To enhance current seismic performance verification measures on crucial civil engineering structures in nuclear power plants, we examined the effects of vertical ground motions on seismic performance of reinforced concrete underground structures. For this purpose, computational works using nonlinear FEM analysis were performed for representative structures such as circulating water pipe supporting duct and water inlet pit. Emphasis was placed on the response nature of these structures subjected to simultaneous horizontal and vertical ground motions and the response fluctuation arising from peak value time lag of respective ground motion. Finally, the handling of vertical ground motion in terms of a seismic load in the seismic verification system was discussed.

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In this study, the fundamental properties and mechanical behaviors of thin plate units of the 10mm thickness using a three-dimensional hollow structure glass fabric and expansive paste were examined. This plate unit has cracking strength of 15N/mm², flexural strength of 70N/mm², and high-durability.
This plate unit was used as highly durable permanent formwork of RC beam, and then the loading tests of RC beams were carried out. The ultimate load and stiffness of RC beams which applied the plate as permanent formwork were improved by using the silica sand spraying between concrete and plate.

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It is clear that there is some effect of the shear reinforcement with stirrups in deep beams. However the quantitative evaluation has not been enough and the mechanism has not been clarified. In this research, these are examined by the model experiments and the analysis. As a result, it is clarified that stirrups expand the concrete fracture area and the effect of the shear reinforcement is influenced by the shear span ratio and the shear reinforcement ratio. Based on the experimental results, the accurate calculation method of the shear strength of deep beams with stirrups is proposed.

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Subdividing the cross-section of a main girder, into suitable sections in a factory-made precast segmental bridges, was a viable solution for the construction of bridges that were difficult to build using conventional techniques, considering the weight limits on the national routes and narrow roads as found in Japan. However, the subsections need to be made monolithic in site. To connect the individual box section to form a twin box girder, a double looped joint connection developed by the authors was adopted. This paper describes the flexural behavior of the transverse RC slab formed by the monolithic joint and its mechanical characteristics based on flexural load tests. Comparison is also made on the flexural behavior and on the safety of such joints with the conventional reinforcement arrangement. As a result, valuable information was obtained for adopting this innovative technique for practical applications.

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The ratio of asphalt pavement failures due to stripping is increasing. The examination of property of stripping over a long term and the method of improving it are needed to develop the technology of pavement for used over a long term. In this study, immersed wheel tracking test was performed and measured the time of destruction. In this test, mechanism of pot-hole in asphalt pavement on bridge-decks was researched. And a sort of aggregates and structure of pavement were examined to improve the anti-stripping property of asphalt pavement. The property of stripping of mixtures that had high anti-fluidity by mixed with plastic pellets were researched, too.

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Aim for the paper is to propose a rational panel point structure of PC bridge with steel truss webs. First, connection details of compressive steel diagonal to panel point concrete are examined, in which 4 types of connecion models are comparably studied through both model tests and FEM analysis. Second, a panel point model crossing compressive and tensile diagonal is examined by fatigue test, loading capacity test and FEM analysis. Special attenstion is paid on cracking mechanism of panel point concrete and ultimate loading capacity. Last, from both the experimental and numerical results obtained, discussion is made to find rational panel point details from the aspects of serviceability and ultimate limit states.

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It is useful in an urban expressway to reduce a section of concrete bridge piers used high strength reinforcing bars. There is a JIS standard for SD490 bars, but the standard provides for lower elongation to failure than ordinary bars. There was concern that lower elongation fatigue failure lead to early failure of the axial bars. The cyclic loading test was carried out on a specimen bridge pier using D490 for the axial reinforcements. It was found that the ultimate displacement could be calculated with seismic design. In fatigue tests of deformed bars with buckling, it demonstrated that SD490 bars had fatigue strength in the same class as SD345 bars. Utilizing the rebar fatigue life obtained from these results, it was found to be possible to use Miner's rule to compute failure cycle of axial reinforcements in a reinforced concrete bridge pier.

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According to the appearance of salt damage occurred in concrete structures, many investigation data on chloride contents in the concrete have been reported and accumulated. They are very important but are thought to be far from the effective use. In this research, data of the chloride diffusion into concrete which were investigated and reported for the past 28 years in Japan were arranged as a database. And, on the base of the database, diffusion coefficient of chloride and chloride concentration on concrete surface were evaluated quantitatively with influence of some factors to them, such as water cement ratio, the kinds of cement, unit weight of cement, construction years of structure and investigated objects. Finally, it was made clear that the database constructed in this study were quite useful for the chloride diffusion process into concrete.

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In case that a defect exists inside of concrete structure, the temperature of the surface of the defective portion will become higher as compared with that of sound portion in the daytime. The detection of the defect becomes possible by sensing the temperature distribution of the surface in the thermal image. However, detecting the defect in the thermal image is greatly influenced by environmental conditions, such as sunshine, and temperature.
Therefore, in this study, we observed the thermal images of the railway viaducts in the field and made numerical analyses of the heat balance model based on the observed data to verify in which quantitative condition the defects were able to be detected using thermal image. As a result, we propose an efficient inspecting method for a defect inside of concrete structure using thermal image.

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Crack data acquisition system with CCD camera was developed, and diagonal cracks and flexural cracks generated in reinforced concrete beams were measured in detail by this system. Crack width distribution and crack angle distribution, total length of crack, average crack width and crack area were calcurated using detailed crack data.
Relationship between crack data and damage degree of concrete beams were considered. It was found that crack density is suited as damage index of concrete structures.

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It is necessary to understand the influence of environmental conditions quantitatively to apply evaluation methods for durability of carbonation to existing structure because carbonation rate varies by environmental conditions. In this research, it is shown that carbonation rate varies by height in columns, the sunshiny and rain condition, based on investigations of railway RC rigid frame viaducts after tens of years from completion. Then, it is clarified to be able to presume carbonation depth within about 10mm in the error margin when the evaluation method that JSCE adopts is used.

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The objective of this research is to study the creep and drying shrinkage mechanism of concrete based on microscopic approach. The authors experimentally studied drying shrinkage and creep behaviors by exchanging water inside for various liquids in order to investigate the influence of liquid characteristic in micro-pore. As a result, shrinkage and creep occurred only when water existed in pores. Furthermore, when the specimens are submerged with water, almost all the pores including nano-scale pores are saturated, whereas the pores are partially filled with other liquids. The experimental fact suggested that special characteristics of water in micro-pores may control shrinkage and creep behaviors.

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X-ray system has often been employed in order to survey the arrangement of steel-fiber in concrete. The arrangement of plastic fiber, however, cannot be sufficiently evaluated by X-ray system. This paper presents a discernment method of plastic-fiber in concrete, and proposes the evaluation method of orientation factor. Black light and image analysis are employed for obtaining the orientation factor of vinyl fiber. Furthermore, the arrangement of else plastic-fiber is evaluated by using an image of colored concrete with phenol phthalein. By using such evaluation method, this study investigated an orientation factor of plastic-fiber in concrete lining of model tunnel.

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This study investigates the effect of length change at early ages on flexural performance of reinforced high-strength concrete members, and proposes design equations for evaluating the crack width and deformation of RC flexural members considering the effect of length change prior to loading. The results show that length change before loading affect serviceability limit states such as flexural cracking load, crack width and deformation of the RC beams. In addition, flexural crack widths and curvatures of RC beams can be accurately calculated by the proposed equations, taking into account the stress change in the tension reinforcement from the state where the stress in concrete at the depth of the tension reinforcement is zero.

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Early-age concretes with high degrees of water saturation were examined for their deterioration behavior and internal damage by subjecting them to slow freeze-thaw cycles which simulated a severe cold weather condition in Japan.
It was found that, if concretes were exposed to cold weather at a compressive strength level higher than 4.0N/mm², their internal damage during the first winter would be such magnitude as to cause little expansion. Concrete with a lower water content than its sealed condition had little internal damage, provided its water-cement ratio was smaller than 60% and exposure strength exceeded 5.0N/mm². Lowering water-cement ratio was quite effective to prevent the frost damage in concrete. A proposal was also made for the length of protection period for cold weather concrete.

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The relation between vibrations of concrete members due to impact and radiating sounds is investigated. In experiments, resonance vibrations of the flexural mode and the longitudinal mode were studied by using bar-shape and flat-slab specimens. For the measurement, an accelerometer and a microphone were used to record the surface vibrations and radiating sounds generated by impact, respectively. The relation between the surface vibration and the radiating sound was investigated by frequency spectra. As a result, the difference of surface vibrations and radiating sounds was clarified from the viewpoint of the resonance vibration and the sound source.

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Generally, backcalculation analysis is greatly affected by errors in the measured deflection data. Average of several data set is normally used in static backcalculation in order to reduce effect of these errors. However, this procedure can not be employed in case of time series data. A rather time consuming procedure is used, where backcalculation is performed for each data set and then an average of the backcalculated layer properties is determined. This paper proposes a new method where several sets of time series data can be used in dynamic backcalculation to determine an average result. Computation time is similar to the case of one data set. Analysis domain and the number of nodes were also examined.

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In this study, the generalized Voigt model is employed to represent the dynamic behavior of asphalt mixtures. Parameter values of the rheological model were identified using a method based on a system identification approach. From the results of parameter identification using dynamic flexural test data, it was found that the frequency range that the model covers broadens with increasing the number of elements and that the eight elements model covers the range of 0.01 to 100Hz. The estimated parameters showed that the elastic moduli of the model are independent on temperature, while viscous moduli decrease with temperature rising.

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A macroscopic constitutive law specified in the centimeter scale of a referential control volume was proposed by coupling with nano-micro pore structures and thermodynamic status of water in the fine spaces. A solidification theory, in which finite fictitious clusters are formed with the hydration progress, was applied to represent both aging and hardened concrete Pore water in a cementitious material was classified into several components condensed water in capillary pores, gel water, adsorbed water, and interlayer water. In the model, each of these components is assumed to play a different role in macroscopic mechanical behaviors according to their intrinsic thermodynamic natures. The proposed model was verified with experimental data under arbitrary couplings of ambient temperature, relative humidity, and sustained external load

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Due to expansion of corrosive product, various patterns of cracks are nucleated around reinforcement in concrete. Crack kinematics are identified by acoustic emission (AE)-SiGMA (Simplified Green's function for Moment tensor Analysis) procedure. Numerical analysis is conducted by the boundary element method (BEM) based on the concept of the linear elastic fracture mechanics (LEFM). Crack traces due to corrosion are simulated by the two-domain BEM. The behaviors of the dimensionless stress intensity factors (K_I/K_IC and K_II/K_IC), and the cracking modes are studied for the different types of crack patterns. It is found that cracking mechanisms due to corrosion of reinforcement are mostly associated with the mode-I failure.

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This paper proposes a structural damage identification method using genetic algorithm. This method estimates the location and severity of damage by minimizing the difference between measured and estimated natural frequencies and by using some a priori information on damage such as test results and theoretical guesses. By giving a priori information which contains some correct information on the damage, the importance of a priori information and the influence of information quality on estimation accuracy are examined. As a result, it was shown that better a priori information produces better estimation accuracy and that the influence of errors in a priori information will be reduced in estimation.

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The structural damage identification method using genetic algorithm, which estimates the location and severity of inflicted damage by considering natural frequencies and inferred damage patterns has been proposed by the authors. In this paper, the validity of this method is tried by applying it to the estimation of the progress of damage due to cyclic uniaxial loading of a rectangular concrete specimen. At each loading stage, impact sounds and acoustic emissions are measured. By using these as a priori information, the decreased degree of elastic modulus is estimated. By implementing it successively, it is possible to estimate the progress of damage.

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