An experimental study on the ultimate strength and ductility of reinforced square columns with confining reinforcement is described. Sixty specimens, each 200mm square by 800mm high, containing either 8 or 12 longitudinal steel bars and different arrangement of square or octagonal steel hoops, were subjected to concentric or eccentric loads to failure under uniaxial or biaxial bending. Other variables were the spacing of hoops and the eccentricities of loads. Based on the test results and analyses, new formulas are proporsed for the ultimate strength and ductility of the columns with confinement subjected to uniaxial or biaxial bending. A new parameter which was defined, in this study, as the confining ratio of confining reinforcement ratio to the longitudinal reinforcement ratio was used in the formulas. As it is difficult to predict analytically ductilities of columns under biaxial bending, a simple design method is proposed.

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In designing a prestressed concrete cable stayed bridge, such important problems like finding the optimal value of cable stay forces and girder prestress as well as the selecting arrangement of stay cable, shape of main girder, etc. has to be overcome.
In this study, a method of optimization considering a combination of the stay cable forces, the girder prestressing, creep and shrinkage of concrete and construction process is developed based on the strain energy criterion proposed by Yamada, Furukawa, et al. And also an optimization system to determine automatically both cable stay forces and girder prestress is developed using a personal computer.
A few prestressed concrete cable stayed bridges on which much data have been published are analyzed to demonstrate the applicability of this system. The results obtained are sufficient to apply in the determination of both the optimal value of cable stay forces and girder prestress of the prestressed concrete cable stayed bridge.

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This paper deals with shape properties of crushed stone aggregate in asphalt mixture. It presents a method that determines the shape of aggregate quantitatively. Also in this paper, the configuration of coarse aggregate in asphalt concrete is examined using an image analysis system. Majority of stones consisting of coarse aggregate in asphalt pavement compacted by a roller are oriented at the angle of less than 30° from the horizontal plane. Using a flakey shape of crushed stone is grown Dynamic Stability by the Wheel-Trucking Test. And outdoor experiments by Trucks are made for confirmation of the Wheel-Trucking Test results. In conclusions, the coarse aggregate lined up in horizontal direction shows advantage of deformation phenomenon of asphalt pavement. Therefore, flakey shape aggregate is the best shape for asphalt mixture if it is arranged with the angle almost horizontal.

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The aim of this study is to develop a constitutive law for a reinforced concrete panel element subjected to reversed cyclic in-plane stresses. The authors formulated the constitutive law for a reinforced concrete panel element by using the constitutive laws for cracked concrete and for reinforcement. These constitutive laws have been developed and verified with the reversed uniaxial testing of reinforced concrete elements. The proposed constitutive law for a reinforced concrete panel element have been verified with the experiments conducted by Ohmori et al. and Stevens et al.. The response of the reinforced concrete panel element subjected to reversed cyclic in-plane stresses can be predicted by the proposed analytical model.

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The authors proposed a constitutive equation that relates relative displacements and applied stresses on cracked surfaces of concrete in the plane stress state.
In the paper, the four basic coefficients, such as the shear stiffness, the normal stiffness, the dilatancy ratio and the frictional coefficient, are identified making use of experimental results from the presently available literature.
The proposed model is then compared with the mechanical response of direct shear tests and reasonably good agreement is obtained.

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The authors have been developing the constitutive model for a single crack in concrete and making experimental identification of the four basic coefficients.
In the present paper, the nonlinear behavior characterizing the crack surface is discussed on the basis of numerical results calculated from the authors' proposed constitutive model. Moreover, comparison to Bazant·Gambarova's model is made, and pathdependency and Coulomb's friction law being compared with rock joints are examined. It is found that numerical simulation may be a useful tool to quantitatively analyze the characteristics of cracked concrete, being comparable to experimental studies.

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With enlarging scale of concrete structures, thermal cracks in massive reinforced concretes have become one of the pressing problems of the day. This paper deals with the development of a moderate prestressing method using an expansive demolition agent for thermal cracking control. In order to examine the degree of prestressing in new unbonded tendon, several experiments are carried out by cylindrical model in a laboratory. This new method is proved useful by several field experiments. In addition, the experimental results are compared with some numerical calculations to clarify the applicability of a newly proposed theoretical method to predict the control effect of thermal crack.

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The following experimental facts regarding the compaction process of prismatic concrete specimen compacted by surface vibrator were clarified. Cement paste moved downward at early compaction stage, after this time the moving direction changed to upward and the interstitial spaces between aggregate particles were filled up thoroughly by cement paste. The pressure of cement paste near the layer bottom increased gradually with compaction periods and reached the maximum value just at the time the spaces were filled up. On the other hand, the periods taking to reach the maximum compressive strength were nearly equal to that corresponding to the maximum pressure. Accordingly the compaction degree could be evaluated by measuring the pressure. Subsequently the following facts were found. The propagation of compacting effect to lower part was difficult with increase in specimen height. The methods of concreting one lift by dividing into several layers and compacting each layer up to the certain compaction degree were more successful than those of concreting and compacting the lift at a time, and thin mortar layer placed on joint before concreting was also useful to make effective compaction. Combining the frequency and amplitude of surface vibrator appropriately was more successful than increasing its weight to make effective compaction. Especially combining high frequency and low amplitude was the most effective practically.

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It is very important for the concrete industry to find adequate methods of using low quality aggregate, because the quality of aggregate has become lower and recently it is not easy to obtain proper aggregate for concrete. In this experiment, it is examined whether low quality aggregate can be effectively used by the following two methods. One method is to adjust mix proportion of concrete in order to cover the defect of using low quality aggregate. In another method, good quality aggregate is mixed with low quality aggregate in order to improve the average characteristics of aggregate. Although the problem is not solved completely by these methods, there seems to be the possibility of using the low quality aggregate by properly adapting these methods according to the required properties of concrete.

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Oxygen transmission through concrete related to reinforcement corrosion is measured using electro-chemical procedures. Based on the measurement, the influence of cover thickness, curing condition, ambient humidity etc. on the oxygen transmission is discussed. The main conclusions in this paper are summarized as follows. (1) Cover thickness has not always remarkable influence on oxygen transmission related to reinforcement corrosion. (2) The influence of curing condition and ambient humidity is very large.

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The effect of external restraint is one of the most important factors in discussing the mechanism of the thermal stress in massive concrete. From the results of recent theoretical investigations, relative displacement in both horizontal and vertical direction is suggested to be occurring at a joint of restrained concrete and restraining body such as rock or soil or even old concrete cast sometime ago before the casting of new concrete. These phenomena, however, have not confirmed by experimentally. In this paper, it was shown that the results of the thermal stress experiment with large scale massive concrete specimens were made having two parts, the base and wall on it. Each specimen has the different rigidity at its joint. The thermal deformation of these specimens was observed with high sensitive displacement meter, and the above mentioned phenomena were confirmed. The relationship between thermal deformation and rigidity of a joint was discussed based on the results of this experiment.

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This paper describes the results of experimental research to the brittle properties of asphalts by means of Fraass breaking point test and new method measuring fracture temperatures of asphalts due to thermal stress at low temperatures (Moriyoshi Breaking Point Test). In this study, it is concluded that the brittle temperatures of asphalts (Moriyoshi Breaking Point) depend upon the refinery, the mixing plant, the date, the shape and thickness of vessel made of stainless steel and glass transition point of asphalt, and cracked shape of asphalt is closely related to the quality of asphalts.

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Concrete manufactured from cement paste prepared by double mixing (DM) under the optimum deviding proportion of water, exhibited higher strength and yielded less bleeding than those observed for concrete of the same mix proportion prepared by conventional mixing (SM). In order to explain this effect, several series of experiments and FEM analysis of model concrete were conducted. Based upon the observations such as positive corelation between compressive strength and bleeding, crack propagation initiated from the artificial bleeding flaw provided under coarse aggregate and strength reduction enhanced with increasing size of aggregate etc., GEM (Gravel Enveloped with Mortar of low bleeding) model is proposed in stead of the original model named as SEC (Sand Enveloped with Cement).

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The objectives of this study are to analyze factors which are considered to affect concrete quality changes and to develope adequate concrete quality control system based on data analyses. The data used in this study are mainly those of the concrete placed in expressway construction works and commonly ready-mixed concrete placed all over Japan.
Through a lot of large amount of data analyses, it became evident that concrete qualities became deteriorative or multifarious with range throughout Japan due to producing equipment, quality control system, aggregate condition, regional difference and so on. Comments are also made on those particular factors for more reasonable concrete quality control system.

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In designing statically indeterminate structures of partially prestressed concrete under service load conditions, it is reasonable to take into account the reduction of flexural rigidity due to cracking for computing redundant forces.
In this paper, experiments are conducted to clarify flexural deformation of partially prestressed concrete beams, and a simplified moment-curvature relationship is proposed for rapid nonlinear analysis of continuous girder bridges.
Furthermore numerical examples clarify effects of the level of prestressing and the pattern of cracking on redundant forces under service load conditions.

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Although the most of National Codes of Practices which deal with cracking recommends a limit for crack widths in order to control the risk of corrosion of reinforcement, the research to date has not sufficiently discussed the effect of cracks on carbonation of concrete. Therefore, this study has been carried out to improve the understanding of the effects of cracking on carbonation process. Mortar beams were used to investigate the effect of crack width on carbonation depth under an accelerating neuteralization test. Comparisons were made between the accelerated and exposure test results to evaluate the effect of acceleration on the carbonation depth. Also the influence of various constituents and curing time on carbonation depth was discussed.

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A source inversion procedure for determining crack types and crack orientations is proposed as the quantitative waveform analysis of acoustic emission (AE), based on the integral representation and the moment tensor. The procedure is applied to AE events monitored during the pull-out tests of hooked anchor-bolts from concrete block.
The integral representation is first applied to the stress analysis by the boundary element method (BEM). It confirms that the failure surface is generated as perpendicular to the direction of the maximum tensile stress.
AE waveforms detected at five sensor locations during the failure process are analyzed by the source inversion procedure. Crack kinematics determined are in good agreement with experimental findings.

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The objective of this research is to evaluate the kinematics and deformation of solid phase in flowing two-phase material for the purpose of understanding the segregation process of fresh concrete as liquid-solid material. Studying the segregation process of flowing fresh concrete, the motion of coarse aggregates having close correlation with blocking of flow was observed in the visualized test with model material simulating fresh concrete. The image analysis was conducted and all solid particles were processed by a video-computer system. Not only Lagrangian but also Eulerian expression of aggregate phase, spatial averaging technique was found to be so useful as to understand the flow and segregation of two-phase model concrete.

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The objective of this research is to investigate the deformation and segregation process of fresh concrete as two-phase material around bifurcations in a pipe line network Visualized tests with model concrete simulating fresh concrete under idealized two-dimensional condition were carried out. By Lagrangian and Eulerian evaluations of aggregate phase with the use of an image analysis, the deformation and segregation of model concrete around bifurcations was clarified, which was highly affected by boundary conditions and liquid viscosity. High viscous liquid phase was found to relax the mutual interaction between aggregate particles and to unify the localization of shear deformation of aggregate phase around the bifurcation point.

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An experimental study was carried out to develop a durable cement-asphalt mortar as the shock-absorbent filler to be used under the slab track of Tohoku and Joetsu SHINKANSEN lines in cold climate.
This study has revealed that development of a cement-asphalt mortar durable under freezing and thawing will be possible by introducing the entrained-air. And it has proved that for improvement of anticracking and toughness properties it is necessary to utilize highmolecule materials and alkari-resistant glass fibers.

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The applicability of the plastic theory by M. P. Nielsen to predicting the in-plane shearr strength of reinforced concrete is discussed. The plastic theory is compared with both the diagonal compression field theory by M. P. Collins and the drafted Japanese design criteria for concrete containment vessels. It is found that those three theories provide reasonably good agreement with experimental results.

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