Prestressed concrete continuous box-girder bridge with hinge at mid span is one of the popular type of bridge, and many bridges of this type have been constructed in highway. It is evaluated in its cost performance in construction. On the other hand, there are some reports on its repairment for reduction of its function such as its large time dependent displacement due to creep and shrinkage in concrete. This paper describes the result of investigation about certain factors which affect on such displacement by the use of an analytical method as well as field observations.

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Reinforced polymer impregnated concrete beams are manufactured by the processes of curing, drying, evacuation, impregnation, and polymerization. The initial stress of concrete in the reinforced polymer impregnated concrete beams can generally be tensile stress. Therefore, it is important to grasp the initial stress in accurately analysing the flexural behavior of reinforced polymer impregnated concrete beams. The strain generated in each manufacturing process is studied experimentally as to the reinforced polymer impregnated concrete beams using expansive concrete and steel fiber. Based on the experimental results, the methods for estimating the initial stress of the beams are proposed.

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A method for estimating crack spacings of reinforced concrete beams subject to flexure is proposed. In the proposed method, it is assumed that the tensile extreme fiber stress of concrete between each pair of adjacent cracks is caused by the sum of two tensile stresses. The one is the tensile stress of concrete based on the model of uniaxial tensile test of the reinforced concrete prism. The other is the tensile stress of concrete caused by the compressive resultant force acting eccentrically on the concrete at the cracked section. It is presented that the crack spacings of reinforced concrete beams can be estimated with relatively good accuracy by the proposed method.

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In order to assess durability of binders, authors have analyzed liquid and solid phase of mortar specimens made from ordinary portland cement, flyash, blast furnace slag and silica fume which have been mixed. Liquid phase was analyzed by the method of measuring ion concentrations in pore solution. Solid phase was analyzed by powder X-ray diffraction and differential thermal analysis. Specimens were sealed cured and submerged in saturated NaCl solution. The results were obtained as follows. The trinary mixture of cement, flyash and slag is most durable to alkali-aggregate reaction because alkali ion concentration of pore solution is the lowest. The trinary mixture is most durable to salt contamination because chloride ion concentration from environment is lowest.

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We were proposed a practical monitoring method for concrete placing by thermography, using an infrared radiometer, for measuring the discrepancies of temperature on the external surface of forms. The height of concrete layer can be determined during placing, and voids and honeycombs caused due to poor consolidation in concrete can be located. In this paper we tried to find out the classification method for the defects in concrete. We applied the image processing and obtained satisfactory results to improve detection accuracy.

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Paying the attention to the fracture around coarse aggregates and of mortar, fracture mechanism of concrete on split-cylinder tensile test is investigated. Split-cylinder tensile tests on specimens with the diameter 30cm are carried out. Stress-strain curves are obtained. These experimental results and the analytical results in plane elastic problem are used to investigate the fracture mechanism. These analytical results are stress singular values at a corner of inclusion, a debonded tip and a crack tip in linear fracture mechanics. On the basis of the fracture mechanism, splitting tensile strength of concrete is discussed.

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Longitudinal surface cracking (LSC) is one of the major problems of asphalt pavements. In this paper, our assumption, that LSC is induced by tensile strains in the pavement close to tire edge at high temperature, is discussed based on FEM analysis. Surface temperature conditions in summer are investigated by the measurements conducted on an experimental pavement and an actual road. The FEM analysis considering the measured temperature distribution in the surface course shows that large tensile strains occur in the pavements close to tire edges at high temperature and the strain is concentrated at the tip of a small crack induced at the surface. It is also found that large compressive strains occur at tire edge. The strains could heal up micro cracks in the pavement, if its surface is not hardened.

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Effects of vacuum and other dry environments on properties of hardened mortar are discussed aiming at studying feasibility of lunar concrete. Mortar specimens cured in water for first several days were exposed to various dry environments which include; (1) a vacuum, (2) furnace dry at 110°C for 24 hours immediately before strength tests, (3) air dry at 20°C and 60% R. H., and (4) continuous furnace dry at 110°C. Weight losses and strength gains caused by the drying effect were observed for most of the dried specimens. Since the vacuum dried specimen showed the largest strength gain among these specimens, it was expected that well-cured mortar could be used in a vacuum environment.

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Expansive demolition agents have been widely used to demolish rocks and concrete structures. To design the demolition works using expansive demolition agents rationally, it is important to estimate the expansive pressure exactly and to determine its action on the inner surface of a borehole. The authors have developed new pressure transducers which can directly measure the expansive pressure in a borehole. Several variables affecting the nature of expansive pressure in a borehole were investigated with the transducers. As a result, we determined the following: 1) Expansive pressure is transmitted in a manner similar to that of fluid. 2) The influence of the physical restraint of surrounding materials is very small. 3) The expansive pressure depends on thermal conditions including ambient temperature, but the relationship between expansive pressure and the degree of hydration of CaO is plotted on the same curve without dependence on temperature.

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This paper describes the basic properties of permeability coefficients which are needed to evaluate the function of drain asphalt. It is also aimed at showing the conditions needed for in-situ test to check the functions to be applied for proper construction management or maintenance. Then, a new in-situ test method which can estimate the permeability coefficient quantitatively, and not qualitatively as have been done in most research, is presented. The accuracy of the new method is also investigated. Generally, the permeability of drain asphalt is anisotropic, and the flow is turbulent which is out of the range of Darcy's law. The new method shows good accuracy in practical applications.

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Experiments were carried out by an alternative x-ray technique using contrast medium to investigate the inside behavior of the compact tension concrete specimens. As a result, successful detection of fracture process zone that was consists of numerous fine cracks forming from the tips of notch cut in the tension specimen was possible. The fracture process zone increased in width with larger aggregate. The fracture energy G_F calculated by the area of the fracture plane also increased with larger aggregate. The fracture energy W_F calculated by the volume of the fracture process zone was nearly constant regardless of the aggregate size.

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This paper describes the use of rutting depth data measured by automatic high speed devices. This kind of devices was developed in 1985 by four different firms. Though enormous data have been acquired since then, they have not been used for numerical analysis. The authors have been trying to find the method of rational treatment of these data and have come to the following conclusions from the analysis of Metropolitan Expressway.
(1) Rutting depth values at a certain service period cannot be determined as one value, but should be treated as they are statistically distributed.
(2) Future rutting depth and volume of rehabilitation required can be roughly estimated.
(3) Rutting depth data measured by automatic devices can be used for numerical analysis according to the method described in this paper.

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One underground concrete structure was severely damaged and its deterioration was thought to be caused by metabolites of microorganisms. In this study several types of bacteria in a soil around the structure were isolated and cultured under aerobic condition, and mortar simulation tests using the bacteria were performed in addition to analysis of composition of metabolites of bacteria. As a result, calcium ion was dissolved out from mortar soaked in the culture medium bred with the bacteria, and it was found that much organic acids and carbonic acid were metabolized by the bacteria. It has been known that concrete could be severely damaged by anaerobic bacteria, but this study suggests that organic acids and carbonic acid metabolized by aerobic bacteria could also cause concrete deterioration.

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Importance as well as difficulty of pavement management planning at the project level lies in pavement rehabilitation timing and selection of rehabilitation methods in order to minimize maintenance and rehabilitation costs during pavement life time. Timing and rehabilitation methods make planning difficult and less reliable due to the actual life of pavement differing from its design life and tending to vary widely for various reasons. This paper proposes an optimal method for pavement management planning based on probabilistic dynamic programming (PDP), which can include uncertainties in a statistical sense. Efficiency and reliability of PDP are demonstrated through example problems.

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One of the most common backcalculation procedures from nondestructive testing data is called the Gauss-Newton method which evaluates the layer stiffnesses of pavement from a set of measured surface deflections. On the other hand Uzan and his coworkers have utilized the Hook-Jeev's pattern search algorithm to find the layer modulus ratios before they obtain layer moduli. The use of modulus ratios is expected to improve computational efficiency due to a reduced number of unknowns. Hence the authors developed a new Gauss-Newton algorithm based on the reduced number of unknowns and demonstrates its efficiency and stability through example problems.

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When we measure expansive pressure of expansive demolition agent, “outer pipe method” has been generally adopted, which is calculated by the strain of strain gauges put on the outersurface of steel pipe. But in this method, steel pipes are not reusable because hardened materials in steel pipes are too hard to remove. Authors discovered that expansive pressure of expansive demolition agent is transmitted in a manner similar to that of fluid. And utilizing this character, authors developed new measuring method of expansive pressure using pressure transducer. This paper examines the accuracy of measuring value comparing the conventional outer pipe method. Test result are as follows: The standard deviation of expansive pressure using this method is 40% less than that of using outer pipe method. Besides, steel pipes are reusable due to the taper rod set inside the steel pipe when using this method.

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