To investigate the evolution of grain crushing during extremely large shear under constant confining pressure, a series of rotary shear tests was performed for two types of sands with various confining pressure, shear strain rate and total shear strain. Grain size distribution after the test was also measured for each sample. It turned out that (1) all the specimens reached an identical critical state with the same shear stress ratio, void ratio and gran size distribution described by a fractal (or power-law) distribution after a sufficiently large shear strain application, (2) the plastic compression occurred rapidly in the early stage of the test, and (3) the shear rate (from 0.21 to 210 (1/s)) did not affect the overall behavior. Based on such observation, a micromechanical model that connects the single grain crushing behavior with the bulk shear behavior was proposed. The model successfully described that a decrease in porosity with shear strain is a straight line in log - log plot, and that the threshold strain from where the plastic compression dominates is related to the ratio of confining pressure to the single grain crushing strength.

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Dynamic mechanism of crater formation process caused by meteorite impacts plays an important role in the evolution of topography and geology on planet surface. The present study surveyed the morphological features and rock abundance of 136 relatively fresh impact craters on the moon by using Lunar Reconnaissance Orbiter Camera (LROC) of NASA and compared with 2-D Smoothed Particle Hydrodynamics (SPH) simulations. The simulation results quantitatively reproduced the diameter-depth relation and central peak formation. Moreover, it turned out that the material forming the central peak comes from several kilometers deep underground because of the circular slip mechanism commonly observed in slope failure analysis in geomechanics. It was also found that the large-scale circular slip modifies the morphological trend of crater which causes the bilinear relation of diameter-depth curve in log-log plot.

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This paper reports a numerical simulations about the pile-ground interaction behavior. The analysis code is the soil-water coupled finite deformation analysis (GEOASIA), which is capable of expressing the behavior of soils ranging from sand up to clay within the same theoretical framework. The elasto-plastic equation of the soil skeleton mounted on this code is the SYS Cam-clay model, which describes the soil skeleton structure (structure, overconsolidation and anisotropy) at work.
Analysis result shows comparatively good agreement with model test result. Moreover, further conclusion as follows can be derived with systematically conducted analyses. 1) With the movement of the pile, ground deformation occurs widely especially around the front of pile. 2) If loading speed is slow, density increases with ongoing migration of the excess pore water at the pile front which makes subgrade reaction force grows large. On the other hand, if loading speed is rapid, migration of pore water cannot be occurred which means that subgrade reaction force is smaller than that of slowly loaded case. 3) Virtually-imaged highly structured ground showed localized deformation with ongoing destruction of the structure which leads to non-smooth load displacement curve.

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This study attempts to present the theoretical analysis on the erosion of beaches adjacent to a river mouth which has got reduction of sediment supply and along-shore shifting of the opening, based on the analytical solutions of one-line model. The erosion of the beach adjacent to one side of river mouth when the river mouth opening shifting to the other side is presented through superposition of an existing analytical solution. Similarly, superposition of analytical solution for the case river delta formation can explain the retreat of river delta shoreline due to the reduction of sediment supply and the advance after the recovery of sediment supply. An analytical solution, which describes the evolution of river delta shoreline in case the adjacent beaches are bounded by rigid boundaries at the ends (shore-perpendicular structures), is also introduced. Theoretical comparison on the evolution of river delta shoreline during the processes of formation, reduction and recovery for the cases with and without rigid boundaries is also made.

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It is important to predict driftwood motions around hydraulic structures. We proposed a numerical model to simulate driftwood motions based on the coupling of a Euler type three-dimensional flow model and a Lagrangian type two-dimensional driftwood model. Laboratory tests on the driftwood motions in a curved channel and around obstacles are also carried out for obtaining the reference data. The computational results showed that three-dimensional flow features consierabley affect the motion of driftwood in a curved channel. We defined the driftwood Richardson number to consider the three-dimensional behavior of driftwood. The experimental results showed that if the driftwood Richardson number increases, the driftwood shows more three-diemensional behavior and the captureing rate by the obstacle decreases. In addition, we developed a two-way model to consider the drag force from the driftwood toward the flow to simulate the change of flow structures around stacked driftwood.

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In order to improve water quality in stagnant stream, we invented consecutive slit walls. As to the parameter of slit wall, slit width, slit location and streamwise interval of walls were changed. The flow structures in a slit-wall region were measured by using PIV method and the effects of flow structures on the concentration of dissolved oxygen was investigated numerically. By setting the slit walls, fast meandering flow and accompanying recirculating vortices were generated. The average velocity in the slit-wall region increases with a decrease of the slit width and as the slit location approaches to the side wall. When the slit walls are submerged, the average velocity in the slit-wall region becomes significantly small, the flow structure becomes three-dimensional and the vertical velocity increases. The depth-averaged 2d numerical model can reproduce the flow structures in the slit-wall region. It is demonstrated that the dissolved oxygen increases in the center region of recirculating vortices and the total concentration increases as the recirculating area becomes larger.

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This report presents the drainage ability of sloped pipe connected to reservoir facility. In order to clarify the relationship between the installation of sloped pipe (e.g., slope angle and pipe length) and the drainage ability in pipe with free outlet flow, the discharge coefficients were investigated experimentally by using physical models. The experimental results yield that the drainage ability depends on the slope of pipe under given diameter and length of pipe and discharge. Also, for either a steep slope of pipe or a short pipe, a supercritical flow is formed in the pipe even if the water level is increased at the upstream of pipe, and the drainage ability is diminished drastically.

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In this paper two numerical models are analyzed and then, the advantages of each model are combined in order to simulate bank erosion in a river bend. The coupled model includes the effect of slump blocks produced by cantilever failure in cohesive banks and a corrected velocity profile that takes into account the lateral inclination of velocity profile at a bend. The model is developed for simulating flow in an infinitely long circular channel and is applied to seven cases. Four cases are tested for cohesive banks and three cases in non-cohesive materials. The capacity of the model to simulate the effects of slump blocks in cohesive banks is qualitatively analyzed and, for the case of non-cohesive banks, the numerical model is validated using experimental data obtained from the literature.

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When a pure jet or a force plume is discharged into semi-infinite quiescent environments, it increases its width and cross-sectional volumetric flux by involving the ambient fluids. In order to correctly calculate the so-called entrainment phenomena with CFD, open boundaries are needed to allow fluids pass through the boundary. This paper firstly compared the advantages and disadvantages of several mostly used boundary conditions, with a laminar planar jet discharged into stagnant fluids. A simplified traction-free boundary condition is then proposed for the lateral open boundaries. The new boundary condition makes the entrainment possible with a higher numerical stability. It is easy to implement, was introduced to laminar planar and round jet, then was validated with turbulent planar and round jet under standard and realizable k-ε models.

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Linear stability analysis of fluvial sand bars with bank erosion is performed with the use of shallow water equations in two-dimensional flow, Exner equation and a process-based bank erosion model. An initially straight channel with erodible bed and constant width is assumed. The bank is also assumed to be erodible and composed of fine-grained sediment. The conditions allowed for alternate sand bars to grow are investigated considering the variation of aspect ratio, the magnitude of the transverse bank slopes, and the case of a channel with non-erodible banks. It is found that there exists a stable region in the range of small aspect ratios and small wavenumbers for the case of bar instability with bank erosion. The results also suggest that aside from the aspect ratio, the bank slope is one of the parameters that influence bed instability for the case of channels with erodible banks. This reveals that bank erosion has a stabilizing effect on the formation of alternate bars by increasing sediment supply, leading to an increase in bar wavelength.

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Accurate estimation of flow resistance because of vegetation is important for river management tasks. In the last decade or so, a new measurement technique using an airborne laser bathymetry (ALB) with a green laser has remarkably developed in the discipline of river engineering. This effective technique efficiently enables us to conduct high-resolution measurements of both the planar river bathymetry including the underwater bed profile and vegetation height for long river reaches. Flow resistance because of vegetation in rivers generally depends on the vegetation species. Therefore, we can expect the accuracy improvement of flooded river analysis, provided we readily obtain the spatial distribution data of vegetation species establishing in targeted rivers.
For this paper, we developed a methodology to determine the vegetation species (herbaceous plants, woody plants and bamboo trees) in the lower Asahi River, focusing on the spatial distribution of ALB point cloud data. Using these results, we estimated hydraulic parameters relating to flow resistance. Then, we examined the validation of the methodology by comparing results of numerical simulations of flood flows using the parameters with observations. Results showed that the simulated results using the present data are relatively consistent with observations for both the longitudinal water level and the distributary discharge into the Hyakken River, compared with the results using the conventional data.

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The effects of particle shape on settling behavior of monodisperse sand particles in an initially quiescent water environment have been studied by a two-dimensional numerical experiment. The present study is an extension of Yokojima et al. (J. JSCE A2 71(2) I_719 2015), where the influence of aspect ratio of elliptic particle was examined closely, and aims to obtain a more generalized conclusion by introducing rectangular particles. While a singular behavior happens in the early stage of the sedimentation process depending on the initial orientation of particles, it does not detract from the applicability of the spherical assumption of particle shape greatly. In terms of the settling behavior in the terminal stage, the influence of particle shape and aspect ratio is found to be reduced by the presence of surrounding particles. The circular particle case, however, still presents significant differences in the averaged terminal settling velocity compared with other particles. The present study calls for caution in the spherical assumption and encourages a deeper understanding the effects of particle shape.

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The vegetation in rivers significantly affects the flow resistance and reduces the flood carrying capacity. A lot of studies have been performed on the flow structure at the presence of the riparian vegetation. Many of them have focused on the flow characteristics in fully developed regions. Few studies have discussed the development process through submerged vegetation and the effects of vegetation inclination. Putting the main emphasis on the flow characteristic in the wake region of the vegetation zone, this study aims to understand the flow development process through submerged vegetation and to clarify the influence of inclined vegetation model. It is shown that the primary velocity and the turbulent shear stress take the maximum values just after the end of vegetation zone and gradually recover the profiles over the flat bed. It is also demonstrated that the inclination of vegetation model induces the decrease in flow resistance and the increase in primary velocity in the vegetation layer, which may come from the different flow field around inclined vegetation models from the vertical vegetation models.

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Exerimental study was performed on flow pattern on alternate bars, including supercritical flow and subcritical flow, and its influence on bank erosion. It is shown that the flow patterns are classified into four patterns. Type A: flow with both of supercritical and subcritical flow which is directed to side wall due to sand bar effect. Type B: flow with both of supercritical and subcritical flow which is directed to downstream along the straight river. Type C: transision between type B and type D. Type D: flow with only subcritical flow. Characteristics of these four flow patterns were clarified by the flow field measurement. And it is concluded that bank erosion intensity is closely related to these flow patterns.

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In steel bridge maintenance, it is important to evaluate the soundness of bridge bearing. Movable bearing which doesn't work properly against external loads may cause stress concentrations that ultimately lead to fatigue damage.
In the present study, field measurements in a bridge in service were first performed to determine bridge displacement responses at the longitudinal center and movable bearing by using MEMS sensors. Then, based on the determined displacemet responses at the longitudinal center and movable bearing, the method to evaluate the soundness of bridge bearing against external load was proposed. Finally, by conducting FE analysis, the effectiveness of the proposed method was verified.

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Recently, patch bonding repair method has been applied to the deteriorated steel structures. However, the bonding patch repair method is still concerned about the brittle debonding of patch plate. Generally, a tensile shear bond strength given by the single-lap bonded specimen with 1.6mm steel plates is often used for the quality control of adhesives. However, it is known that the tensile shear bond strength of single-lap joint cannot be applied for the evaluation of debonding of patch plate.
In this study, to employ the single-lap joint used for the quality control of adhesives for the evaluation of debonding of patch plate, stresses introduced in the adhesive of single-lap joint were given by using the eigenvalue analysis and the geometric nonlinear beam theory. Furthermore, it was revealed that the test results are scattered in the same region of that given by the large size specimens by the applying the principal stress of adhesive ends.

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Recently, many fatigue cracks are observed at welded toe of steel bridges. Fatigue cracks initiated at actual bridge is generaly inspected by magnetic-particle test, MT. However, in case of inspection by using MT, removal of painting and re-painting takes a lot of time and cost, and MT can not inspect wide area at one time. Therefore, in this study, by visualising propagation of surface acoustic wave by using image processing, it is clarified whether fatigue cracks initiated on the painted steel member can be detected or not. As the results of measurement results, fatigue cracks initiated at painted out-of-plane gusset joint or T gusset joint can be detected even if painting cracks are generated. However, fatigue cracks initiated at the painted welded joint can not be detected in case that both of peeling and cracking of painting are generated.

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When welding is considered as a joining method for repair and reinforcement of steel structures, welded joints have disadvantages such as influence of residual stress on fatigue strength and embrittlement of heat affected zone by welding heat input. Post-weld heat treatment is an effective method to solve these problems. However, civil steel structures assembled by thin plates are possible to be deformed easily by PWHT. For investigating residual stress change and deformation behavior of welded thin plates by PWHT, a series of experiment and analysis were carried out. A condition of PWHT for reducing residual stress and out-of plane deformation was proposed with considering generation mechanism of them.

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This study attempts image sharpening of concrete voids with the application of parasitic discrete wavelet transform. For detection of flaws existing inside the concrete, Linearized Inverse Scattering Methods (LISM) based on Born and Kirchhoff approximation can be applicable to reconstruct the shape of flaws with ultrasonic waves. The frequency characteristic components in the scattering wave from flaws are extracted by parasitic discrete wavelet transform with real-signal mother wavelet (RMW). RMW is created from the scattering wave from the targeted flaw. Scattered waves are filtered by parasitic discrete specialized for the targeted flaw, then they are processed with Kirchhoff based LISM. The reconstructed images show the improvement of flaw sharpening.

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A reliable estimation of surface fault displacements is a crucial for design and safety assessment of important facilities like nuclear power plants. It is necessary to develop a numerical method for the estimation. In this study, we develop a finite element method to which the following two functions are implemented: 1) a rigorously formulated joint elements of high order; and 2) a symplectic time integration of explicit scheme to properly conserve the energy of the fault. The finite element method is enhanced with parallel computing capability. We carry out verification of the developed method solving simple three-dimensional models of a fault embedded in a rock mass. It is shown the method is applicable to a model of one million degrees-of-freedom and the time to solution is sufficiently short.

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It has been hard to apply fast CG solvers for RC structures solid element model in FEM analysis because stiffness matrix is not symmetric and positive-definite. Implementation of reformulated constitutive relation of concrete in PDS-FEM is proposed as a solution, but its computational cost is high. Then, it is effective to implement tension part of the constitutive relation instead of performing failure analysis. We validate this newly implemented constitutive relation and make a RC shear wall model, based on previous experiment, for large-scale FEM analysis. We show that convergence is not assured under a certain element size using this model. Also, we propose that steel can be modeled as beam elements instead of solid elements. This is because load-displacement error of the former hybrid model is as small as the latter full solid model. Thus, we can use hybrid model as an alternative to full solid model, which leads to significant reduction of computational cost of RC-structures solid element model in FEM analysis.

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The steel girder ends of existing bridges in the Hokuriku region are locally corroded due to deck joint leakage, and this may result in decreased thickness of steel material in some cases. To aim for an inspection method using web vibration mode, this study conducted experimental models based on an actual steel girder end and undergone different damage scenarios such as variation in the corrosion range and thinning amount. Then, the natural vibration analysis was carried out to investigate the influence of the simulated deteriorations on natural frequency and vibration mode shape. In particular, specimens simulating the corrosion part was manufactured, and vibration measurements were later performed to confirm the detectable frequency and the vibration mode shape, the influence of web thickness and corrosion range, the validity of the analysis values, and to figure out efficient approaches for on-site measurement. Based on the results of above investigations, an inspection method using vibration modes focusing on web vibration against the corrosion of steel girder end was proposed.

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Development of E-Simulator, which aims at reproducing the damage/collapse mechanism of soil, bridge and building structures against strong earthquakes, is a project of E-Defense. Data measured in E-Defense shake table tests are used for validation of E-Simulator. As a research subject in the field of soil structures, we aim to simulate the large-scale experiment of soil and underground structures conducted at E-Defense in February 2012. In this study, we conduct elastic analysis by using detailed solid model of soil and underground structures. Our main objectives of this research are to determine the suitable mesh of analysis model and to identify appropriate technique to impose lateral boundary condition. Then, we clarify how the detailed solid model can simulate the experimental result and the limitation of the elastic analysis and identify the issues to be taken care of in the elasto-plastic analysis.

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This study evaluates internally present flaws in RC deck using Ultrasonic Testing. The ultrasonic waves are input from the surface of the asphalt pavement. Wavelet analysis with original mother wavelets CRMW successfully emphasizes the location of the horizontal cracks in the RC deck.
The original wavelets are developed by the reflected waves from the horizontal crack or interfaces that have similar face of the horizontal crack. The wavelet is specialized to detect and extract the horizontal crack. The results show the good agreement with the real location of the horizontal crack.

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Mass spring model is used in structural earthquake response analysis because of its low computational cost. Today constructing mass spring model which is consistent with solid element model and clarifying its applicability are desired. This study proposed the methodology of constructing mass spring model by reducing solid element model based on meta-modeling theory. At first, we proved there is no mass spring model whose eigenvalue and mode are the same as solid element model, then we constructed mass spring model whose eigenvalue and mode are approximately close to solid element model. In numerical analysis, we conducted linear and nonlinear dynamic analysis and clarified new model's applicability. At last, we made reference to mass spring model's applicability for structures which has more complicated configuration.

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Fatigue failure origin of out-of-plane gusset welded joints used for steel bridges is usually weld toe with high stress concentration. In this case the fatigue strength evaluation is carried out using nominal stress on main plate and the fatigue strength obtained from a lot of fatigue test data. Weld root also becomes originating point of fatigue failure in case that weld toe is finished. However a stress parameter and fatigue strength are still unknown in the case of root failure. In this study, the fatigue test data for root fatigue failure have been collected, and they are arranged using nominal stress on main plate, hot spot stress, stress at the reference point, and effective notch stress. The fatigue strength evaluation method using effective notch stress and stress gradient is proposed by using fatigue test data and parametric FE analyses.

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This study undertakes a large scale computing by using supercomputer to obtain non-linier seismic behaviors of a long span cable-stayed bridge. The main objectives of the study are to verify the computation accuracy and to examine whether the sophisticated structural element modelling can accurately reproduce non-linear seismic behaviors of bridge members as estimated. The target bridge of the analysis is a long span cable-stayed bridge in Kobe which was severely damaged by Hyogo-ken Nanbu Earthquake in 1995.
Through the comparison between real situations of damaged members observed after the earthquake and reproduced damage situations the analysis with same seismic input, it is verified the accuracy of the calculation and the good reproducibility of the member damage by the proposed structural element modelling. This paper describes the detail contents and results of this large scale model analysis.

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This study is to develop a detector that automatically detects deteriorations such as cracks, efflorescence, and chalk markings from the photographs of concrete structures, using convolution neural network which is a kind of deep learning. Firstly, photographs of concrete were collected for the learning data. Secondly, images of single cracked part, multiple cracked part, efflorescence part, efflorescence with cracks part, chalk marking part, construction joint part, surface part, rust part and others part were producted from these photographs for the learning dataset. Thirdly, a classifier to classify images into these 9 class was developed using the learning dataset and convolution neural network. Fourthly, the automatic detector was constructed using this classifier. Finally, a web system to receive a photograph and return detections was implemented based on Twitter.

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This paper presents a method to produce heterogeneous spatial distributions of hydraulic conductivity in embankments considering self-correlation length and distribution width based on probability statistics. The heterogeneous distribution of hydraulic conductivity has been applied to unsteady seepage analysis due to rainfall, and the effects of heterogeity on seepage behaviours have been investigated. Using the density width and the layer thickness of a real embankment, realistic heterogeneous fields of density has been obtained. Rainfall seepage analysis with use of the heterogeneous field of hydraulic conductivity provided by the relation between void raito and hydraulic conductivity has been carried out. It is found that the layer-by-layer heterogeneity of density creates local saturated region in the embankments.

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The aging and durability performance of numerous infrastructures that were constructed during the high economic growth period of Japan constitutes one of the current social issues. In this study, in order to consider the trigger causing a residual displacement considering a large deformation such as the P-delta effect, we investigate the nonlinear earthquake response characteristics using two types of rocking SDOF models (approximate and rigorous (include P-Δ effect)). Furthermore, we have carried out a non-linear response analysis and performed the characteristics extraction of the absolute acceleration wave pattern using the discrete wavelet transform. From these analysis, the triggered residual displacement indicates a predictable relationship between the sum of square accumulation value of the wavelet coefficient and time history of spectrum intensity value.

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In Japan, many bridges have passed long time after construction and are progressing aging by corrosion and other factors. In order to maintain the soundness of bridges, efficient and reliable inspection technique for screening inspection point is required. In this study, we discussed damage identification method focused on deterioration degree of bridge members and position of damaged members by using Self-Organizing feature Map (SOM) which is a kind of Neural Networks. We considered damages by changing the thickness of stiffening girder as deteriorated member. We were using the Power spectrum as learning and recognition data to SOM. In order to calculate the Power spectrum, FEM analysis model was created based on the small arch bridge experimental model. In conclusion, it is found that there is a possibility of performing damage identified by the proposed method.

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A reliable estimation of surface fault displacement is necessary for ensuring the safety of nuclear power plants. This paper proposes a numerical method for the estimation of fault displacement based on three dimensional finite element method. Evaluations of fault displacement using a simplified fault model are conducted to analyze the fundamental fault behavior. As a result, surface fault displacement do not smoothly change with input slip on the bottom of the main fault, but rather suddenly increases at a critical input value. Furthermore, when forced displacement is used for the input slip, it is likely that the auxiliary fault displacement is underestimated. It has been found that using equivalent nodal force as the tension boundary condition could avoid the underestimation of the auxiliary fault displacement.

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We suggest economic and efficient bridge damage sensitivity by bridge screening of VRA. VRA is a method to detect bridge damage by using vehicle vibration which is obtained from running vehicle on the bridge. In previous study, the availability of SSMA (Spatial Singular Mode Angle) is indicated as an indicator of bride damage sensitivity. But, SSMA is subject to road roughness and vehicle charasterisitic. They are problems for putting it into practical use. So we reveal the influence of Vehicle characteristics to SSMA. In considering it, The sensitivity and change of SSMA are verified by using numerical truss bridge and vehicle, and changing its characteristics.

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