Geological characteristics of the Ryukyu Island Arc are overviewed and geology and its development of Okinawa Island in Central Ryukyus are described. Ryukyu Arc extends for ∼1200 km from Kyushu to Taiwan, which has been divided into three segments (North, Central, and South Ryukyus) with tectonic boundary of the Tokara Strait in the north and Kerama Gap in the south. The northern part of Okinawa Island consists of older (Permian to Eocene) basement rocks, which form zonal structure from west to east along the extension of Ryukyu Arc; these are products of accretionary processes associated with plate subduction. Southern Okinawa Island is composed of younger (late Miocene to Quaternary) Formations. Drastic change in oceanic environment from `muddy' sea for the Shimajiri Group to `coral reef' sea for the Ryukyu Limestone at lower to middle Pleistocene was caused by crustal movement (Shimajiri Movement), which involved the formation of a young back-arc basin (Okinawa Trough). After the deposition of Ryukyu Limestone during upper Pleistocene to Holocene, the Uruma Movement, involving block faulting, took place and resulted in the present island arc configuration.

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In the paper, the ranges in application of the classical theory and the first-order shear deformation theory, called the Mindlin theory, for bending problem of a rectangular plate under surface force on an elastic foundation were discussed by comparing the three-dimensional (3-D) theory of elasticity. A circumferentially simply-supported rectangular plate on the Winkler foundation was analyzed when the plate was subjected to a fully distributed uniform load at the top surface. The solutions of the theories are mathematically expressed by using the double Fourier series. We computed the distributions of displacements or stresses along the in-plane or transverse direction of the plate, the strain energies of the plate and the elastic energies of the Winkler foundation. The ranges in application of the classical and Mindlin theories were clarified on the basis of displacements, stresses, strain energies and elastic energies computed with the 3-D theory of elasticity.

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This article focuses on the analysis of cross-sectional deformations for single- and multi-walled carbon nanotubes using a molecular dynamics method. Carbon nanotubes consist of a graphene sheet (two-dimensional hexagonal lattices of carbon atoms) rolled up into a cylinder. This nanoscale structure has generated enormous interest in the research field of science and engineering in the last decades because of its excellent mechanical properties, such as extremely high elastic modulus and tensile strength. For example, the Young's modulus of nanotubes is estimated to be on the order of TPa (i.e., several times stiffer than steel) and the tensile strength is as high as tens of GPa. On the other hand, carbon nanotubes are known to have its remarkable flexibility when subjected to external hydrostatic pressure and bending force. Owing to such mechanical properties, they are regarded as an ideal material for superstrong nanofiber and thus hold great promise for use as next-generation materials. It has also been broadly accepted that mechanical deformation of a carbon nanotube causes significant changes in its physical and chemical properties. Precise knowledge of its deformation mechanism and available geometry is, therefore, crucial for understanding the precise physics and in developing nanotube-based applications. In earlier work, we carried out simulations based on the thin cylindrical shell theory to predict the occurrence of wavy-shaped carbon nanotubes, called “radial corrugation”. However, the shell theory is valid only within linear elastic region, thus being unavailing for discussing large deformation behaviours beyond elastic approximation. Against the backdrop, we have performed molecular dynamics simulations to explore the post-buckled behavior in the cross-section of carbon nanotubes under high pressure. We have confirmed various deformation modes with large amplitude, in which the stable mode is strongly dependent on the tube diameter and the number of concentric walls.

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There are large uncertainties in progress of deterioration of structures depending on their environment and characteristics. This study proposes a method to perform grouping and regression of a group of deterioration curves with respect to age of structure at the same time statistically. The deterioration is expressed by two parameters, i.e, health index and characteristic index. The proposed method can be interpreted as multi-objective regression method with combination of PSO (Paricle Swarm Optimization) method and EM (Expectation Maximization) algorithm. Since heavily deteriorated sutructures tend to have larger uncertainties, the uncertainty around the regression curve is formulated depending on progress of deterioration. The proposed mehod is applied to inspection data about bridges in Gifu prefecture. The result shows good agreement with grouping and regression result performed independently with detailed information.

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In recent years, effective use of regional resoures have received much attention in constructing infrastructure. The purpose of this study is to examine material properties of the magnesium improved soil mixed with rice husk ash (RHA) and rice straw fibers (RSF) in splitting test. Splitting test was conducted on three types of soil (normal, mixed with RHA, and mixed with RHA and RSF). Fracture process was qualitatively evaluated by image analysis and acoustic emission (AE). These results indicate that RHA and RSF change the mechanical property of magnesium improved soil. Three improved soils tend to different characteristics of AE in spitting fracture. Image analysis and SiGMA analysis suggest a concentration of horizontal stain and internal fracture process.

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This paper presented a new ensemble estimation for capture zones of pumping well as well as for those area and perimeter using backward particle tracking. Geostatistically generated hydraulic conductivity fields having different heterogeneity were of concern to estimate time-related capture zones, showing that the increase of heterogeneity leads to ambiguous capture zones. Random walk particle tracking was applied to assess the capture probability of well that initial particle distributions comprising capture zones are extracted by the well. Ensemble of the mass evolutions associated with all realizations exhibited the effects of heterogeneities not only in hydraulic conductivity fields but in retardation fields on the capture probability.

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This paper investigates the practicability of a damage detection technique utilizing the statistical patterns of modal parameters to a real simply supported steel-truss bridge, which was consecutively subjected to five damage scenarios. The modal parameters are identified from the bridge vibrations excited by a passing vehicle via the stabilization diagram aided multivariate autoregressive analysis. The damage detection task is achieved using the Mahalanobis-Taguchi System (MTS), a multivariate pattern-recognition method. Several combinations of modal parameters as MTS variables are tested for their efficiency. Observations demonstrate that considering multiple modal frequencies as MTS variables yielded highly sensitive Mahalanobis distance (MD) to not only the presence but also the severity of the artificial damage. On the other hand, it was hard to utilize damping ratios as MTS variables for the damage detection.

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This study is intended to investigate a way to consider changes in temperature and vehicle weight as environmental and operational factors for long-term bridge health monitoring by applying a Bayesian approach to long-term monitoring data and artificial damage data. The Bayesian approach consists of three steps: step 1 is to identify damage indicators; step 2 is to calculate residuals by means of the Bayesian regression; step 3 is to make a decision utilizing the probability of residuals within a threshold and the Bayesian hypothesis testing. Observations showed that validity of using the data observed at a specified time to reduce the influence of traffic loads can be confirmed. In the Bayesian hypothesis testing utilizing data from the healthy bridge, the probability of the bridge damage was judged as `very small'. The number of data can influence the results of the Bayesian hypothesis testing.

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In recent years, the accelerated corrosion of steel sheet pile in an agricultural canal has been problems. In this research, evaluation of bending characteristics is conducted in corroded steel sheet pile with concrete coating by using AE and DICM. The test specimens are made of three-layer composite which is composed of steel sheet pile, concrete and precast panel. Thus, the deformation behavior of testing samples could be evaluated by AE and DICM parameters. A relation between torsional behavior due to the concavo-convex shape of steel sheet pile and bending behavior of composite was correlated.

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As a detailed inspection of a concrete structure in service, core samples are usually drilled out and then mechanical properties are measured. In this study, damage estimation of structural concrete from concrete-core samples is developed, applying acoustic emission method. By the authors, the quantitative damage evaluation of concrete has been proposed, by applying acoustic emission (AE) and damage mechanics in the compression test. In this study, development of damage parameters is conducted with the Kriging method, which is evaluation of spatial characteristics. In the experiments, AE behavior of damaged concrete under compression is dependent on the local distribution of cracks, and could be approximated by applying damage parameter and P wave velocity. These experimental results suggest that the decrease in physical properties could be evaluated by detected AE parameters, which is incorporated with the Kriging estimation. These values are affected by the internal actual damage. Thus, the damage of concrete could be quantitatively evaluated by damage parameters based on detected elastic waves with the Kriging analysis.

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The neutron radiography as well as X-ray radiography is one of the non-destructive evaluation methods. The difference in the permeability of the neutron ray between the hydrogen and the other element in concrete is effective to understand the moisture distribution of concrete by using the neutron radiography. The neutron radiography is usually taken by the spherical lens in the camera, and it makes the picture distortion by the inflection of light. In addition, the neutron ray is scattered, and it disturbs the result of neutron strength. This means there are some points in the neutron radiography to be improved in order to obtain the high accuracy.
Recently, in the field of reinforced concrete structures, some cracks and stress-loss of concrete structures have been reported. One of the reasons is the lack of mechanism about the volume change caused by shrinkage and creep of concrete. In order to solve the volume change of concrete, the study of moisture movement, in other words, the continual measurement of the moisture distribution in concrete is effective.
The objective of this paper is to improve the neutron radiography by considering the effect of scatterd neutron ray and the distortion of pictures. The distortion was corrected by the neutron radiography of the slit specimen made by the aluminum and the paraffin setting with the identical interval. The scattered rays were modified by the convolution of the pictures. By applying the proposed method to the plate made by mortar, the moisture distribution changing by the age was visualized clearly, and the water movement from the coarse aggregate to the mortar was estimated.

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In recent years, the accelerated corrosion of steel sheet pile in an agricultural canal has been problems. Prior to reconstruction and retrofit of these structures, renewal method of in-situ structure is now in urgent issue. In this study, development of nondestructive evaluation method for quantitative evaluation of crack characteristics on repair concrete member of agricultural canal is going to be performed, applying steel sheet pile-concrete composite. Quantitative damage nondestructive evaluation method is proposed by applying infrared thermography method and the semi-variogram analysis of spatial-statistics. The semi-variogram analysis is a quantitative evaluation method of the spatial distribution of physical properties. In the experiments, the damaged composite canal wall is examined. The semi-variogram appeared different semi-variance characteristics depending on the damage level. Thus, the damage level of concrete surface layer could be quantitatively evaluated by the semi-variogram analysis using infrared image.

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Soil consists of three phases that show significantly different thermal conductivity. The overall thermal conductivity depends not only on the phase composition but also the geometry. In this study, we made a 3-dimensional porous material model with a micro structure of the soil, and estimated the macroscopic thermal conductivity of the model by un upscaling heat conduction analysis. On the other hands, we carried out laboratory experiments aiming to estimate soils thermal conductivity by using column specimens of water content soil. Finally we verified the validity of the numerical model by comparing the experimental results with the numerical ones.

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This study proposes a damage detection technique in the space and wave-number domains. A tone burst force is input to a structure at one point and the acceleration responses are measured at gridiron points. If the damage is inside the grid, the position of damage is detected from the contour of the acceleration power in the space domain. If the damage is outside the grid, its position is detected in the wave-number domain through the 3D and 2D Fourier transforms. Numerical analysis was carried out on a plate structure, and the effectiveness is verified.

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Image analysis methods based on the digital image correlation (DIC) for measuring strain distribution together with crack propagation in concrete are developed in this paper. The hierarchical modeling in the DIC is introduced to construct high resolution grids of measurement. The tracking of material points and the updating of displacement vector using finite element interpolation are also introduced to increase the accuracy of the DIC. We first show the detail of our image analysis method based on the DIC. After the validation test of strain is performed, we apply the present method to compressive tests of mortar specimen and examine how to detect crack propagations clearly. Finally, the present method is applied to concrete to visualize the complicated crack propagations due to coarse aggregates.

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The pore pressure coefficient B, which is measured on triaxial test, is useful for evaluating degree of saturation of specimen. However, the influential factors on this B value other than degree of saturation have not been investigated in detail up to now. In this study, first, Henry's law that indicates dissolved air in pore water was applied to the existing constitutive model for unsaturated soil in order to express the behavior of pore air on unsaturated soil extremely close to fully saturated state. Next, the influential factors, such as degree of saturation, confining stress and back pressure, were investigated through numerical simulations with using newly obtained model. Consequently, it was found out that B value depends on not only degree of saturation but also stress state.

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In 2011 off the Pacific coast of Tohoku Earthquake, lots of seawalls were destroyed by Tsunami. By the survey of destroyed seawalls, not only the wave pressure to dyke but also seepage force in ground have been reported to contribute to the instability of seawalls. However, it has been difficult to consider the effect of seepage force in the stability analysis of seawalls. This paper presents the hybrid stability analysis of rigid plastic finite element method and seepage finite element method in order to evaluate the total stability of seawall against tsunami. To simplify the problem, ultimate bearing capacity of caisson is investigated under the specific seepage condition by setting the sea water levels of upstream and downstream of caisson. Through case studies, the effect of seepage force on the instability of seawall is examined by handling the magnitude of seepage force. The effect of embedment of caisson on ultimate bearing capacity is also investigated. The depth of embedment works to the stabilization of seawall from the two aspects. One is the mechanical stabilization of caisson by overburden pressure and the assistance in shear strength of overburden ground. The other is the decrease in seepage force by embedment. The obtained ultimate bearing capacity shows the proposed analysis method well simulated the stability of caisson under the seepage force condition.

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This paper presents a new computational method based on a multiphase model to deal with thermal interactions between compressible fluids and solids. In the present method, conservative governing equations for multiphase fields are solved with the numerical method for compressible fluids. The present method was applied to the natural convection in a enclosure cavity with a square cylinder conducting body. As a result of the computation, heat transfer in the multiphase field was reasonably simulated. In addition, through the numerical experiment for the helium leakage from a container, the applicability of the present method was discussed.

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It is well known that the mechanical behavior of material mainly depends on the geometric properties of the microstructure, such as material distribution, shape or size of the material. It is said that it will be possible to maximize the mechanical performance of a macro-structure, if ‘types or kinds of materials to be mixed or the combinations thereof’ are optimized and ‘the geometric properties of micro-structure’ are optimized. For this reason, the authors have developed topology optimization of microstructure using the general finite element method as a numerical approach. However, the general finite element mesh is not necessary appropriate to express the complicated real material distribution of microstructure and furthermore depends considerably on the initial value of some parameters. Thus, the present study applies a new approach, the phase-field method, to express the complicated topology of microstructure and introduces the formulation to maximize the stiffness of the microstructure with a prescribed material volume under linear elastic regime. For the fundamental research, we firstly start from investigation of the initial value dependency of the present method on the final optimization solution by making use of a series of numerical examples.

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In this study, a dynamic load-balancing parallel computation method is investigated to predict the motion of multiple solid objects in fluids, taking account of their collisions and fluid-solid interactions. The parallel computation method is based on the 3D domain decomposition method using flat MPI. The “slice-grid method” enables us to dissolve three-dimensional deviation of the number of blocks included in the “block-computation domain”. On the other hand, the “fluid-computation domain” is fixed throughout the computation. Numerical experiments have been conducted for comparisons of the computational efficiencies between the present and previous methods. As a result, we found 256-process simulation of water mass collapse, including 1,000,000 objects in the water, exert 129.90 speed up compared to sequential execution.

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This paper presents a road-traffic noise evaluation system using virtual reality technology. In order to provide an experiencing person with a virtual world with so much presence, the 3-D acoustic spatialization using Ambisonics techniques is employed. A complex acoustic field under mixed traffic is reconstructed in VR space. Therefore, it is able to understand and assess traffic noise intuitively, around various environments such as building complex, tunnels, elevated structures and so on. This system is applied to several examples in order to investigate the validity of the method.

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To better understand the characteristics of ultrasonic wave propagation in concrete, we propose a time domain simulation tool. The tool is based on the elastodynamic finite integration technique (EFIT). When modeling ultrasonic wave propagation in concrete, it is important to introduce a three-dimensional (3D) concrete structure including aggregate distribution. Because ultrasonic waves in solids are propagating as a consequence of the mechanical interaction between adjacent media. In this paper, the wave velocity, center frequency, and attenuation of ultrasonic wave in concrete were quantitatively evaluated by comparing the waveforms obtained by the EFIT simulation with those found in experimental measurements. These values were in good agreement between the simulation and the measurement. Since the amplitude of the ultrasonic wave is sensitive to the allocation pattern of aggregates, it can be understood that the scattering attenuation is more dominant than attenuations due to the intrinsic absorption and geometrical spreading in concrete.

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In 2011, Tohoku-Kanto earthquake tsunami caused serious damage on the port structures such as breakwater and seawall. Damage mechanisms of these structures have been studied in the past, and there are mainly three causes; I. horizontal force due to the water level difference between the front and rear breakwater, II. soil scour and erosion behind the seawall during overflow and III. piping destruction associated with the decline of the bearing capacity by seepage flow. Fluid-Structure-Soil coupling simulation is desired for a systematic comprehension of seawall collapse mechanism, and it may help to develop next disaster prevention method. In this study, a particle simulation tool based on the SPH has been developed to solve seepage failure problem. This simulation should treat the surface flow and seepage flow interactions, and the particle simulation tool has been modified and improved to solve this interaction problem. In this study, as a first step, surface flow and seepage flow are described by the same government equation, and a SPH formulation has been developed. After that, efficiency and adequacy of the proposed simulation technique has been validated through an application to one test. This numerical result shows a reasonable surface flow and seepage flow behavior. In the future works, quantitative comparison with experimental results is required, and this tool may be developed to a Fluid-Structure-Soil coupling simulator.

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Based on meta-modeling, which allocates structural mechanics as mathematical approximation of con-tinuum mechanics, this paper proposes a conversion method from a solid element solution to a beam element solution. A key issue is the rigorousness of the proposed conversion method, since meta-modeling ensures that the most suitable beam element solution is the one that is close to the solid element solution by defining a distance between these solutions in a function space of continuum mechanics. Examples of applying the conversion method are presented. It is shown that the conversion method produces a more accurate beam element solution from a solid element solution, compared to an ordinary method. It is also shown that the conversion method is applicable to a practical problem of an actual large-scale tunnel structure.

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The nonlinear ultrasonic testing is expected to be an effective technique for detection of closed cracks which cannot be detected by the linear ultrasonic testing. However, although the nonlinear ultrasonic waves such as higher- and sub-harmonics are considered as generated by the interaction of the crack faces such as clapping motion or friction, the mechanism of generation has not been understood clearly from theoretical viewpoints yet. Therefore, the boundary integral equation for an interface crack with nonlinear boundary conditions in 3-D is formulated, and numerically solved using the convolution quadrature time-domain boundary element method (CQ-BEM) in order to investigate the behavior of nonlinear ultrasonic generation.

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Inspired by work of Payen et al.^1),2), this paper seeks to make mechanical interpretation of nodal force, in order to more accurately evaluate stress field using linear element of finite element analysis. A new mechanical interpretation is presented for nodal forces, which is an abstract quantity with a rigorous mathematical definition. Use of Lagrangean and particle discretization scheme reveals that nodal force gives total force acting on middle plane of element. Based on the aforementioned interpretation, this paper proposes a method for more accurately evaluating stress field. Numerical experiments indicate that stress field of proposed method is smoother and accurate compared to ordinary element stress evaluation. Moreover, it is found that the error of J-integral, for a mode-I crack problem, is several times smaller when estimated with nodal force based stress evaluation.

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In this work, a finite element procedure for overlapping meshes based on domain decomposition approach, which is developed by the authors for the stable heat equation, is applied to linear elastic problems. In the proposed procedure, solutions on different meshes are connected on the domain interface by using the Lagrange multiplier method extended from the Nitsche's method in order to avoid the limited selection of discretization of the Lagrange multiplier. The local domain in which kinetic boundary condition is not involved and the stiffness matrix is singular is recongnized as “floating” subdomains. In this work, a new stabilizing technique by using independent intermidiate nodes and virtual spring is proposed.

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Theoretical stability and error analysis on a Conforming Petrov-Galerkin Finite Element (CPGFE) scheme with the fitting technique for solving the Advection-Dispersion-Decay Equations (ADDEs) on connected graphs is performed. This paper is the first research paper that applies the concept of the discrete Green's function (DGF) to error analysis on a numerical scheme for the ADDEs on connected graphs. Firstly, the stability analysis shows that the scheme is unconditionally stable in space for steady problems and is stable in both space and time for unsteady problems if the temporal term is appropriately discretized with a lumping technique. Secondly, basic properties of the DGF on connected graphs, which provide key mathematical tools in the error analysis, are presented. The error analysis with the DGF reveals a direct relationship between the regularity conditions on the known functions and accuracy of the scheme, explicitly indicating that the accuracy of the scheme is strongly influenced by the accuracy of the discretized known functions. The error analysis also shows that the scheme is uniformly-convergent in the L^∞-error norm with respect to the diffusivity, which cannot be achieved in the conventional numerical schemes. This unique and remarkable property is a significant advantage of the present CPGFE scheme over the conventional ones.

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With the increase of extreme climate events due to the global climate change, urban areas have been becoming more prone to flooding. This trend highlights the importance of effective schemes to mitigate the damage and loss due to inundation. The advancement of numerical prediction method for heavy rainfall is a key technology for early warning. The objectives of this study are twofold. One is to clarify the applicability of the combination of WRF (Weather and Research Forecasting) model and a data assimilation method LETKF (Local Ensemble Transform Kalman Filter). The other is to discuss the evolution of rainfall system that caused heavy rainfall based on the numerical results. We carried out numerical simulation of heavy rainfall in western Shimane prefecture in August, 2013. Comparison between the calculated results and those measured by a radar-AMeDAS shows that the numerical results fail to reproduce the intensity and the location of the heavy rainfall with small success during the latter half of the rainfall event. It is found that the ensemble mean rainfall provides a slightly better results about the peak value and peak time of rainfall compared to those by the deterministic approach without assimilation, showing the effectiveness of LETKF. The heavy rainfall event over Shimane prefecture is considered to have occurred by the southwest moisture flux converge near the front with the orographic effect of the Chugoku distract.

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This paper presents a parallel 3D computational method for compressible flows with both high and low Mach numbers. The present numerical method is applicable to shock wave problems and is able to capture discontinuity without artificial viscosity. In order to solve large scale problems efficiently, the computations were parallelized by flat MPI or OpenMP. The proposed computational method was applied to the spherical explosion problem with high Mach numbers as well as the Rayleigh-Benard convection with low Mach numbers. It was shown that the conservation of mass and other physical properties are sufficiently satisfied and that the predicted results agree reasonably with the theoretical values and reference values.

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This paper studies the extension of particle discretization scheme (PDS) in order to improve finite element method implemented with this discretization scheme (PDS-FEM). Polynomials are included in the basis functions, while original PDS uses a characteristic function or zero-th order polynomial only. It is shown that including 1st order polynomials in PDS, the rate of the convergence reaches the value of 2 even for the derivative. 1st order polynomials are successfully included in PDS-FEM. A numerical experiment is carried out by applying 1st order PDS-FEM, and the improvement of the accuracy is discussed.

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This paper presents a 2D-3D hybrid stabilized finite element method that enables us to analyze both tsunami offshore propagation and runup in urban areas with high accuracy and relatively low computational costs. The shallow water equations are employed for 2D simulation of the offshore flow in a global oceanic area, while the incompressible Navier-Stokes equations are used to analyze 3D flow behavior in a local urban area. The SUPG method is commonly applied to stabilize both the 2D and 3D FE discretized equations, and the VOF method is used to capture the 3D free-surface flow. Meshes for 2D and 3D simulations are generated independently of each other and the method of multiple-point constraint is applied to impose the continuity conditions of flow velocities and pressures at the interface between the 2D and 3D meshes of different topologies. Several numerical examples are presented to demonstrate the performance and efficiency of the proposed hybrid method.

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The present study introduces a derivation of analytical sensitivity for topology optimization of composites considering elastoplastic deformation to maximize the energy absorption capacity under a prescribed material volume. For optimization applying a gradient-based method, the accuracy of sensitivities is critical to obtain a reliable optimization result, especially in the vicinity of undifferentiable points such as yield points and unloading starting points in the stress-strain curve. In the previous authors' work¹⁾, it is verified that the proposed analytical sensitivity can provide highly accurate sensitivities over yield points under loading situation. In this study, as an extension to a more realistic loading situation, we demonstrate topology optimization under cyclic loading condition and verify the accuracy of the proposed sensitivity approach by comparing with that evaluated from the finite difference approach.

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A couple of years have passed since the Great East Japan Earthquake Tsunami, new Tsunami disaster prevention and mitigation methods of bridges are actively discussing toward the next millennium Tsunami. A numerical simulation can be useful way for predicting the damage of bridges, because real size experimental tests are almost impossible and too costly. In this study, particle method, which is widely applied not only for fluid dynamics and but also for solid mechanics, is utilized for fluid-rigid body interaction simulation. Mainly velocity based and force based formulations have been proposed for the fluid-rigid body treatment in the framework of particle methods. After a modified technique in the force based formulation related to the boundary condition is proposed in this paper, the difference of these two formulations has been discussing through a simple bridge wash out simulation.

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This paper presents an interactive 3D unstructured mesh modification system using virtual reality (VR) technology. The mesh quality is evaluated and the quality is improved by the node relocation and mesh refinement. The user can change the position of nodes and refine the element in VR space by using a handy controller. The software is developed by VR programming languages; Open GL and CAVE library. The present system is applied to the mesh modification for the simulation of 3D solid analysis and is shown to be a useful tool to assist the high quality computing.

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This paper presents a numerical method based on CIVA-Stabilized finite element method (CIVA-SUPG) for tsunami simulations. The Boussinesq equation is employed for the governing equation of motion. The equation system is divided into two phases; an advection phase and a non-advection phase. The equations for advection phase are solved by CIVA method, and the equations for non-advection phase are solved by a stabilized finite element method based on SUPG method. The present method is applied to several numerical examples to show the validity and efficiency.

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A simulation model to estimate the drying shrinkage of aggregate by curing in arbitrary relative humidity is presented. This paper describes procedures for predicting drying shrinkage of aggregate based on the pore size distribution measured by mercury porosimetry, change of capiraly tension and surface energy based on the water content inside of cylinder type pore under arbitrary humidity and cray mineral content. To evaluate the effectiveness of this model, simulation results were compared with experimental results. As a result, it was found that the experimental and simulated results were in close agreement, and the effectiveness of simulated model based on the pore structures, water content and cray mineral content was verified.

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The Jaumann stress rate of the Cauchy stress is usually used to represent hypoelasticity. Since this stress rate takes into account only the effect of finite rotation; i.e. spin during motion, we here examined the effects of deformation rate terms which can be included in the definitions of the stress rates. First we have shown that the Truesdell stress rate can be defined as a rate of the 2nd Piola-Kirchhoff stress with the current state as reference; i.e. an updated Lagrangian measure. In order to compare the characteristics of the stress rates, localization of deformation was predicted by using the Truesdell stress rate and the convected stress rate, and the results were compared with those by the Jaumann stress rate of the Cauchy stress. All rates predicted the localization at the softening state which is far after the peak of the load-deformation diagram in 3D axisymmetric stress state. However, in plane strain state, the predicted stresses of incipience of the localization by the Truesdell stress rate become close to the experimental critical stresses, Also, the orientations of the localized deformation obtained by the Truesdell stress rate showed consistency with those by the infinitesimal deformation theory, when the stress levels of the localization were in practical order.

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Fiber reinforced plastic (FRP) materials have many advantages over traditional civil engineering ones. However, it is difficult to exactly understand their mechanical characteristics which are affected by various kinds of properties of polymer as a matrix and fibers as inclusions. In the case of designing and developing FRP, it is often modeled as a macroscopically anisotropic elastic material, whose elastic constants are already determined, and no microstructures are directly considered. In this study, we attempted to identify elastic modulus of vinylester resin and fibers, which make up hybrid FRP composite beams used in bending tests by three-phase Mori-Tanaka averaging method in which a virtual matrix is introduced to a two-phase composite. Moreover, by inputting macroscopic elastic constants calculated from the identified values to a versatile finite element analysis software, we simulated bending behavior of the hybrid FRP composite beams and proposed a simple model for delamination of the upper flange from the result of stress analysis.

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In the present paper, the bi-axial cyclic loading tests of reinforced concrete columns (i.e., UN-SFRC columns) in which the boundaries between rebar and steel-fiber reinforced concrete are un-bonded in the plastic-hinged zone, have been performed under the different loading histories. The experimental data have been compared with those of previous experiments on RC columns that are respectively RC column, SFRC column and RC columns with the intermediate reinforcements. The buckling and breaking of rebar during cyclic loading have been examined and it has been found that the use of UN-SFRC column is effective against the breaking of rebar. Also, flexural strength and ductility of the different types of RC columns have been examined in details in the post-peak loading region. The buckling characteristics of re-bar, the progressive deterioration of core-concrete and the energy absorption capacities have been discussed during cyclic loading process. It has been found that the use of UN-SFRC column might be effective to make the plastic hinged zone of RC column more ductile, particularly for the column with large spacing of hoop tie, i.e., the spacing of 120 mm in the present study.

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Case study regarding a shallow slope failure by heavy rainfalls is described in this paper. The site where the slope failure took place is located in Chita Peninsula, Aichi Prefecture in Japan. The catastrophic failure occurred on a slope consisting of strongly weathered Conglomerate and Siltstone with the inclined angle of 40 to 45 degrees. The collapse was definitely triggered by heavy rainfall brought by Typhoon No.18 in 2009. In an attempt to manifest a possible scenario of the slope failure, the geological profile of the slope was in detail examined by in-situ tests, together with the engineering properties of the surface soil by various laboratory tests using undisturbed soil sample. Two-dimensional saturated-unsaturated seepage flow analysis simulating the rainfall record before and at the collapse was also carried out. Similar analysis was performed for a heavy rainfall recorded in the preceding year of 2000, for which no collapse was observed. It was manifested that the slope collapsed involving with some loss of apparent cohesion of the surface soil due to saturation of the surface soil. In a comparison with similar heavy rainfall in 2000, it was suggested that the amount of preceding rainfall before the collapse seems vitally important to govern the occurrence of the slope failure.

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The mechanical properties of Calcium Silicate Hydrate (CSH) matrix, which is dominant in cement, is of importance for clarifying the mechanical properties of cement block. It will provide the information for the best design of cement materials. The unit component in C-S-H matrix called Globules is crucial for building the model for C-S-H matrix. However, there is difficulty to measure the properties of Globules due to their nano-scale structure. We investigate the mechanical properties of tobermorite14Å and jennite, which have structural similarity with Globules, by using molecular dynamics, where dynamic measurement of stress-strain relationship has been utilized. We could investigate temperature dependence and destructions, which are difficult to obtain by static calculations. It was suggested that the water layer inside the C-S-H solid have the key role both for elastic and yielding properties.

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In this study, we attempt to use the recent general-purpose finite element code by applying artificial damping from which we can overcome the difficulty in performing the analysis due to local instability. This paper describes the application of the artificial damping technique for the generation of singularities in large-deformed thin flexible structures, including elastic and viscoelastic cylindrical shells and foam materials with microstructure.

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This paper presents a new Distinct Element Method to simulate coupled behavior of water and gravels. A spherical shape water element is proposed. The element has an isotropic pressure controlled by shrinkage volume of its body, and transfers the pressure to adjacent elements in proportion to the contact section area. Combining the water elements and conventional element, i.e., spherical or aggregate rigid body experiments, debris flow behavior obtained by experiment are simulated. The experiments are performed on the dehydrate behavior of debris flow captured by a bottom drainage screen dam. Draining out water from debris flow, the gravels lose its fluidity on the screen. The proposed method simulates such behaviors very well, and the coupled mechanism is analyzed in viewpoints of reaction force between rigid and water elements, and coordination number transition in the rigid elements.

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Numerical simulations of tri-axial compression tests are performed in order to investigate the effectiveness of Material Point Method for large deformation geotechnical problems. Mohr-Coulomb constitutive model is adopted as a geotechnical nonlinearity, of which parameters are obtained by an experimental results. The stress-strain relationship obtained by simulations shows a good agreement with that by the experiments at the large strain level, showing the effectiveness of MPM.
Parameter studies are also performed in order to investigate factors that influence on the relationship between initial shear bands and final shear bands, which are observed during simulations of tri-axial compression tests. Then, followings are obtained as the main findings of this study. (1) Initial shear bands are generated near the constrained edges of specimen; (2) When both top and bottom edges of specimen are constrained, initial shear bands near the edges, at which external forces are applied, finally form clear shear bands; (3) A geometry of specimen gives great influence on the formations of shear band when rectangular specimens are used.

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In order to solve large deformation problem of geomaterials, the SPH method is used which is a kind of particle method based on the meshless Lagrangian scheme. The method can solve large deformation problems without mesh distortion. Moreover, it can handle the governing equations and existing constitutive models for geomaterials based on a continuum mechanics. However, numerical inaccuracy is one of the disadvantages of this conventional SPH method. In this paper, the improved methods (CSPM and SSPH method) were introduced comparing them with the conventional method in terms of the numerical accuracy. Verification of discretization accuracy of spatial gradient and validation of a simulation of simple shear problem of elastic and elasto-plastic materials were carried out using these methods. As a results, it was confirmed that it is possible to significantly improve the numerical accuracy using SSPH method.

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Resistivity imaging of underground is widely used to infer the behavior of groundwater flow and to comprehend the changes of ground state caused by ground improvement. In order to increase the accuracy in the estimation of geological properties derived from resistivity imaging, we need to reveal the relationship between the resistivity and several physical parameters such as porosity, degree of saturation, and electrical conductivity of pore fluid. We have conducted a series of finite element simulations with above parameters to directly determine resistivity of porous media with the detailed three-dimensional porous models obtained from the high-resolution X-ray CT. Subsequently, the simulation results are compared with those obtained from experiments and with those derived from an empirical law, i.e., Archie's equation. According to the comparison, the simulation results are in good agreements with experimental results and indicate similar function form that proposed in the empirical equation being available for unsaturated state. Finally, we discuss the limitation of the empirical equation and infer that the empirical equation is applicable to geo-materials having a degree of saturation exceeding 40%.

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We examined aggregation rates of colloidal particles in a shear flow as a function of KCl (potassium chloride) concentration at different shear rates. The analysis was based on the trajectory analysis with non-linear Poisson-Boltzmann (PB) solution that calculates the double layer force between highly charged particles. The trajectory analysis here is performed without any adjustable parameters. The PB solution enables us to analyze the experimental data of orthokinetic aggregation of highly charged particles where linearized PB solution is not valid. It should be noted that the comparison of the calculation with the experimental data of aggregation rates in a simple shear flow in the presence of the double layer repulsion had never been attempted until we analyzed. The theoretical calculation with trajectory analysis qualitatively describes the experimental data. However, theoretical values of critical coagulation concentration (CCC) being a bending point of capture efficiencies plotted against the KCl concentration, and capture efficiencies in the presence of double layer force are not quantitatively consistent with experimental ones. These discrepancies might be caused by the additional forces and charge heterogeneity which are not included in the present calculation.

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The failure of slope and levee triggered by heavy rainfall is a great threat to people's lives and properties, thus this research aimed at proposing a new numerical simulation tool and investigating the failure mechanism of slope and levee under heavy rainfall. The new Smoothed Particle Hydrodynamics (SPH) model with the coupling of three phases, water, soil and air, has been proposed based on the basic principles. Using the proposed SPH program, the rising and burst of air bubble in water was simulated to validate the application in fluid phase (water and air). After that, a conceptual slope model with different coefficients of permeability has been built and analyzed by the SPH model. The simulated infiltration showed that the proposed SPH model can simulate the interaction force between soil and water well. The model test of slope failure conducted before was simulated by the proposed SPH model with two cases, one without the effect of air phase and another one with the effect of air phase. The infiltration process, slope deformation and air behavior were revealed from the three-phase SPH simulations and the results proved that the proposed SPH model could be a useful tool to evaluate the stability of slope and levee under heavy rainfall.

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Cushioning materials, such as sand cushion and granular mats placed on rock sheds, can effectively disperse and reduce rock fall energy before rocks collide with protection works. Although the construction costs for sedimentary layers are low, these layers are attracting attention as construction devices that can substantially improve the margin of safety ratio. To elucidate the cushioning mechanism of cushioning materials, such as sand cushion, the present study examines the transmission behavior of the impact force in a sand mat from different external forces, while paying attention to distribution of mean principal stresses and volume strain rate, which are calculated from contact force and velocity of the particle. The results obtained in this study can be summarized as follows: (1) by calculating the depth distribution of mean principal stresses, the second peak of the impact force of a falling mass was revealed to be due to the wave reflected from the bottom; (2) under the condition of equal input energy, dense and sparse waves were produced when a fast load was applied, but the sparse wave was weaker than the dense wave when a heavy load was applied; (3) in the process that a falling mass collided with the sand cushion, the internal friction angle at the time of the falling mass penetration and stress propagation was smaller than the internal friction angle at the time of the fracture; (4) under the condition of equal input energy, the transmission behavior was stable because the load received was closer to isotropic consolidation when a heavy load was applied than when a fast load was applied.

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