The unltradeep drilling project “M2M-MoHole to Mantle”, is one of the highest priority target of International Ocean Discovery Program (IODP), an international research collaboration of Japan, US and European countries. M2M is a big science that fully requires the capability of the Deep Sea Drilling Vessel Chikyu. The purposes of the M2M project are to penetrate through the 6 km thick oceanic crust to the mantle underneath, and to recover the in-situ mantle rocks for the first time in the human history, in order to understand the nature of the Moho and mantle dynamics, to provide clues for the enigmatic origin of Earth's water and deep carbon cycle, and to explore the limit of deep subsurface biosphere. Scientists have identified three regions as potential M2M project areas; north off Hawaii Islands, off the Costa Rica and west off Baja California. They are preparing for seismic structural surveys of the candidate areas to determine the optimal site for the first MoHole.

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Bending strain distribution on wide flanges does not become uniform because of the shear lag. In solving the problems of the shear lag, an analytical approach with assumptions of the shear lag displacement on certain particular cross section was proposed, and was subsequently generalized by the harmonic analysis. Although the shear lag problems can be analyzed directly by the FEM using solid or shell elements, it may not be appropriate from viewpoints of the designing processes and the cost of analyses. Moreover, even for a particular cross section, such numerical results are not so consistent with those assumed by the analytical methods. We here propose a new approach to resolve such problems. The method uses the homogenized beam theory with FEM for a representative volume element which consists of the solid elements to obtain the pattern of the shear lag displacement and, at the same time, employs the classical analytical approach. Accuracy and feasibility are examined by comparing results with FEM analyses.

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A characteristic function for the near-field equation is developed to reconstruct cavities and/or cracks in 3D elastic wavefield. The method itself is originated from the linear sampling method developed by Colton and Kirsch. The present method uses the singular value decomposition of the near-field operator, that realizes a simplified method to reconstruct cavities and/or cracks. Several numerical calculations are carried out to verify the effectivness of the present formulation.

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In steel structures, brittle crack propagates very fast and easily makes fatal damage on whole of the structures, so it has been studied from both aspects of numerical methods and experiments. However, there has been no valid equations governing brittle crack propagation. Nowadays, the local critical stress model is said to be able to explain brittle crack propagation behavior including the long brittle crack problem. Even though the model focuses on the stress field near the tip of crack, conventional models developed from the model does not evaluate stress precisely and it is needed to study the stress and other parameters near the crack tip to construct the more precise model.
This paper implements fundamental study on the simulation of the crack propagation by the nodal force release FEM in which crack velocity is an input variable. First, we compare error of dynamic stress intensity factor derived from the method releasing counterforce and find Linear counterforce releasing method is better than Jump counterforce releasing method. Second, we consider the effect of the crack acceleration and temperature gradient against stress, equivalent plastic strain and other parameters near the crack tip and these results show crack acceleration and temperature gradient does not affect the parameters when the material has strain-rate dependency. Generally, steel has strain-rate dependency and this result means we do not need to consider the temperature gradient and crack acceleration for simulating brittle crack propagation in steel structures.

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The mechanical behavior of corroded steel members is of interest due to the increased age of steel structures around the world. Though considerable literature exists on the tensile behavior of corroded steel plates, relatively few studies have been reported on buckling behavior. For example, while simple evaluation formulas have been proposed by a few researchers, buckling test results were not used in the development of many of these equations. As a result, the accumulation of data on the buckling behavior of corroded steel plates is lacking. To address this issue, we conducted both buckling tests and finite element analysis to obtain extensive information about the effects of surface profiles on the buckling strength of steel plates. A finite element model of corroded steel plates was developed from a spatial autocorrelation model, which can represent several types of corroded surfaces, including pitting corrosion.
After obtaining the results, we trained an artificial neural network model, of which input is the characteristics of corroded steel plates including the surface profile and materials properties, and verified the accuracy of the model by leave-one-out cross validation. It was found that the model can evaluate the buckling strength of corroded steel plates with much higher accuracy than conventional equations.

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An experimental study was performed on the simple technique for upgrading the seismic performance of a rectangular water tank. To apply the filter installation which can decrease the sloshing wave to an exsiting tank, the effects of filter installation method and position on the damping of sloshing wave were exexamined. A model tank and two real scale cubic tanks with 3000 and 2000 mm were shaked, and the maximum wave heights were measured.
The methods of filter installation damping of sloshing wave were obatained from the model tank, and these were found to be effective for the real scale tanks. The optimum position of filter installation was obtained corresponding to the filter number. The present filter installation was very effective for decreasing the sloshing wave and kinematic pressure at the long period earthquake, but it could not surpress the kinetic pressure derived by the bulging at the short period earthquake.

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This study has investigated the applicability of the existing filtering algorithms to reliability evaluation of civil engineering structures by focusing on estimation accuracy of posterior probability distributions. This study focuses on six algorithms, the Particle Filter (PF), the Ensemble Kalman Filter (EnKF), the Merging Particle Filter (MPF), the Gaussian Mixture Filter (GMF), the Markov Chain Monte Carlo (MCMC) method, and the Iterative Particle Filter with Gaussian Mixture Models (IPFGMM). These algorithms were applied to estimation of posterior probability distributions of interstory stiffnesses in a two-degree-of-freedom shear building model. When the posterior probability distribution is unimodal, most of the algorithms can estimate the distribution with high accuracy. The EnKF, however, cannot accurately estimate even unimodal posterior probability distributions if it does not follow the Gaussian distribution. When the posterior probability distribution is bimodal, the EnKF and the MPF are not capable of computing the probability distribution. The PF is recommended, when a sufficient number of samples can be used with low computational cost, because of its simple algorithm and high feasibility. The IPFGMM can be more efficient when the simulation for each sample is computationally expensive.

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We consider an identification of the number, shape and location of scatterers in a target object using scalar waves in anticipation of application to ultrasonic quantitative non-destructive estimate (QNDE). We calculate the scattering wave field numerically and introduce a objective functional which consists of the difference between the numerical and observational scattering field. The scatterers are determined as the minimizer of the objective functional. We also consider the topology change of the target object in order to execute the identification considering the generation and extinction of scatterers. We define a topology derivative as the sensitivity of the objective functional with respect to the topology change and execute the identification of the scatterers using the topology derivative via the level set method. We solved some numerical examples and determined the number, shape, and location of scatterers at the same time.

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This paper presented a methodology for delineating capture zones of multi-pumping wells using backward particle tracking in geostatistically generated hydraulic conductivity fields based on field data. Under multi-pumping conditions, random walk particle tracking was applied to estimate spatial probability distributions of introduced ensemble cells having the probability that particles within cells reach the pumping wells. Ensemble of the particle evolutions toward pumping wells from a cell was also proposed as the ensemble travel-times and was presented another aspect relevant to spatial distributions of travel-times of cells. Proposed methodologies provided some proper outcomes corresponding to the pumping rates and pumping locations.

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Acoustic emission method is a most useful method for detection of cracks generated in concrete structure. Burst-type AE signals from cracks are to be discrinated from environmental noises under noisy conditions from water flow in a concrete canal bridge. Consequently, FFT, AR model, and AIC method are applied to classify AE signals. Results show that the frequency ranges and the amplitudes of AE signals become high in the case of low water level. AE signals from cracks are effectively discriminated by combination with AIC method. The detection ratio is improved by employing the peak frequencies in AR model. Thus, it is promising to detect crack damages by AEsignals with the relation to water levels in concrete canal bridges.

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The validated modeling of existing bridges will take important roles; however, there are a lot of uncertainties in the properties of existing structures due to deteriorations, seismic loading histories, and the other factors during their operations. Authors have been working on the model V&V of existing structures that is the systematic methodology to deal with those uncertainties in the modeling process. The V&V basically consists of (1) verification process of the numerical model, (2) data acquisition, (3) difinition and sensitivity analysis of prior uncertainties, (4) estimation of posterior distributions by the Bayesian inference with the Marcov Chain Monte Carlo (MCMC), and (5) discussion of quantified parameter uncertainties for obtaining a validated model. In this paper, we especially focused on the time-variant uncertainties due to the detoriaration process; the corrosion process in the bridge bearings that was one of the most significant issues in the maintenance of existing bridges. The experimental verification was conducted by using a beam structure with the steel bearings. Here, the corrosion was promoted in one of two bearings by squirting salt solution, and the strain data were acquired by the loading tests several times during the corrosion process. The Phenomenon Identification and Ranking Table (PIRT) was then applied to consider uncertainties and sensitivities of the FE model parameters. It was then shown that the the systematic decision-makings for updating uncertainties was realized by using the PIRTs in each corrosion process. The posterior distributions indicated that: as the corrosion was promoted, the range of high probability was moved to high coefficient of friction value only in the corroded bearing. It was then concluded that the uncertainties of model parameters that were influenced by the corrosion process could be systematically and appropriately quantified by the V&V process.

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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 concrete structures from core samples is developed, applying acoustic emission (AE) and X-ray CT. Concrete-core samples were taken from reinforced concrete of an existing canal. These samples are strongly influenced by freezing and thawing process. The crack distributions of concrete-core samples were inspected with helical CT scans. After helical CT scan, damage of testing samples was evaluated, based on fracturing behavior under unconfined compression with AE. AE behavior is dependent on the degree of damage, and could be approximated by applying the AE rate process analysis. The AE generation behavior is associated with crack volume responsible for damage in concrete. The characteristics of cracking damage is calculated from X ray CT images with spatial statistics parameters. Thus, the accumulation of cracking damage could be evaluated by comparing spatial parameter with AE. These values are affected by the internal actual cracks. The damage of concrete structures could be quantitatively evaluated by acoustic emission and X-ray CT.

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The X ray CT test is one of the most useful method for detection and visualization of cracking damage of concrete. In recent years, damage evaluation of in-situ concrete structures is now in urgent demand. By the authors, quantitative damage estimation of concrete is proposed to be performed, applying acoustic emission (AE) measurement in a uniaxial compression test with X-ray CT test. In this study, crack concentration properties of concrete samples is quantitatively analyzed, based on X ray CT images with the spatial statistics, because notable discrepancy of spatial statistics parameters are observed between damaged concrete and undamaged concrete. The concrete damage is quantitatively defined as decrease of mechanical characteristics, such as compressive strength and Young's modulus. Correlating concentration index with the damage parameter, quantitative estimation of damage is proposed in terms of the parameter ‘C_δ’. Concrete core samples were taken from reinforced concrete columns of an existing canal which is strongly affected by freeze and thawed process. Prior to the mechanical test, distribution of micro-cracks in a concrete-core sample was inspected by helical X-ray CT, which scans at one-millimeter intervals. Thus, the results suggest that the damage of concrete could be quantitatively evaluated by X-ray CT images. A relation between X-ray CT images and damage parameters is correlated, and the damage of concrete is quantitatively estimated using X-ray CT parameter with spatial statistics.

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The contact-points information of the large-scaled ballast aggregate model (21.1-million-DOFs) is modeled by using both of the Multi-Point Constraints (MPCs) and the nonlinear contact springs. To introduce the direct solver MUMPS corresponding to the parallel computing of a distributed memory type, the whole model is divided into 24 sub-domains for the large-scale parallel computing of FrontISTR. The finite element transient response analysis reveals that the natural frequency of the 1st order vertical elastic vibration mode of the ballasted track exists around 310 Hz and that the rigid body vibration mode of the sleeper occurs at around 1/3 frequency of the elastic vibration mode. The analytical results coincide substantially with the one obtained by the field measurement and the full-scale experimental one. It is inferred that the occurrence of the ballast resonance modes is the cause of the shift and the flow of the ballast gravel.

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Based on meta-modeling which allocates structural mechanics as mathematical approximation of continuum mechanics, we propose a consistent mass spring model (CMSM) for structural seismic response analysis; the consistency guarantees agreement of dynamic characteristics of CMSM with a solid element model. We develop a method of constructing CMSM and verify the method using a simple example. We apply the method to a part of highway bridge consisting of deck and a few piers. It is shown that the constructed CMSM has identical dynamic characteristics of the original model, and is able to estimate dynamic responses such as displacement and cross-sectional forces.

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A numerical method for solving 1-D time-independent Hamilton-Jacobi-Bellman equations, which are referred to as 1-D HJBEs, is presented and applied to test cases for assessing its computational performance. An HJBE in this paper is a nonconservative second-order ordinary differential equation having linear diffusion and nonlinear drift terms. This paper applies a regularization method to the drift coefficient of the HJBEs, which helps well-pose the boundary value problems of the equations in the classical sense. A mathematical analysis on consistency errors between the solutions to the original and regularized HJBEs is performed. The derived results of the analysis show that the regularization method is mathematically consistent. The regularized HJBEs are solved with a Petrov-Galerkin finite element scheme, which is referred to as the PGFE scheme. The scheme is based on the fitting technique and is unconditionally stable for linear problems. Application of the scheme with the regularization method to the HJBEs with bounded drift coefficients demonstrates its satisfactory high computational accuracy. The optimal regularization parameter value as a function of the element size is then numerically identified. The computational results show that the PGFE scheme without the regularization method would fail to accurately capture solution profiles even if thousands of elements are used, which is not the case for the scheme with the regularization method even with hundreds of elements. Impacts of incorporating an adaptive re-meshing method, which is the moving mesh partial differential equation method, into the PGFE scheme are also assessed, demonstrating that it can enhance robustness of the scheme with regularization.

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A method for simulating mass transfer in cracked concrete by means of a damage model and finite elements is proposed in this paper. The damage model, which is based on fracture mechanics for concrete with the modified von-Mises criterion, is applied to model crack propagations in concrete. The mass transfer in concrete is represented by the unsteady diffusion equation. The diffusivity coefficients in cracked concrete are modeled by using the damage variables obtained from the crack propagation analysis with the damage model. We first show the formulation of mechanical problem with the damage model and unsteady diffusion problem in consideration of the damage. Then, after verifying the mesh-dependency and mesh-objectivity of the proposed model, the numerical FE results are compared with the experimental results available in literatures to demonstrate the validity of the proposed method.

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Recently, torrential rainfall frequently occurs due to global climate change and it causes sediment disasters. It is difficult to predict when and where slope failure because of localization of rainfall area. Knowing precursory phenomena is effective for disaster reduction. However, some of them have not been explained in the framework of geotechnical engineering. Organic smell and strange sound, known as a precursory phenomenon of slope failure, are generated by air movement. This study focuses on pore air behavior within the ground due to rainfall infiltration. Here, rainfall infiltration to sloping ground was simulated with using the soil/water/air coupled finite element code, DACSAR-MP. Consequently, it was found out that distribution of pore air pressure is dependent on drainage condition of air and there is interinfluences between pore air behavior and rainfall infiltration behavior.

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We formulate a monolithic thermomechanical coupling method to analyze internal frictional heating of linear viscoelastic material under sinuosidal loads. To construct the monolithic coupled equations, we linearize the weak forms of the equilibrium equations and the heat conduction equation. We apply the present method to a viscoelastic damper model under periodic loads to analyze time histories of the temperature. As a result, we confirm that the present method can decrease the error compared to a staggered method.

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We propose a method of multiscale numerical experiments for evaluating disaster-reductoin characteristics of tide-protection forest against tsunami energy. To conduct the experiments in a hierarchical way, a tide-protection forest is stratified into three spatial scales; the branch-scale is the smallest, the forest-scale is the largest and the tree-scale is intermediate. Tide-Protection Forest is assumed to be porous media and we identify its porous term as reduction characteristics. With the help of the stabilized finite element method, several cases of lower-scale analyses are carried out with different initial and boundary conditions to construct a response surface of the overall resistances at the upper-scale. Thus, with this information about the porous medium's characteristics, a whole costal region can be a analysis target with relatively low computational cost to make a risk assessment for structures behind the forest.

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This paper presents stabilized finite cover based fluid-structure interaction analysis including fracture of structure. The fracture of structure and the contact of structure uses the discrete element method using Cohesive model. The stabilized method based on SUPG/PSPG methods are employed to solve the incompressible Navier-Stokes equation. Since the physical domain is defined independently of the mathematical domain in the finite cover method, the physical boundaries of the structure are represented explicitly in a spatially fixed mesh so that the continuity condition can be imposed directly on the actual interface within the framework of Eulerian approach, and the continuity conditions of velocity and stress vectors at the interface are imposed with the penalty method. Several numerical examples are presented to demonstrate the validity and efficiency of the proposed fluid-structure interaction method.

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In this paper, we proposed a computational method for thermal interaction problems between compressible fluids and solids, which enables us to improve CFL (Courant-Friedrichs-Lewy) conditions based on the speed of sound. In this method, the updating of density and the local averaging operations for velocities are conducted so that new time-step variables satisfy discretized equations in the implicit pressure calculation stage. Through the application to the natural convection in the cavity containing a thermal conductive solid, it was shown that the present method enables us to calculate low Mach number compressible flows free from CFL conditions based on the speed of sound and decrease the computation time.

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This paper proposes and validates a numerical method based on the unconditionally stable dual-finite volume (DFV) scheme for Kolmogorov's forward equations (KFEs) in 1-D unbounded domains, which can be optionally equipped with a mass-conservative moving mesh partial differential equation (MMPDE) method. A KFE is a conservative and linear parabolic partial differential equation (PDE) governing spatio-temporal evolution of a probability density function (PDF) of a continuous time stochastic process. A variable transformation method is proposed for effectively solving the KFEs in 1-D bounded domains. Application of the DFV scheme to a series of test cases demonstrates its satisfactory computational accuracy, robustness, and versatility for both steady and unsteady problems. Impacts of modulating a parameter in the variable transformation method on computational performance of the DFV scheme are then numerically assessed. Advantages and disadvantages of using the MMPDE method are also investigated.

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The present study addresses thermoelastic topology optimization of a minimum compliance problem. It is well-known that the thermal loading depends on the material stiffness coefficient and the thermal expansion coefficient; this causes physically unrealistic situation if both coefficients are regularized in a conventional interpolation scheme. This study applies a specific regularization, so-called the thermal stress coefficient to avoid the problem. This approach is examined by a series of numerical examples for porous and composite materials.

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The present study proposes a method of topology optimization of microstructures (in-plane unit cell) that maximizes the overall mechanical performance of composite plates. The proposed method hinges on the method of numerical plate testing for two-scale composite plate model, in which thick plate theory is employed at maco-scale and 3D solids are assumed at the micro-scale. Since the macroscopic generalized strain and stress are respectively related to the microscopic strain and stress distributed in the unit cell, the homogenizad plate stiffness approriately reflects the geometrical feature of microstructures. Several optimized topologies a maximeze the macroscopic stiffness are presented to demonstrate the capability of the proposed method.

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Wave analysis in rocks is widely used in seismology and geophysical exploration. Rocks under the ground have pores and cracks which are saturated with pore fluid. Therefore, in the numerical analysis, consideration of effects of both cracks and pore fluid is required. The aim of this study is development of a frequency-domain boundary element method for 3-D wave scattering in general anisotropic fluid-saturated porous solids. Some numerical results show the validity of our proposed method.

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A simulation tool which can predict possible damages to the structures in coastal area plays decisive roles to mitigate and prevent next huge tsunami. According to the previous researches on the analysis of tsunami, two-dimensional shallow water simulation have been developed to project tsunami height and tsunami arrival times, as well as three-dimensional analysis have been utilized to evaluate tsunami fluid force in local scale. The authors have developed multi-zooming tsunami simulation having both advantages of two-dimensional tsunami analysis (finite difference method) and three-dimensional tsunami analysis (particle method). However there are no boundary treatments which can manipulate measured values in each analysis with high accuracy. In this study, matrix array shaped virtual wave-making plate was suggested as a boundary treatment method for multi-zooming tsunami simulation by using particle method. Limitation of application of previous scheme was described based on two validation problems. Besides we confirmed that complicated velocity distribution can be replicated correctly using suggested method.

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This paper presents two greedy scheduling algorithms for recovery of damaged lifeline network. Unlike genetic algorithms or simulated annealing, the proposed algorithms do not involve random processes. One of the algorithm is for assigning multiple heterogeneous engineers and prepare schedules for repairing independent damaged components, while the other is for finding repair schedule for a single engineer considering network constraint. Both the algorithms uses rate of benefit gain as an index in deciding which component should be repaired next by whom. The target application of these algorithms is to serve as an initial solution for a multi agent system which includes fine grain details. With numerical experiments, it is demonstrated that the proposed algorithms can find near-optimal repair schedules and solve problems involving large number of variables.

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This paper presents experimental results and numerical simulation of direct pull-out tests of basalt fiber reinforced polymer (BFRP) bars embedded in concrete. First, two patches of experimental pull-out tests are briefly descried. In the first experimental patch, the influence of surface texture configuration of BFRP bars on the bonding characteristics between BFRP bars and concrete is investigated through direct pull-out tests carried out on concrete cubes reinforced with BFRP bars. Pull-out test on ribbed steel reinforced concrete cube was also carried out for comparison. In the other experimental patch, pull-out tests were carried out on BFRP bars embedded inside pre-drilled holes into heavy concrete blocks. Through these pull-out tests, the efficiency of two different adhesive materials; namely: epoxy putty and polymer cement, and the effect of cross-section diameter of BFRP bars on the BFRP bar-concrete bond mechanism were investigated. Second, a finite element model (FEM) was employed to analyze the interfacial behavior between BFRP bars and the surrounding materials. Through the FEM, the influence of the tested parameters on the characteristics of local bond-slip models of BFRP bars was assessed by considering different material properties as well as different fracturing bond mechanisms. The experimental and numerical results showed that the bonding behavior of BFRP bars-reinforced concrete structures can be improved by treating the surface texture configurations of BFRP bars. In addition, the properties of the adhesive material between BFRP bars and concrete are key factors controlling the bond mechanism of strengthened concrete structures. Moreover, the proposed FEM was found to be capable of simulating the fracturing bond mechanism of BFRP bars.

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The nonlinear ultrasonic testing has attracted notice as a new technique for detection of closed cracks which cannot be found by the linear one. However, the generation mechanism of sub-harmonic wave, which is one of the nonlinear ultrasonic waves, has not been understood clearly from theoretical point of view yet although it is considered as caused by the dynamic interaction of crack faces such as clapping or friction. In this paper, the boundary integral equation for two-dimensional crack problems is formulated and numerically solved to investigate the behavior of the sub-harmonic wave. Some numerical results of sub-harmonic generation are obtained and discussed.

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This paper presents a numerical simulation method for transient acoustic field analysis based on boundary element method and its application to the auralization of road traffic noise. For the governing equation, the unsteady wave equation is employed. In order to solve a large scale problem, the fast multipole boundary element method (FMM) is applied. Three dimensional wave scattering problem with a road trafic noise is solved by the time domain FM-BEM. The auralization is investigated by using the computed sound pressure.

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In finite element analyses of beam-like structures, finite elements based on the beam theory are efficient to represent overall behavior. On the other hand, it is necessary to use solid elements to resolve local behavior such as beam and column joints. In this work, we discuss numerical procedures to connect beam and solid elements.
In conventional procedures to connect beam and solid elements, continuity condition is considered for only displacements. In such procedures, over constraint is applied to solid elements on the interface between solid and beam elements and unreasonable deformation of solid elements near the interface may be observed.
In this work, we propose a numerical procedure based on the Nitsche's method, which allows us to consider continuity condition for both displacements and stress vectors. Then solid and beam elements can be connected with reasonable deformation and stress distribution.

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This paper presents implementation of higher order PDS (HO-PDS) in FEM framework (HO-PDS-FEM) to solve a boundary value problems involving cracks in linear elastic bodies. Further, an alternative approach based on curl free restriction to extend the current PDS is also presented. This alternative curl-free implementation is scrutinized and compared with a former proposal for HO-PDS whose derivative is not guarantee to satisfy curl free condition. Analysis of traditional plate with a hole problem shows that curl free implementation does not have any specific advantage. Further, techniques for modeling cracks in HO-PDS-FEM are presented. Comparison of two formulations with mode-I crack problem indicates that former proposed HO-PDS-FEM is superior to the proposed curl free formulation, and there is a significant improvement compared to 0^th-order PDS-FEM.

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In the rigid plastic finite element method (RPFEM) the locking phenomenon often arises when three node triangular (T3) elements are used. To avoid the problem, the node-based element can be applied, but the application of the node-based element does not always give a correct failure mechanism. Therefore, we apply the edge-based element to the mixed RPFEM and evaluate its validity. We solve four typical problems and compare the results of the T3 element, the edge-based element and the node-based element. It turns out that the mixed RPFEM with the edge-based element gives valid results except the problem under a strong restriction condition.

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This paper presents a simulation method based on the wave-acoustic theory and its application to the auralization of traffic noise. The CIP method using adaptive mesh refinement (AMR) is employed for solving the governing equation accurately. In order to obtain the accurate numerical solution by CIP method for the propagation of an impulse wave, an imitation impulse developed by Lubich is employed. The auralization of traffic noise is performed by the convolution using the results and the sound source data. The present method is applied to three-dimensional wave propagation problems in order to investigate the validity of the method. The present method is shown to be an useful tool to investigate the traffic noise.

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Very heavy rain on July 28^th in 2013 in Yamaguchi and Shimane prefectures resulted in severe damages of railway bridges in the Abu river. To evaluate the water preressure induced in the bridges, we conducted numerical analysis using the Smoothed Paricle Hydradynamic Method. The numerical result shows that the heading up of the water flow induces the gap height between the front face and back face of the bridge pier. It can be found that these gaps cause the unbalance of the static water pressure and increase the bending moment and shear force to the bridge pier. We finaly proposed the equation of shear force and bending moment estimated from the gap height of water surface.

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This paper discusses the movements and rearrangements of about 30,000 sand particles due to the impact of a water-drop using a multiphase computational method (MICS) parallelized with MPI. The computational method can deal with the movements and collisions of individual sand particles as well as the mechanical interaction between fluids and sand particles. The amounts of the removed volumes, which had been occupied by sand particles, due to the impact were calculated by varying the momentums and shapes of the water-drop. As a result, it was shown that the calculated results are in good agreement with the experiments and that the computation time is shortened by the parallel computations.

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In the Great East Japan Earthquake in 2011, a large number of tsunami drifts increase the devastating damage. In order to develop the computational method that can deal with many tsunami drifts, a multiphase model (MICS) was improved so that it can take account of the collisions among drifts, buildings and ground surfaces. The numerical experiments were conducted with the present computatinal method. As a result, it was shown that the present method allows us to calculate many floating objects transported among non-uniform ground surface and the debris control structures. In addition, fluid forces acting on structures were estimated. Finally, the efficiency of the present parallel computations was discussed.

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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. piping destruction associated with the decline of the bearing capacity by seepage flow and III. soil scour and erosion behind the seawall during overflow. 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 soil scour problem. By using the empirical equation based on the correlation between shear velocity and sediment discharge, we implemented the numerical analysis to replicate phenomenon of scouring in the back of breakwater. The experiment tests with 1/25 scale breakwater are utilized for the validation of our numerical simulation model, then we have discussed the applicability and limitation of the empirical equation.

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In this study, a constitutive rule for the stress-strain relation in which the grain crushing of normally consolidated sand under one-dimensional compression was developed based on the behavior of the soil structure of sand grains. The constitutive rule is based on the phenomenological hypothesis that the logarithmic void strain gradient Δε_es/Δσ (Area I), which corresponds to the elasto-plastic components of the soil structure, and the logarithmic void strain gradient Δε_c/Δσ (Area II), which corresponds to of the failure component attributed to grain crushing, both follow the power law with respect to the compressive stress σ. Furthermore, we developed an evolution rule for the strain, considering the degradation of soil structure associated with failure due to grain crushing (Area III) along with the strain in the soil structure during failure due to grain crushing ε_c as an internal variable. The proposed constitutive rule that describes Areas I, II, and III in a unified manner was validated through verification against actual measurements. This constitutive rule is considered to be significant for improving the expressive capabilities of existing numerical models because it describes an extensive strain area.

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This study aims to develop a stress-strain model for concrete under compressive stress that has undergone freeze-thaw deterioration. A stress-strain equation is proposed based on an examination of the results of compression tests on cylindrical specimens. First, cylindrical specimens with various degrees of deterioration were created, and these underwent compression testing to determine the stress-strain relationship. A simple model was assumed in which the strain caused by closing of the voids created by freeze-thaw action was factored into the stress-strain relationship of concrete under compressive stress, as described in the JSCE Standard Specifications for Concrete Structures. The relative dynamic modulus of elasticity was used as a parameter for the model, since it is widely used as a deterioration index for concrete that has undergone freeze-thaw deterioration. The stress-strain relationship proposed in this study was verified as roughly agreeing with the results of the experiment on concrete freeze-thaw deterioration.

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Installation of steel sheet piles at the toe of a levee has been adopted as a countermeasure against liquefaction of the levee foundation in earthquake. Recently, installation of the steel sheet piles at the shoulders of the levee with tying the sheet pile heads by rods is proposed to secure the function of the levee both in earthquake and in overtopping. Since installation of the sheet piles alters the seepage flow in the foundation ground, use of permeable steel sheet piles is also proposed. On the permeable sheet pile, there are holes sufficient to secure the water flow in the ground so that the existence of the sheet pile does not interrupt the seepage flow. However, near the holes, onset and development of internal erosion might occur by the concentrated seepage flow due to the large hydraulic gradient around the holes. In this study, development of internal erosion near the holes on the permeable steel sheet pile is simulated by combining seepage flow analysis and internal erosion analysis. Comparison with physical model test reveals that the experimental result can be captured by the numerical analysis as a whole. However, the clogging of fines in the experiment cannot be modelled, as fines once detached from the soil skeleton cannot be redeposited again with the internal erosion model used in this analysis.

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Embankments are constructed with compacting soil with the aim of improving their stability and deformation characteristics. Typhoons and guerrilla rainstorms are occurring frequently due to the abnormal weather of recent years, and there have been many reports of cases of collapses of embankments due to their effects. Drainage measures for embankments against rainfall are different during construction and after commencement of use, and the effects are sustained intermittently from the start of construction to after the commencement of use. In this study, soil/water/air-coupled F.E. analysis was used to perform analyses of embankments which take into account compaction and the history of rainfall/evaporation. Further, changes in the stresses inside the embankment by the effects of rainfall sustained after commencement of use are considered. In addition, the effectiveness of current drainage measures for embankments is considered.

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Earthquakes constantly hit Japan and liquefaction always lead serious damage to structures. Therefore, countermeasures against the liquefaction are urgently needed to prevent the small structures such as personal houses and underground structures from the damage. Unfortunately, however, countermeasures for small structures are not so intensively studied compared with the massive structures in civil engineering, especially there are few countermeasures for existing structure. In this paper, particular attention is paid to the enhancement effect of the dissipation of excess pore water pressure using drainage diaphragm wall with high permeability and large restraining effect of soft soil. The drainage diaphragm wall is made of the soil materials having high internal frictional angle and permeability, whose countermeasure against liquefaction is investigated by 1g shaking table test and finite element analyses. The results obtained in this research can be summarized as follows: (1) by using the drainage diaphragm wall around structure, it is possible to suppress the subsidence and inclination of the structure; (2) Due to the drainage diaphragm wall, the defamations of the wall and the soil near the wall are suppressed significantly due to the quick dissipation of the excess pore water pressure and the restraining effect of the diaphragm wall; (3) improvement effect by the drainage diaphragm wall is higher than those by column-shaped improvement wall, and so does the deformation; (4) improvement effect of the diaphragm wall depends not only on the wall depth, the rigidity of the wall but also on the permeability of the wall ; (5) the wall made of drainage material does not collapse even in the completely liquefied ground due to the strong recovery ability of the effective stress near the wall and the resistance against the horizontal osmotic pressure toward the wall.

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Though a lot of bridges which are made from steel or concrete were constructed until now in Japan, it was found here and there for decrepit or damaged bridges now. It needs for these bridges to repair and reinforcement by suitabale and practical methods. In this paper, one of the reparing method of the deteriorated RC slabs are proposed using aluminum alloy which has lightweight and good corrosion resistance. The aim of this study is to investigate the possivility of use aluminum alloy as members of the girder bridge by comparison with steel girder bridge. The static and dynamic behavior of four girder bridge models combined of RC slab, steel girder, aluminum slab and aluminum girder was clarified by numerical analysis using ABAQUS program. From these results, it was found that the ultimate strength of the girder bridge with aluminum slab replace of RC slab was enough and the 30% weight of this girder was able to reduce.

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A slip on the strike-slip fault causes flower structures and Riedel shear band within the overlying cover. This paper simulates the formation of these structures, employing the dynamic elasto-plastic finite deformation analysis code GEOASIA^®.
The main conclusions are as follows: (1) A set of Riedel shear structures accompanies the plastic expansion of the material, (2) A pattern of the initial material imperfections dominantly influence the formation process of Riedel shear structures and (3) Riedel shear bands don't appear in larger models, whose bottoms have more lightly overconsolidated by higher overburden pressure.

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It has been pointed out that increased earth pressure in the ground which acts on pipes buried under frozen ground, and increased stress exerted by vehicle load that in the ground during removal and clearance of snow may have caused serious breakages of gas conduits in cold region in the past. Attempts have been made to bury pipes at a shallower depth in order to reduce replacement costs of aged water pipes in cold region. There are, however, very few studies of detailed examinations of stress in the ground changes owing to the freezing of surrounding ground.
This study, therefore, measured detailed temperature distribution around a water pipe buried under the pavement and vertical earth pressure in the ground, as well as seasonal changes of stress exerted by vehicle load. Results revealed that these measured values change significantly as a result of the ground's freeze-thaw process. In addition, this study found that stress analysis using the multi-layers elastic theory can represent to some extent the seasonal changes of stress exerted by vehicle load.

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The influence and contribution of fiber reinforcement to shear moduli and shear strength of granular materials such as soils have been widely investigated by geotechnical engineering.A modelling approach for evaluating the constitutive behavior of fiber reinforced granular material have been strongly required to understand the reinforcement effect of fiber depending on type, volume fraction, length and tensile moduli. This paper presents a new constitutive model of fiber reinforced granular material under triaxial conditions based on rule of mixtures. In this model, the stress distribution tensor, which is calculated by stiffness matrix of both fiber and granular material, is introduced to combine the characteristics of between fiber and granular material. The stiffness matrix of fiber is defined by assuming that fibers are working in their elastic domain. Fiber orientation distribution can be evaluated by probability theory. The stiffness of granular material is evaluated by the elastic-perfectly plastic Mohr-Coulomb model. The constitutive model for fiber reinforced granular material is calibrated against experimental data of the previous study. Simulations captured the reinforcement effect depending on fiber fraction, tensile moduli and fiber orientation qualitatively.

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There are several studies that examine the changes in the engineering properties associated with the increase in the water content ratio of compacted ground material by microscopic soil structure. However, in previous studies, the microscopic structure of the soil a tool role for interpreting the mechanical test behavior. Therefore, the physical meaning of the microscopic structure of the soil is not clear.
In this study, the mechanical tests were performed to sandy soil were prepared by changing the water content. Furthermore, the change in deformation and strength characteristics from the mechanical tests evaluated by the suction and the coordination number obtained by X-ray CT scans. From the test results, it found that coordination number is affected the deformation and strength properties of compacted geomaterial of varying water content.

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We propose a rheology-based viscoelastic-viscoplastic constitutive model that takes into account the self-heating phenomenon of thermoplastic resin. Different kinds of hyperelastic constitutive laws are used for the viscoelastic and viscopelastic rheological elements. A generalized Maxwell model is used to characterize the viscoelastic material behavior at small or moderate strain regime, while a finite strain viscoplastic model is employed to transient creep deformations due to frictional resistance of molecular chains. Also, back stress is introduced to represent the hardening due to orientation of molecular chains. After verifying the fundamental performance of the proposed model in reproducing typical material behavior of resin, we carry out several numerical analyses for simple structures to demonstrate its applicability for practical use.

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