Journal of Japan Society of Civil Engineers, Ser. A2 (Applied Mechanics (AM))
Online ISSN : 2185-4661
ISSN-L : 2185-4661
Volume 74 , Issue 2
Showing 1-50 articles out of 71 articles from the selected issue
Journal of Applied Mechanics Vol.21 (Special Feature)
  • Isao SAIKI, Ryuta FUJIMOTO, Takeki YAMAMOTO
    2018 Volume 74 Issue 2 Pages I_3-I_11
    Published: 2018
    Released: January 31, 2019
    JOURNALS FREE ACCESS
    The estimation of shear stiffness of beams began with the analytical approach based on the elasticity. Subsequently, the numerical approach discretizing cross-section has been developed. The numerical method can estimate the shear stiffness of beams with arbitrary shape cross-section. However, the applicability of the method to heterogeneous or composite cross-section has not been studied well. We found that the existing method does not work well for the heterogeneous cross-section. In this paper, we propose that an original definition of rotation of the cross-section considering material properties. The validity of our method has been confirmed by the comparison with a finite element solution of the elasticity.
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  • Hasuka KANNO, Shuji MORIGUCHI, Kenjiro TERADA, Shunsuke HAYASHI, Yusak ...
    2018 Volume 74 Issue 2 Pages I_13-I_21
    Published: 2018
    Released: January 31, 2019
    JOURNALS FREE ACCESS
    We propose an rockfall prevention methodology coupling numerical simulation, risk assessment, and the optimal design of protective measures on a transport corridor. Firstly, rockfall simulations are carried out and the location and the kinetic energy when rocks reached the transport corridor respectively is recorded. Secondly, the rockfall hazard is quantified, followed by the mitigation effect of placing a protective measure. Thirdly, an optimization problem that aims to maximize the total mitigation effect under constraints is formulated. Its solution finally shows the optimal placement of protective measures on the transport corridor. In this study, the effectivity of the proposed methodology is validated in a simplified application.
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  • Kensuke KASAYUKI, Hiroaki T-KANEKIYO, Toshiyuki ISHIKAWA, Hiroshige DA ...
    2018 Volume 74 Issue 2 Pages I_23-I_31
    Published: 2018
    Released: January 31, 2019
    JOURNALS FREE ACCESS
    A numerical approach is developed to apply to numerical calculations for a CFRP strengthened steel member, in which multiple precistion arithmetic is used for removing numerical instability inherent in numerical schemes constructed under a fixed precision arithmetic method. First, by supposing a steel member with a bonded CFRP plate under tensile loading, a system of differential equations describing spatial variation of axial force and shear force of CFRP plate. A numerically solving framework is further constructed based upon a transfer matrix method, where a boundary value problem is equivalently replaced by an initial value problem. It is shown that the numerical instability appearing in a numerical scheme under the fixed precision arithmetic method defined by IEEE 754 can be effectively removed by the use of the multiple precision arithmetic method. Further it is clarified that (i) a proposed approach can be applied to a case of bonding CFRP with tapers at their ends, (ii) obtained solutions show qualitatively good agreement with finite element analysis results and (iii) a proposed approach can give accurate estimations for stress concentration closely near the end of CFRP plate.
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  • Kazuya INOUE, Mariko SUZUKI
    2018 Volume 74 Issue 2 Pages I_33-I_44
    Published: 2018
    Released: January 31, 2019
    JOURNALS FREE ACCESS
    Swarm-based algorithms are a powerful family of optimization techniques inspired by forming flocks, colonies and swarms. In this paper, the swarm intelligence concepts of particle swarm optimization (PSO), which is an effective and reliable algorithm, gravitational search algorighm (GSA) and cuckoo search algorithm (CKA), which are recently developed meta-heuristic algorithms, were analyzed. The numerical optimization problem solving successes of these algorithms were compared by testing about 50 different benchmark functions. Numerical results revealed that CKA exhibited the highest performance in solving various nonlinear functions, while PSO and GSA produced better results on multimodal and multivariable problems. The obtained results also showed that GSA and CKA supplied more robust than the PSO. The CKA is essentially expressed by Lévy flight and allows more efficient in exploring the search space as its step length is much longer in the long run, leading to better performace in convergence, precision and robustness.
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  • Shutaro TSUBOKAWA, Keita WAKABAYASHI, Shun-ichi KOBAYASHI, Shoichiro N ...
    2018 Volume 74 Issue 2 Pages I_45-I_54
    Published: 2018
    Released: January 31, 2019
    JOURNALS FREE ACCESS
    In emergency, the importance of resilient road networks is widely accepted. As probabilities of rare huge disasters are low and varied, vulnerability analysis of road networks which depend only on shapes and other features of road networks is imporant. In this article, a triage method to choose important links is proposed to keep the connectivity of representative nodes on the network. The proposed method is based on the analogy of a mass-spring system mechanics and a Laplacian matrix of road networks. A triage analysis of the emergency transportation road network in Hokuriku, Shiga and Gifu region is carried out to demonstrate the applicability of the proposed method.
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  • Junya INOUE, Kiyoshi MASUMOTO
    2018 Volume 74 Issue 2 Pages I_55-I_64
    Published: 2018
    Released: January 31, 2019
    JOURNALS FREE ACCESS
    Saturated-unsaturated flow inversion program with adjoint method and least norm method was made to estimate saturated hydraulic conductivity and boundary conditions for multi-layers heterogeneous aquifer model. Vertical two dimensional numerical experiments assuming inclined ground consisting of three layers with different permeability were carried out using this program. Some inversion were carried out by changing the cofficient of least norm term to investigate the strength of constraints on the unknown parameters based on the reference value. The result show that it is possible to estimate the uniqe value of saturated hydraulic conductivity and boundary conditions for multi-layers heterogeneous aquifer model by the method.
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  • Takahiro SAITOH, Takashi ONODERA, Akira FURUKAWA, Sohichi HIROSE
    2018 Volume 74 Issue 2 Pages I_65-I_74
    Published: 2018
    Released: January 31, 2019
    JOURNALS FREE ACCESS
    In recent years, the carbon fiber reinforced plastic (CFRP) and austenitic steel have attractive attention in many engineering fields. Therefore, it is desirable to develop an accurate reconstruc- tion method for defects in such anisotropic materials. In this paper, a linearized inverse scattering technique has been developed for the reconstruction of a crack in anisotropic materials. A far-field approximation of a traction fundamental solution for 2-D pure anti-plane anisotropic elastody- namics is derived by using the stationary phase method, and its accuracy is verified. The inverse scattering with the Kirchhoff inversion is applied to a crack in general anisotropic elastic solids. The scattered wave forms used in this inverse scattering technique are calculated by the convolution quadrature boundary element method (CQBEM) which can produce stable numerical solutions better than conventional time-domain BEM. The scattered wave forms in time-domain are trans- formed into those in frequency-domain in order to apply them to the inverse scattering analysis. Numerical results show that the proposed inverse scattering technique with the aid of the CQBEM can properly reconstruct the image of a crack in the uni-directional CFRP and austenitic steel.
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  • Kazuyuki NAKAHATA, Atsushi TSUJITA, Kazunori FUJISAWA, Akira MURAKAMI
    2018 Volume 74 Issue 2 Pages I_75-I_84
    Published: 2018
    Released: January 31, 2019
    JOURNALS FREE ACCESS
    For a sophistication of ultrasonic testing, the particle filter (PF) was applied to the estimation of size and location of a defect in a solid. In the PF, particles express the probability distribution of a state variable. The particle distribution is updated while merging measured data and simulation data, then the convergence of the particles indicates a plausible state variable. When the state variable to be identified increases, the use of a large number of particles are required. This leads to the cost escalation in numerical simulation. To enhance the accuracy of the PF as well as reduce the computational cost, we considered the introduction of the scattering amplitude. According to the theory of a time-shift invariant system, the scattering amplitude was extracted from an ultrasonic scattered signal from a defect, and then applied at the likelihood calculation. As the numerical simulation tool, we adopted the elastodynamic finite integration technique accelerated by a graphic processing unit calculation. The proposed PF approach was investigated in the ultrasonic measurement, and it was shown that the size and position of a side-drilled hole in an aluminum specimen was identified with a small number of particles.
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  • Hikaru MORIKAWA, Takahiro SAITOH, Kazushi KIMOTO
    2018 Volume 74 Issue 2 Pages I_85-I_93
    Published: 2018
    Released: January 31, 2019
    JOURNALS FREE ACCESS
    In this paper, a novel shape reconstruction method based on the time-reversal technique is presented for the purpose of quantification of the ultrasonic nondestructive testing. First, a forward analysis of elastic wave scattering by defects in an elastic solid is solved by using the convolution quadrature time-domain boundary element method (CQBEM), which can produce higher accuracy than conventional time-domain boundary element method (BEM). In the proposed method, the topological sensitivity is used to identify the shape and position of defects in elastic solid, and it is obtained by solving the corresponding adjoint problem of the forward one with the aid of CQBEM. As numerical examples, some results of shape reconstruction of defects in a homogeneous and isotropic solid using the proposed method are demonstrated. The reconstruction ability of the proposed method is investigated by changing the radiation pattern of ultrasound from a phased array transducer.
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  • Tatsuya UETA, Shin-ichi NISHIMURA, Kazunari IMAIDE, Toshifumi SHIBATA, ...
    2018 Volume 74 Issue 2 Pages I_95-I_104
    Published: 2018
    Released: January 31, 2019
    JOURNALS FREE ACCESS
    In this research, synthesized approach of the sounding results and the shear wave velocity is proposed to evaluate the distribution of the ground strength. For this task, the surface wave method is used to obtain the shear wave, and the piezometer cone penetration test (CPT) is employed as a sounding test. The CPT N value, Nc is derived from the results of CPT, namely, the tip resistance, the side friction and the pore water pressure, and transformed to the standard penetration N value, NSPT. The shear wave velocity Vs is also transformed to NSPT. Two kinds of NSPT are applied to the indicator simulation method (IS), which is one of the geostatistical approaches, and the IS can synthesize two NSPTs. The spatial distribution of the NSPT is simulated by the IS. The method to incorporate the two kinds of the transformation errors from Nc to NSPT, and from Vs to NSPT into the IS, is proposed in this research. Consequently, the effect of the transformation errors on the simulation results has been clarified.
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  • Yuiichi NAKAJIMA, Kazushi KIMOTO, Katsuyuki KAWAMURA
    2018 Volume 74 Issue 2 Pages I_105-I_114
    Published: 2018
    Released: January 31, 2019
    JOURNALS FREE ACCESS
    In this study, we develop a numerical analysis method to investigate the characteristics of heat conduction in unsaturated porous media. In particular, we propose a numerical modeling technique to investigate the overall thermal conductivity of unsaturated porous media taking into account the pore structure filled partially or fully with water. Specifically, a predetermined amount of pore water is arranged to minimize the interfacial free energy in a porous structure created by arranging solid phase particles randomly. We set the solid phase and the liquid phase region by the Markov Chain Monte Carlo method and efficiently generate models from a small set of input data. Moreover, we investigate the relationship between water content and macro thermal conductivity by analyzing thermal conductivity of numerical unsaturated porous media models. As the result, we clarified that regularity of solid phase particle arrangement and uniformity of particle size affect the change behavior of macro thermal conductivity in low saturation region thereby demonstrates the usefulness of the proposed method.
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  • Kazushi KIMOTO
    2018 Volume 74 Issue 2 Pages I_115-I_123
    Published: 2018
    Released: January 31, 2019
    JOURNALS FREE ACCESS
    This study develops a discontinuous Galerkin finite element method (DG-FEM) for the analysis of contact acoustic nolinearity (CAN) problems. DG-FEM is employed for this purpose since it can easily handle the discontinuity in material constants as well as the wave field quantity and amenable to explicit time stepping. In this study we extend the elastodynamic DG-FEM for 1D CAN problems by incorporating crack-face contact detection algorithm without compromising the above mentioned advantages of DG-FEM. The accuracy of the numerical solution is then validated by comparing exact and FE solutions of 1D CAN problem. The developed DG-code for 1D wave problems is used also to simulate ultrasonic nondestructive testing to demonstrate the necessity and usefulness of numerical techniques in designing CAN based NDE techniques.
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  • Mayuko NISHIO, Masaki MIURA, Takayuki SHUKU
    2018 Volume 74 Issue 2 Pages I_125-I_136
    Published: 2018
    Released: January 31, 2019
    JOURNALS FREE ACCESS
    This study aims to show the applicability of sparse modeling, which is drawing attention in the field of machine learning in recent years, to the surrogate modeling of the finite element (FE) analysis for the use in the structural reliability analysis of aging exiting bridges. The target of surrogate modeling here was the Monte Carlo calculation of the FE model of a steel plate-girder bridge with corrosion at the ends of girders and bearings. The inputs were uncertain FE model parameters, such as material propertyies and boundary conditions, and the output was the maximum Mises stress at the ends of main girders under the loading of designed live load. The performance of some regression methods; least-square method (LSM), Ridge, and Lasso, which can give the sparse solution, were compared in applying them to the surrogate modeling. As a result, the Lasso regression can make a proper surrogate model only by using 50 training data that was the one-third of training data required in the LSM. The reliability index β derived by the Lasso surrogate model then showed good agreement with that derived by the Monte Carlo FE model calculation with 500 samples. Moreover, the solution of Lasso, which showed sparsity, indicated the FE model parameters that had significant sensitivities to the output, i.e., the maximum Mises stress, under the corroded condition. It was then concoluded that the surrogate modeling by Lasso was effective in the structural reliability analysis of existing bridges, which has high uncertainties in a number of FE model parameters due to detoriaration or damages.
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  • Ramy Gadallah, Seiichiro Tsutsumi, Naoki Osawa
    2018 Volume 74 Issue 2 Pages I_137-I_146
    Published: 2018
    Released: January 31, 2019
    JOURNALS FREE ACCESS
    This paper investigates the influence of a single tensile overload (OL) on fatigue life by means of finite element method. For a realistic evaluation of fatigue life, a combination of elastic-plastic material and fracture mechanics approach was applied. The interaction integral method available in WARP3D code, a multifunctional open source code, was employed to calculate stress intensity factor (SIF) based on elastic-plastic analyses. Numerical analyses performed in this study are based on experimental data taken from literature. A Single Edge Notch Tension model was applied in the numerical analyses. Two loading conditions, namely, pure constant amplitude loading (CAL) and CAL with a single tensile OL were employed. On the other hand, the geometry of the crack due to fatigue-cyclic loading was investigated. The distributions of stress/strain ahead of the crack tip, as well as the size of the induced plastic zone, were also examined. The behavior of SIF along the crack tip was discussed for loading and unloading cycles. Further, fatigue crack propagation material properties (C and m) were proposed based on elastic-plastic analyses to be used in crack propagation calculations in which their effectiveness was verified with experiments. The evaluated fatigue lives under pure CAL and CAL with a single tensile OL were validated with experiments.
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  • Takeki YAMAMOTO, Takahiro YAMADA, Kazumi MATSUI, Isao SAIKI
    2018 Volume 74 Issue 2 Pages I_147-I_158
    Published: 2018
    Released: January 31, 2019
    JOURNALS FREE ACCESS
    In the finite element analysis, it is important to evaluate the local behavior at the portion where the thickness is discontinuous or near the corners. If such structure is discretized with structural elements, the numerical results are often unreliable, because the plane stress condition is assumed in the transverse direction and the incompressibility could not be considered appropriately. Thus, the authors proposed that the effective procedure of discretizing the model is to connect shell and solid elements properly by using Nitsche's method.
    When the different types of elements are connected at the boundary including corners, the stiffness near such boundary may become larger than that of the model discretized with only one type of element. Thus, the authors propose the approach to avoid this problem by improving the mesh geometry near the boundary.
    The proposed procedure can be applied to the elastoplastic problems, but it is necessary to divide the domain so that the plastic region does not progress on the connecting interface. This is because the numerical calculation becomes unstable due to the disorder of the stress state when discontinuous stress state is connected.
    This paper presents a numerical procedure for connecting shell and solid elements in elastoplastic problems. In the proposed approach, shell and solid elements can be coupled with reasonable deformation near the connecting interface, only when the plastic range is not included on the connecting interface.
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  • Yusuke IMOTO, Mitsuteru ASAI
    2018 Volume 74 Issue 2 Pages I_159-I_166
    Published: 2018
    Released: January 31, 2019
    JOURNALS FREE ACCESS
    The stabilized ISPH method is a kind of particle methods for the incompressible Navier-Stokes equations and is defined as an incompressible SPH method with a pressure Poisson equation added with a stabilization term with respect to density of particles. By some numerical experiments in previous studies, it has been verified that the stabilization term contributes to avoiding a localization of particles; then, numerical results with a computational stability, volume conservation, and higher accuracy have been obtained. However, because the stabilization term is derived from a discretization of the continuity equation of compressible fluid, it is not clarified whether the stabilization term contributes to keeping uniformness of particle distributions theoretically. Therefore, based on mathematical theory alone, the stabilization term is derived as an approximate solution of an energy minimization problem with respect to errors of incompressibility of fluid and uniformness of particle distributions.
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  • Jian CHEN, Muneo HORI, Hideyuki O-TANI, Satoru OISHI
    2018 Volume 74 Issue 2 Pages I_167-I_178
    Published: 2018
    Released: January 31, 2019
    JOURNALS FREE ACCESS
    This paper presents an improvement of a mathematical interpretation of moving particle semi-implicit (MPS) method. The mathematical interpretation leads to a mathematical reformulation of MPS (MRMPS) based on Taylor expansions. The improvement of MRMPS in this paper is featured by solving a system of 9 × 9 (or 5 × 5 for two dimensional settings) equations for the gradient vector and for all the components of the Hessian matrix. Numerical experiments with various types of target functions showed that the improved MRMPS possesses a second-order convergence rate for the relative error of the gradient and a first-order convergence rate for the relative error of the Laplacian, in three-dimensional settings with randomly distributed neighboring particles. Moreover, there is no deterioration of accuracy for realistic particle configurations near free surfaces, where the neighboring particles are distributed not only randomly but also one-sided. Further, the aforementioned accuracy of the improved MRMPS can be obtained by using about 40 to 50 neighboring particles considerably less than conventional particle methods. A simplification for the improved MRMPS is also presented with less computational complexity, solving two 3 × 3 systems instead of one 9 × 9 system, at the cost of losing one order of convergence rate of error.
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  • Taizo MARUYAMA, Terumi TOUHEI
    2018 Volume 74 Issue 2 Pages I_179-I_189
    Published: 2018
    Released: January 31, 2019
    JOURNALS FREE ACCESS
    Steady-state solutions are obtained without distinction of stability if a scattering problem by a crack with contact acoustic nonlinearity is solved by means of a harmonic balance-boundary element method. The present article deals with stability analysis for the steady-state solution. The proposed formulation is based on Hill's method, and the stability analysis comes down to an infinite-dimensional nonlinear eigenvalue problem. The infinite-dimensional matrix is truncated, and the eigenvalue problem is solved by means of the Sakurai-Sugiura method. The obtained numerical results are compared to the conventional transient solutions to demonstrate the validity of the proposed method.
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  • Yuki YAMAKURI, Shun-ichi KOBAYASHI, Jun SAITO, Tatsunori MATSUMOTO
    2018 Volume 74 Issue 2 Pages I_191-I_202
    Published: 2018
    Released: January 31, 2019
    JOURNALS FREE ACCESS
    In this article, the formulation of hybrid type three dimensional rigid finite element method based on the second cone programming with the yield function of Drucker-Prager model is presented. As a spatial discretization, the classical four-node tetrahedral (C3D4) element is used for a velocity field and a facet based constant stress field is employed. To avoid instability in numerical calculations due to the semi-positive definiteness of the second invariant of a deviatoric stress tensor J2, a stabilization term based on the eigenvector of zero eigenvalue is added. Three examples are solved with the proposed method. It is found that the stabilization term is effective, and the importance of spatial discretization around highly sheared areas is confirmed. The proposed method provides over-estimated results, especially for the cases of higher internal friction angles. This discrepancy is perhaps due to the deformation constraints of C3D4 elements.
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  • Kouhei KITOU, Takuma KOTANI, Yuya YAMAGUCHI, Shinsuke TAKASE, Shuji MO ...
    2018 Volume 74 Issue 2 Pages I_203-I_211
    Published: 2018
    Released: January 31, 2019
    JOURNALS FREE ACCESS
    This study presents a new method which can visually evaluate the spatial distribution of snow avalanche risk against a human body. An empirical formula of the impact force and 3D stabilized FE analysis based on SUPG/PSPG method are efficiently combined to estimate the snow avalanche risk under the low calculation cost. In the 3D FE analysis, flow characteristic of snow is modeled by a Bingham-type fluid model in which the shear strength can be controlled with the internal friction angle and the cohesion. The impact force of snow avalanche against human body is then estimated at every points on the slope surface with the help of calculated flow properties and the empirical formula, and high-risk area is visually defined in the hazard map.
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  • Tadanobu SATO, Kohei TANAKA, Yoshitaka MURONO, Takayoshi NISHIMURA
    2018 Volume 74 Issue 2 Pages I_213-I_224
    Published: 2018
    Released: January 31, 2019
    JOURNALS FREE ACCESS
    Because the time history of the response spectrum compatible earthquake motion (RSCEM) is affected by the assigned Fourier phase spectrum we propose a method to extract the uncertainty of Fourier phase spectrum form an observed earthquake motion at the design site and to simulate many sample Fourier phase spectra that can be used as the uncertainty of Fourier phase supectrum at the design site. We also can see some minor effects of the initial Fourier amplitude spectrum on a simulated RSCEM and therefore discussed a method to minimize this effect. Based on these studies we investigate the effect of Fourier phase spectrum uncertainty on the nonlinear response of a structural system. The structure considered is a designed one using the yield seismic coefficient demand spectrum that the response ductility is kept constant. Our main concern is to evaluate the uncertainty of response ductility of the designed structure caused by the uncertainty of Fourier phase spectrum uncertainty.
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  • Jun SAITO, Yuki HISAMOTO
    2018 Volume 74 Issue 2 Pages I_225-I_232
    Published: 2018
    Released: January 31, 2019
    JOURNALS FREE ACCESS
    This study shows formulation of ISPH (Incompressible Smoothed Particle Method ) using Lagrange's equation of the first kind. The formulation by Lagrange's equation of the first kind determine the equation expressions of pressure gradient and velocity divergence uniquely. Moreover, adding constraint condition of fluid particles and wall particles into the Lagrangian causes repulsive force of fluid particle from wall boundary. While penetration of fluid particles into wall boundary often happens in the conventional IPSH formulation, the penetration can be prevented by applying the new formulation. Two numerical problems, simple one-dimensional problem and three-dimensional dam break problem, are solved to show the validity of the proposed method.
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  • Yuto SOMA, Mao KURUMATANI
    2018 Volume 74 Issue 2 Pages I_233-I_241
    Published: 2018
    Released: January 31, 2019
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    This paper presents a damage model which is extended to simulate fracture behavior involving frictional contact on crack surfaces. The behavior of frictional contact is formulated in the local coordinate system along the crack surface, which is introduced into an isotropic damage model based on fracture mechanics for quasi-brittle materials. After showing the formulation of the damage model incorporated with the model of frictional contact, several basic examples are solved to verify the performance of the proposed model. The model is then applied to the analysis of a single shear test of masonry structure, and the results are compared to the test results.
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  • Ryosuke IBA, Akira FURUKAWA, Takahiro SAITOH, Sohichi HIROSE
    2018 Volume 74 Issue 2 Pages I_243-I_252
    Published: 2018
    Released: January 31, 2019
    JOURNALS FREE ACCESS
    This paper presents a new BEM using DE-Sinc method, DE-Sinc BEM, for 2D antiplane wave problems. We apply the proposed method to wave scattering by a circular scatterer which is cavity or fixed-rigid cylinder via two approaches. One is a formulation using a regularized boundary integral equation. The other is that using a singular boundary integral equation and analytical evaluation of strong singular kernel on the boundary. The comparison of accuracy and computational time of the coefficient matrices between the proposed approaches and the conventional BEM using constant elements provides that the DE-Sinc BEM is enable to shorten computational time with enhancing the accuracy.
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  • Koji NISHIGUCHI, Rahul BALE, Shigenobu OKAZAWA, Makoto TSUBOKURA
    2018 Volume 74 Issue 2 Pages I_253-I_263
    Published: 2018
    Released: January 31, 2019
    JOURNALS FREE ACCESS
    This paper focuses on a solid-fluid interaction scheme using PIC (Particle-in-cell) method based on a spatially-fixed Cartesian mesh and proposes a novel implicit scheme to relax the limitation of time-step size. In the present PIC scheme, a solid region is represented by a set of Lagrangian particles, which carry internal variables of solid. Basic equations and spatial derivatives are computed on a fixed Cartesian mesh. A forth-order Jacobian tensor is introduced for the proposed implicit scheme. The present method is validated from the viewpoint of solid deformation, time history of energy, and spatial convergence in solid-fluid interaction benchmark problems.
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  • Takahiro YAMADA
    2018 Volume 74 Issue 2 Pages I_265-I_275
    Published: 2018
    Released: January 31, 2019
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    The method of nearby problems (MNP) developed by Roy et al. is a sophisticated verification procedure, in which the problems with exact solutions near the target problem of interest can be generated by a curve fitting of a numerical solution to a continuous function. In this work, we apply this approach to large deformation problems of nearly incompressible hyperelasticity. Nearby solutions are constructed by the projection of a finite element solution of displacement onto an approximating function space using the inner product in the Sobolev space H1. In this projection, a penalty term associated with volumetric deformation is introduced to impose the nearly incompressible property on nearby solutions.
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  • Kodai NAGANO, Daisuke TORIU, Satoru USHIJIMA
    2018 Volume 74 Issue 2 Pages I_277-I_284
    Published: 2018
    Released: January 31, 2019
    JOURNALS FREE ACCESS
    In this study, numerical methods for the basic equations of the Maxwell fluid, which is one of the viscoelastic fluids, were investigated on the two-dimensional collocated grid system by the finite volume method. On the basis of the numerical method proposed by the authors previously, that for the stress terms in the momentum equations were proposed in this study. By the proposed numerical method, the stress terms are calculated with the spatially compact velocity distribution, and it was demonstrated by the numerical experiments that the method can avoid the unphysically oscillated results. Additionally, for the pressure calculation, the C-HSMAC method which controls the divergence of the velocity was applied to the Maxwell fluid and in the numerical experiments it was shown that the method prevented the numerical oscillation of stresses which may happen by using the SMAC method. Furthermore, the proposed method was applied to the numerical experiments in which the elastic character is dominant. As a result of the computations, it was demonstrated that the proposed method and the C-HSMAC method enable to qualitatively predict the elastic behaviors of the Maxwell fluid.
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  • Norichika SHIGA, Taisuke ONO, Kazuki IN, Tsuyoshi IDA, Hirokazu HIRANO
    2018 Volume 74 Issue 2 Pages I_285-I_294
    Published: 2018
    Released: January 31, 2019
    JOURNALS FREE ACCESS
    It was found by the damage survey of the Great East Japan Earthquake and the Kumamoto earthquake that many water tanks which had been designed and manufactured according to the latest standard was damaged due to sloshing and bulging phenomenon. Although there is a countermeasure against sloshing which causes vibration of water surface, no countermeasure against bulging which cause mainly vibration of structure. For that reason, this paper aims to grasp bulging characteristics by using vibration tests of acrylic rectangular water tank and numerical fluid flow analysis. This study reveals bulging phenomenon has different characteristics from sloshing. Concretely, comparing results of vibration tests and analysis confirms that bulging occurs in a relatively wide frequency range. Result of analysis indicates that high pressure is applied to the corners in the bulging, the center and contact part with the bottom of the side plate of the water tank, although sloshing damages the ceiling and the upper part of the side plate. The results suggest that we need to find a countermeasure against bulging in the water tank which is different from that against sloshing.
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  • Mao KURUMATANI, Ryota AIDA, Kazuya HASHIGUCHI
    2018 Volume 74 Issue 2 Pages I_295-I_302
    Published: 2018
    Released: January 31, 2019
    JOURNALS FREE ACCESS
    We visualize crack propagation behavior around coarse aggregates in concrete by the DIC (Digital Image Correlation) measurement of a concrete cross-section. The DIC measurement used in this study is an original method that we have developed to measure the crack propagation in concrete at high resolution with a general digital camera and lighting equipments. The summary and characteristic of the DIC measurement is first explained. We show the visualization results of crack propagation behavior around coarse aggregates in concrete measured by the DIC method. In addition, the behavior of crack propagation and crack opening under compressive load can be visualized by showing the direction vectors of maximum principal strain.
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  • Masato KOMURO, Momoka HATTORI, Hisashi KONNO, Nobuya ARAKI
    2018 Volume 74 Issue 2 Pages I_303-I_313
    Published: 2018
    Released: January 31, 2019
    JOURNALS FREE ACCESS
    In order to establish a numerical analysis method for appropriately evaluating impact resistant behavior of the conventional rockfall protection fence, a 3D elaso-plastic impact response analysis method with precisely modeling steel wire-net and wire-rope using beam and solid element, respectively, was proposed. The applicability was investigated comparing with the experimental results for full-scale model under falling-weight impact loading. The results obtained from this study were as follows: 1) time histories of dynamic responses obtained using the method were similar to those of the experimental results; and 2) dynamic behavior of the fence including trapping of falling rocks may be estimated by using the proposed method.
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  • Masato KOMURO, Tomoki KAWARAI, Norimitsu KISHI, Yusuke KURIHASHI
    2018 Volume 74 Issue 2 Pages I_315-I_326
    Published: 2018
    Released: January 31, 2019
    JOURNALS FREE ACCESS
    In order to establish a numerical analysis method for the RC beams strengthened with near-surface mounted (NSM) Aramid FRP (AFRP) rods under impact loading, proposing a 3D elaso-plastic FE analysis method assuming fictitious tensile strength based on an equivalent tensile fracture energy (Gf) concept for concrete element under the condition applying a smeared crack model, an applicability of the method was investigated comparing with the experimental results. From this study, it was seen that the RC beams can be better simulated by using fine meshes following proposed Gf concept excluding the case of bigger input impact energy.
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  • Kenta TAKEDA, Yuki ICHIHASHI, Ayumi WATANABE, Hidetaka UMEHARA
    2018 Volume 74 Issue 2 Pages I_327-I_336
    Published: 2018
    Released: January 31, 2019
    JOURNALS FREE ACCESS
    In this research, results of loading tests of prestressed concrete (PC) beam and PC column with different bond condition of PC bars were selected as a research object. The load bearing capacity of the PC beam and column were evaluated with Finite Element (FE) analysis. PC bars were simply expressed by using two kinds of line elements in analysis. As a result, numerical results succeeded to simulate the loading test of PC beam by using appropriate constitutive model. By contrast, it was found that the accuracy of evaluation of PC column reduces if the load bearing capacity of PC column were evaluated by using the constitutive model for PC beam.
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  • Seiichiro TSUTSUMI, , Yuki KIYOKAWA, , Riccardo FINCATO, Yosuke OGIN ...
    2018 Volume 74 Issue 2 Pages I_337-I_347
    Published: 2018
    Released: January 31, 2019
    JOURNALS FREE ACCESS
    In order to improve the fatigue life of welded joint, additional weliding, glinder and peening technologies have been used, and also the effeciancy of the techniques have been provened by experiment evidences. However, great concerns are remained for the experimental verification that it is not enough because of time and cost limit. It's not fully understood for the influence on fatigue life of welding process conditions like heat input, welding position and target, because welding bead is sensitive to them. The purpose of present study is to evalate the influence of additional welding condition on fatigue life of welded joint, by using weld pool analysis which can simulate welding process and FE analysis which can describe the cyclic plasticity under fatigue loading. In particular, we conducted the cyclic plasticity analysis considering bead shape and thermal history obtained by weld pool analysis, and then discussed thier influence on the fatigue carack initiation life.
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  • Tan NGUYEN, Thirapong PIPATPONGSA, Takafumi KITAOKA, Hiroyasu OHTSU
    2018 Volume 74 Issue 2 Pages I_349-I_360
    Published: 2018
    Released: January 31, 2019
    JOURNALS FREE ACCESS
    The local minimum pressure in embankment initiated by the base deflection is revisited by an elastic model; whereby, the effect of elastic input parameters such as Young's modulus, Poisson's ratio, and basal roughness conditions on the pronounced local minimum pressure is also disclosed by mean of the elastic model. On the other hand, the characteristic of stress dip from the elastic solution was evaluated by comparing with that of an elasto-plastic solution. Finally, the effect of the geometric features such as the height of the embankment as well as the inclination angle of the slope on the pronounced local minimum pressure was also considered. The method of IsoGemetric Analysis (IGA) was implemented for discretizing the spatial domain instead of Finite Element Method; therefore, the superiority of IGA over FEM in terms of computational cost was also demonstrated.
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  • Takaki MATSUMARU, Ryosuke UZUOKA
    2018 Volume 74 Issue 2 Pages I_361-I_371
    Published: 2018
    Released: January 31, 2019
    JOURNALS FREE ACCESS
    In this paper, series of numerical studies were conducted aimed to the influence of the values of suction and degree of saturation to the liquefaction resistance of unsaturated soil. First, the numerical study about the initial value of the suction and the degree of saturations were examined. Both initial values caused the change of the liquefaction resistance. However, it became clear that the factors of the change of the liquefaction resistance for each value were different. Furthermore, the numerical study about the pass of the soil water characteristic curve was performed. The simulated results showed that the pass also affected the liquefaction resistance of unsaturated soils.
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  • Shin-ichi KANAZAWA, Shinya MATSUZAKI, Atsushi IIZUKA
    2018 Volume 74 Issue 2 Pages I_373-I_380
    Published: 2018
    Released: January 31, 2019
    JOURNALS FREE ACCESS
    Embankments are constructed with compacting soil with the aim of improving their stability and deformation characteristics. In late years, increase of the torrential rain becomes the factor, and a lot of collapse examples of embankments are reported. 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 of air dissolution type of embankments which take into account compaction and the history of rainfall/evaporation. Further, sudden torrential rain falls on the embankment after the commencement of use, and it aims to grasp how embankment destroys.
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  • Shinnosuke KATAOKA, Masuhiro BEPPU
    2018 Volume 74 Issue 2 Pages I_381-I_392
    Published: 2018
    Released: January 31, 2019
    JOURNALS FREE ACCESS
    The damage of structures subejected to tornado debris and volcanic cinder frequently occured. Because wind bone or volcanic induced-missiles could be deformed by the impact to structures, the effects of the defomaton of a projectile on the failure chactristics of RC slabs should be investigated. This study presents an investigation of the effects of buckling of a circular tube projectile on the failure characteristics of reinforced concrete slabs subjected to a projectile impact by conducting impact experiments and numerical simulations. The results of the experiments and numerical simulations showed the damage of RC slabs subjected to a deformable projectile decreased comparing to the case of a hard projectile because of change of impact load chacteristics due to the buckling of a circular tube.
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  • Xiaoyu JIANG, Takashi MATSUSHIMA
    2018 Volume 74 Issue 2 Pages I_393-I_402
    Published: 2018
    Released: January 31, 2019
    JOURNALS FREE ACCESS
    We have performed a systematic simulation study of dry, granular, gravity-driven, free-surface steady flow in two-dimension, investigating the rheology of cohesionless granular particles in rough inclined plane geometries by discrete element method (DEM). DEM simulation results are compared to a widely accepted μ(I)-rheology model. Microscopic parameters such as coefficient of inter-granular friction and particle size distribution are changed to investigate the influence on macroscopic behaviors like velocity field, volume fraction and effective bulk friction qualitatively. It turned out that more polydisperse system and more frictional particles leads to a low volume fraction and high effective friction. Influence of the inter-granular friction becomes stronger when it is smaller than 1 and becomes weak rapidly when it increases continuously.
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  • Yuma SHIMAMOTO, Tetsuya SUZUKI
    2018 Volume 74 Issue 2 Pages I_403-I_410
    Published: 2018
    Released: January 31, 2019
    JOURNALS FREE ACCESS
    Quantitative evaluation of binding power is important for porous material. In this study, the binding power in the compressive stress field was estimated by AE energy parameter in the case of stabilization of soil with cement and rice husk ash. As a result, the ratio of compressive strength in water for 28 days to compressive strength in water for 7days was more than 2.4 in stabilization of soil with by replacing more than 50% cement with rice husk ash. Total AE energy was positively correlated with binding power. AE energy seems to be an effective index parameter for evaluationing material quality.
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  • Takuryo SEGUCHI, Takashi MATSUSHIMA
    2018 Volume 74 Issue 2 Pages I_411-I_420
    Published: 2018
    Released: January 31, 2019
    JOURNALS FREE ACCESS
    The shape of clay agglomerates reflects the properties of interactions of clay particles and is also expected to predict microstructures inside clay deposits. We carried out the shape analysis of agglomerates of spherical latex beads, Kaolinite clay and Bentonite clay under various ion concentrations of the solutions. A series of Discrete Element simulations with both the DLVO interaction and the linear spring-dashpot contact model was also performed to investigate the detailed agglomeration process. It was found that (1) they all have fractal nature and the obtained fractal dimension is a good measure to quantify their shape; (2) a high ion concentration leads to high fractal dimension which means a compact structure with small voids because large void structure cannot stand against larger attractive intergranular force; (3) the ion concentration lower enough near the agglomeration limit also results in the compact structure because of the lack of intergranular friction between the fine particles.
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  • Shori HAMADA, Masuhiro BEPPU, Tatsuya MASE, Tatsuya NAKADA
    2018 Volume 74 Issue 2 Pages I_421-I_429
    Published: 2018
    Released: January 31, 2019
    JOURNALS FREE ACCESS
    In recent years, the damage to the vital structures such as nuclear power facilities by tornado-born missiles has been concerned because tornadoes have frequently occurred in Japan. Although a steel plate usually shows ductile elongation under low velocity impact by absorbing an impact energy, few studies have conducted an impact phenomenon with the estimated velocity of approximately 50m/s for the tornado-born missile. This study investigated a fundamental study on the perforation of SS400 steel plates by conducting impact tests and numerical simulations. As a result of the impact test, a 4.3kg-mass projectile yielded a perforation hole in 6mm-9mm-thick steel plates at an impact velocity of 57m/s. Numerical results reproduced the local deformation of the steel plates and impact velocity time history of the steel projectile.
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  • Takaaki OKAMOTO, Takumi OKAZAKI, Masato TAKENAKA, Michio SANJOU, Keiic ...
    2018 Volume 74 Issue 2 Pages I_431-I_438
    Published: 2018
    Released: January 31, 2019
    JOURNALS FREE ACCESS
    In this paper, we investigated the development of a vortex structure (horseshoe vortex and coherent vortex) around a vegetated groyne. Four groyne types (impermeable groyne (P=0) and the vegetated groynes(P=0.256∼0.512)) were used. For vegetated groynes, the vegetation on the weir crest was modeled by using circular cylinders. The results showed that (i) the horseshoe vortex is formed in front of the groyne, (ii) the horseshoe vortex is heterogeneous in the spaniwise ditrection and the downward flow occurs in Main-channel (iii) The spanwise vortex is generated behind the vegetated groyne and the flow separation length depends on the spanwise vortex strength.
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  • Obaidullah SAFIE, Akihiro TOMINAGA
    2018 Volume 74 Issue 2 Pages I_439-I_448
    Published: 2018
    Released: January 31, 2019
    JOURNALS FREE ACCESS
    Flow structure around permeable pile-group dikes was investigated experimentally by PIV method. The purpose was to reduce the flow velocity to protect the bank while the influence on the mainstream is small and reduced local scour is expected. The effects of number of piles and arrangement type on the flow structure were studied. The flow structure generated by two pile-group types, namely in-line and staggered arrays was compared. Different number of piles per group which was defined as pile-group density was considered. The results indicate that by changing the arrangement of the piles from in-line to staggered arrays, desirable changes on the flow structure occurred. The following features are particularly noteworthy for staggered array cases. It generated suitable velocity pattern in the downstream of the pile-group. In a lateral section at downstream of the structure it minimized the velocity near the bank and then it was increasing gradually to the mainstream, however, for the in-line arrays it was the opposite. Furthermore, to obtain a certain velocity near the bank, staggered arrays had the advantages of using less number of piles and hence less effect on the mainstream flow. In addition, staggered arrangement significantly reduced the generation of strong turbulence in the channel.
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  • Youichi YASUDA
    2018 Volume 74 Issue 2 Pages I_449-I_455
    Published: 2018
    Released: January 31, 2019
    JOURNALS FREE ACCESS
    This report presents water surface profiles and their lengths from brink to critical depths in rectangular smooth channels. As a non-dimensional expression, a similar water surface profile can be obtained under various types of channel slopes (horizontal to critical slopes). Also, the experimental investigation yields that the relative length from brink to critical sections depends on channel slope and Reynolds number. Appling the momentum equation to the control volume from brink to critical sections supported the experimental evidence on the similar water surface profile and the change of relative length with channel slope and Reynolds number. Further, the comparison of the water surface profile on the trapezoidal weir has been shown. The similar water surface profile could be obtained as in the case of recatangular channels. For the length from brink to critical sections, the relative length depends on the relative drop height under a given Reynolds number.
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  • Yu NISHIO, Makoto YAMAUCHI, Seiichiro IZAWA, Yu FUKUNISHI
    2018 Volume 74 Issue 2 Pages I_457-I_464
    Published: 2018
    Released: January 31, 2019
    JOURNALS FREE ACCESS
    A body swept away by a water flow is calculated using an incompressible Smoothed Particle Hydrodynamics method and compared to experiments in order to develop a method which can predict the behavior of the floating body in flash flow. Although the translational motion of the body in the simulation agrees with the experimental result, a discrepancy is found in the rotational motions, showing that there is a room for improvement in the model. When the wall exists at the downstream end, the spherical body weakens the averaged hydrodynamic load to the downstream wall but increases the flow velocity. It is also shown that high pressure regions appear at the downstream wall right after the water flow reaches the wall.
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  • Kaho YAMAGUCHI, Keisuke YOSHIDA, Shiro MAENO, Koji MANO, Ryosuke AKOH, ...
    2018 Volume 74 Issue 2 Pages I_465-I_474
    Published: 2018
    Released: January 31, 2019
    JOURNALS FREE ACCESS
    Developing technologies of Airborne Laser Bathymetry (ALB) have recently enabled us to obtain topographical data on river channels including underwater area. The reproducibility of river channel topography is estimated to effect on numerical analysis for river. However, there are few studies using ALB data, so the effect of it on analysis results has not been considered in particular.
    In this study, the topography data obtained by ALB measurement is examined the accuracy. Furthermore, we studied the effect of the topography data on analysis by comparing results of river-bed variation analysis and the difference data of ALB measurement.
    The topography data obtained ALB measurement showed the same topographical shape as cross-sectional survey result. In addition, by comparing analysis results and the difference data of ALB measurement, analysis using ALB data showed a trend similar to measured value than using conventional data.
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  • Naohiko SASSA, Akihiro TOMINAGA, Yuka KUNO
    2018 Volume 74 Issue 2 Pages I_475-I_484
    Published: 2018
    Released: January 31, 2019
    JOURNALS FREE ACCESS
    Planform vortices are observed in a flow field where the water depth increases in streamwise direction as seen in a large scour hole in the Kiso River, but the generation mechanism of such planform vortices are still not clear. In this study, 3-D numerical analysis was performed in a laboratory open channel with one-sided pool and the reproducibility of the characteristic flow structure with a planform vortex was confirmed. In order to investigate the topographic condition for the generation of the planform vortex, a PIV experiment was conducted in an open channel with laterally uniform 2-dimensional pool. As a result, a pair of planform vortices were generated near both the side wall and the accelerated flow was concentrated on the center of the channel. The observed flow structures were well reproduced by the 3-D numerical model and the generation condition and flow structures are analyzed.
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  • Robert Lado Wurda NYARSUK, Akihiro TOMINAGA
    2018 Volume 74 Issue 2 Pages I_485-I_492
    Published: 2018
    Released: January 31, 2019
    JOURNALS FREE ACCESS
    In open channel flow, a secondary flow can be generated using a strip roughness that is at an angle to the direction of flow. In this study, we investigated the influence of the oblique angle of installation of the roughness elements on the secondary flow generation experimentally by the PIV method. A clear secondary current was formed due to oblique sharpness, which flows upwards at the near wall region and downward at the middle of the channel in the lateral direction, but the strength and structure of each of the components of the secondary currents varied depending on the installation angle. In the vicinity of the bottom surface, the flow velocity in the lateral direction (V) is remarkably weak in the case of the installation angle of 30°, and in the case of 45° and 60°, the flow velocity becomes almost equally large. On the other hand, the vertical flow (W) at the near wall region is noticeably strong in the case of installation angle of 60° and becomes weak and weaker in magnitude in the case of installation angle 45° and 30° respectively. Furthermore, the downflow at the middle of the channel is weak in the case of installation angle of 60° and increase in magnitude in the case of 45° and attains peak in the case of 30°.
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  • Yasuo HATTORI, Yuma HASEBE, Hitoshi SUTO, Keisuke NAKAO, Shuji ISHIHAR ...
    2018 Volume 74 Issue 2 Pages I_493-I_500
    Published: 2018
    Released: January 31, 2019
    JOURNALS FREE ACCESS
    Aiming to develop evaluation methods for estimating deposition distributions of sea salt particles on a surface in a steel pipe, we have performed numerical simulations for air flow approaching the inside of a pipe. The special attention was paid to the behavior of shear stress predicted by a turbulence model, which corresponds to the deposition of sea-salt particles with small diameters. First, a benchmark test among two-low Re type turbulence models, Launder-Sharma and Kato-Launder models, used in engineering applications was carried out; the Kato-Launder model, which has an advantage for prediction of turbulence kinetic energy near structures, has a capability to capture transition of the boundary layer from laminar to turbulence and also separation flows at the edge of the pipe; the advantage is vital for reproduction of axial distributions of wall shear stress, which shows rapid increases and decreases of entrance regions. The simulations with Kato-Launder model under various wind conditions show that the large values of shear stress only appear at the entrance region, which corresponds to observations for distributions of corrosion rate and deposited sea salt inside a steel pipe.
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  • Hirohito KATSUDA, Mikihito HIROHATA
    2018 Volume 74 Issue 2 Pages I_501-I_511
    Published: 2018
    Released: January 31, 2019
    JOURNALS FREE ACCESS
    In order to investigate the influence of welding residual stress on load-carrying-capacity of patch plate joints under the compressive loading, a series of experiment and analysis was carried out. The temperature history and stress distribution of welding and post-weld heat treatment processes were accurately simulated by the thermal elastic plastic analysis. The characteristics of welding residual stress distribution of patch plate joints were shown. The compressive residual stress generated in the base plate reduced the yielding load of joint under the compressive load. To this problem, the effectiveness of residual stress reduction by post-weld heat treatment was confirmed.
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