The unsaturated soil is a heterogeneous and non-uniform material which is composed of solid-phase, liquid-phase and gas-phase, i. e., a multi-phase material. In this paper the relationship among inter-particle force, suction and Bishop's parameter χ in effective stress equation are derived based on Kitamura Model which is based on the mechanical & probabilistic consideration on the scale of particle size. Then the numerical experiments are carried out to obtain these relations and the discussion on the obtained results is done. It is found that the contribution of suction to inter-particle force at contact point depends on the grain-size distribution and void ratio of unsaturated soil.

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The purpose of this paper is to evaluate displacement property of sand in three dimensions using X-ray CT. Here in this paper, the displacements in the soil are visualized under triaxial compression. So called “Yamazuna sand” which has the wide range of the size of soil particles is used in this test and the displacement property is evaluated by tracing a large number of the represented soil particles in the resulted X-ray CT images. First of all, the displacements in the soil under one dimensional compression are visualized in order to develop the proper image processing analysis and this method is also used in the case of triaxial compression test. Finally, the displacements in the soil specimen are visualized and also quantified as well in three dimensions.

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This paper examines the effects of particle properties such as particle shape and grain size distribution of particle assemblage on the bearing capacity of railroad ballast in numerical simulations with discontinuous analysis. Here, two evaluation indexes of particle shape, namely “angularity” and “sphericity”, were employed. To evaluate the effect quantitatively, a series of numerical simulations that regard a ballast particle as a regular or an irregular polygon were performed. As the result, it can be observed that the particle shape of numerical models, especially the angularity has a greater effect on the bearing capacity of railroad ballast than the grain size distribution, and that the imitation of the shape of real ballast particles makes numerical results similar to experimental results.

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This paper shows the conditions of the occurrence of waves on the high viscous flow with solid particles as viscous debris flow surges. And it is discussed about the theoretical and experimental results considering the flow mechanism of the viscous debris flow as a high viscous laminar flow laden with solid particles. Under the rectangular channel, laminar flow condition and the flow with constantly dispersed solid particles in the depth, the occurrence of the roll wave dose not depend on the viscous and concentration of the particles.

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This paper presents recent progress of a multi-agent simulation for post-earthquake mass evacuation process, assuming a state where various people run in an un-ordered manner. An agent which can see, think and move is constructed with special function of passing, and a simulation model in which agents move around is automatically constructed by using available GIS. The multi-agent simulation is applied to a town which has network with small and winding roads, and the results of the evacuation process of various agents running in an un-ordered manner are discussed.

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This study aims at clarifying the effect of embedment of cellular bulkheads on the seismic stability by using the two-dimensional earthquake response analyses. We classified the deformation of cellular bulkheads into two portions: deformation in the foundation ground and the deformation by the inclination of the wall body. We found that deformation in the foundation ground is reduced and that by the inclination of the wall body is increased in accordance with the embedded length. We discussed the reason by observing the shear stress and the shear strength of the ground. We also found that the deformation mechanism was not necessarily in harmony with that by the present design code from the viewpoint of the effect of embedment

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Hydraulics experiments showed that under undular bore, the maximum wave height rise was 1.4 times that under still water without flow and the wave height was up to twice the initial wave height at the downstream end. One-dimensional calculations using conventional shallow-watertheory equation unestimated the calculated wave height and over estimated the wave velocity, relative to experimental measurements. Calculations using a Boussinesq-type equation produced good agreement with experimental data.

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The liquid sloshing in petroleum tanks is one of severe problem against huge earthquakes such as the Tokai Tonankai and Nankai earthquakes. In this study, we are developing a damper to reduce sloshing. The damper consists of partitions with slits which gives resistance to liquid moving in the tank. Model experiment and numerical simulation are performed to study the effect of the damper. As a result, the experimental results show that the present dumper is effective to reduce sloshing of cylindrical tank. And the numerical results show that our numerical simulation method can accurately simulate the sloshing behaviors of the cylindrical tank in which the dumper is installed.

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A new IES wrapper is constructed for an advanced simulation program, UNIVERSE, for dam seismic response analysis. Modifying the program structure of the member functions and finding an alternative of generating visualization data are the two key strategies in constructing the wrapper. The performance characteristics of the new wrapper such as scalability and modularity are compared with those of the previous one. The unified visualization of a virtual city in which a large arch dam is located is made, to demonstrate the performance of the new wrapper which handle huge amount of UNIVERSE results.

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Two typical suffering cases of slightly-inclined residential ground at the time of Mid Niigata Prefecture Earthquake 2004 are examined. Around the houses on the thickly filled ground, large residual settlement was observed clearly. Probably, the liquefaction of saturated sand in the ground may be related to the damage. In this study, the mechanism of damage is examined based on the 2-D dynamic elasto-plastic finite element method. In the analysis, the material parameters have been determined based on the distribution of shear wave velocity in the ground, which was estimated by the surface-wave investigation. It is shown that the dynamic elasto-plastic finite element analysis with the surface-wave investigation is very effective for the evaluation of the seismic stability of the ground.

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This paper presents a method of estimating the elastic properties of the soils and their variation with depth using the characteristics of P-SV wave fields caused in the surface of an elastic multi-layered half space by the vertical harmonic point load applied also on the soil surface. To demonstrate the capability of the proposed method, the two numerical examples are presented, for the estimation of S wave velocity, P wave velocity and thickness of each soil layer, using a three-layered half space and a five-layered half space. In the numerical examples, the stiffness matrix method is used for an accurate simulation of all P-SV wave fields.

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Earthquake resistant design of quay wall is usually carried out by using pseudo-static method for Level-one earthquake ground motion. Although the method is easy to be implemented, it is not necessarily in harmony with the failure mechanism of quay walls. Therefore, it is very important to establish an earthquake resistant design method of quay walls that is both simple and precise enough for practical design. This paper presents a fundamental study as a first step to establish a simple evaluation method of the seismic performance of sheet pile quay walls with vertical pile anchorage. The proposed method employs frame model analysis and one-dimensional earthquake response analysis of ground. We found that distributed and concentrated soil spring is adequate for sheet pile and vertical pile anchorage respectively. We then examined the applicability of the proposed method by comparing the results by the proposed method and those by the two-dimensional earthquake response analysis.

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Dynamic rupture propagations on seismic faults are numerically simulated based on finite element method, finite-difference method and boundary integral equation method. Boundary integral equation method provides the accurate stress field near the fault surface, while the method is just applied for a simple homogeneous medium. Domain based method, such as finite element method, is applicable to complex media, while low accuracies for the stress field near the fault surface are expected. We apply a combination method of integral equation method and finite element method. Fault rupture process and excited wave propagations are numerically calculated in the simple half space 2-D P-SV medium.

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It is difficult to evaluate the sloshing load acting on a fixed roof of tank because it depends on the collision of the liquid to the roof. In this paper, the SPH simulation was introduced to evaluate the load acting on a fixed roof. The results obtained by the simulation showed good agreement with those obtained from other method. In addition, the effect of the roof-liquid clearance on the sloshing load acting on the roof was investigated by using the SPH simulation. The load acting on the roof increases with the tank width even though the clearance between the roof and liquid is constant.

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This paper presents calculation method for displacement from acceleration record in easy way. Using recursive digital filter is good for easy calculation, so simple formula is proposed, which is combined of integration and low-cut filter. Shaking table test is carried out in order to investigate accuracy of calculated displacement The movement of the shaking table is measured by laser displacement meter, and two acceleration meters are installed on the table. Though data from laser meter include long period noise, calculated displacement is rather consistent with laser meter, after filtering noise. Proposed digital filter is useful for on-site health monitoring measurement.

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This paper prensents a new GPS positioning algorithm and show the results of performance evaluation. This algorithm takes account of the condition that the GPS antennas do not move in a short period of time and are deployed densely in a local area. These conditions enable to apply a linear function to the time seires data of double differenced carrier phases. This constraint helps to improve the condition number of coefficient matrix of unknown vector in the observation equation. Then, the accuracy and reliability of GPS positioning are improved. In the performance evaluation, at first, two experiments are conducted in an ideal condition to observe carrier phases for 24 hours. The observed data is analyzed using the developed program and the results show that the new algorithm gives better accuracy and success rate of GPS positioning.

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It is very important to find small damages such as cracks on steel structure with less works. Because, for example, we have to detect quickly the health level of structures after a big earthquake. For this purpose, we propose a method using the Hilbert spectrum which is a time-frequency distribution obtained from the Hilbert-Huang transform. To discuss the applicability of the proposed method we carried out some experiments and found that the waves with higher frequencies show more quick damping than waves with lower frequencies for damaged steel plates. Consequently, this suggests that we can possibly detect the damages from the damping of waves in high frequency range.

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This paper proposes two indices to measure the similarity of seismic waves based on the time-frequency characteristics. One index uses Wigner distribution and it can represent energy misfit of seismic waves on the time-frequency region. The other uses wavelet transform and it allows us to discuss envelope misfit and phase misfit of seismic waves. The performance of the two proposed indices are compared based on the numerical examples. The results indicate that the index using wavelet transform is suitable for similarity estimation of seismic waves in the time frequency domain.

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Two-in-tandem circular cylinders are an important combination, which is widely encountered in several areas such as flow around bridge piers and vegetated open channel flow. One of typical Japan-river characteristics is the sudden change of discharge due to big amount of rainfalls so that the bridge piers are affected by surrounding instantaneous flows such as separated and wake flows which lead to the serious scouring problem. In order to reveal such kind of flow effects, flow visualization around two-in-tandem cylinders is conducted under non-submerged condition in the present study by means of particle tracking velocimetry (PTV), which is developed to estimate more accurate velocity under conditions of large-velocity difference. In addition, the POD analysis of typical fluctuating pattern, spectral analysis and conditional sampling analysis are applied to reveal the coherent structures.

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The discharge formula of side-weir constructed beside of a rectangular open-channel flow was obtained by De Marchi. However, such a formula which is able to apply in trapezoidal open-channel flows has not been suggested as yet. In this study, the discharge formula of side-weir constructed beside of a rectangular open-channel flow can be obtained under the condition that the specific energy is constant in the flow direction and also that the friction and bed slope are negligible small. Rather, the discharge coefficients were obtained from the present experiments, in which the Froude number, relative flow depth, relative weir height, relative weir length and side-wall slope were changed. A new discharge formula was suggested. It was conformed that the accuracy of the suggested formula is high as compared with that of previous one.

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The investigation method for generation of cavitation in return-flow type submerged energy dissipater has not been established enough, from the problem in the measurement in the hydraulic model test, especially, when the gate is not opened completely and the released water from the gate has the downward angle. Then, in this research, numerical analysis for flow in return-flow type submerged energy dissipater is carried out, in a case study of the A Dam. As a result, it is clarified that there is a possibility of generation of cavitation on the end-wall when the gate is opening almost completely, or on the bed of the energy dissipater when opening ratio at the gate are about 10%.

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Fishways are river constructions which facilitate migration of fish. The pool-and-weir fishway is typical type. There are three types of flow regimes in pool-and-weir fishways such as a plunging flow, streaming flow and intermixed flow of plunging and streaming flows. Onitsuka et al.(2005) found that the number of parameters of the plunging flow are four. However, it is quite difficult to conduct the systematically experiments. From the point of view of the engineering, it is necessary to predict the flow pattern roughly and easily with a few parameters. If effects of some parameters on the flow regime are small, such parameters may be neglected. In this study, order comparison of each parameter was conducted. As a result, the strength of effects of each four parameter on the flow regime is made clear. A new criterion formula, which can predict the flow regime in the pool-and-weir fishways with three parameters, was suggested.

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This paper deals with a computational method which enables us to predict the movements of arbitrarily-shaped objects floating on free-surface flows. The objects are modeled as rigid bodies represented by tetrahedron elements. The present method is applicable to non-potential flows, since it is based on the MICS, which is a computational method for incompressible multiphase fluids. It was shown that natural frequencies and stability of the initial attitudes of floating objects are successfully predicted by this method and that it is also effective to predict the movements of floating objects in wave flows.

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The wall function is one of approaches to treatsolid boundaries in turbulent flow analysis using the κ-ε model. The conventional one is based on the logarithmic law. The analytical wall function proposed by Craft et al. is not based on the logarithmic law. The feature of the analytical wall function is that the effects of the convective transport and the pressure gradient are reflected. In the present study, the analytical wall function is developed by the finite elementmethod and employed to a channel flow and a flow over a backward step. As a result, the analytical wall function effects the backflow in the region modeled by the wall function.

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Flows with large scale vortices are often observed in many natural, geophysical as well as anthropogenic activities. In this study, the Stuart vortices having both the singular points (the vortex and saddle points) are considered to study the basic turbulent properties. Using a realizable non-linear κ-ε A model, the approximate solutions are derived and numerical simulations are carried out. Using the approximate solution, the values of model constants are tuned considering the predictability of turbulent structures at the vortex center. The numerical results prove the effectiveness of the approximate approach, and reveals that the model with the estimated constants is applicable to simulate large scale vortices. The spatial changes in the topological structures of turbulent energy and turbulent stresses are found compatible with the previous experimental results.

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This paper proposes of real wind speed prediction method over complex terrain by using CFD. It is an attempt to convert the wind distribution on the computer into the scalar wind speed of a real scale in consideration of the correlation with the observed data. The reproducibility and the accuracy of the real wind speed were performed by using the high resolution elevation data with 5m resolution for the Noma cape wind power plant in Kagoshima prefecture. As for the monthly average wind speed, the error relative to the observed value was within 20%.

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Characteristics of wave boundary layer are key factor controlling sediment movement due to wave motion. Theory of solitary wave is suitable for representation of wave motion which enters into water area under still condition. Although there have been numerous researches on wave boundary layers, most of them have dealt with sinusoidal wave motion for simplicity. It is expected that the characteristics of bottom boundary layer under solitary wave motion is different from those under sinusoidal waves because of rapid accelerating effect. The present study describes characters of bottom boundary layer under solitary wave. Using an oscillatory flow generator, laboratory measurement of velocity profile is conducted. Furthermore, numerical experiment using Baseline k-co model is carried out to make a comparison with experiment regarding velocity profile, turbulent kinetic energy and wall shear stress.

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Numerical simulation of Tsunami propagation has been carried out based on four algorithms of wave dynamical equation. Besides non-linear shallow water equation which is common for the simulation, dispersive wave model (i.e. Boussinesq-type equations) is a challenge to make more reasonable model while taking care of the low computation cost. This paper discussed numerical simulation results of tsunami propagation model based on dispersive and non-dispersive models. Satellite image data is used to compare the numerical results with real field sea levels data of tsunami. Simulation results show that the dispersive models give better prediction but still need high computation cost while non-dispersive one give consistent result.

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In this study, the characteristics of inertia and viscous regions of shallow flow are investigated by means of dam break flow with finite volume occurring in a smooth rectangular channel. Inviscid fluid and viscous fluid, comprising of Newtonian and non-Newtonian are studied theoretically and similarity solutions describing both inertia and viscous regions are derived. Theoretical findings are verified with two numerical models: a depth averaged model and a Lagrangian grid-less model (MPS or Moving Particle Semi-Implicit).

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Large-Eddy Simulation (LES) technique has been applied to calculate the three-dimensional turbulent unsteady flow in the real intake channel of a small-scale hydroelectric power station. The method computes the motion of the free surface with a modified HSMAC method. The turbulence is modeled with a modified Smagorinsky sub-grid scale model with near-wall damping. With the total number of grid points of about one million, the complex and unsteady flow with localized vorticity can be reproduced reasonably well for the basic configuration as well as the case with a vortex-suppressing device. By using a similar grid that marginally resolves the near-wall flow, it may be used for predicting similar intake flows. The turbulence model, however needs an improvement to better representhe flow impinging on the end wall.

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In this study, the sloshing characteristics in a circular tank on an oscillation table are investigated. Firstly, laboratory experiments were conducted under the various hydraulic conditions, and the characteristics of water surface oscillation were examined. To simulate the flow fields in experiments, a shallow water equation in generalized curvilinear moving coordinate system was used, in which a pressure distribution was assumed to be hydrostatic, and linear and nonlinear solutions were derived. In addition, a Boussinesq equation is also applied. The sloshing characteristics obtained from the theoretical and numerical solutions were verified by comparing with the experimental results.

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Aquatic vegetation frequently determines the mean and turbulent flow sttucture in natural river and impacts the transport of sediment and nutrients. These vegetation communities are often observed to grow in stripe pattern or patches within main stream channel. In this paper, the influence that interaction of longitudinal vegetation zones gave the momentum transport and coherent vortex generation in an open-channel was examined experimentally. Laboratory experiments were conducted using a two-component electromagnetic current-meter and a particle-image-velocimetry (PIV). Results showed that horizontal large scale vortex generation significantly depended on the lateral distance between longitudinal vegetation zones and these vortices controls the momentum transporthrough the interaction.

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Enviromental problems about aquatic plants are now increasing in actual rivers. Coherent turbulence events such as ejections and sweeps are generated by the shear instability near the boundary between above-canopy layer and within-canopy layer. When wind-induced water-waves appear on the free-surface flows, a large amount of oxygen gas may be transported toward the vegetation layer, and it is infer red that the mass and momentum exchanges are promoted significantly by the coherent motions. It is thus very important in river environment to investigate these turbulence structure and coherent motions in such flows. In this study, we conducted turbulence measurements by using a high-speed PIV technique. It was found from time-averaged velocity profiles that some wave effects appear even in the canopy layer. The correlation analysis was also conducted in order to examine turbulence transport process promoted by the wind-induced air/water interface. Furthermore, relation between the coherent event and waves were revealed on the basis of the present PIV data.

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In this study, we conducted the fluid-particle simultaneous measurements in order to reveal the fluidparticle interaction mechanism in the developing stages of sand dunes. Instantaneous velocity vectors over the growing sand dunes were measured by the discriminator particle-image velocimetory (D-PIV) and discriminator particle-tracking velocimetory (D-PTV), which was developed by Nezu & Azuma (JHE, ASCE, 2004). In this D-PIV&PTV system, the fluid tracers and the sediment particles are discriminated accurately by their occupied particle sizes, and thus, the particle velocity U_p and the fluid velocity U_f can be measured simultaneously.
As the results, turbulence intensities and Reynolds stress became larger with the growth of sand dunes. There exist two coherent eddies behind dunes; one goes along the dune, and the other lifts up from the reattachment point when the kolk-boils occur.

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The open-channel flow with a side cavity is known to exhibit various types of free surface oscillations within the cavity zone. A typical type of oscillation observed is similar to the one by a seiche generated in a closed box; however it has been reported that other types of oscillation can also be generated depending on the geometrical and hydraulic conditions. In this paper, a novel technique for measuring two dimensional water surface variations as well as surface velocity distributions is developed and the technique is applied to the flow at the side cavity zone with various aspect ratios of the side cavity. The water surface variation is analyzed by the POD technique while the velocity field is measured simultaneously by the PIV method. It was found that the surface oscillation can be categorized into four types and the water surface oscillation within the cavity zone is closely correlated with velocity variation.

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Pool-riffle sequences are important for improvement of habitats and restoration of channelized urban streams. However, their hydrodynamic behavior has not yet fully understood to date. In this study, we pay attention to the flow characteristic of pool in pool-riffle sequence The pool was made at fixed bed condition imitating actual river channel of mountain section in a straight channel. 3-D flow structures in this open channel with a pool were analyzed by measuring three-dimensional velocities with electromagnetic velocimeters. A cylindrical separation vortex was generated in the case of rectangular pool. Flow is deflected toward the side pool in the case of trapezoidal pool. 3-D flow structures are changed with an increase of discharge and flow depth.

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The instability of water flow has been studied by a large number of researchers from a variety of points of view for a long time. In this study, a linear stability analysis is performed with the use of the Reynolds averaged Navier-Stokes equations and Darcy's law extended to more general cases in order to investigate the instability of flow on permeable river beds, and resulting water exchange between flowing water in rivers and seepage water beneath flat river beds. The spectral collocation method incorporated with the Chebyshev polynomials is employed in order to perform numerical solution of perturbed equations. It is found from the analysis that, in the case of permeable beds, flow becomes unstable in the range of small Froude numbers where flow is stable in the case of impermeable beds.

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This paper deals with the lateral intrusion process of water into porous media consisting of large grain size, which seems to simulate the storm water storage into pervious road sub-base from a side drainage channel, under constant water level and constant inflow discharge conditions. The common fundamental equations for solid-liquid multiphase flows with the inertia term are used as the basic model. The fundamental characteristics of lateral intrusion process are firstly investigated theoretically using the depth averaged equations with the inertia term and the viscous or turbulent drag force terms in the momentum equation. It is pointed out that there are distinct two power law regions with respect to time in the unsteady intrusion processes. The theoretical results are verified by carrying out the vertical 2-D numerical simulation and simple hydraulic experiment.

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In this study, conventional saturated-unsaturated seepage analysis or two-phase flow analysis of air and water through porous media coupled with 1/ƒ^-ζ model as the geostatistical model of hydraulic conductivity are carried out to investigate fingering flow caused by heterogeneity of soil or pore air. Results show that in multilayered aquifer that have relatively low permeability stratum between high permeability layers, fingering flow occur clearly under the middle stratum. In the ponded condition, the “fingering flow of air” occurs by pore-air pressure even if the variance of hydraulic conductivity is very low. The results of 3-dimensional analysis show that air flow paths are obviously changed by progress of time and water saturation distributions are more intricate than results of 2-dimensional analysis.

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In this study, conventional saturated-unsaturated seepage analysis or two-phase flow analysis of air and water through porous media coupled with 1/ƒ^-ζ model as the geostatistical model of hydraulic conductivity are carried out to investigate fingering flow caused by heterogeneity of soil or pore air. Results show that in multilayered aquifer that have relatively low permeability stratum between high permeability layers, fingering flow occur clearly under the middle stratum. In the ponded condition, the “fingering flow of air” occurs by pore-air pressure even if the variance of hydraulic conductivity is very low. The results of 3-dimensional analysis show that air flow paths are obviously changed by progress of time and water saturation distributions are more intricate than results of 2-dimensional analysis.

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Patterns of parallel submarine gullies with regular transverse spacing are observed at continental margins. These gullies are thought to be formed by turbidity currents. In this study, the existing model is extended to more general cases in which the slope profile is arbitrary and the entrainment of fresh seawater cannot be neglected. A linear stability analysis is performed with the use of the layer-averaged momentum and continuity equations of turbidity currents, a dispersion equation of suspended sediment, and the Exner equation extended for the seabed subject to erosion and deposition due to turbidity currents. The analysis shows that the dominant spacing of submarine gullies on slopes with arbitrary shapes is of the order of 800-1600 times the Richardson-critical layer thickness of turbidity currents.

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In order to estimate circulation process of nutrients and to improve the water quality in an inner bay, it is important to be evaluated characteristics of flow field at the first setout In this analysis, it has a problem with assignment of tidal level at open boundary, because it is impossible to get measurement values for arbitrary position and time. In this paper, it is presented a new method with the aid of a tide program, Naotide, for estimation of tidal level at open boundary. It can be calculated tidal level of any point and time, because Naotide is calculated it based on interplanetary forces. Effectiveness of the method was proved by applying it to calculation of tidal flow field in Harirnanada It could be effectively used for modeling and simulation of flow field, especially, in the case of existing several open boundaries.

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It is very important to reveal the horizontal eddy strucutre in meandering compound open-channel flows for predicting the transport properties of suspended sediments in rivers in flood. However, flow-visualization techniques such as PIV system, have not sufficiently been applied to such flows in previous studies, and thus, there is almost no detailed information on coherent turbulence such as the horizontal eddies in meandering compound open-channel flows. Therefore, in this study, we conducted PIV measurements with a high-speed CMOS camera. The time-averaged velocity distributions and coherent turbulence structure were investigated and considered on the basis of the present measured data.

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The time averaged characteristics of hydraulic jump such as a conjugate depth and the length of hydraulic jump have been almost clarified. The time averaged pressure distributions around the end sill are also measured by several researchers. On the other hand, bed materials near the roller of hydraulic jump are sometimes picked up by the pressure fluctuations, so that it is quite important to investigate on characteristics of the pressure fluctuations in and around the hydraulic jump. In this study, the pressure fluctuations on the bed wall in and around roller were measured with pressure gauges. Further, free surface fluctuations were also measured with supersonic wave gauges, simultaneously. It was found that the strength of the pressure fluctuations on the bed wall takes maximum at the toe of the roller. The values of the time averaged pressure are less than those of hydrostatic pressure and this tendency becomes more remarkable with an increase of the Froude numbers.

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Natural rivers, being predominantly meandering, are usually composed of a deep main channel and adjacent shallow floodplains. This results in a meandering compound channel. When the main meander channel is flanked by floodplains with meandering levee, it results in a doubly meandering compound channel. This paper explores the effect of bed slope on flow pattern in a doubly meandering compound channel. The effect of slope on the exchange of momentum between main channel and floodplain, flow patterns in the transverse and longitudinal direction, difference in magnitude between maximum and minimum velocities, retardation and deviation of flow fields, the position and strength of eddies and augmentation and reduction of the main channel discharge has been discussed.

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It is important to prepare sets of detailed and accurate experimental data obtained in a large-scale channel to develop a reliable numerical model for inundation flows. This study makes a detailed measurement of temporal and spatial variation of water depth for overland flows caused by the break of channel dyke. A two-dimensional numerical model is also proposed employing CIP-CSL2 method to directly capture the variations of flow and complex geometry within a computational cell. The comparison between the experimental data and the numerical results reveals that the present numerical model can reproduce the characteristics of inundation flows under steady and unsteady conditions and with and without buildings.

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This paper presents the micromechanical modeling of fiber bridging constitutive law of a discontinuous fiber reinforced composite (DFRC) under cyclic loading. Fiist, the derivation of fiber bridging constitutive law under monotonic loading is briefly reviewed to highlighthe approach to obtain the bridging stress carried by randomly distributed discontinuous fibers. Second, the relation between single fiber pa-out/push-in load amplitude and crack opening displacement amplitude under cyclic loading is derived. Third, fiber bridging constitutive l aw under cyclic loading is derived and obtained in two ways: numerically and analytically. Finally, the fiber bridging constitutive law is compared with experimental data of a cyclically loaded fiber reinforced concrete (FRC), and its validity is shown.

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RC structure sometimes suffers from internal defect caused by inferior construction or from internal damage caused by deterioration. In this study, post-peak behaviors of those beams were investigated both experimentally and analytically. The rock pocket was simulated in RC beams as an example of internal defects. The deterioration of concrete strength and Young's modulus, and breaking of lateral confinement caused by alkali-silica reaction (ASR), were simulated as examples of internal damages. The results of this study can be summarized as follows; The rock pocket and breaking of hoop tie deteriorate mechanical performances of RC member in post-peak region. The deterioration of mechanical performance was caused by the decrease in lateral confinement and can be simulated by changing the gradient of strainsoftening curve in strain-softening constitutive model of concrete.

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This paper presents a simulation analysis of fatigue crack growth by X-FEM (eXtended Finite Element Method). It is necessary to estimate fatigue crack growth accurately for prevention of fatigue fractures. In this simulation, the effective stress intensity factor range is applied to the propagation law of JSSC. To investigate applicability of the simulation, fatigue crack propagation analysis for linear crack was compared with experimental results of the past fatigue tests under constant amplitude loading at various stress ratios and biaxial forces.

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Damages of steel bridges from corrosion are the major factor in their replacement. From a view point of rational maintenance, it is necessary for the damage to be assessed by use of their ultimate strength. Therefore, this study develops a finite element method that estimate the ultimate strength of steel structures, and proposes a shell element that take into consideration with a process of volume being decreased by corrosion. With numerical example, the proposed method is demonstrated.

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