Although fatigue strength is one of the important limit states for the design of concrete structures, fatigue lives of reinforcing bars and concrete exhibit wide variations. The present research deals with the fatigue lives of reinforced concrete beams subjected to bending moment, when fatigue lives of reinforcement is supposed to be a random variable. The fatigue strength of reinforced concrete beams under the repeated bending moment, steel bars with different fatigue being arranged, is formulated based upon the Miner's rule. Then, the Monte-Carlo technique for random simulation is employed to investigate the effect of variation and correlation of fatigue lives of reinforcing bars on the fatigue lives of reinforced concrete beams. The characteristics of fatigue behavior of reinforced concrete beams containing multiple reinforcement are discussed.

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Continuous grillage composite girders are statical indeterminate to a high degree, and they are completed by multi-stage constructions which involve variations of composite section and structural system. In these structures, suitable analysis of time-dependent change in forces and deformations due to creep and shrinkage, are not proposed yet. An analysis combined with the step-by-step method and the stiffness matrix method is proposed in this paper. Furthermore, the composite section is composed of plural concrete section and steel section which have different mechanical properties. The auther reports the result of calculations on a two-span continuous grillage PC composite girder under service load condition and discuss them in this paper.

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We are studying the agitating efficiency of the truck agitator by visualization technique using model agitator and model concrete. We tried to quantify the velocity and the direction of concrete flow in agitating. In this study, we cleared distribution of velocity vector of coarse aggregates and mortar by analyzing the image data obtained by visualization experiment. In the result, it was cleared that the concrete flow contributing agitating was only the overflow among three types of flow, and that the segregation of the mortar occurred when the large amount of concrete was agitated because only the mortar stuck to the inner surface of drum on the right side of the agitator and the mortar flowed forward.

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The analytical model for water migration which is apply to the porous materials such as concrete and rock, is constructed. The analysis for pore water pressure occurring in concrete is carried out, and then the applicability of proposed model is shown according to compare with the experimental results. Further, the mechanism for the effects of pore water pressure on the property of strength for concrete using the proposed model is probed analytically, and then it is shown that water migration in concrete is thought to be very important.

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Chemical activity of rice husk ash is greatly controlled by the burning condition for rice husks. In this report a burning principle that is named “Two Step Burning Method” and two examples of furnace based on the principle were shown. The rice husk ash produced from these furnaces was very active, and it was confirmed by compressive strength test for concrete specimens. Furthermore, some physical properties for secondary agglomeration of ground rice husk ash were studied. The agglomeration causes to block the dispersion of ground rice husk ash when concrete is mixed. A grinding aid (di-ethylene glycol) was used to prevent that. It was also shown that theuse of the grinding aid was so effective to prevent the agglomeration. Highly active rice husk ash was also very effective to prevent bleeding of fresh concrete even in the case of water binder ratioof 70%. No bleeding was observed, and concrete which had ractical strength for concrete structure was obtained.

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The paper investigates how significantly the errors in deflections and analysis model affect backcalculated layer moduli. The Monte Carlo simulation and sensitivity analysis are utilized for this purpose. It is found that as number of repeated measurement increases and as number of measuring points increases, the effect of error in deflection reading decreases, but that of analysis model error remains same. Furthermore by using the sensitivity analysis, confidence regions of backcalculation moduli, radial and vertical strains are derived. This will serve as a useful tool for reliability analysis of pavement structure from FWD test.

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The mathematical modeling for water migration of concrete of which properties are changes from homogeneous to non homogeneous material applied the external load, is presented in detail. Then applicability is confirmed by comparison with the experimental results, and the relationship between crack widths and permeabilities are investigated. In proposed model, concrete, which is composed of aggregate, cement paste, water, interfacial crack between aggregate and cement paste, and crack band, is considered as the composite material, and discontinuities for displacement and hydraulic gradient on cracks are considered in micro-level.

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In this study, we developed a network level pavement management system based on dynamic programming. Using this system, we can decide its optimal repair program in the case when the total budget of the network during its analysis period is given.

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A series of laboratory tests and a full scale test pavement were carried out to examine the effects of classified fly ash (CFA) on improving quality and workability of roller compacted concrete (RCC) pavements. From those experiments, it became clear that CFA can improve the compactibility and reduce the unit water content. Furthermore, CFA can contribute to increase RCC slab thickness up to 35cm executed in one layer without loss of flexural strength in lower part of compacted slabs. These are desirable results to apply RCC for heavy duty pavements such as airport and seaport pavements.

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As a source of temperature rise, the hydration heat of cement in concrete has to be modeled for thermal crack control in the durability design. This paper is to propose the multi-component model for hydration heat applicable to wide variety of portland cement types. Specified chemical components of clinker minerals are treated as characteristic parameter of cement in the model. The hydration heat rate of each mineral compound is expressed with the referencial heat rate at constant temperature and the thermal activity based on the Arrhenius's law of chemical reaction. The proposed model was verified through the analysis of the adiabatic and semi-adiabatic temperature rises.

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A new technique for modeling the crack behaviors of concrete structures is described, where the softening band inside the element is represented by two rod elements whose behaviors are based on the fracture-oriented constitutive relations. This new method, like the discrete model, can reflect the localized nature of cracking, and at the same time can easily be applied without the difficulty of modifying the existing finite element mesh and pre-defining the concrete crack. In this paper, examples are given to show the phenomenon of crack localization and to show the objectivity of this method.

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This paper describes and discuss the results of an experimental study on the bond characteristics of fiber reinforced plastics in concrete and the transfer length for pretensioned type prestressed concrete structures.
The experimental results are then used to derive a simple relationship by using a family of curves with varying coefficient of friction μ, and poisson ratio ν against transfer length of FRP rods.

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Change in phase composition, pore structure and compressive strength of mortar due to carbonation was studied experimentally by controlling other parameters such as initial water curing, type of cement and concentration of CO₂. Then relationship between compressive strength and pore structure was obtained. It was also found that carbonation doesnot only change pore structure but also the matrix strength of mortar. Strength development of carbonated mortar has been explained not only by change in pore structure but also in phase composition.

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Microcomputer methods are widely used to backcalculate pavement layer moduli from deflections measured on the pavement surface. To increase the precision of the backcalculated moduli, a new, layer moduli backcalculation method based on the stable deflection was developed for concrete pavements. This stable deflection is defined as being independent of the slab modulus. Thus, it is a critical parameter for uniquely determining the foundation reaction modulus and for further backcalculating the slab modulus.
This procedure was used to evaluate the structural condition of concrete pavement in a working airport, and the usefulness of the method was verified as a result.

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