We present a review on the formation and evolution of the universe based on recent observations and theoretical considerations. In particular, we summarize the observational properties and theoretical perspectives on both the dark matter and dark energy that occupy 95 percent of the mass density in the universe.
The critical buckling characteristics of hydrostatically pressurized complete spherical shells filled with an elastic medium are presented. A model based on small deflection thin shell theory, the equations of which are solved using exact methods in conjunction with variational principles, is presented. In the current formulation, axisymmetric and inextensional assumptions are not used initially and the elastic medium is modelled as a Winkler foundation, i.e.using uncoupled radial springs with a constant foundation modulus that is independent of wave numbers of shell buckling modes. Critical buckling pressures and characteristic modal shapes are demonstrated for a wide range of material and geometric parameters. A phase diagram is established to obtain the requisite thickness to radius, and stiffness ratios for a desired mode profile. The present formulation can be readily extended to apply to more general cases of non-axisymmetric buckling problems.
A simple vibration control system proposed here involves two combined structures with some simple vibration dissipation material between them. By combining two inclined cantilever-like constructions at the top of these structures and placing highly damping rubber where they join, the vibrational energy can be effectively dissipated by a small amount of vertical oscillatory motion. Experiments involving two conditions, in which vibration is controlled and not controlled are considered. Under these conditions, the effectiveness of these structures for both free and forced vibration is demonstrated. Numerical analyses have also performed to make sure the effectiveness obtained by the experiments.
In this paper, an acoustical sensing unit for temperature distribution measurement is proposed. The acoustical sensing unit has been proposed by authors and there is still a room to improve its performance; improvement of measurement resolution and optimization of total measurement cost. In this paper, an effective sensor aliment and application of wireless communication system, ZigBee, for acoustical sensing unit is proposed. In newly proposed sensor aliment, the spatial resolution is improved around 10 % than previous sensor aliment, and ZigBee enables reliable and low-cost wireless communication between sensors. Performance evaluation is conducted experimentally and the obtained results suggest that the new acoustical sensing unit has sufficient resolution in temperature distribution and performance of data collection via ZigBee is enough for temperature measurement.
Damage detection of a bridge based on vibration induced by moving vehicles is proposed. Accuracy of damage detection depends on observation and damage points. In this research, sensitivity of observation or damage points is estimated by using posterior covariance matrix of estimation error and information entropy. The estimation is not reliable where the sensitivity is low because it is strongly affected by prior information. New type of prior information is proposed and applied to a simple numerical problem for illustration of usefulness. The method is applied to the damage detection of experiment model with vehicle-induced vibration.
This paper first presents an estimation method of the imaginary part ratio of the frequency response functions (FRFs) from simultaneous measurements at two different locations on a linear structure. The method is based on the reciprocity theorem and the principle of causality, and assums 1) the structural damping matrix is proportional to the identity matrix and 2) force acts on only one point of the structure at a time, which moves throughout the structure with a constant Fourier amplitude. Then, this paper presents a damage identification method for structures using change in the imaginary part ratios of the FRFs. Structural damage is assumed to be accompanied by changes in element stiffness and structural damping. The validity of the estimation method and the damage identification method is verified through a numerical simulation.
Horizontal directional drilling (HDD) is the method expected to prevail for laying lifelines that avoids the need to make an open cut. However, the location of the drill -bit underground must be known at all times when conducting this method. As conventional electromagnetic wave-based methods are known to have several problems, herein we suggest a new method based on the propagation of elastic waves in the ground. In this study, “Vibro” is used as the generation method of elastic waves. This is a feature loaded on the heavy machineries used for HDD. Differences of arrival time are obtained from first peak times of the waveforms measured by the geophones set up on the ground. The possibility to actualize this method is examined by application of an approximate three-dimensional (3D) location method to the differences. As the result of this study, there is the possibility to actualize this method but accuracy improvement is challenges for the future.
This paper proposes an evaluation method of surface tension without using curvature of interface. Curvature of interface is needed to evaluate surface tension in the existing methods such as CSF model. However, stable evaluation of curvature requires finite region of interface between fluids which prevents efficient simulation of violated multi phase flow with large numbers of bubbles and droplets. The objective of the proposed methods is efficient surface tension modeling which enables simulation of highly violated air-water flow with minor number of computational cells. The proposed model directly evaluates surface tension from cross line between cell boundary and interface and does not require finite width of interface region. Two and three dimensional test cases are carried out to confirm that the method provides qualitatively appropriate results.
A model order reduction has been utilized as a booster of FEM, mainly in the design of micro-electromechanical system, by using orthogonal basis vectors of the Krylov subspace. However, there is no clear procedure to determine a n effective reduced order, which indicates the number of the orthogonal basis vectors, because of the lack of error definition. In this paper, a practical use of the model order reduction via Krylov subspace (KS-MOR) is proposed to simulate low frequency responses of structure dynamics accurately. One of the important approximation properties of KS-MOR is the Moment Matching (MM). The MM provides a certain accuracy of KS-MOR in frequency domain, but the accurate frequency range cannot be defined. Then, a stepwise iterative frequency response analysis is utilized to evaluate an effective reduced order before it is applied in the time transient analysis. In the frequency analysis, simple error estimation is performed to c heck the comparison between the KS-MOR results with different number of basis vectors. Fin ally, a couple of numerical example has been simulated to validate our proposed procedure.
In the time-domain BEM with Haar wavelets for 2-D diffusion problems, the relation between the number of non-zero entries of the coefficient matrices and the degree of freedom (DOF) N is theoretically investigated using the information on the size and the arrangement of the support of the basis functions. The coefficient matrices are compressed using the Beylkin-type level-independent truncation scheme with a DOF-independent prescribed threshold value. The number of non-zero entries of the matrix G(L,p) and H(L,p) (1 ≤ p ≤ L, L: current time step), N(G(L,p)) and N(H(L,p)), increases in proportion to the factors log N, N1/2, N and N log N, except for the behavior in the smaller DOF range where N(G(L,p)) and N(H(L,p))∼O(N2). For M»1 and N»1, N(G(L,p)) and N(H(L,p)) show O(N log N) in matrix compression with a prescribed threshold value λ.
Due to difficulty to obtain reliable ground data, layout of rockbolts is determined entirely in a classical way assuming an isotropic rock stress condition. The present study assumes anisotropic stress condition and optimizes layout of rockbolts in order to maximize the stiffness of unstable ground of tunnels and slopes by applying multiphase layout optimization. It was verified that this method has a certain possibility to improve the stiffness of unstable ground.
In this work, a finite element procedure for overlapping meshes based on a domain decomposition approach is presented. In the proposed procedure, solutions on different meshes are connected on the domain interface. For the formulation to connect solutions, the Lagrange multiplier method extended from the Nitsche's method is employed to avoid the limited selection of discretization of the Lagrange multiplier. Further a rectangular mesh on the background of the overlapping meshes is introduced. The interface to connect solutions on overlapping meshes is defined by using jointed cell edges of the background mesh and it is independent to each calculation mesh.
The rocking motion of tanks due to earthquakes causes the uplift and partial of large deformation of the tank bottom plate that has been considered to contribute to the various damage of the tanks. For analyzing the stress of the tank bottom plate numerically, this paper develops the analytical finite ring element with effects of the large deformation. The ring element is defined as a semi-analytical model. Fourier series give its circumferential displacement function, while polynomial gives its radial displacement function. For evaluating analytical accuracy of the proposed method, numerical results are compared with experimental ones that measure deformation of circular aluminum plate subjected to hydro static pressure.
A numerical analysis for electromagnetic NDE(nondestructive evaluation) is considered. In electromagnetic NDE, electromagnetic waves attenuate in the target objects such as concrete structures. We investigate a time domain BIEM with the Lubich CQM(convolution quadrature method) to deal with attenuating electromagnetic waves in the target objects. By using the Lubich CQM, the layer potentials are represented with the Laplace transform of the fundamental solution. We solve wave scattering problems that electromagnetic waves attenuate in the target object. We show the scattered electric field can be calculated numerically by using time domain BIEM with the Libich CQM.
This paper presents a convolution quadrature time-domain boundary element method for fluid-elastic half space. Application of convolution quadrature method (CQM) to time-domain boundary element method (BEM), which is called CQ-BEM, can help improve numerical stability of time-stepping procedure. However, the conventional CQ-BEM for fluid-elastic half space has two disadvantages. First, it requires much memory to evaluate retarded potentials of time-stepping procedures. Second, it is difficult to couple both boundary integral equations for fluid and elastic half space with time-domain boundary conditions on fluid-elastic interface directly. The formulation presented herewith improves these disadvantages by transforming boundary values in time-domain into Fourier-domain. As numerical examples, air-coupled ultrasonic simulation is shown to validate the presented method.
Real composite materials such as concrete, mortar, etc. sometimes contain unintended voids in itself. The voids govern the macro brittle behavior due to the micro cracks. We propose a special element containing a micro void, namely BE-FE blending element. The displacement inside the element is represented by a superposition of the accurate solution from boundary element method and the continuous shape functions. The stiffness matrix implicitly accounts for the the effects from the void, and is applied to the stiffness matrix of conventional finite element method. The accracy of the stress fields is gurannteed when the void size is less than 10% of the element size. We exhibits the applicabliity to the deformation analysis for the extention of elastic plate with a single void, multiple voids and also a inclusion.
In recent years, a new ultrasonic nondestructive testing that utilizes nonlinear ultrasonic behavior generated in cracks or at material joints has emerged. However, the mechanism of generating subharmonics and higher harmonics used in testing is still not well understood theoretically. In this research, in order to simulate the higher harmonics, dynamic contact problems of a solid-solid interface with nonlinear boundary conditions are investigated by convolution quadrature time-domain boundary element method (CQ-BEM), which can stably analyze wave propagation with small time increments. Numerical results show that higher harmonics are excited by the P-wave incidence to the interface defect, but that only odd order harmonics are generated in case of S-wave incidence.
Particle-based solid/structural analyses have been presented. In the particle-based analyses, solid or structure are discretized by particles and there are no meshes like FEM. Then, it is relatively easy to treat large deformation analyses. There are Reproducing Kernel Particle Method (RKPM) or Hermite RKPM (HRKPM) as the generalized formulation of particle-based analyses. In this paper, we perform a basic study to develop the structural element adjusted to nonlinear analysis using combination of these methods. A geometric nonlinear formulation of that the in-plane and the bending deformations are represented by RKPM and HRKPM respectively, is presented.
Many recent numerical models for predicting flood inundation flows are based on the system of shallow water equations. Though the shallow water equations are highly precise to describing the motion of inundation flows in the flood inundated area where the water is continuous, it is not appropriate to be applied at the frontal area of the inundation flows, because the water is not only discontinuous, but the neighboring dry bed is also beyond the describable range of shallow water equations. Present research gave a focus to the front of flood inundation flows. The impacts to the gradient of water depth at flow front due to different mesh size, the effects of critical depth for water motion, and the contribution of the velocity conditions, etc, were investigated here with one dimensional, axisymmetrical and two dimensional dam breaking problems for an incompressible ideal fluid on a horizontal bed.
Analysis of hole formation on the hypervelocity impact penetration of metal targets subjected to projectiles is presented. The proposed approach establishes one governing equation for target, projectile and fluid (air) using mixture theory assuming incompressibility in the full Eulerian framework. The Eulerian formulation is attractive for the analysis of hole formation on penetration because it can generate new free surface in natural manner. We validate computational results comparing with a physical based hole diameter relationship.
This paper presents a new Eulerian type numerical method for Fluid-Structure Interaction (FSI) problems with free surface based on the finite cover method (FCM). Since the physical domain is defined independently of the mathematical domain in the FCM, which is known as a generalized version of the FEM, 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. The VOF and Level Set method are employed to represent interfaces, and the stabilized method based on the streamline-upwind/Petrov-Galerkin (SUPG) and pressure-stabilizing/Petrov-Galerkin (PSPG) methods are employed for flow analysis. The weak coupling scheme is employed for the interaction between fluid and structure. The proposed method is applied to several numerical examples to show the validity and efficiency of the method.
Simulation of turbulent air flow over terrain influenced by objects like buildings is done using terrain fitting curvilinear coordinate system with obstacles represented by the Immersed Boundary Method (IBM). With a slight increase in computational efforts compared with the commonly used IBM on rectangular grids, the properties of the ground boundary layer and the effects of the disturbances by the obstacles can efficiently be represented in Large Eddy Simulation (LES) of the local wind field. The detailes of the technique are explained and an application to a real terrain in Toyama prefecture of Japan is presented. Though the Reynolds number used in these demonstrations is relatively low, the results are good and encourage further development to full scale flows.
This paper presents a numerical study of the identification of parameters for the tidal fluctuation. Tides can be expressed in the sum of regular trigonometric function which is controlled by the movement of astronomical objects. This trigonometric function is called tidal constituents. In this research, the main four constituents (M2, S2, K1, O1) are treated. The parameters, which are identified, are the amplitude and the phase difference of the four constituents. The parameter identification is carried out based on the optimal control theory. In this research, the sensitivity coefficient method coupled with finite element method is applied. As numerical study, a parameter identification in Tokyo bay is carried out.
The ground pollution is one of the most serious environmental issues all over the world now. Industrial wastes discharged from various human activities infiltrate to the ground, diffuse and damage to plants and animals indirectly. Therefore, it is strongly requested to know the transfer behavior of contaminant movement in the ground. In this study, continuous equations and advection-dispersion equation are derived from mass conservation laws in soil, water, air and dissolved material phases. These governing equations are applied to the constitutive model for unsaturated soil and formulated in the framework of the initial boundary value problems with the finite element method The soil/water/air coupled analysis program, DACSAR-M_ad, applied mass transfer equation to is coded. Here, the mass within the ground due to loading is simulated with this code.
The authors have proposed a hybrid type formulation of rigid plastic finite element method for two-dimensional problems. This formulation has been modified to handle with shear locking and hourglass mode with the introduction of the linearly distributed stresses within an element. In the context of previous studies, a hybrid type rigid plastic finite element method for three-dimensional problems is investigated in this paper. Firstly, spacial discretization of a stress field in an element is discussed. Secondly, a numerical code is developed with the implementation of the abovementioned stress distribution. Finally, four example problems, i.e., plastic load of a plate with a hole, stability of a tube with defects under inner pressures or bending moments, stability of conical slopes and bearing capacity of circular footing are solved to check the numerical performance of the developed code. The results show good agreements with others' studies. It can be concluded that the numerical method proposed in this paper is reliable and promising.
This paper proposes a new analysis method to estimate a residual deformation of soil structure for external loads. It employs a rigid plastic constitutive equation for soil which needs a small number of soil constants in comparison with general elasto-plastic constitutive equations. The purpose of this method is to simulate a large amount of deformation caused by failure of soil structure based on finite deformation theory. The features of proposed method are (1) simulation for large deformation of soil structure, (2) no effect of initial stress distribution, and (3) application to dynamic load. This study expresses the formulation of rigid plastic dynamic finite element method based on finite deformation theory. It examines the applicability of proposed method by applying to Prandtl's limit bearing capacity of foundation for static monotonically increasing load. The result clearly shows the applicability of rigid plastic constitutive equation to deformation analysis. Both kinematical effect and time rate dependency on limit bearing capacity were clearly presented by employing Rigid Plastic Dynamic Deformation Analysis Method.
Stability of multiple underground openings (tunnels) in cohesive-frictional soil subjected to surcharge pressure has been theoretically and numerically investigated assuming plane strain conditions. Unlike the case of a single tunnel, the center-to-center distance appears as a new problem parameter, which plays a key role in tunnel stability. A continuous loading is applied to the ground surface. For a series of tunnel diameter to depth ratios and material properties, rigorous lower and upper bound solutions for the ultimate surcharge pressure which can be exerted on the considered soil mass are obtained by applying recently developed numerical limit analysis. For practical suitability the results are presented in the form of dimensionless stability charts. As an additional check and also a handy practical means, upper bound rigid block mechanisms for dual tunnels have been developed and the predicted collapse loads compared with the results from numerical limit analysis.
This paper presents the results of a numerical investigation conducted to study the effect of vertical loads on lateral response of a free head and a capped pile group in sand. A coupled soil-pile system is idealized through 2D finite elements with soil models idealized by a hyperbolic type multiple shear mechanism. The analysis focuses on the five piles in the middle row of a 3x5 pile group spaced at 3.92-pile diameters. The interaction between a pile and the surrounding soil in the 3D type is idealized in the 2D analysis using soil-pile interaction springs with a hysteretic non-linear load displacement relationship. The presence of vertical loads on free head piles increases the confining pressures in the sand deposit confined by the piles but the rate of increase in those outside the group is relatively small, resulting in the difference in a balance of lateral soil pressures acting at the back of and in front of individual piles. A vertical load applied to a group pile with a uniform vertical displacement of 0.1 pile diameter decreases the lateral resistance of the leading pile (pile 1) by 10 % and increases the lateral resistance of piles 3 and 5 by 14 and 35 %, respectively. The same trend with higher percentages of increase or decrease is observed in the capped pile group case.
The stress level of the incipience of localized deformation in ductile materials is shown to be considerably higher than the observed stress when it is estimated analytically by a bifurcation criterion with constitutive laws using the Jaumann stress rate of the Cauchy stress. In our investigation, we employed the Truesdell stress rate to predict the localization stress with the same criterion. While only the compressive localization stress can be predicted, the predicted stress level is smaller than that measured by the Jaumann stress rate by as much as a factor of ten. This is consistent with many experimental results. Even in three dimensional stress states, the localization stress is ten times smaller than the elastic moduli. Furthermore, the constitutive relation using the Truesdell stress rate yields straightforward results during simple shearing and uniaxial loading, indicating that the Truesdell stress rate should be preferably considered as a measure for describing material properties in rate form.
Numerical methods that can accurately evaluate the failure behavior of a rock mass are required to evaluate the stability of a rock slope and of the foundation site of important structures during major earthquakes. Therefore, in this study, plane strain compression tests were conducted on artificial rock masses with several discontinuities to obtain data that can enable the verification and improvement of existing numerical methods. It was observed that the applied confining pressure and the arrangement of the discontinuities in the rock masses greatly influenced the strength and deformation characteristics of the test pieces. In addition, the failure behavior of the rock masses was investigated in detail by image analysis.
In this paper, we carried out uniaxial compression experiments of some gypsum samples with many pre-existing flaws. Some simplified tools of the image processing are utilized, in order to make an observation about the deformation of specimens during experiments. The results enable us to discuss the fracture mechanisms, such as localization deformation failure, in the samples with pre-existing flaws. This result shows that the fracture of them are controlled by both wing cracks and secondary cracks.
In the present paper, the bi-axial cyclic loading test of RC columns with the different intervals of lateral hoop tie has been performed under the different loading histories. By comparing the results obtained from the uniaxial cyclic loading tests which had been so far performed by the authors, the influence of loading direction and interval of lateral hoop tie on the deformational performance, such as the lateral strength and ductility of RC columns, and on the buckling behavior of re-bar has been examined in details. Furthermore, the loading-path dependency has been discussed with the comparison of the buckling behavior of re-bars and damage inside the RC column induced by the different loading paths up to the same displacement level.
This paper proposes an application of the distinct element method on damming up performance of drift wood capturing structure subjected to woody debris with root. In order to simulate the behavior of drift woods, an assembled element model made of column shape elements is developed. In advance to analysis works, the debris flow experiments, with various combinations of the length of drift woods and the intervals of vertical columns of the structure, were carried out, and those are simulated by the proposed method. Simulation results are in good agreement with the experimental results from the viewpoints of debris flow and the capture mechanism of the capturing structure.
We propose the Multi-Size-Mesh Hermite Scheme to perform the N-body simulations with short-range interactions and apply it to the sedimentary simulations of granular materials in fluid. The Multi-Size-Mesh Hermite Scheme is effective to the simulations with a wide range of scales both spatially and temporarily, because both the time steps and the mesh sizes of each particle are discretized as the power of 2. As for the sedimentary simulations of monodisperse spheres, we found that the porosity increases as the deposition intensity is enhanced. As for the sedimentary simulations of polydisperse spheres, on the other hand, the porosity depends not only on the intensity but also on the grain-size distributions. In fact, the porosity decreases as the fraction of smaller particles increases for the simulations with strong deposition intensity, while it becomes almost constant for those with weak deposition intensity. Especially, in the latter, segregation was found to occur in the deposit, i.e., the smaller particles sink from the top to the bottom in deposit, which suggests that the segregation plays a key role in determining the packing states in the sedimentary simulations of polydisperse spheres.
Some intermittent surges on instability are known as roll wave. Lots of intermittent surges of muddy debris flow had been observed at Hasegawa, Nojiri River and other rivers on the Sakurajima basin and other areas. We got a solution of first order approximation on wave length of roll wave based on a turbulent - particle collision flow model. This paper shows a theoretical wave length of roll wave of the flow with non-cohesive sediment, and discusses relationships of the results and some experimental results.
The effect of a soil mat is to reduce rock-fall energy and impact force. Although the construction costs for soil mats are low, these layers can substantially improve the margin of safety factor. This study examined the performance of a soil mat in reducing rock-fall energy using the discrete element method to investigate the transmission of the impact force in the granulated soil mat caused by rock-fall. The impact force received by a falling body (rock-fall impact force) and the impact force transmitted to the bottom (transmission impact force) due to rock-fall were investigated by examining the effects of particle properties such as hardness, size, and shape, and the soil mat characteristics such as the packing density and layer thickness on the peak impact force. The relationship between the time history of the impact force transmitted to the soil mats with different layer thicknesses and densities and the stress-strain distribution or energy dissipation in the soil mat was also discussed although the results reported here are restricted only to the case of vertical fall.
MPS (Moving Particle Semi-implicit) method or DEM (Discrete Element Method) is useful to simulate strong nonlinear phenomenon like slope failure. The calculated result, however, is often affected by very small difference of model or material property, even difference of computation environment. It is shown that the variation of the response does not depend on the variation of model stiffness when the nonlinearity is strong, through numerical simulation of slope failure by MPS. It is also shown that the distribution of moving distance of falling rock does not affected by variation of initial position in DEM simulation though the individual response is highly sensitive to the position.
Fiber-cement-stabilized soil method is an effective way to recycle high-water content mud. The modified soil has several advantages such as high failure stress and high failure strain. However, the quality of the modified soil is not constant and depends on the water content of the mud and additives. Therefore, experimental verification to obtain the strength characteristics of the modified soil is necessary, but conducting experiments under various conditions is ineffective and uneconomic. In this study, a numerical model to estimate deformation-strength characteristics of the modified soil is investigated by using Distinct Element Method (DEM). It was shown that the developed model was effective way to estimate deformation-strength characteristics. Moreover, it was confirmed that the modified soil had high earthquake resistance.
This paper presents an application of the distinct element method on shear resistance evaluation technique of steel frame check dam, as a fundamental study of estimation method of the shear resistance force and the earth pressure of fill materials in the steel made Sabo structure by analytical approach. The simple shear test which is carried out in advance is modeled by using 3-D distinct element method; and the shear resistance force was evaluated by the analysis. The relationship between shear resistance of the cell and the displacement is analyzed, and compared with the experimental one. The effect of friction model of element on the shear resistance of the cell is discussed.
This paper describes a finite element vibration analysis of crushed stone aggregate used in the ballasted track to examine the frequency characteristic up to the high frequency area of about 1 kHz. In the modeling, we tightened the crushed stones expressed as a polyhedron model using the three dimensional discrete element method, and built a finite element model from the numerical arrangement and contact data of the crushed stone. Inputting a train load to this model, we simulate the behavior and the stress distribution of crushed stone aggregate under a train passing. Numerical results were compared with measurement results to confirm the reproducibility of this model. Finally, we also clarify characteristics of the vibration and the wave propagation of crushed stone aggregate by the vibration analysis using this model.
The mechanical properties of a rock or a soil are different in a narrow area. However, it is difficult to get their sample and to perform a various types of tests from the view points of time and economy. Thus, in this study, Equotip hardness test is focused. Because the test is easy to measure, it is possible to carry on the test at several points in a short time. Additionally, the cost performance of the test is excellent. In this article, the compression test for several artificial specimens is conducted, Equotip hardness test is also conducted before and after the compression test. Through the comparison between the measured data by the Equotip hardness test and the various properties, it turned out that the various properties can be presumed by Equotip hardness test.
Kitamura et al. have proposed the numerical models to establish the unsaturated soil mechanics aided by probability theory and statistics, and to apply the unsaturated soil mechanics to the geo-simulator, where the numerical model for the thermodynamical behaviors of unsaturated soil are essential. In this paper the thermodynamics is introduced to investigate the heat transfer through unsaturated soil and the evaporation of pore water in soil based on the first and second laws of thermodynamics, i.e., the conservation of energy, and increasing entropy. On the other hand the lysimeter equipment is used to obtain the data for the evaporation of pore water during fine days and seepage of rain water during rainy days. The numerical simulation is carried out by using the proposed numerical model and the results are compared with those obtained from the lysimeter test.
GPS on Every Roof is a system for visualizing displacement distribution immediately after large earthquake. In this system, the sensor node which has a L1 GPS receiver and wireless sensor module shares raw GPS data between neighboring sensor nodes locally and estimates the relative positions from them. The server machine collects the estimated relative positions via wireless sensor network and connects the relative positions properly to determine the whole sensor node location. This paper presents the appropriate method of data sharing and relative positioning for GPS on Every Roof which suppresses amount of wireless communication and improves reliability of sensor node location detection. The experiment using 53 sensor nodes is conducted and the results show the presented method gives higher reliability of localization.
A scheme for generating the design input motion is validated through numerical simulations. The characteritic of a ground motion is described by nonlinear response values of structural systems which have flucutuation in parameters. The input motion is generated by searching an appropriate wave in the information geometry space, which is a space of probability density distributions. The scheme is applied to a RC bridge pier model. The results show that the scheme gererate appropriate design input motion.It is also found that a sensitivity of the scheme to initial and other conditions is high.
INDS (Integrated Natural Disaster Simulation) is a seamless simulation of disaster, damage, and social reaction. A model must be constructed from GIS (Geographic Information System) for a target urban area. This paper presents the data conversion of GIS of DMD (Digital Mapping Data) format. A key issue is the compensation of lacked data. Several new algorithms are studied, and the most robust one is found; the successful conversion rate reaches more than 99%. The data conversion is applied to Kochi City, and it is shown that the constructed model is able to be used in simulating seismic structure response and emergency mass evacuation.
Wall-type reinforced concrete piers have been broadly constructed out of urban area under space limitation. However the deformation capacity against earthquake should be evaluated appropriately as a function of the skewed angle. This paper aims to grasp the behavior of wall-type skewed piers under cyclic loading using the three dimensional fiber model analysis. As a result, it was found that the fiber mode l analysis could simulate the experimental results before failure of the longitudinal reinforcement.
The non-linear response of coupled soil-pile-structure systems to seismic loading is parametrically studied in the frequency domain using two-dimensional (2D) finite elements (FE). The soil-pile interaction in three dimensions (3D) is idealized in the 2D type using soil-pile interaction springs with non-linear hysteretic load displacement relationships. The system under investigation comprises of a single degree of freedom structure supported by an end-bearing single pile founded in a homogenous sand layer over rigid rock. Comparisons with established results from the literature suggest that the adopted FE model reasonably captures the essential features of the seismic response of the coupled soil-pile-structure system. Numerical results demonstrate the strong influence on the effective natural period of the foundation properties. The effect of non-linear soil behavior and soil profile as well as the frequency content of excitation on both kinematic and inertial interactions is illustrated. The relative contributions of kinematic and inertial interaction to the development of dynamic pile bending are clarified.
In order to secure the safety of a bridge against tsunami, it is important to examine the tsunami external force acting on a bridge section. This paper describes the effect of the hydrodynamic forces caused by tsunami. The bridge section models in this paper are rectangle, trapezoid, upside down trapezoid and rectangle which has center opening section. The trapezoid section model had smaller horizontal tsunami force. The center opening section model had almost no vertical tsunami force. The relation between the depth of tsunami and the tsunami force coefficients was provided through the force measurement.
In this study, we investigate the characteristics of dam-break flow of low viscosity Bingham fluid by deriving an approximate solution for the time development of the front position and depth at the origin of the flow. The asymptotic solutions representing the characteristic of Bingham fluid in the limit of low plastic viscosity are verified with a depth-averaged numerical model. Numerical simulations showed that with the decrease of plastic viscosity, the time development of the front position and depth at the origin approach to the theoretical asymptotic solution.
Levees of channels formed due to turbidity currents on submarine fans are often covered with step like bedforms. Circumstantial evidences emerged with numerical and experimental studies have suggested these sediment waves should probably be cyclic steps. The formation of cyclic steps in sub-aqueous environments through a mathematical perspective is presented in this research. A mathematical model preserving essential physics of the system is solved for one step wave length to obtain a preserved step shape of upstream migrating steps and the behavior of characteristic parameters governing this cyclic step formation phenomenon.