研究者データベース

佐藤 太裕(サトウ モトヒロ)
工学研究院 機械・宇宙航空工学部門 機械材料システム
教授

基本情報

所属

  • 工学研究院 機械・宇宙航空工学部門 機械材料システム

職名

  • 教授

学位

  • 博士(工学)(北海道大学)

ホームページURL

J-Global ID

研究キーワード

  • パイプインパイプ   カーボンナノチューブ   海洋パイプライン   座屈   複合構造   応力集中   微生物   自然エネルギー   粒状体材料   曲げ特性   曲げ変形   粒子法   個別要素法   パイプインパイプシステム   劣化   再生骨材   パイプライン   合成構造   靭性能   フレキシブルパイプインパイプ   防災   コスト縮減   構造工学   山岳トンネル   凍土   寒冷地工学   活動層   温度解析   支保構造物   温度依存性   

研究分野

  • フロンティア(航空・船舶) / 船舶海洋工学
  • 社会基盤(土木・建築・防災) / 安全工学
  • 社会基盤(土木・建築・防災) / 社会システム工学
  • 社会基盤(土木・建築・防災) / 土木材料、施工、建設マネジメント
  • 社会基盤(土木・建築・防災) / 構造工学、地震工学

職歴

  • 2019年04月 - 現在 北海道大学大学院 工学研究院 機械宇宙工学部門 教授
  • 2012年02月 - 2019年03月 北海道大学大学院 工学研究院 北方圏環境政策工学部門 准教授
  • 2017年06月 - 2017年09月 英国ケンブリッジ大学 Visiting Academic Fellow
  • 2016年06月 - 2016年09月 韓国仁川大学校 Visiting Professor
  • 2007年04月 - 2012年01月 北海道大学大学院工学研究科(研究院) 助教
  • 2010年09月 - 2011年03月 英国インペリアルカレッジロンドン Visiting Lecturer
  • 2002年04月 - 2007年03月 北海道大学大学院工学研究科 助手
  • 2005年09月 - 2006年08月 英国クランフィールド大学 Visiting Researcher

学歴

  • 1999年04月 - 2002年03月   北海道大学大学院   工学研究科社会基盤工学専攻 博士後期課程
  • 1997年04月 - 1999年03月   北海道大学大学院   工学研究科社会基盤工学専攻 修士課程
  • 1995年10月 - 1997年03月   北海道大学   工学部   土木工学科
  • 1993年04月 - 1995年09月   北海道大学   教養部理Ⅰ系
  • 1990年04月 - 1993年03月   北海道札幌北高等学校

所属学協会

  • 日本機械学会   日本計算工学会   土木学会   

研究活動情報

論文

  • Inoue, A, Shimada, M, Sato, M, Shima, H
    Journal of Forestry Research 30 6 2069 - 2078 2019年12月 [査読有り][通常論文]
  • Inoue Akio, Koshikawa Kazuki, Sato Motohiro, Shima Hiroyuki
    JOURNAL OF FOREST RESEARCH 2019年11月18日 [査読有り][通常論文]
  • Umeno Yoshitaka, Sato Masanobu, Sato Motohiro, Shima Hiroyuki
    PHYSICAL REVIEW B 100 15 2019年10月08日 [査読有り][通常論文]
  • Umeno Yoshitaka, Yachi Yu, Sato Motohiro, Shima Hiroyuki
    PHYSICA E-LOW-DIMENSIONAL SYSTEMS & NANOSTRUCTURES 106 319 - 325 2019年02月 [査読有り][通常論文]
  • Akio Inoue, Motohiro Sato, Hiroyuki Shima
    Forest Ecology and Management 425 138 - 144 2018年10月01日 [査読有り][通常論文]
     
    © 2018 The Authors Bamboo forests are likely to be subjected to self-thinning due to their rapid growth rate. In fully stocked bamboo forests, the stand density (ρ) was suggested to be inversely proportional to the square of mean diameter at breast height (D) (ρ ∝ D−2), differing from the conventional power-law for trees, i.e., Reineke equation (ρ ∝ D−1.6). Nevertheless, the validity and mechanism of the inverse-square law remained unclear, despite its significance for managing bamboo forests. In this study, we derived an allometric model that predicts the slope of the maximum size-density relationship (MSDR) between D and ρ on double logarithmic coordinates based on well-known ecological laws. The model indicates that the slope of −2 for bamboo is theoretically valid, with the difference in the slope between bamboo and trees being caused by their differences in inner-culm (or inner-stem) structure. We also determined the MSDR empirically by compiling data of 415 Phyllostachys pubescens Mazel ex Houz. pure stands across Japan. The obtained MSDR describes the upper boundary of the D-ρ relationship well, with a slope of −1.996 that is very close to − 2. We further established a stand density management diagram of P. pubescens stands based on the MSDR. This diagram allows forest managers to regulate ρ depending on D as well as management purposes (production of bamboo shoot, bamboo charcoal and culm wood).
  • Masanobu Sato, Hiroyuki Shima, Motohiro Sato, Yoshitaka Umeno
    Physica E: Low-Dimensional Systems and Nanostructures 103 130 - 142 2018年09月01日 [査読無し][通常論文]
     
    © 2018 Elsevier B.V. To reveal the atomistic scale mechanism of buckling of single-walled carbon nanotubes (SWCNTs) under axial compression, we carried out molecular dynamics (MD) simulation and atomistic structural instability (ASI) analysis. The ASI analysis enables us to reveal the development of ‘latent’ instability modes until buckling of structure, which cannot be clarified with MD alone. Euler-type buckling was found in relatively thin and long nanotube models, while buckling triggered by change of cross-sectional shape (i.e., radial buckling) was found in thick and short models. With growing radius, a crossover between the Euler-type and radial buckling modes was clearly found in the ASI analysis. Even when the deformation behavior was apparently the same, the buckling can be triggered by different instability modes. We also analyzed the structural instability using the Flügge theory based on linear continuum mechanics (LCM) to compare the results with the ASI analysis. Initial eigenvalues and development of instability modes were different between the ASI and LCM results, leading to a significant deviation of buckling strain and instability crossover points. We investigated the effect of chirality of CNT which is difficult to explain by LCM.
  • Akio Inoue, Yoshiyuki Miyazawa, Motohiro Sato, Hiroyuki Shima
    Forests 9 2018年05月25日 [査読無し][通常論文]
     
    © 2018 by the authors. It is strongly debated whether bamboo forest ecosystems are a carbon sink or a carbon source because of insufficient knowledge regarding carbon loss via CO2 emissions from these forests. The surface area (S) of bamboo culms (stems) is important for estimating culm respiration, a major component of carbon cycling in bamboo forests. However, few studies have attempted to formulate predictive equations for S. In this study, we developed allometric equations for predicting S in three bamboo species grown in Kyushu Island, western Japan: Phyllostachys pubescens Mazel ex Houz., P. bambusoides Sieb. et Zucc. and P. nigra var. henonis. We used a power equation between S and diameter at breast height (D) and a linear equation between S and D × total culm length (H). The results indicated that P. bambusoides and P. nigra shared common site-independent equations. In contrast, P. pubescens required species-specific equations due to interspecific variation in culm slenderness and tapering. We also found that D was a better predictive variable than DH when quantifying S because of its satisfactory predictive performance and simplicity. These findings will be beneficial for evaluating the contribution of bamboo forest ecosystems to carbon cycling.
  • 谷内 湧, 梅野 宜崇, 島 弘幸, 佐藤 太裕
    土木学会論文集A2(応用力学) 74 1 51 - 62 公益社団法人 土木学会 2018年 [査読有り][通常論文]
     
    本研究は,一定圧力を作用させたカーボンナノチューブの断面座屈挙動を,分子動力学法によって精査することを目的とした.また,分子動力学法と薄肉円筒シェル理論の各々によって得られた結果を比較し,それらの適用限界を検証したうえで,カーボンナノチューブの直径や層数がその座屈特性に与える影響を調べた.更に,後座屈領域の時間発展追跡計算が可能という分子動力学法の利点を生かして,シェル理論では解析が困難な大変形過程の定量的検証と載荷-除荷曲線の導出を行った.
  • Teeranai Srimahachota, Hao Zheng, Motohiro Sato, Shunji Kanie, Hiroyuki Shima
    PHYSICAL REVIEW E 96 6 2017年12月 [査読有り][通常論文]
     
    Granular surfaces subjected to repeated passage often spontaneously develop a corrugated pattern. In this study, we scrutinized the growth dynamics of surface corrugation in a self-rotating sand bed that is traced by the edge of a vertically oscillating arm. We found that both the rotation velocity and the frequency of the oscillator strongly affect the occurrence rate of corrugation as well as the time evolution in the corrugation pattern, due to the intermittent collision between the oscillator and sand bed. We also discovered that the growth dynamics involves two distinct collective modes that describe the translational motion of the corrugation pattern on the sand bed.
  • Akio Inoue, Shiori Tochihara, Motohiro Sato, Hiroyuki Shima
    TREES-STRUCTURE AND FUNCTION 31 4 1271 - 1278 2017年08月 [査読有り][通常論文]
     
    Bamboo exhibits unique structural properties that distinguish it from most other woody plants. One of the most remarkable properties is that the long hollow culm is separated into many small chambers by a sequence of nodes. The node distribution along the culm is, in general, sparse at the mid-culm and dense near the ends of the culm. In this study, we examined the intraspecific and interspecific variation in the node distribution of three species of the genus Phyllostachys (Phyllostachys pubescens Mazel ex Houz., Phyllostachys nigra var. henonis and Phyllostachys nigra Munro) with different culm sizes. The node distribution followed a single fitting curve via the normalization procedure, indicating the existence of a hidden universal law that governs the node distribution of the three species, despite their different appearances. Our findings also suggest that the node distribution along the mature culm could be determined at the stage of bamboo shoot by its base diameter.
  • M. Sato, S. Harasawa, Y. Konishi, T. Maruyama, S. J. Park
    JOURNAL OF MECHANICS 33 3 369 - 374 2017年06月 [査読有り][通常論文]
     
    In the fields of engineering, nanoscience, and biomechanics, thin structural members, such as beams, plates, and shells, that are supported by an elastic medium are used in several applications. There is a possibility that these thin structures might buckle under severe loading conditions; higher-order, complicated elastic buckling modes can be found owing to the balance of rigidities between the thin members and elastic supports. In this study, we have shown a new and simple 'power law' relation between the critical buckling strain (or loads) and rigidity parameters in structural members supported by an elastic medium, which can be modelled as a Winkler foundation. The following structural members have been considered in this paper: i) a slender beam held by an outer elastic support under axial loading, ii) cylindrical shells supported by an inner elastic core under hydrostatic pressure (plane strain condition), and iii) complete spherical shells that are filled with an inner elastic medium.
  • Motohiro Sato, Akio Inoue, Hiroyuki Shima
    PLOS ONE 12 5 2017年05月 [査読有り][通常論文]
     
    The optimal distribution of the reinforcing fibers for stiffening hollow cylindrical composites is explored using the linear elasticity theory. The spatial distribution of the vascular bundles in wild bamboo, a nature-designed functionally graded material, is the basis for the design. Our results suggest that wild bamboos maximize their flexural rigidity by optimally regulating the radial gradation of their vascular bundle distribution. This fact provides us with a plantmimetic design principle that enables the realization of high-stiffness and lightweight cylindrical composites.
  • Yoshitaka Umeno, Masanobu Sato, Hiroyuki Shima, Motohiro Sato
    Solid State Phenomena 258 SSP 61 - 64 2017年01月 [査読有り][通常論文]
     
    © 2017 Trans Tech Publications, Switzerland.We carried out the atomistic structural instability (ASI) analysis with an empirical interatomic potential for carbon nanotubes (CNTs) under axial compression with the aim to reveal the mechanism of buckling. We investigated how ‘latent’ instability modes develop until one of them is activated at the structural instability. For pristine single-walled carbon nanotubes (SWCNTs), Euler-type buckling was found in relatively thin nanotubes, while buckling modes corresponding to change in the cross-sectional shape (radial buckling) were found in thick nanotubes. The crossover between the Euler-type buckling and radial buckling modes was clearly seen in the ASI analysis. While the reduction of Hessian eigenvalues in the pristine nanotubes and nanotubes with a vacancy is nearly linear until instability, rapid decrease of eigenvalues just before instability was found in models with Stone-Wales defects. This is due to localization of instability mode vectors around the defects that tends to arise before structural instability.
  • Motohiro Sato, Yu Yachi, Ikuyo Koike, Hiroyuki Shima, Yoshitaka Umeno
    Solid State Phenomena 258 SSP 65 - 68 2017年01月 [査読有り][通常論文]
     
    © 2017 Trans Tech Publications, Switzerland.This contribution provides simulated results of cross-sectional deformations observed in carbon nanotubes under high pressure. Molecular dynamics (MD) simulations were performed to explore radial buckling characteristics of multi-walled carbon nanotubes, and confirmed a variety of large-amplitude deformation modes. The energetically stable deformation mode turned out to be strongly dependent on the diameter of the innermost tube and the number of concentric walls. Critical buckling pressure obtained by MD simulations was compared with that estimated from a continuum elastic approximation, by which the validity of the continuum approximation was assessed.
  • Hiroyuki Shima, Motohiro Sato, Akio Inoue
    PHYSICAL REVIEW E 93 2 2016年02月 [査読有り][通常論文]
     
    Bamboo has a distinctive structure wherein a long cavity inside a cylindrical woody section is divided into many chambers by stiff diaphragms. The diaphragms are inserted at nodes and thought to serve as ring stiffeners for bamboo culms against the external load; if this is the case, the separation between adjacent nodes should be configured optimally in order to enhance the mechanical stability of the culms. Here, we reveal the hitherto unknown blueprint of the optimal node spacings used in the growth of wild bamboo. Measurement data analysis together with theoretical formulations suggest that wild bamboos effectively control their node spacings as well as other geometric parameters in accord with the lightweight and high-strength design concept.
  • Hiroyuki Shima, Motohiro Sato, Akio Inoue
    Physical Review E - Statistical, Nonlinear, and Soft Matter Physics 93 2016年02月 [査読有り][通常論文]
     
    © 2016 American Physical Society.Bamboo has a distinctive structure wherein a long cavity inside a cylindrical woody section is divided into many chambers by stiff diaphragms. The diaphragms are inserted at nodes and thought to serve as ring stiffeners for bamboo culms against the external load; if this is the case, the separation between adjacent nodes should be configured optimally in order to enhance the mechanical stability of the culms. Here, we reveal the hitherto unknown blueprint of the optimal node spacings used in the growth of wild bamboo. Measurement data analysis together with theoretical formulations suggest that wild bamboos effectively control their node spacings as well as other geometric parameters in accord with the lightweight and high-strength design concept.
  • Atomistic model analysis of deformation of carbon nanotubes under axial compression
    M. Sato, Y. Umeno
    Key Engineering Materials 725 451 - 455 2016年 [査読有り][通常論文]
  • 佐藤 太裕, 谷垣 俊行, 佐藤 諭佳, 島 弘幸, 井上 昭夫
    土木学会論文集A2(応用力学) 72 2 I_25 - I_34 公益社団法人 土木学会 2016年 [査読有り][通常論文]
     
    自然界に生息するタケは中空円筒であり,かつ節と組織構造を有する植物である.これは適者生存の厳しい環境下でできるだけ強く,高く生育するためにタケ自身が進化の過程で獲得してきた形態であり,力学的に極めて高い合理性を有すると考えられる.本研究は,タケの生態を構造力学的に紐解き,節配置の高さ方向分布と維管束の横断面内分布の不均一性が織り成す力学的優位性を実証するものである.この研究により,曲げを受けるタケの節配置による断面偏平抑制効果を剛性に関する異方性を考慮した無次元パラメータにより記述し,タケが外力により生じる曲げモーメント分布に合わせて断面偏平を効率的に抑制していること,また横断面内維管束分布は曲げ剛性を高めるように効果的に配置されていることが初めて理論的に示された.
  • S. Harasawa, M. Sato
    JOURNAL OF MECHANICS 31 3 241 - 247 2015年06月 [査読有り][通常論文]
     
    The goal of this study was to investigate analytically the buckling phenomena of slender beam structures embedded in an elastic medium. In such cases, there is a possibility that spiral-shaped buckling modes can occur due to the restraining effect of the surrounding medium. As a result of analytical investigations, helical buckling occurs radically. Furthermore the pitch of the helix does not fluctuate as the radius of the helix increases. The interesting mechanical implications of the embedding effect are demonstrated by the theoretical approach established in this study.
  • M. Sato, Y. Konishi, S. -J. Park
    JOURNAL OF MECHANICS 31 1 29 - 36 2015年02月 [査読有り][通常論文]
     
    This study examined the critical buckling characteristics of hydrostatically pressurized double-walled complete spherical shells. An analytical model based on small deflection thin shell theory is presented; the equations are solved in conjunction with variational principles. Axisymmetric and inextensional assumptions are not initially used in the exact formulation. This approach therefore avoids any discussion about the validity of the solution and allows the model to be extended to cover more generic nonaxisymmetric cases with relative ease. The analytical results are presented using illustrative buckling modes. Based on the developed formulation, only axisymmetric eigenmodes were found to occur despite the inclusion of the effect of interactions between outer and inner shells. Critical modes that are symmetric or antisymmetric about the equator may be determined depending on the combination of the stiffness connecting the outer and inner shells and the radius-to-wall thickness ratios.
  • Hiroyuki Shima, Yoshitaka Umeno, Motohiro Sato
    MECHANICS OF ADVANCED MATERIALS AND STRUCTURES 22 6 423 - 427 2015年 [査読有り][通常論文]
     
    Molecular dynamics simulations of multiwalled carbon nanotubes under hydrostatic pressure are performed to elucidate the novel class of radial buckling in the systems. It is revealed by all-atom simulations that the initial circular cross section transforms into a flower-like wavy configuration at critical pressure on the order of hundreds mega pascals or less. This kind of radial buckling, called radial corrugation, originates from the competition of the three relevant energies in the system: in-plane strain energy, van der Waals interaction energy between adjacent tubes, and out-of-plane bending energy. Their possible consequences for physical properties of carbon nanotubes are also discussed.
  • Motohiro Sato, Yuta Ishiwata
    STRUCTURAL ENGINEERING AND MECHANICS 53 1 17 - 26 2015年01月 [査読有り][通常論文]
     
    The cross sections of hollow cylindrical tubes ovalise under a pure bending condition, and this reduces their flexural stiffness as their curvatures increase. It is important to accurately evaluate this phenomenon, known as the, Brazier effect., to understand the bending behaviour of the systems considered. However, if the tubes are supported by an elastic medium or foundation, the ovalisation displacements of their cross sections may decrease. From this point of view, the purpose of this research is to analytically investigate the bending characteristics of single-and double-walled elastic tubes contacted by an elastic material by considering the Brazier effect. The Brazier moment, which is the maximum moment-carrying capacity of the ovalised cross section, can be calculated by introducing the strain energy per unit length of the tube in terms of the degree of ovalisation for the tube and the curvature. The total strain energy of the double-walled system is the sum of the strain energies of the outer and inner tubes and that of the compliant core. Results are comparatively presented to show the variation in the degree of ovalisation and the Brazier moment for single-and double-walled tubes.
  • Yoshitaka Umeno, Ikuyo Koike, Ayako Kusano, Hiroyuki Shima, Motohiro Sato
    PHYSICA E-LOW-DIMENSIONAL SYSTEMS & NANOSTRUCTURES 65 135 - 140 2015年01月 [査読有り][通常論文]
     
    We perform molecular dynamics simulations of a few-walled (with 3-4 walls) carbon nanotubes using empirical interatomic potential. We demonstrate that the radial corrugation occurs in such thin nanotubes under hydrostatic pressure, which is apparently similar to the corrugation in thicker (e.g., several tens-walled) nanotubes that had been predicted using continuum mechanics approximation. The mechanism underlying the corrugation of a few-walled nanotubes, however, is found to be much distinct from thick nanotubes; i.e., the sp(3) bonds between adjacent concentric walls and registry of atom arrangement take important roles in the formation and stabilization of corrugation modes in a few-walled nanotubes. (C) 2014 Elsevier B.V. All rights reserved.
  • 古屋健, 岡本佳子, 佐藤諭佳, 佐藤太裕, 島弘幸
    形の科学会誌 29 2 156 - 157 2014年11月 [査読無し][通常論文]
  • Hiroyuki Shima, Motohiro Sato, Sung-Jin Park
    ADVANCES IN CONDENSED MATTER PHYSICS 2014 2014年 [査読有り][通常論文]
     
    When a straight hollow tube having circular cross-section is bent uniformly into an arc, the cross-section tends to ovalize or flatten due to the in-plane stresses induced by bending; this ovalization phenomenon is called the Brazier effect. The present paper is aimed at theoretical formulation of the Brazier effect observed in multilayered cylinders, in which a set of thin hollow cylinders are stacked concentrically about the common axis. The results indicate that mechanical couplings between stacked cylinders are found to yield pronounced suppression of the cross-sectional ovalization. Numerical computations have been performed to measure the degree of suppression in a quantitative manner and to explore how it is affected by the variations in the bending curvature, the number of stacked cylinders, and the interlayer coupling strength.
  • 小池育代, 草野彩子, 佐藤太裕, 梅野宜崇, 島弘幸
    土木学会論文集 A2(応用力学)(Web) 70 2 I.25-I.32 (J-STAGE)  2014年 [査読有り][通常論文]
  • Motohiro Sato, Hiroyuki Shima, S-J Park
    JOURNAL OF MECHANICS 29 4 583 - 588 2013年12月 [査読有り][通常論文]
     
    ABSTRACT Shell theory solutions for radial buckling of multiply-concentric hollow cylinders are presented. Multi-cylindrical systems are those composed of two or more concentically mounted hollow tubes, wherein the annular space mediates inter-tube forces, attractive or repulsive depending on structural details of composites. Reflecting the multiple core-shell structures, the systems often exhibit peculiar radial buckling modes, which should be relevant to macro scale applications for deep water oil and gas transportation andmicroscale realization in lipid bilayer tubes. In this article, we focus on an illustrative example of such the multiply-tubular systems with nanometric dimension, the so-called multiwalled carbon nanotubes (MWNTs). Theoretical analysis based on a thin shell theory allows us to find anomalous radial buckling behaviors of MWNTs driven by hydrostatic pressure. The obtained buckling modes are characterized by petal-like wavy cross sections, which is what we call the radial corrugation of MWNTs. An important observation is the mechanical consequence of stiff core-tube insertion into the innermost hollow region of a given MWNT. The insertion results in a significant variance in the critical buckling pressure, above which the MWNT undergoes radial corrugation. The insertion-induced-variance in the critical pressure is due to the primary role of inter-tube interaction between adjacent constituent tubes, as explained within our theoretical model. Copyright © 2013 The Society of Theoretical and Applied Mechanics, R.O.C.
  • 平 久夫, 佐藤 太裕, 島 弘幸
    物理教育 61 4 194 - 197 日本物理教育学会 2013年12月 [査読有り][通常論文]
  • Sung-Jin Park, Hiroyuki Shima, Motohiro Sato
    INTERNATIONAL JOURNAL OF MODERN PHYSICS B 27 31 1350179.1-1350179.9  2013年12月 [査読有り][通常論文]
     
    Cross-sectional deformation of multiwalled carbon nanotubes under isotropic radial pressure is investigated in a realm of continuum elastic approximation. The nanotube we assumed is subjected to the embedment into an elastic medium and stiffener insertion into the core cavity. Combination of the two reinforcement manipulations is found to cause kaleidoscopic mode changes in the radial corrugation, in which the cylindrical walls exhibit wavy patterns along the circumferential direction. Physical consequences of the diverse corrugation patters are also discussed.
  • Radial deformation and band-gap modulation of pressurized carbon nanotubes
    H. Taira, H. Shima, Y. Umeno, M. Sato
    Coupled Systems Mechanics 2 2 147 - 157 2013年 [査読有り][通常論文]
  • Effect of open-core screw dislocation on axial conductivity in semiconductor crystals
    H. Taira, M. Sato
    Effect of open-core screw dislocation on axial conductivity in semiconductor crystals 1 3 171 - 182 2013年 [査読有り][通常論文]
  • SATO Motohiro, TAIRA Hisao, IKEDA Tetsuro, SHIMA Hiroyuki
    J Nanomater (Web) 2013 3 ARTICLE ID 767249,1-9  2013年 [査読有り][通常論文]
  • M. Sato, M. A. Wadee, K. Iiboshi, T. Sekizawa, H. Shima
    INTERNATIONAL JOURNAL OF MECHANICAL SCIENCES 59 1 22 - 30 2012年06月 [査読有り][通常論文]
     
    The critical buckling characteristics of hydrostatically pressurized complete spherical shells filled with an elastic medium are demonstrated. A model based on small deflection thin shell theory, the equations of which are solved in conjunction with variational principles, is presented. Axisymmetric and inextensional assumptions are not used initially in the exact formulation 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. Simplified approximations based on a Rayleigh-Ritz approach are also introduced for the critical buckling pressure and the mode number with a considerable degree of accuracy. 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 exact formulation can be readily extended to apply to more general cases of non-axisymmetric buckling problems and the approximate method can be extended to the post-buckling range. (C) 2012 Elsevier Ltd. All rights reserved.
  • Hiroyuki Shima, Susanta Ghosh, Marino Arroyo, Kohtaroh Iiboshi, Motohiro Sato
    COMPUTATIONAL MATERIALS SCIENCE 52 1 90 - 94 2012年02月 [査読有り][通常論文]
     
    The radial deformation of multiwall carbon nanotubes (MWNTs) under hydrostatic pressure is investigated within the continuum elastic approximation. A thin-shell theory, with accurate elastic constants and interwall couplings, allows us to estimate the critical pressure above which the original circular cross-section transforms into radially corrugated ones. The emphasis is placed on the rigorous formulation of the van der Waals interaction between adjacent walls, which we analyze using two different approaches. Possible consequences of the radial corrugation in the physical properties of pressurized MWNTs are also discussed. (C) 2011 Elsevier B.V. All rights reserved.
  • Hard-to-Soft Transition in Radial Buckling of Multi-Concentric Nanocylinders
    S. -J. Park, M. Sato, T. Ikeda, H. Shima
    World Journal of Mechanics 2 1 42 - 50 2012年 [査読有り][通常論文]
  • Approximate formulation for Bifurcation Buckling Loads of Axially Compressed Cylindrical Shells with an Elastic Core
    M. Sato, K. Shimazaki
    Interactions and Multiscale Mechanics 4 4 313 - 320 2011年 [査読有り][通常論文]
  • M. Sato
    PROCEEDINGS OF THE TWELFTH EAST ASIA-PACIFIC CONFERENCE ON STRUCTURAL ENGINEERING AND CONSTRUCTION (EASEC12) 14 2366 - 2372 2011年 [査読有り][通常論文]
     
    Carbon nanotubes (CNTs) consist of a graphene sheet (two-dimensional hexagonal lattices of carbon atoms) rolled up into a cylinder. This nanoscale structure has generated enormous interest in the research field of science and engineering in the last decades because of its excellent mechanical properties. For example, Young's modulus of CNTs is estimated to be on the order of TPa (i.e., several times stiffer than steel) and the tensile strength is as high as tens of GPa. This means that CNTs are the stiffest and strongest materials on earth. On the other hand, CNTs are known to have its remarkable flexibility when subjected to external hydrostatic pressure and bending force. Owing to such mechanical properties, CNTs are regarded as an ideal material for superstrong nano-fiber and thus hold great promise for use as next-generation materials. It has also been broadly accepted that mechanical deformation of a carbon nanotube causes significant changes in its physical and chemical properties. Precise knowledge of its deformation mechanism and available geometry is, therefore, crucial for understanding the precise physics of CNT systems and in developing CNT-based applications. Here we introduce such remarkable elastic and plastic deformation properties of CNTs, as well as recent theoretical and experimental progresses in the field of many excellent CNT researches. (C) 2011 Published by Elsevier Ltd.
  • SATO Motohiro, WADEE M. Ahmer, SEKIZAWA Takafumi, IIBOSHI Kohtaroh, SHIMA Hiroyuki
    土木学会論文集 A2(応用力学)(Web) 67 2 I.15-I.22 (J-STAGE)  2011年 [査読有り][通常論文]
  • Hiroyuki Shima, Motohiro Sato, Kohtaroh Iiboshi, Susanta Ghosh, Marino Arroyo
    PHYSICAL REVIEW B 82 8 2010年08月 [査読有り][通常論文]
     
    Stable cross sections of multiwalled carbon nanotubes subjected to electron-beam irradiation are investigated in the realm of the continuum mechanics approximation. The self-healing nature of sp(2) graphitic sheets implies that selective irradiation of the outermost walls causes their radial shrinkage with the remaining inner walls undamaged. The shrinking walls exert high pressure on the interior part of nanotubes, yielding a wide variety of radial-corrugation patterns (i.e., circumferentially wrinkling structures) in the cross section. All corrugation patterns can be classified into two deformation phases for which the corrugation amplitudes of the innermost wall differ significantly.
  • SHIMA Hiroyuki, SATO Motohiro, IIBOSHI Kohtaroh, GHOSH Susanta, ARROYO Marino
    Phys Rev B Condens Matter Mater Phys 82 8 085401.1-085401.7  2010年08月 [査読有り][通常論文]
  • 佐藤太裕, 星崎心吾, 蟹江俊仁, 三上隆
    海洋開発論文集 26 801 - 805 2010年06月 [査読有り][通常論文]
  • 佐藤太裕, 嶋崎賢太
    海洋開発論文集 26 531 - 535 2010年06月 [査読有り][通常論文]
  • STRUCTURAL MODELING OF CARBON NANOTUBES BASED ON CONTINUUM ELASTIC THEORY
    Motohiro Sato, Mohammad Rahimi, Marino Arroyo, Hiroyuki Shima
    PROCEEDINGS OF THE INTERNATIONAL CONFERENCE ON MODELLING AND SIMULATION 2010 IN PRAGUE (MS'10 PRAGUE) 387 - 390 2010年 [査読有り][通常論文]
     
    This study presents an applicability of a structural modeling of carbon nanotubes using continuum elastic thin cylindrical shell approximations. Molecular dynamics- or atomistic-based simulations are quite powerful and sophisticated analytical tools to accurately investigate the structural behaviors of carbon nanotubes under external loads. However, computational costs of such high performance numerical methods become expensive especially when we deals with large scale problems such as simulations of "multi"-walled carbon nanotubes (MWNTs). For this reason, continuum models can be frequently applied to analyze its structural and mechanical properties of carbon nanotubes as an alternative way, but the validity of using the continuum model is still under debate. In this study, we firstly formulate hydrostatically pressurized buckling behaviors of MWNTs based on the continuum elastic thin sell theory. Next, the analytical results, such as critical buckling pressures, obtained from shell theory based modeling are compared with the numerical results calculated from atomistic-based modeling.
  • 佐藤太裕, 島弘幸, 飯干晃太朗, 三上隆
    応用力学論文集(CD-ROM) 13 19 - 28 2010年 [査読有り][通常論文]
  • Motohiro Sato, Hiroyuki Shima, Kohtaroh Iiboshi
    INTERNATIONAL JOURNAL OF MODERN PHYSICS B 24 1-2 288 - 294 2010年01月 [査読有り][通常論文]
     
    The present paper investigates the cross-sectional morphology of Multiwalled Carbon Nanotubes (MWNTs) restrained radially and circumferentially by an infinite surrounding elastic medium, subjected to uniform external hydrostatic pressure. In this study, a two-dimensional plane strain model is developed, assuming no variation of load and deformation along the tube axis. We find some characteristic cross-sectional shapes from the elastic buckling analysis. The effect of the surrounded elastic medium on the cross-sectional shape which occurs due to pressure buckling is focused on by the comparison with the shape for no elastic medium case in our discussion. It is suggested that in no embedded elastic medium cases, the cross-sectional shapes of inner tubes maintain circle or oval; on the other hand, an embedded medium may cause inner tube corrugation modes especially when the number of shells for MWNTs is small.
  • Hiroyuki Shima, Motohiro Sato
    PHYSICA STATUS SOLIDI A-APPLICATIONS AND MATERIALS SCIENCE 206 10 2228 - 2233 2009年10月 [査読有り][通常論文]
     
    We demonstrate a novel cross-sectional deformation, called the radial corrugation, of multi-walled carbon nanotubes (MWNTs) under hydrostatic pressure. Theoretical analyses based on the continuum elastic approximation have revealed that MWNTs consisting of more than ten concentric walls undergo elastic deformations at critical pressure p(c) similar or equal to 1 GPa, above which the circular shape of the cross-section becomes radially corrugated. Various corrugation modes have been observed by tuning the innermost tube diameter and the number of constituent walls, which is a direct consequence of the core-shell structure of MWNTs. [GRAPHICS] Cross-sectional views of MWNT under high hydrostatic pressure: elliptic deformation with the mode index n = 2 (left), and radial corrugations with n = 5 (center), and n = 6 (right). The index it indicates the circumferential wave number of the deformed cross-section. (C) 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
  • 佐藤太裕, 渡辺香奈, 白石圭祐, 蟹江俊仁, 赤川敏
    海洋開発論文集 25 737 - 740 2009年06月 [査読有り][通常論文]
  • Buckling Characteristics of Multiwalled Carbon Nanotubes under External Pressure
    M. Sato, H. Shima
    Interactions and Multiscale Mechanics 2 2 209 - 222 2009年 [査読有り][通常論文]
  • Hiroyuki Shima, Motohiro Sato
    NANOTECHNOLOGY 19 49 495705 (8 PP.)  2008年12月 [査読有り][通常論文]
     
    Radial elastic corrugation of multiwalled carbon nanotubes under hydrostatic pressure is demonstrated by using the continuum elastic theory. Various corrugation patterns are observed under a pressure of several GPa, wherein the stable cross-sectional shape depends on the innermost tube diameter D and the total number N of concentric walls. A phase diagram is established to obtain the requisite values of D and N for a desired corrugation pattern among choices. In all corrugation patterns, the cylindrical symmetry of the innermost tube is maintained even under high external pressure.
  • M. Sato, M. H. Patel, F. Trarieux
    STRUCTURAL ENGINEERING AND MECHANICS 30 3 263 - 278 2008年10月 [査読有り][通常論文]
     
    Structural pipe-in-pipe cross-sections have significant potential for application in offshore oil and gas production systems because of their property that combines insulation performance with structural strength in an integrated way. Such cross-sections comprise inner and outer thin walled pipes with the annulus between them fully filled by a selectable thick filler material to impart an appropriate combinations of properties. Structural pipe-in-pine cross-sections can exhibit several different collapse mechanisms and the basis of the preferential occurrence of one over others is of interest. This paper presents an elastic analyses of a structural pipe-in-pine cross-section when subjected to external hydrostatic pressure. It formulates and solves the static and elastic buckling problem using the variational principle of minimum potential energy. The paper also investigates a simplified formulation of the problem where the outer pipe and its contact with the filler material is considered as a 'pipe on an elastic foundation'. Results are presented to show the variation of elastic buckling pressure with the relative elastic modulus of the filler and pipe materials, the filler thickness and the thicknesses of the inner and outer pipes. The range of applicability of the simplified 'pipe on an elastic foundation' analysis is also presented. A brief review of the types of materials that could be used as the filler is combined with the results of the analysis to draw conclusions about elastic buckling behaviour of structural pipe-in-pipe cross-section.
  • 嶋崎 賢太, 佐藤 太裕, 蟹江 俊仁, 三上 隆
    海洋開発論文集 24 1047 - 1050 Japan Society of Civil Engineers 2008年06月 [査読有り][通常論文]
     
    Structural pipe-in-pipe cross-sections have significant potential for application in offshore oil and gas production systems because of their property that combines thermal insulation performance with structural strength and self weight in an integrated way. Such cross-sections comprise inner and outer thin walled pipes with the annulus between them fully filled by a selectable filler material to impart an appropriate combination of properties. For offshore pipelines, bending characteristics become one of the most important factors for the structural design of the pipelines. The purpose of this research is to investigate the bending characteristics of such pipe-in-pipe systems analytically by considering the Brazier effect. Results are presented to show the variation of the degree of ovalization and bending moment with the relative elastic modulus of the filler and pipe materials and the filler thickness.
  • 佐藤 太裕, 星崎 心吾, 蟹江 俊仁, 三上 隆
    海洋開発論文集 24 981 - 985 Japan Society of Civil Engineers 2008年06月 [査読有り][通常論文]
     
    For a type of "perfectly underwater"structures moored by some tension legs, namely submerged floating structures, the dynamic behaviors of the floating body are expected to involve many severe design and computational problems. In addition, three dimensional motions with six degrees of freedom induced by some external forces like strong waves and earthquakes may be very complex and it is difficult to explain the mechanisms of the behavior accurately.<BR>This paper presents the three dimensional dynamic response characteristics of the submerged floating structures. Three dimensional restoring forces due to tension legs are introduced and dynamic properties such as natural period and fluctuating tension force are investigated here. Especially, we focus on the effect of tension leg arrangement on dynamic characteristics of submerged floating structure.
  • Motohiro Sato, Shunji Kanie, Takashi Mikami
    APPLIED MATHEMATICAL MODELLING 32 5 688 - 699 2008年05月 [査読有り][通常論文]
     
    This paper presents the mathematical hypothesis that a beam on equidistant elastic supports (BOES) can be considered as a beam on an elastic foundation (BOEF) in static and free vibration problems. This modeling of BOES as BOEF is presumed to be applicable to a limited range of support stiffness, spacing and flexural rigidity of the beam. The authors investigate the applicability of the modeling of BOEF from the property of characteristic solutions obtained from governing equations of both BOES and BOEF. In this study, the formulation of BOES leads to governing difference equations, and the motions of BOEF are expressed by differential equations. This is because exact solutions must be employed in order to verify their analogy accurately. The characteristic solutions obtained from these two governing equations are compared to each other in order to investigate the relationship between them. (c) 2007 Elsevier Inc. All rights reserved.
  • Motohiro Sato, Minoo H. Patel
    JOURNAL OF MARINE SCIENCE AND TECHNOLOGY 12 4 251 - 262 2007年11月 [査読有り][通常論文]
     
    Structural pipe-in-pipe cross sections have significant potential for application in offshore oil and gas production systems because they combine thermal insulation performance with structural strength and self weight in an integrated way. Such cross sections comprise inner and outer thin-walled pipes with the annulus between them fully filled by a selectable filler material to impart an appropriate combination of properties. Structural pipe-in-pipe cross sections can exhibit several different collapse mechanisms, and the basis of the preferential occurrence of one over the others is of interest. This article presents an exact analysis for predicting the elastic buckling behaviours of a structural pipe-in-pipe cross section when subjected to external hydrostatic pressure. Simplified approximations are also investigated for elastic buckling pressure and mode when the outer pipe and its contact with the filler material is considered as a pipe on an elastic foundation. Results are presented to show the variation of elastic buckling pressure with the relative elastic modulus of the filler and pipe materials, the filler thickness, and the thicknesses of the inner and outer pipes. Case studies based on realistic application scenarios are used to show that the simplified approximations are sufficiently accurate for practical structural design purposes.
  • Motohiro Sato, Shunji Kanie, Takashi Mikami
    MECHANICS RESEARCH COMMUNICATIONS 34 5-6 451 - 459 2007年07月 [査読有り][通常論文]
     
    A new simplified structural model and its governing equations for beams on elastic foundations with elastic coupling are proposed. This modeling system is simple but appropriate for the initial structural design of large-scale submerged floating-beam structures moored by tension legs spaced at uniform interval along the beam. The model is actually for beam on discrete elastic supports rather than on continuous elastic foundations. Therefore, the governing equations are based on finite difference calculus and solutions for beams on discrete elastic supports with elasticity coupling are also proposed. To clarify the applicability limit of the proposed model, the equivalence between a beam on discrete elastic supports and that on continuous elastic foundation is investigated by comparisons of characteristic solutions. (c) 2007 Elsevier Ltd. All rights reserved.
  • 佐藤 太裕, 嶋崎 賢太, 蟹江 俊仁, 三上 隆
    海洋開発論文集 23 907 - 911 Japan Society of Civil Engineers 2007年06月 [査読有り][通常論文]
     
    Structural pipe-in-pipe cross-sections have significant potential for application in offshore oil and gas production systems because of their property that combines thermal insulation performance with structural strength and self weight in an integrated way. Such cross-sections comprise inner and outer thin walled pipes with the annulus between them fully filled by a selectable filler material to impart an appropriate combination of properties. Structural pipe-in-pipe cross-sections can exhibit several different collapse mechanisms and the basis of the preferential occurrence of one over others is of interest. This paper presents a simplified evaluation method for predicting the elastic buckling behaviours of a structural pipe-in-pipe cross-section when subjected to external hydrostatic pressure. Results are presented to show the validity of the proposed simplified formulations for estimating the local and global buckling pressures.
  • 蟹江 俊仁, 鈴木 雄太, 佐藤 太裕, 旭 幸司, 高橋 伸次郎, 井上 卓悦
    海洋開発論文集 23 309 - 314 Japan Society of Civil Engineers 2007年06月 [査読有り][通常論文]
     
    At the time being, deterioration in water quality of closed water body has become a serious issue for local fishery and accumulation of mud layer which covers lakebed has been thought as the cause of deterioration. Then, it can be said that maintenance and preservation of the water environment by retrieving those mud layer is one of the most important subjects to enhance and to promote regional economy in the vicinity with preserving precious marine resources.<BR>The authors have proposed a new retrieving method of lakebed mud on site. This method has been developed as an innovative way that requires neither additional chemicals for condensation of the mud nor a temporary yard for desiccation of the mud. After the first phase with indoor model experiment, it was confirmed that the method successfully retrieve the mud and an on-site experiment is now under planning. In this paper, the authors report a study result on the device, especially the shape of retrieving fan, with 3-D flow analysis. Through this study, important knowledge for designing the shape of fan was obtained in order to expect efficient retrieving. Though further experiment is necessary under various mud conditions to improve the efficiency, the method is getting close to a reality.
  • 佐藤 太裕, PATEL Minoo H, TRARIEUX Florent
    応用力学論文集 9 25 - 32 Japan Society of Civil Engineers 2006年08月 [査読有り][通常論文]
     
    This paper presents an analysis of local collapse mechanisms of a structural pipe-in-pipe cross-section with very soft and thick core when subjected to external hydrostatic pressure. It formulates and solves the elastic collapse problem using the variational principle of minimum potential energy. Effects of therelative stiffness between the outer/inner pipes and the core, and the core thickness on the critical external pressures and the collapse modes are investigated. The paper also proposes a simplified formulation of the localbuckling problem where the outer pipe and its contact with the filler material is considered as a 'ringon an elastic foundation'.
  • HG Tj, T Mikami, S Kanie, M Sato
    JOURNAL OF SOUND AND VIBRATION 290 3-5 785 - 793 2006年03月 [査読有り][通常論文]
     
    Free vibrations of cylindrical shells partially buried in elastic foundations based on the finite element method were examined. The shells are discretized into cylindrical finite elements and the distribution of the foundation in the circumferential direction is defined by the expansion of Fourier series. The present formulation can be simply applied to consider non-uniformities in the foundation both in the circumferential and longitudinal directions. Convergence issues with the present method are explained. Numerical results of the natural frequency and mode for various shell geometries and foundation parameters are given to provide a clearer picture of the shell characteristics in linear vibrations. The relative stiffness ratio of foundation and shell is discussed. The results of free vibration analysis for partially suspended shells on elastic foundations are also presented. (c) 2005 Elsevier Ltd. All rights reserved.
  • TJ Haryadi Gunawan, MIKAMI Takashi, KANIE Shunji, SATO Motohiro
    構造工学論文集 A 52 3 1219 - 1226 2006年03月 [査読有り][通常論文]
  • HG Tj, T Mikami, S Kanie, M Sato
    THIN-WALLED STRUCTURES 43 11 1746 - 1762 2005年11月 [査読有り][通常論文]
     
    The free vibration characteristics of fluid-filled cylindrical shells on elastic foundations are presented by a semi-analytical finite element method. A shell is discretized into cylindrical finite elements where shell governing equations based shape functions in the longitudinal direction are used instead of the usual simple polynomials. Non-uniformities of the foundations in the circumferential and longitudinal directions are handled by the Fourier series and an element mesh Strategy, respectively. The fluid domain is described by the potential flow theory. The hydrodynamic pressure acting on shells is derived from the condition for dynamic coupling of the fluid-structure. The effect of fluid in a shell, shell geometries, and foundation parameters on the dynamic behavior of fluid-containing shells is investigated. Numerical results based on the present method converge more rapidly than those obtained by the simple polynomial formulation. The method is suitable for the problem considered due to its generality, simplicity, and potential for further development. (c) 2005 Elsevier Ltd. All rights reserved.
  • 蟹江 俊仁, 赤川 敏, 三上 隆, 佐藤 太裕, 金 高義
    土木学会論文集 = Proceedings of JSCE 798 157 - 166 土木学会 2005年09月 [査読有り][通常論文]
  • H Gunawan, T Mikami, S Kanie, M Sato
    COMPUTERS & STRUCTURES 83 21-22 1730 - 1741 2005年08月 [査読有り][通常論文]
     
    A method for analyzing cylindrical shells partially buried in an elastic foundation based on the finite element method is presented by using the expansion of a Fourier series in the circumferential direction to define the distribution of the foundation. Numerical analysis of convergence of the results is presented for a gravity load. The effect of the foundation on the distribution of stress resultants was investigated. Numerical results are also given for the internal liquid pressure load. In addition, cylindrical shells partially suspended on elastic foundations are also analyzed. (c) 2005 Elsevier Ltd. All rights reserved.
  • TJ Haryadi Gunawan, MIKAMI Takashi, KANIE Shunji, SATO Motohiro
    構造工学論文集 A 51A 1 1 - 10 2005年03月20日 [査読無し][通常論文]
  • 旭 幸司, 高橋 伸次郎, 井上 卓悦, 蟹江 俊仁, 佐藤 太裕, 鈴木 雄太
    海洋開発論文集 21 879 - 883 Japan Society of Civil Engineers 2005年 [査読有り][通常論文]
     
    At present, deterioration of water quality in closed water body has become a serious issue for the local fishery and an accumulated mud layer which covers lakebed has been thought as the cause of the deterioration. Then, it can be said that the maintenance and preservation of the water environment by retrieving the mud layer is one of the most important subjects to preserve and to promote the regional economy with maintaining precious marine resources.<BR>In this paper, the authors propose a new retrieving method of lakebed mud on site. This method has been developed as an innovative way that requires neither additional chemicals for condensation of the mud nor a temporary yard for desiccation of the mud. This research aims to obtain fundamental knowledge about the retrieving torque and its efficiency to establish this new method. The experimental result shows that the mud can be retrieved with the fan efficiently enough to adopt the method practically. However, further experiment is necessary under various mud conditions to improve the efficiency.
  • 蟹江俊仁, 赤川敏, 佐藤太裕, 三上隆
    寒地技術論文・報告集 20 472 - 478 2004年10月 [査読無し][通常論文]
  • 佐藤 太裕, 蟹江 俊仁, 三上 隆
    応用力学論文集 7 1 31 - 38 土木学会 2004年08月 [査読有り][通常論文]
  • 三倉寛明, 蟹江俊仁, 三上隆, 佐藤太裕
    海洋開発論文集 20 85 - 88 Japan Society of Civil Engineers 2004年 [査読有り][通常論文]
     
    Recently, completely submerged structure resting on piles is expected as a new alternative structure to bridge and/or immersed tunnel for relatively shallow-water crossing. In case of those structures, no change in buoyancy can be expected and only pile must resist against external wave force. As a result, the piles should have enough length to exert their friction strength against pulling out force due to wave. Since high safety factor for pulling out is required, reducing vertical force acting on piles becomes important for economical design. This study aims to evaluate the effect of sectional shape on the wave force and to introduce the relationship between sectional shape and vertical wave force acting on supporting structure.
  • 佐藤太裕, 蟹江俊仁, 三上隆, 小室達明
    海洋開発論文集 20 1277 - 1282 Japan Society of Civil Engineers 2004年 [査読有り][通常論文]
     
    This paper deals with the characteristics of combination resonance for submerged floating structure. The combination resonance takes place in a vibratory system having multiple degrees-of-freedom and under parametric excitation. In this study, it is assumed that the floating structure is moored by some tension legs and located in the water between seabed and water surface. Due to such a structural form, there is much possibility that complicated dynamic phenomena like parametric excitation take place. The parametric excitation is caused by the time-varying tension force of tension legs. The time-varying tension force arises when some dynamic loads such as regular waves act on the floating body and the body moves in the water. In this paper, analytical studies are carried out to confirm the possibility of the occurrence of unstable motions by introducing Mathieu equations and effects of tension leg arrangements on the combination resonance characteristics are investigated in particular.
  • 佐藤太裕, 小室達明, 蟹江俊仁, 三上隆
    海洋開発論文集 20 1283 - 1286 Japan Society of Civil Engineers 2004年 [査読有り][通常論文]
     
    Submerged Floating Structure is a whole new type of strait crossing which is fixed in the water and supported by the balance between buoyancy and drag force of tension legs. This structure is expected to be widely applicable for railway, road, pedestrian walk and transportation system of material and fluid. In order to realize this construction technology, however, there are a lot of problems to be solved.<BR>One of the most important probrems is parametric excitation which is the response caused by time-varying tension force of legs. In this paper, the parametric excitation phenomena of Submerged Floating Structure are studied analytically and characteristics of the dynamic instability are investigated
  • 佐藤 太裕, 蟹江 俊仁, 三上 隆, 小室 達明
    応用力学論文集 7 31 - 38 Japan Society of Civil Engineers 2004年 [査読有り][通常論文]
     
    This paper deals with the characteristics of the parametric excitation, which is one of the dynamic instability phenomena, of Submerged Floating Tunnel. In this study, it is assumed that the structure is moored by some tension legs and located in the water between seabed and water surface. The parametric excitation is caused by the time tension force of tension legs. The time-varying tension force arises when some dynamic loads such as regular waves act on the floating body and the body moves in the water. The analytical studies are carried out to confirm the possibility of the occurrnce of unstable motions by introducing Mathieu-type equations in this study and effects of tension leg arrangements, viscous damping, quadratic damping and external forces on the parametric excitation characteristics are investigated in particular.
  • 佐藤太裕, 蟹江俊仁, 三上隆
    海洋開発論文集 19 649 - 652 Japan Society of Civil Engineers 2003年 [査読有り][通常論文]
     
    For a type of "perfectly underwater" structures moored by tension legs like Submerged Floating tunnel, dynamic behaviors of the floating body are expected to involve many severe design and computational problems. In addition, motions induced by some external forces like strong waves and earthquakes may be very complex and it is difficult to explain the mechanisms of the behavior accurately. Especially, dynamic characteristics in consideration of elasticity coupling caused by restoring force of tension leg arrangement have not been clear so far. When elasticity coupling can arise, restoring forces of tension legs associated with the rotation show some bad influences on the dynamic behaviors. From this point of view, we focus on the effect of tension leg arrangement on dynamic characteristics of submerged floating structure in this study.
  • 蟹江俊仁, 佐藤太裕, 三上隆
    海洋開発論文集 19 653 - 658 Japan Society of Civil Engineers 2003年 [査読有り][通常論文]
     
    In case of completely submerged floating structure, no change in buoyancy can beexpected with its dynamic motion and the restoring force fully depends on cables. Consequently, it is necessary to seize the relation between structural displacement and restoring force and to evaluate the effect ofnonlinear deformation of cables on the dynamic response. This study aims to evaluate the effect of deformation of mooring cable caused by self-weight, inertia and fluid force on the vibration of the structure. This paper introduces nonlinear equations of motion considering the dynamic behavior of the cables and investigates the effect of dynamic deformation of cables on whole behavior with numerical examples.
  • 佐藤太裕, 蟹江俊仁, 三上隆
    構造工学論文集 A 48A 1 27 - 34 2002年03月 [査読有り][通常論文]
  • 佐藤太裕, 蟹江俊仁, 三上隆
    構造工学論文集 A 47A 1 1 - 8 2001年03月 [査読有り][通常論文]
  • Modeling of Submerged Floating Tunnel as a beam on elastic foundation under bending vibration
    M Sato, S Kanie, T Mikami, T Yaginuma, H Hamaguchi
    STRAIT CROSSINGS 2001 535 - 540 2001年 [査読有り][通常論文]
     
    This paper presents a modeling for simplified analysis of the global dynamic behaviors of Submerged Floating Tunnel (S.F.T.). The simple model that we proposed is a beam on elastic foundation. In static problems, it is known that this modeling of S.F.T as a beam on elastic foundation is applicable only to a limited range of support stiffness, spacing and flexural rigidity of the tunnel. However it should be verified that the modeling is applicable also for dynamic response analysis. In this study we investigate the applicability of this modeling in dynamic problems. As a result, we conclude that dynamic effect has no influence on equivalence and the modeling proposed in this study is useful even for dynamic problems.
  • 佐藤 太裕, 横濱 秀明, 蟹江 俊仁, 三上 隆
    海洋開発論文集 17 277 - 280 Japan Society of Civil Engineers 2001年 [査読有り][通常論文]
     
    This paper is concerned with modeling for simplified analyses of Submerged Floating Tunnel (S. F. T.). The simple model that we proposed is a beam on elastic foundation. It is known that this modeling of S. F. T. as a beam on elastic foundation is applicable only to a limited range of support stiffness, spacing and flexural rigidity of the tunnel from the aspect of structural mechanics. If this modeling gives satisfactory solution for global behaviors of the structure, it is very effective for designers to assume structural dimensions and evaluate the basic characteristics quickly. In this paper we investigate the applicability of this modeling in applying the structural conditions and dimensions of really assumed S. F. T. to the condition of equivalence between S. F. T. and beams on elastic foundation. Furthermore, we consider the effects of boundary condition when this beam model on elastic foundation can be applied.
  • 佐藤太裕, 蟹江俊仁, 三上隆
    構造工学論文集 A 46A 1 41 - 49 2000年03月 [査読有り][通常論文]

書籍

講演・口頭発表等

  • 賢い「竹」が生み出す巧みな材料力学的機能の秘密  [招待講演]
    佐藤太裕
    第51回溶融塩化学討論会 2019年10月 口頭発表(招待・特別)
  • Motohiro Sato
    The 9th East Asia Mechanical and Aerospace Engineering Workshop 2019年05月 口頭発表(基調)
  • Learning from bamboo: Plant-mimetic design toward less-material & high-stiffness structure  [招待講演]
    佐藤太裕
    University of Cambridge, Engineering Department Structures Research Seminars 2017年06月 公開講演,セミナー,チュートリアル,講習,講義等
  • Learning from bamboo: Plant-mimetic design toward less material & high-stiffness structure  [招待講演]
    佐藤太裕
    Joint Seminar on the Application of Nano materials in Civil Engineering 2016年12月 公開講演,セミナー,チュートリアル,講習,講義等
  • 構造力学的手法を用いた新しい次世代型構造システムの研究開発  [招待講演]
    佐藤太裕
    北海道コーディネータ・ネットワーク・フォーラム、合同基調報告(平成25年度北海道科学技術奨励賞受賞記念研究報告会) 2014年02月 公開講演,セミナー,チュートリアル,講習,講義等
  • The past, present and future of the Seikan Tunnel  [招待講演]
    佐藤太裕
    6th International Symposium on Strait Crossings 2013年06月 口頭発表(基調)

その他活動・業績

特許

受賞

  • 2019年12月 文部科学省 科学技術・学術政策研究所 科学技術への顕著な貢献2019(ナイスステップな研究者)
     竹が「軽さ」と「丈夫さ」を併せもつ理由の構造・材料力学的解明 
    受賞者: 佐藤太裕
  • 2018年06月 土木学会 土木学会論文賞
     竹の節・組織構造が織り成す円筒体としての合理的な構造特性の理論的解明 
    受賞者: 佐藤太裕
  • 2016年02月 Editors’ suggestion, Physical Review E
     
    受賞者: 佐藤太裕
  • 2016年01月 IASTEM Excellent Paper Award
     
    受賞者: 佐藤太裕
  • 2014年02月 北海道科学技術奨励賞(北海道知事表彰)
     構造力学的手法を用いた新しい次世代型構造システムの研究開発 
    受賞者: 佐藤太裕
  • 2010年07月 Selected paper, International Conference on Modelling and Simulation 2010 in Prague
     
    受賞者: 佐藤太裕
  • 2008年12月 (財)国際科学技術財団(Japan Prize) 研究助成
     
    受賞者: 佐藤太裕
  • 2002年04月 土木学会北海道支部奨励賞
     
    受賞者: 佐藤太裕
  • 2000年12月 土木学会年次学術講演会優秀講演者表彰
     
    受賞者: 佐藤太裕

共同研究・競争的資金等の研究課題

  • 空間周期性の構造安定論的解釈と合理化社会・構造システム設計思想のパラダイムシフト
    文部科学省:科学研究費助成事業(基盤研究(A))
    研究期間 : 2018年04月 -2023年03月 
    代表者 : 佐藤太裕
  • 竹の優れた機能に関する経験知・言い伝えの理論的解釈と新しい竹林資源利用技術の開発
    文部科学省:科学研究費助成事業(基盤研究(B)(特設分野研究))
    研究期間 : 2018年07月 -2021年03月 
    代表者 : 佐藤太裕
  • ナノ技術および生物科学の積極導入による新しい多重機能型構造システムの研究開発(国際共同研究強化)
    文部科学省:科学研究費助成事業(国際共同研究加速基金(国際共同研究強化))
    研究期間 : 2016年04月 -2019年03月 
    代表者 : 佐藤太裕
  • 自然界における周期性の自発的パターン形成機構解明と社会システム設計への合理的応用
    文部科学省:科学研究費助成事業(挑戦的萌芽研究)
    研究期間 : 2016年04月 -2018年03月 
    代表者 : 佐藤太裕
  • 文部科学省:科学研究費補助金(基盤研究(B))
    研究期間 : 2015年04月 -2018年03月 
    代表者 : 佐藤 太裕
  • 竹の節と組織構造に学ぶ合理的な構造システムの設計技術開発
    寿原記念財団:研究助成金
    研究期間 : 2016年04月 -2017年03月 
    代表者 : 佐藤太裕
  • 文部科学省:科学研究費補助金(挑戦的萌芽研究)
    研究期間 : 2014年04月 -2016年03月 
    代表者 : 佐藤 太裕
  • 文部科学省:科学研究費補助金(若手研究(A))
    研究期間 : 2012年04月 -2015年03月 
    代表者 : 佐藤 太裕
     
    本研究は、海洋構造物、社会基盤構造物等に広く用いられる既存の構造材料、複合構造の概念を大きく覆す、「剛・柔材料を効果的に組み合わせることにより高靭性・応力集中の低減を容易に実現可能な、ナノテクの知見を応用した新しい発想に基づく構造システム」の研究開発を目的とするものである。初年度である平成24年度に得られた研究成果を以下に列挙する。(1)剛・柔の簡易な二次元規則積層構造モデルを構築し、定式化を行った。その結果、柔層の存在しない構造に対して剛・柔の規則積層構造は亀裂進展に対する応力集中低減効果があることが解析的に確認された。(2)他媒体に埋め込んだカーボンナノチューブの機能を解析的に検証した。具体的には他媒体との相互作用による外圧印加時のカーボンナノチューブの力学的性質の変化を、分子動力学モデルおよび連続弾性体モデルを構築し、両モデルに対して座屈変形解析を実施した。その結果外圧印加の状態や多層化などによりいくつかの特異な幾何形状の変化がみられ、それによる導電性変化の可能性が見出された。分子動力学解析においては大変形の解析を正確に行うことができ、連続体モデルでは計算負荷の少ない解析を行えることから、双方の利点を活かした諸特性の検証が可能となった。(3)高靱性パイプとして期待されるパイプインパイプの曲げ挙動について、断面偏平の観点から検証し、塑性領域での高靱性化に提案する砂粒子コア材の有用性を確認した。
  • 極微スケール炭素繊維を用いた高機能構造材料開発を可能にする革新的マルチスケール構造解析技術の開発
    寿原記念財団:研究助成金
    研究期間 : 2013年04月 -2014年03月 
    代表者 : 佐藤太裕
  • 文部科学省:科学研究費補助金(挑戦的萌芽研究)
    研究期間 : 2012年 -2013年 
    代表者 : 佐藤 太裕
     
    現在世界を取り巻く地球環境の悪化、およびそれに伴う甚大な自然災害問題は、人類が取り組むべき喫緊の最重要課題の一つである。本研究は将来的な環境保全技術として、係留索を用いて水中に安定化させる水中係留浮体構造の「動揺しやすい」性質を積極活用することでエネルギーを得るとともに、波浪・災害から陸地を守るという二重の機能を有した革新的次世代洋上施設の技術成立性について多角的に検討することを本研究期間の目的としている。初年度である平成24年度は、国内外の海洋エネルギー、防災施設に関する調査を実施するとともに、構造力学的観点から以下の課題に取り組んだ。得られた知見を以下に示す。(1)水中係留浮体構造解析モデルの検証:浮体部を質点系としてモデル化し、係留索のゆるみ(スラック状態)を考慮可能な解析モデルを構築した。(2)上記解析モデルによる大波浪の作用による非線形動的挙動の時刻歴計算:上記の解析モデルを用い、波浪入射時の構造挙動の時刻歴解析を実施し、大波浪時のスラック状態と係留索の急激な張力回復に伴い生じる準衝撃的な力(スナップ荷重)の発生メカニズムを再現した。(3)浮体を円筒シェルとした場合のモデル構築:構造挙動は係留索配置の状態とともに、浮体と浮体をジョイントする部分の剛性や浮体自身の弾性も大きく影響することから、これらに関するモデル化と、その基本的な構造特性について差分方程式を用いたモデルを構築し、検討を行った。
  • 文部科学省:科学研究費補助金(若手研究(B))
    研究期間 : 2009年04月 -2012年03月 
    代表者 : 佐藤 太裕
     
    本研究は、二重管パイプの間に中詰コアとして砂などの粒状体材料を挿入することにより高靭性を発揮し、かつ中詰コアの物性を変化させることにより曲げ特性を容易に制御可能とする、新しい「フレキシブルパイプインパイプ」の開発を行うことを目的としたものである。研究期間内に理論的、実験的両面から多角的な検討が行われ、本提案形式の優位性が実証された。
  • 文部科学省:科学研究費補助金(基盤研究(B))
    研究期間 : 2008年04月 -2011年03月 
    代表者 : 蟹江 俊仁, 赤川 敏, 三上 隆, 岩花 剛, 佐藤 太裕, 赤川 敏
     
    天然ガス資源に恵まれる北方寒冷地域を対象に,冷却ガスパイプラインの新しい構造形式として,中詰材に砂などの可塑性材料を用いるパイプインパイプの開発を行なった.特に中詰材に水を飽和させ凍結することで,より高い靭性が発揮され,材料の非線形領域まで有効に利用できるため,周辺環境の変化に対しても柔軟に対応できる.さらに,周辺土の凍結・融解を人為的に制御することで,曲げ剛性の回復や漏洩防止も可能となった.
  • チューブ状構造の複雑な変形挙動に関する構造力学的研究~ナノからマクロスケールまでを包含する新しい力学的数理モデルの構築~
    北海道大学大学院工学研究科:若手教員在外研究助成
    研究期間 : 2010年 -2011年 
    代表者 : 佐藤太裕
  • 二重管構造の採用による埋設配管の応力集中回避性能に関する解析的検討
    北海道ガス:大学助成制度
    研究期間 : 2010年 -2011年 
    代表者 : 佐藤太裕
  • ナノ構造体の優れた力学特性を利用した新しい高強度構造材料の創製
    北海道大学:重点配分経費(若手研究者自立支援)
    研究期間 : 2009年 -2010年 
    代表者 : 佐藤太裕
  • 災害安全性の高い埋設配管構造技術とその構造力学的特性に関する研究
    北海道ガス:大学助成制度
    研究期間 : 2009年 -2010年 
    代表者 : 佐藤太裕
  • 文部科学省:科学研究費補助金(若手研究(B))
    研究期間 : 2006年04月 -2009年03月 
    代表者 : 佐藤 太裕
     
    海洋パイプラインは、大水深域での極めて大きな静水圧作用など、厳しい海洋環境下でも安定したエネルギー輸送が要求される構造物である。本研究はこの要求性能を高い次元で満足し、かつ構造設計の自由度が大きい海洋パイプラインとして現在世界的に注目されている「パイプインパイプシステム」について、その構造設計に関わる構造解析モデルの構築と、構造挙動の把握を行ったものである。
  • パイプインパイプ構造における曲げ挙動評価システムの構築
    北海道ガス:大学助成制度
    研究期間 : 2008年 -2009年 
    代表者 : 佐藤太裕
  • 文部科学省:科学研究費補助金(基盤研究(B))
    研究期間 : 2004年04月 -2007年03月 
    代表者 : 三上 隆, 須藤 敦史, 佐藤 京, 蟹江 俊仁, 佐藤 太裕
     
    トンネルの支保構造物の設計は、その多くを過去の経験に基づく設計法によるため、ややもすると地上のコンクリート構造物の設計に比べて過大な設計になりがちである。本研究では、設計段階における建設コスト縮減を意図し、さらに寒冷地特有の諸条件を加味した道路トンネルの支保構造設計法の提案を目的に行ったもので、主な成果は以下となる。1.支保工特性曲線の提案:円筒殻理論(吹き付けコンクリート)及びリング理論(鋼アーチ支保工)に基づき、両者の相互作用を考慮した解析モデルより、支保剛性評価式を提示した。主な結果は以下となる。(1)リング理論による従来法の支保剛性は、本算定式による支保剛性より常に大き目の評価をし、その差は最大で20%程度である。(2)鋼製アーチ支保の有効支保間隔は、鋼製アーチ支保間隔をLと記せば、(0.35〜1)Lである。2.トンネル延長方向の温度(気温)算定式の提案:寒冷地トンネルでは、寒さに起因する変状を防止するために、断熱材が施工されるが、その合理的な施工のためにはトンネル延長方向の温度分布が必要となる。ここでは、トンネル-地山系の熱伝達・熱伝導及びトンネル内風速を考慮した解析的モデルに基づき、温度評価式を求めた。(1)本算定式より得られるトンネル延長方向の温度及び道内トンネルの実測値との比較によれば、両者には良好な一致が認められ、本算定式の有効性・妥当性が確認された。(2)その結果、本算定式によれば、トンネル坑口からの断熱材の施工範囲が合理的に決定できる。
  • 係留浮体式風力発電システムの技術成立性に関する調査研究
    (財)東電記念科学技術研究所:研究助成(電気・エネルギー一般研究)
    研究期間 : 2006年 -2007年 
    代表者 : 佐藤太裕
  • 水中浮遊式トンネルの実現に向けた動的不安定問題の解明
    鹿島学術振興財団:研究者海外派遣援助(長期)
    研究期間 : 2005年 -2006年 
    代表者 : 佐藤太裕
  • 水中浮遊式トンネルにおける動的不安定挙動発生機構の解明
    ノーステック財団:基礎的研究開発育成事業(若手研究補助金)
    研究期間 : 2004年 -2005年 
    代表者 : 佐藤太裕
  • 文部科学省:科学研究費補助金(萌芽研究)
    研究期間 : 2003年 -2004年 
    代表者 : 角田 與史雄, 佐藤 太裕, 佐藤 太裕, 松村 宇, 伊藤 正澄, 佐藤 靖彦
     
    本研究は,バクテリアリーチングにおいて利用されてきた方法を基本とし,微生物を利用して再生骨材を製造し,その品質を明らかにすることで,再生骨材の製造に微生物を利用することの有用性を示そうとするものである.本研究において,多種多様な微生物の中から硫黄酸化細菌と鉄酸化細菌に着目した基礎実験を行った.すなわち,細菌の有無,骨材の有無,コンクリート塊の大きさ,炭酸化の有無がペースト及びモルタルの劣化度に及ぼす影響を実験的に明らかにした.得られた知見を以下に列挙する.・硫黄酸化細菌及び鉄酸化細菌が増加すると培地のPHを低下させ,モルタルをよく剥離させ,カルシウムイオンを溶脱させる.・硫黄酸化細菌と鉄酸化細菌の活動は,コンクリート塊のサイズが5-20mmの範囲の方が,5mm以下の範囲よりも活発化した.これは塊のサイズが小さいと培地に溶け出すアルカリ量が多くなるためである.それゆえ,微生物を摂取する前に炭酸化させた方が良い.・硫黄酸化細菌と鉄酸化細菌が骨材に及ぼす影響は工学的に無視できる.・酸性硫黄温泉水を培地として利用した場合,効率よくカルシウムイオンを遊離させることができる.しかし,コンクリート塊の表面に生成される腐食性生物が硫酸イオンの浸透を阻止する為,反応速度が著しく低下する.

教育活動情報

主要な担当授業

  • Structural Mechanics for Sustainable Environment(寒冷地構造力学E)
    開講年度 : 2018年
    課程区分 : 修士課程
    開講学部 : 工学院
    キーワード : Structural mechanics, Finite Element method, Elastic problem, Truss, Beam
  • 寒冷地構造力学特論
    開講年度 : 2018年
    課程区分 : 修士課程
    開講学部 : 工学院
  • Structural Mechanics for Sustainable Environment(寒冷地構造力学E)
    開講年度 : 2018年
    課程区分 : 博士後期課程
    開講学部 : 工学院
  • 寒冷地構造力学特論
    開講年度 : 2018年
    課程区分 : 博士後期課程
    開講学部 : 工学院
  • 構造力学Ⅰ
    開講年度 : 2018年
    課程区分 : 学士課程
    開講学部 : 工学部
    キーワード : はり、カラム、断面力、影響線、断面一次モーメント、断面二次モーメント、主断面二次モーメント
  • 構造力学Ⅱ
    開講年度 : 2018年
    課程区分 : 学士課程
    開講学部 : 工学部
    キーワード : 変形、応力、座屈、不静定、トラス
  • 構造力学演習Ⅰ
    開講年度 : 2018年
    課程区分 : 学士課程
    開講学部 : 工学部
    キーワード : 力のつりあい 支点と反力 はり 断面力
  • 構造力学演習Ⅱ
    開講年度 : 2018年
    課程区分 : 学士課程
    開講学部 : 工学部
    キーワード : トラス、変形、応力
  • 構造解析学
    開講年度 : 2018年
    課程区分 : 学士課程
    開講学部 : 工学部
    キーワード : ひずみエネルギー、カステリアノの定理、最小仕事の定理、仮想仕事の原理、有限要素法 

大学運営

委員歴

  • 2019年10月 - 現在   北海道財務局   国有財産北海道地方審議会委員
  • 2018年01月 - 現在   東日本高速道路(株)北海道支社   狩勝第二トンネル土石流対策検討会
  • 2016年01月 - 現在   北海道札幌建設管理部   総合評価審査委員会委員
  • 2015年11月 - 現在   鉄道・運輸機構   北海道新幹線冬季対策委員会委員・幹事
  • 2013年04月 - 現在   東日本高速道路(株)北海道支社   トンネル技術検討会委員
  • 2012年06月 - 現在   道路管理技術センター   道路管理技術委員会委員
  • 2011年07月 - 現在   Editorial Board, "Coupled Systems Mechanics(CSM)", An International Journal of Interactions of Structures, Fluids, Soil, Wind, Foundation and Multiple Systems
  • 2009年10月 - 現在   土木学会応用力学委員会   委員
  • 2002年04月 - 現在   北海道土木技術会   鋼道路橋研究委員会委員
  • 2002年04月 - 現在   北海道土木技術会   トンネル研究委員会委員
  • 2013年04月 - 2018年03月   北海道大学大学院工学研究院   広報・情報管理室員
  • 2015年10月 - 2016年03月   札幌市   道路トンネル補修計画検討会議委員
  • 2011年04月 - 2013年03月   土木学会構造工学委員会   構造工学論文集編集小委員会委員(構造力学・構造工学一般部門担当)
  • 2008年04月 - 2009年12月   日本鉄鋼連盟   鋼構造ネットワーク北海道地区代表幹事
  • 2008年05月 - 2009年04月   土木学会   土木学会誌編集委員(特集担当)
  • 2005年05月 - 2009年04月   土木学会   北海道支部幹事
  • 2004年11月 - 2005年10月   平成15年(2003年)十勝沖地震検討会委員・幹事


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