared with the calculated values. The mathematical model to express the rotation at jointed corner and the effects of initial prestress and bonded condition to the hysteretic behavior under cyclic loading are discussed.

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Prestressed concrete has been recognized as an excellent containment structure for storages of low temperature liquid such as LNG (-164°C). The study was conducted to evaluate mechanical properties of prestressing steel, prestressing tendon systems and prestressed concrete for cryogenic applications. Emphases were laid on the evaluation of material and structural behaviours in terms of ductility and liquid tightness. The experimental research was divided into five phases. Phase 1 tested and evaluated the notch sensitivity of prestressing wire, while Phase 2 examined the ductility of anchorage materials. In Phase 3, full size prestressing tendon systems of 12 T 15.2 were subjected to static and cyclic loading under low temperature conforming to the FIP recommendation. Phase 4 examined the structural behaviour of prestressed concrete beams under the impact loading at low temperature. Phase 5 tests the response of prestressed concrete beams subjected to various axial stresses and temperature gradient. Prestressed concrete and its steel materials have shown superior mechanical properties for cryogenic storage structure.

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The influence of different types of cement, cement content per unit volume of concrete, and concreting temperatures on adiabatic temperature rise were evaluated during this study. The Adiabatic temperature rise was measured with a new testing apparatus, with high reliability that has been confirmed through comparison with time-dependent temperature changes in mass concrete structures. Before the evaluation, the most suitable equation for approximating the adiabatic temperature rise as a functional formula of time was selected based on the experimental results. Further, comparison of the above approximate values with standard values proposed by JSCE or JCI was done, and problems involved in these standard values were pointed out.

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Studies were made on cases of using blast-furnace slag sand and of using air entrainment as methods of improving freezethaw resistance of extremely stiff-consistency concrete for instant stripping. The results show that there is considerable variation in resistance depending on the variety of slag sand, while stable resistance is obtained with air-entrained concrete. A method of measuring entrained air out of the air content of concrete was studied for extremely stiff-consistency air-entrained concrete, the reliability of the method was ascertained, and the conditions for selecting air-entraining agents suitable for extremely stiff-consistency concrete were examined.

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This paper describes the results of 3 kinds of thermal fracture tests of asphaltic mixture and stress relaxation test of asphaltic mixture in tension at low temperatures. Test results indicate that the difference between the fracture temperature and the temperature at intercept is about 20°C under various thermal loading conditions, thermal stress under thermal repeated loading conditions corresponds to thermal stress under stress relaxation at constant temperature and the characteristics of stress relaxation under various thermal loading conditions is similar with that of stress relaxation in tension.

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It was found that bleeding of fresh cement paste mixed with the same final water cement ratio is strikingly changed with divided addition of water each addition being followed by mixing (referred as double mixing: DM). Depending upon the amount of water which is added at the first stage mixing (referred as the primal water: W₁), bleeding of the cement paste can be minimized or maximized.
In this paper, mechanism of these DM effects and influences of various factors, such as fineness of cement, mixing time, type of mixing water, temperature and chemical components of cement etc., on the DM effects were experimentally investigated.
From these experiments it was suggested that the double mixing effect is not only associated with physico chemical interaction between liquid and cement powder but also with chemical reaction of cement particles with water and electrostatic charge of cement particles that might be related to the early stage chemical reaction of cement with water.

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From field pumping tests, it was made clear that pumpability of poor mixed concrete might be improved by adding stone dust or fly ash. It was also made clear that pumpability was closely related to the amount of mortar containing sand whose grain size was 0.3mm or less, and that the pressurized bleeding test was effective for exactly estimating the pumpability of even poor mixed concrete for pipelines having a diameter of 125mm. Mixing large amount of fine stone dust did not have any bad influence on the strength and the durability of concrete.
In this paper, the authors propose a procedure to design the mix proportion of concrete having the property of good pumpability, and show necessary mortar content with fine sand of 0.3mm or less

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The saturated surface-dry condition of fine aggregate has been obtained usually by the flow-cone method. However, we have indicated that this method is so sensible for judgement that the individual difference is large. Then we studied in the method of preparing the saturated surface-dry condition mechanically by utilizing centrifugal dehydration. It has been found that the percentage of water content at the inflection point of the dehydration curve on a certain dehydration condition closely resembles it of water absorption by the flow-cone method. According to the kinds of fine aggregate, the percentage of water absorption in the saturated surface-dry condition, which is prepared on the constant dehydoration condition, closely resembles it of water absorption prepared by the flow-cone method and its experimental or personal error is far smaller than it of the flow-cone method.

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In order to investigate the splitting crack patterns due to the wedge action and dowel action of deformed bars and estimate the splitting bond strength, the two-dimensional non-linear finite element analysis was carried out on reinforced concrete members. The wedge force or dowel force was replaced by uniform or non-uniform internal pressure, respectively, and the subject of analysis was limited to concrete only. Concrete cover and bar spacing were selected as analytical parameters.
The analytical results show that three splitting crack patterns proposed by Jirsa and Morita: V-notch, side splitting and corner splitting type are also observed by this analysis, and that the dowel action aggravate especially the side splitting failure. On the basis of the analytical results, a tentative equation to estimate the splitting bond strength was proposed.

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This paper presents a comprehensive study to investigate compaction-strength mechanism as well as drying shrinkage characteristics on cement mix materials for base course with water content from low water content region which is suitable for roller-compaction to high water content region which is suitable for vibration-compaction. From the experiment results, dry density changes continuously with respect to water content of both regions and is maximum at the boundary. But at that boundary, compressive strength is different and incontinuous. In other words, compressive strength is not always governed by dry density and is found to be governed by cement-paste/void ratio. The drying shrinkage of these materials is linearly proportional to water content and cement content during mixing.

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This test program was implemented to determine the fatigue behavior of reinforcing bars in air and the effect of cold-work on fatigue strength. A lot of studies have been conducted to investigate the fatigue behavior of reinforcing bars embedded in concrete beam, however, only few studies have been reported for reinforcing bars alone. This test was performed to provide information that may aid in interpretation of beam fatigue test. Fatigue characteristics of cold-worked (pre-strained) reinforcing bars were analyzed using Manson's hypothesis. The test results may seem to agree with the hypothesis.

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