Details of a Researcher - OBATA Makoto

Papers - OBATA Makoto

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IMPROVEMENT OF STRESS-STRAIN RELATION UNDER MULTIAXIAL LOADING OF RUBBER FOR BEARINGS Reviewed

Makoto Obata, Takemasa Ebisawa, Yoshiaki Goto

Journal of Japan Society of Civil Engineers Ser A1 (Structural Engineering & Earthquake Engineering (SE/EE)) 76 ( 2 ) 320 - 330 2020.08

Authorship：Lead author Language：Japanese Publishing type：Research paper (scientific journal) Publisher：Japan Society of Civil Engineers

DOI： DOI: 10.2208/jscejseee.76.2_320

Observation of suspended sea salt particles and its numerical simulation as estimation of corrosive environment Reviewed

Makoto Obata, Taro Murakami

Kozo Kogaku Ronbunshu. A (Journal of Structural Engineering. A) 60 ( A ) 596 - 604 2014.04

Authorship：Lead author Language：Japanese Publishing type：Research paper (scientific journal) Publisher：Japan Society of Civil Engineers

It is important to estimate corrosion environment of steel bridges for an appropriate corrosion prevention and maintenance program. Estimation of environment has heavily depended on insitu observation and many data have been collected. However, versatile numerical approaches to this problem has not fully pursued yet. To this end, observation of airborne sea salt particles was performed with a standard low volume sampler (JIS Z 8814) beginning from April, 2013 to August, 2013 in the city of Nagoya and compared analytical estimation. A meso scale meteorological analysis employed here is WRF-Chem Ver. 3.4. Although WRF uses land use and terrain data based on USGS by default, the data is sometimes incorrect in Japan and yields inaccurate results especially for wind. Introduction of more accurate land use and geographic data supplied by the Geospatial Information Authority of Japan improves accuracy of basic meteorological data and therefore concentration of airborne sea salt particles. Other factors affecting accuracy of airborne sea salt concentration will also be discussed.

DOI： 10.11532/structcivil.60A.596

Global-local approach to numerical simulation of adhesion of seasalt particles on bridge girders Reviewed

Makoto Obata,Li Guotai, Yasunari Watanabe, Yoshiaki Goto

Journal of Structural Engineering A 58 668 - 678 2012.03

Authorship：Lead author Language：Japanese Publishing type：Research paper (scientific journal) Publisher：Japan Society of Civil Engineers

It is important to estimate corrosion environment of steel bridges for a proper corrosion prevention and maintenance program. Adhered sea-salt particulate matter (SSPM) is an influential factor especially in coastal areas. To this end, it is better to know the adhesion behavior of SSPM to bridge girders. The objective of this manuscript is to pursue numerical method to simulate the adhesion behavior of salt particles oriented from sea surface. Specifically, two scale approach is proposed. Mesoscale Meteorological Analysis and Lagrangian type two phase flow analysis are used in global and local analyses respectively. The comparisons between the numerical and observed results showed that the numerical analysis can reproduce essential behaviors of airborne SSPM.

DOI： 10.11532/structcivil.58A.668

Numerical analysis of fracture phenomena observed in a locally buckled circular steel column Reviewed

Hideyuki Fujiwara, Makoto Obata, Yoshiaki Goto

Journal of Structural Engineering A 58 310 - 318 2012.03

Language：Japanese Publishing type：Research paper (scientific journal)

Construction of a practical finite element model from point cloud data for an existing steel truss bridge Reviewed

Nao Hidaka, Naofumi Hashimoto, Kazuya Magoshi, Tetsuya Nonaka, Makoto Obata, Ei Watanabe

Proceedings of 23° International Conference on Construction Applications of Virtual Reality 1155 - 1166 2023.11

Language：English Publishing type：Research paper (international conference proceedings)

Construction analysis model of steel bridge by using point cloud data and accuracy verification Reviewed

Hidaka Nao, Hashimoto Yoshifumi, Nakamura Masaki, Magoshi Kazuya, Nonaka Tetsuya, Obata Makoto

Journal of structural engineering 69A 637 - 647 2023.04

Language：Japanese Publishing type：Research paper (scientific journal)

YIELDING STEEL DAMPERS TO REPLACE CONCRETE SHEAR KEYS FOR SEISMIC RETROFIT OF BRIDGES WITH UNEQUAL HEIGHT PIERS Reviewed International coauthorship International journal

Nailiang Xiang, Y Goto, Makoto Obata, M. Shahria Alam, Jianzhong Li

Proc. 17th World Conference on Earthquake Engineering 2020.09

Language：English Publishing type：Research paper (international conference proceedings)

Irregular multi-span continuous bridges with unequal height piers are commonly adopted in mountainous areas when crossing steep-sided valleys. As common practice, economical unbonded laminated rubber bearings and concrete shear keys are usually installed in such bridges as superstructure-to-substructure connections. In strong earthquakes, the sliding of rubber bearings and the shear key failure are mostly expected, which may weaken the seismic resistance of the irregular bridges. The current study is mainly divided into three parts: the first one investigates the effect of concrete shear keys on the transverse seismic performance of the irregular bridges by incorporating the potential sliding of laminated rubber bearings; the second part proposes the concept of using yielding steel dampers to replace shear keys for mitigating the irregular seismic responses of the unequal height bridges with the practical design method being developed; the third part demonstrates the retrofit effectiveness by conducting nonlinear time-history analyses. The results indicate that the existence of concrete shear keys increases the bridge irregularity by inducing a significant in-plane superstructure rotation response around the vertical axis, posing nonuniform displacement demands at the substructures. The shear keys also contribute to the unbalanced ductility demands on the unequal height substructures, rendering the taller piers more vulnerable to the seismic damages. This differs from the case with fixed bearings, where the shorter piers are more subjected to damages. Using yielding steel dampers that are appropriately designed as per the proposed method, the seismic rotations of the bridge superstructure can be considerably mitigated with a relatively uniform superstructure movement maintained. The steel dampers are also effective in distributing the inertia forces among the unequal height piers. The effectiveness of yielding steel dampers replacing concrete shear keys in unequal height irregular bridges is successfully verified by the results from the numerical simulation.

Shake-table tests of an innovative structural fusing system for small to medium-span highway bridges

Nailiang Xiang, Y Goto, Makoto Obata, M. Shahria Alam, Jianzhong Li

Proc. 17th World Conference on Earthquake Engineering 2020.09

Language：English

Irregular multi-span continuous bridges with unequal height piers are commonly adopted in mountainous areas when crossing steep-sided valleys. As common practice, economical unbonded laminated rubber bearings and concrete shear keys are usually installed in such bridges as superstructure-to-substructure connections. In strong earthquakes, the sliding of rubber bearings and the shear key failure are mostly expected, which may weaken the seismic resistance of the irregular bridges. The current study is mainly divided into three parts: the first one investigates the effect of concrete shear keys on the transverse seismic performance of the irregular bridges by incorporating the potential sliding of laminated rubber bearings; the second part proposes the concept of using yielding steel dampers to replace shear keys for mitigating the irregular seismic responses of the unequal height bridges with the practical design method being developed; the third part demonstrates the retrofit effectiveness by conducting nonlinear time-history analyses. The results indicate that the existence of concrete shear keys increases the bridge irregularity by inducing a significant in-plane superstructure rotation response around the vertical axis, posing nonuniform displacement demands at the substructures. The shear keys also contribute to the unbalanced ductility demands on the unequal height substructures, rendering the taller piers more vulnerable to the seismic damages. This differs from the case with fixed bearings, where the shorter piers are more subjected to damages. Using yielding steel dampers that are appropriately designed as per the proposed method, the seismic rotations of the bridge superstructure can be considerably mitigated with a relatively uniform superstructure movement maintained. The steel dampers are also effective in distributing the inertia forces among the unequal height piers. The effectiveness of yielding steel dampers replacing concrete shear keys in unequal height irregular bridges is successfully verified by the results from the numerical simulation.

Passive seismic unseating prevention strategies implemented in highway bridges: A state-of-the-art review Reviewed International coauthorship International journal

Nailiang Xiang , Yoshiaki Goto, Makoto Obata, M. Shahria Alam

Engineering Strucures 194 77 - 93 2019.09

Language：English Publishing type：Research paper (scientific journal) Publisher：Elsevier

DOI： 10.1016/j.engstruct.2019.05.051

Analysis of rubber bearing behavior with material deterioration Reviewed International journal

Makoto Obata, Yoshiaki Goto

Proceedings of ICASS2018 2018.12

Language：English Publishing type：Research paper (international conference proceedings)

Analysis of rubber bearings with mullins effect uner cyclic loading Reviewed

Makoto Obata, Chisa Koiwa, Yoshiaki Goto

１ ( １ ) 335 - 338 2017.07

Authorship：Lead author Language：Japanese Publishing type：Research paper (conference, symposium, etc.)

Ultimate Behavior of Steel and CFT Piers in Two-Span Continuous Elevated-Girder Bridge Models Tested by Shake-Table Excitations Reviewed International journal

Yoshiaki Goto, Takemasa Ebisawa, Makoto Obata, Jianzhong Li, Yan Xu

JOURNAL OF BRIDGE ENGINEERING 22 ( 5 ) 2017.01

Language：English Publishing type：Research paper (scientific journal) Publisher：ASCE-AMER SOC CIVIL ENGINEERS

Bidirectional shake-table tests were performed on two types of relatively large two-span continuous elevated-girder bridge models. One was supported on thin-walled hollow steel (HT) piers, and the other was supported on concrete-filled tubular (CFT) piers. The CFT piers were made by filling the hollow columns of the HT piers with normal concrete. One objective of the shake-table tests was to acquire basic data to establish an advanced seismic design method of the HT and CFT piers under bidirectional horizontal seismic accelerations, considering the interaction between the piers, rubber bearings, and a superstructure. The other objective was to experimentally confirm the effectiveness of upgrading the elevated-girder bridges with the HT piers by using CFT piers. It was shown by the present tests that the ultimate state of the respective HT piers in the bridge model was predicted reasonably well by the interaction equation expressed in terms of the multiaxial force and moment components acting at the top of the columns. As soon as all the piers reached their ultimate states, the entire physical bridge model with the HT piers started to collapse in the transverse (TR) direction. Because of the load redistribution between the HT piers in the bridge model during the shake-table test, the energy dissipation capacity of the piers increased considerably compared with that evaluated by the conventional shake-table test on single cantilever column models with a mass fixed to their top. The physical bridge model with the CFT piers exhibited an excellently upgraded seismic performance (i.e., small local buckling deformations of the piers and negligibly small residual sway displacements of the bridge system) despite the increased input acceleration wave with an amplitude 1.5 times larger than that used for the physical bridge model with the HT piers. This upgraded performance of the CFT piers was due to their enhanced energy dissipation capacity and unique local buckling restraining and/or restoring behavior.

DOI： 10.1061/(ASCE)BE.1943-5592.0001021

鋼製橋脚で支持された連続高架橋における積層ゴム支承の水平2方向地震動下の挙動特性 Reviewed

奥村徹，海老澤健正，後藤芳顯，小畑誠，Jianzhong Li, Yan Xu

第１８回性能に基づく橋梁等の耐震設計に関するシンポジウム論文集 1 49 - 56 2015.07

Language：Japanese Publishing type：Research paper (other academic)

円形断面鋼製橋脚を持つ連続高架橋模型の２方向加振実験のFE解析と終局挙動特性 Reviewed

海老澤健正，後藤芳顯，小畑誠，Jianzhong Li，Yang Xu

第１８回性能に基づく橋梁等の耐震設計に関するシンポジウム論文集 1 ( 1 ) 57 - 64 2015.07

Language：Japanese Publishing type：Research paper (other academic)

Effects of land use data on numerical simulation of corrosive environment caused by airborne sea salt particles Reviewed

Makoto Obata, Masato Fukushima, Seiya Suzuki

Proc. the 7th ISSS 1 ( 1 ) 228 - 229 2013.11

Authorship：Lead author Language：English Publishing type：Research paper (international conference proceedings)

Corrosion of steel bridges in a coastal area is mainly caused by sea salt particles coming from ocean. Appropriate estimation of such airborne sea salt particles is critically important for a proper anticorrosion management program. At present, the most reasonable simulation of sea salt concentration can be performed as a part of meso scale meteorological analysis. However, accuracy of such simulation is not verified well so far. The objective of this work is to verify and to improve the accuracy of numerical simulation of airborne sea salt particles by introducing enhanced land use data. Other factors affecting accuracy of airborne sea salt concentration will also be discussed.

Numerical simulation of adhesion of sea-salt particles Reviewed

Makoto Obata, Li Guotai, Yasunari Watanabe, Yoshiaki Goto

Structure and Infrastructure Engineering 52 398 - 408 2013.01

Authorship：Lead author Language：English Publishing type：Research paper (scientific journal)

It is important to estimate corrosion environment of steel bridges for a proper corrosion prevention and maintenance
program. The governing factors of corrosion are temperature, humidity and various dusts on the surfaces. Among them, the
adhered sea-salt particulate matter (SSPM) is most important and therefore airborne SSPM near a bridge site must be
considered in its design. To prevent degradation of protective paint, removal of adhered SSPM by wash out has been tried in
some bridges. To this end, it is better to know the adhesion behaviour of SSPM to bridge girders. The objective of this
manuscript is to pursue numerical method to simulate the adhesion behaviour of salt particles oriented from sea surface.
Specifically, two scale approach is proposed. Mesoscale meteorological analysis and Lagrangian type two phase flow
analysis are used in global and local analyses respectively. The comparisons between the numerical and observed results
showed that the numerical analysis can reproduce essential behaviours of airborne SSPM.

DOI： 10.1080/15732479.2012.757328

Other Link： http://www.tandfonline.com/action/showAxaArticles?journalCode=nsie20

Numerical Estimation of Corrosion Environment by Airborne Sea Salt Particles Reviewed

Liu Chen Chen, Makoto Obata

Advanced Materials Research 599 220 - 223 2012.11

Language：English Publishing type：Research paper (scientific journal)

Anticorrosion of steel bridges has been an increasingly important problem in Japan. For a proper anticorrosion
and maintenance program, it is important to estimate corrosion environment of steel bridges. In Japan, airborne
sea salt generated from ocean is a predominant factor. Authors have been working on establishing a consistent
framework to estimate corrosion environment numerically. It consists of a local and a global approach. While
adhesion of airborne sea salt particles to bridge structures are simulated locally by a CFD analysis, the large
scale analysis yields a boundary conditions of the local analysis and is given by a part of a mesoscale
meteorological analysis. The objective of this work is to numerically investigate reliability of such large scale
analysis in estimation of corrosion environment caused by airborne sea salt particles.

DOI： 10.4028/www.scientific.net/AMR.599.220

Numerical Prediction of Ductile Crack Initiation in a Steel Column under Cyclic Loading Reviewed

Makoto Obata, Hideyuki Fujiwara, Yoshiaki Goto

Proc. of the 10th international conference on advances in steel concrete composite and 1 ( 1 ) 207 - 214 2012.07

Language：English Publishing type：Research paper (international conference proceedings)

DOI： 10.3850

Numerical simulation of adhesion of sea salt particles for anticorrosion of steel bridges Reviewed

Makoto Obata, Shunya Yokoi, Li Guotai, Yoshiaki Goto

Proceeings of ASEM 1 ( 1 ) 5262 - 5269 2011.09

Authorship：Lead author Language：English Publishing type：Research paper (international conference proceedings)

Investigation of corrosion environment of a steel bridge for effective washing of girders Reviewed

Kazutoshi Nagata, Kota Ito, Jin Yamada, Makoto Obata and Shigenobu Miyamoto

Journal of Structural Engineering 57 2011.03

Language：Japanese Publishing type：Research paper (scientific journal)

Prediction of Adhesion Behavior of Sea-Salt Particles on Bridge Girders Reviewed

Makoto Obata, Yasunari Watanabe, Li Guotai, Yoshiaki Goto

Proceeding of EASEC12 2011.01

Authorship：Lead author Language：English Publishing type：Research paper (international conference proceedings)

It is important to estimate corrosion environment of steel bridges for a proper corrosion prevention and maintenance program. The governing factors of corrosion are temperature, humidity and various dusts on the surfaces. Among them, the adhered sea-salt particulate matter (SSPM) is most important and therefore airborne SSPM near a bridge site must be considered in its design. To prevent degradation of protective paint, forced wash out of adhered SSPM has been tried in some bridges. In order to make a proper plan of wash out, it is better to know adhesion behaviors of SSPM to bridge girders, which in turn depend mainly on the amount of airborne sea salt particles and wind on a bridge site. The objective of this manuscript is to pursue numerical method to simulate the adhesion behavior of salt particles oriented from ocean. To this end, amount of airborne SSPM at a given location will be estimated by a meteorological analysis which can reasonably considers a generation of SSPM on ocean surface. Detailed adhesion behaviors of salt particles are estimated using CFD analysis with the help of the amount of SSPM and wind data given by a meteorological analysis. The comparisons between the numerical and observed results showed that the numerical analysis can reproduce essential behaviors of airborne SSPM.

Position Determination in Three Dimensional Structural Testing System Reviewed

XianFeng Wang, Feng Xing, Makoto Obata, Yoshiaki Goto

ADVANCES IN STRUCTURES, PTS 1-5 163-167 4478 - + 2011

Language：English Publishing type：Research paper (international conference proceedings) Publisher：TRANS TECH PUBLICATIONS LTD

A three dimensional structural testing system for static and pseudo dynamic test is developed, in which a coordinate system has been used in the measurement. The center of the ball joint hinge in an almost neutral position for the displacements of three actuators was the origin. However n process since the initial error cannot be controlled. This makes it difficult to exactly compare the results for different coordinate systems though the error is small. In this paper, to eliminate this difference, we set up a new coordinate system with the origin being the point of absolute zero of the actuator displacements. Since the origin usually cannot be measured directly, the new coordinate system is determined by appending three unknowns and a set of equations at the origin. The transformation between the new coordinate system and the previous one is obtained using a shift and Eulerian angles.

DOI： 10.4028/www.scientific.net/AMR.163-167.4478

日本海側の鋼橋を洗浄して防錆　その費用と効果

「宮本重信」，「北島浩」，「小島高志」，「篠原正」，「小畑誠」，「永田和寿」，「奥村茂」，「古木敬三」

ゆき 21 ( 4 ) 32 - 36 2010.10

Language：Japanese Publishing type：Research paper (other academic) Publisher：雪センタ-

Error effect analysis in shape measurement of bridge pier model by laser transducer Reviewed

XianFeng Wang, Feng Xing, Makoto Obata, Yoshiaki Goto

Proc. of 2nd international symposium on service life design for infrastructure 2 1027 - 1034 2010.10

Language：English Publishing type：Research paper (international conference proceedings)

Numerical Analysis of airborne Sea-Salt Particulate Matter on a Bridge Site(jointly worked) Reviewed

Li Guotai, Shigenobu Miyamoto, Yoshiaki.Goto

Proc. PSSC2010 1196 - 1202 2010.10

Authorship：Lead author Language：English Publishing type：Research paper (international conference proceedings)

A novel size measurement method for a column type specimen Reviewed

Makoto Obata, Weng Fung, Yoshiaki Goto

Journal of Structural Engineering 56 68 - 76 2010.03

Authorship：Lead author Language：Japanese Publishing type：Research paper (scientific journal)

Numerical analysis of sea-salt particulate matter adhesion on bridge surfaces Reviewed

M. Obata, T. Hasegawa, K. Nagata, Y. Goto

Proc. ICASS09 369 - 376 2009.04

Authorship：Lead author Language：English Publishing type：Research paper (international conference proceedings)

Ultimate State of Thin-Walled Circular Steel Columns under Bidirectional Seismic Accelerations Reviewed

Y. Goto, M. Muraki, M. Obata

J. Structural Engineering, ASCE 135 2009.04

Language：English Publishing type：Research paper (scientific journal)

Pull-out strength of interacting bond-type anchors Reviewed

M. Obata, Y. Goto

Steel and Composite Structures 441 - 447 2008.04

Authorship：Lead author Language：English Publishing type：Research paper (international conference proceedings)

Stability of thin-walled stiffened square steel columns under bi-directional seismic excitations Reviewed

Y.Goto,R. Koyama,M.Obata

Proc. CIMS2008 563 - 570 2008.04

Language：English Publishing type：Research paper (international conference proceedings)

Effects of stiffeners on stability and ductility of stiffened thin-walled steel columns with rectangular cross section under bi-directional loading Reviewed

M.Obata,H.Suzuki,Y.Goto

Proc. CIMS2008 555 - 562 2008.04

Authorship：Lead author Language：English Publishing type：Research paper (international conference proceedings)

固気２相流解析による飛来塩分の付着シミュレーション Reviewed

小畑誠,長谷川高士,永田和寿,後藤芳顯

構造工学論文集 54A 590 - 598 2008.04

Authorship：Lead author Language：Japanese Publishing type：Research paper (scientific journal)

２方向繰り返し荷重を受ける矩形断面鋼製橋脚柱の履歴特性 Reviewed

後藤芳顯,江坤生,小畑誠

土木学会論文集 63 122 - 141 2007.04

Language：Japanese Publishing type：Research paper (scientific journal)

Ultimate States of Thin-walled Steel Columns under Bi-directional Seismic Accelerations Reviewed

Y.Goto,N.Taki,M.Obata

Proc. ICASS07 CDROM 2007.04

Language：English Publishing type：Research paper (international conference proceedings)

Numerical simulation of corrosion environment inside steel box-girders Reviewed

M.Obata,T.Hasegawa,K. Nagata,Y.goto

Proc. ICASS07 CDROM 2007.04

Authorship：Lead author Language：English Publishing type：Research paper (international conference proceedings)

Development of multidirectional structural testing system applicable to pseudodynamic test, Reviewed

M. Obata, Y. Goto

J. Structural Engineering, ASCE 133 638 - 645 2007.04

Authorship：Lead author Language：English Publishing type：Research paper (scientific journal)

熱流体解析による箱桁内の腐食環境シミュレーション Reviewed

小畑誠,安田大樹,永田和寿,後藤芳顯

構造工学論文集 53A 834 - 843 2007.04

Authorship：Lead author Language：Japanese Publishing type：Research paper (scientific journal)

Development of multidirectional structural testing system applicable to pseudodynamic test Reviewed

Makoto Obata, Yoshiaki Goto

Journal of Structural Engineering 133 ( 5 ) 638 - 645 2007

Language：English Publishing type：Research paper (international conference proceedings)

An accurate multidirectional structural testing system is developed. This testing system is used to carry out a multidirectional pseudodynamic test with the help of a unique three-dimensional hinge and a spatial truss-type transducer. With this testing system, multidirectional seismic behaviors of thin-walled circular steel columns are examined in comparison with their in-plane behavior. Further, the accuracy of the testing system is confirmed by the numerical results of nonlinear FEM shell analyses. © ASCE.

DOI： 10.1061/(ASCE)0733-9445(2007)133:5(638)

２方向擬似動的実験において制御誤差が精度に与える影響 Reviewed

小畑誠，羽根史浩,後藤芳顯

構造工学論文集 52A 511 - 519 2006.04

Authorship：Lead author Language：Japanese Publishing type：Research paper (scientific journal)

Stability and ductility of thin-walled circular steel columns under cyclic bidirectional loading Reviewed

Y.Goto,K.S. Jiang,M.Obata

J. Structural Engineering, ASCE 132 1621 - 1631 2006.04

Language：English Publishing type：Research paper (scientific journal)

On the accuracy of 3D loading and measuring systems for quasi-static column experiment

M. Obata, Y. Goto

Proc. of AESE05 757 - 764 2005.04

Authorship：Lead author Language：English Publishing type：Research paper (international conference proceedings)

Effect of displacement control on the effect of multi-directional pseudo-dynamic experiment Reviewed

M. Obata, Y. Goto

Proc. of AESE05 275 - 282 2005.04

Authorship：Lead author Language：English Publishing type：Research paper (international conference proceedings)

Experimental and analitical study on stability and ductility of thin-walled columns under bidirectional cyclic load Reviewed

Y.Goto,K.S. Jiang,M.Obata

Advances in steel sructures 479 - 486 2005.04

Language：English Publishing type：Research paper (international conference proceedings)

Effect of geometric non-linearity and displacement control on the everall accuracy of multi-directional pseudo-dynamic test Reviewed

M. Obata, Y. Goto

Advances in steel sructures 1217 - 1222 2005.04

Authorship：Lead author Language：English Publishing type：Research paper (international conference proceedings)

２方向繰り返し荷重を受ける薄肉円形断面鋼製橋脚柱の履歴特性 Reviewed

後藤芳顯,江坤生,小畑誠

土木学会論文集 I-70 ( 780 ) 181 - 198 2005.04

Language：Japanese Publishing type：Research paper (scientific journal)

Development of three-dimensional pseudo-dynamic testing system and its application to assesing the seismic behavior of thin-walled circular steel columns Reviewed

Y. Goto, M. Obata

Proc. Of 5th Japanese-German Joint Symposium on Steel and Composite bridges 2005.04

Language：English Publishing type：Research paper (international conference proceedings)

DEVELOPMENT OF 3D PSEUDO-DYNAMIC EXPERIMENT SYSTEM FOR BRIDGE PIERS AND COLUMNS Reviewed

OBATA Makoto, GOTO Yoshiaki

Doboku Gakkai Ronbunshu 2004 ( 752 ) 253 - 266 2004.04

Authorship：Lead author Language：Japanese Publishing type：Research paper (scientific journal) Publisher：Japan Society of Civil Engineers

It has been pointed out that the interaction of 3D components of earthquake waves plays a critical role on the ultimate seismic behavior of structures. In fact, numerical analyses have shown some results to support the importance of considering multi-directional nature of seismic loads. However, this fact has rarely been examined by experiments primarily because of the difficulty in applying 3D loads, not to say the difficulty in carrying out 3D pseudo-dynamic tests. Herein, we developed a 3D structural experiment system that is capable of conducting pseudo-dynamic tests and then, confirmed its validity by some cyclic loading tests and pseudo dynamic tests on thin-walled circular steel columns.

DOI： 10.2208/jscej.2004.752_253

Development of a simple general 3D displacement measurement system using traditional type of transducers

M. Obata, Y. Goto

Proc. Of 2nd international conference on steel & composite structures CDROM 2004.04

Authorship：Lead author Language：English Publishing type：Research paper (international conference proceedings)

Stability and ductility of thin-walled circular steel columns under cyclic biaxial bending Reviewed

Y. Goto, K.S.Jiang, M. Obata

Proc. Of 2nd international conference on steel & composite structures CDROM 2004.04

Language：English Publishing type：Research paper (international conference proceedings)

ON A VERSATILE VISUALIZATION METHOD OF LARGE DEFORMED 3D BEAM ELEMENTS BY USING CG Reviewed

GOTO Yoshiaki, OKUMURA Toru, OBATA Makoto

Doboku Gakkai Ronbunshu I-67 ( 759 ) 309 - 324 2004.04

Language：Japanese Publishing type：Research paper (scientific journal) Publisher：Japan Society of Civil Engineers

By employing CG techniques, we herein present a versatile and accurate method to visualize the numerical results for the 3D seismic analysis of framed structures such that their over-all behavior can be grasped directly in terms of CG pictures. In this method for visualization, we include a rational procedure to magnify the small deformations of beam elements under the beam assumptions. The CG pictures of large deformed 3D beam elements are produced only from the nodal kinematic data such as displacements and rotations calculated by the usual commercial FEM soft wares. From numerical examples, it is confirmed that various large deformed shapes are accurately reproduced by the proposed method even with small number of nodal kinematic data.

DOI： 10.2208/jscej.2004.759_309

On the analysis of fracture phenomena observed in steel structures during the Kobe earthquake Reviewed

H. FUJIWARA, Y. GOTO, M. OBATA

Proc. ICASS'02 2 2002.12

Language：English Publishing type：Research paper (international conference proceedings)

Multi-directional pseudo dynamic experiment of steel bridge pier Reviewed

M. OBATA, Y. GOTO

Proc. ICASS'02 1 171 - 178 2002.12

Authorship：Lead author Language：English Publishing type：Research paper (international conference proceedings)

Hysteretic modeling of thin-walled circular steel columns under biaxial bending Reviewed

JIANG, L.Z. Y. GOTO, M. OBATA

J. Struct. Engineering, ASCE 128 ( 3 ) 319 - 327 2002.01

Language：English Publishing type：Research paper (scientific journal)

Multi-directional pseudo dynamic experiment of steel bridge piers Reviewed

M Obata, Y Goto

ADVANCES IN STEEL STRUCTURES, VOLS I & II, PROCEEDINGS 1 171 - 178 2002

Language：English Publishing type：Research paper (international conference proceedings) Publisher：ELSEVIER SCIENCE BV

The control of the local damage to prevent overall failure of steel or composite structure has drawn interests in the seismic design of steel highway bridge piers. In such a case, it is critical to know the ultimate behavior of the structures during severe earthquake. Also important is to consider the effect of multi-directional, or the three-dimensional ground motion. Despite this inherent nature of earthquake waves, the vast majority of the experiments and analytical efforts are devoted to the unidirectional behaviors because the current design codes ignore the interaction of the structural response in the different directions. Although some researchers have been studying the multi-directional seismic response of structures to remedy the oversimplification in the design code, there still needs in-depth understanding of these behaviors to establish the more enhanced design code. Regarding these problems, recently, the authors have developed the testing system that is capable of the multi-directional pseudo-dynamic test as well as fully three-dimensional loading with the help of the unique three-dimensional hinge. In this work, we carry out pseudo dynamic tests of circular steel bridge piers using about 1/8 scaled model specimens and discuss the effects of multi-directional seismic loading on the damages of them.

Multiple spring model for 3D-hysteretic behavior of thin-walled circular steel piers Reviewed

L.JIANG, Y.GOTO, M.OBATA

J. Structural Mechanics and Earthquake Engineering, JSCE 689 1 - 17 2001.04

Language：English Publishing type：Research paper (scientific journal)

Experimental Study on Strain Localization and Ductile Fracture of Steel-Pipe due to Cyclic Horizontal Loading Reviewed

M.OBATA, N.MATSUO, Y.GOTO

Proc. of the First international conference on steel & composite structures, Pusan, Korea, 14-16 June,2001 2 1533 - 1540 2001.04

Authorship：Lead author Language：English Publishing type：Research paper (international conference proceedings)

Alternative solution methods for crack problems in plane anisotropic elasticity with examples Reviewed

A. AZHDARI, M. OBATA, S. NEMAT-NASSER

Int. J. Solids Struct. 37 6433 - 6478 2000.04

Authorship：Lead author Language：English Publishing type：Research paper (scientific journal)

Experimental studies on the dynamic behaviors of pc cable fallout prevention system Reviewed

H. MAENO, T. KINOU, M. OBATA, Y. GOTO

Proc. Of 2nd Colloquium on base isolation and vibration control 179 - 186 2000.04

Language：Japanese Publishing type：Research paper (other academic)

Pull-out strength of interacting multiple bond type anchors Reviewed

M. OBATA, T. OGURI, Y. GOTO

J. Struct. Engineering, JSCE 46A 1517 - 1524 2000.04

Authorship：Lead author Language：Japanese Publishing type：Research paper (scientific journal)

Alternative solution methods for crack problems in plane anisotropic elasticity, with examples Reviewed

Abbas Azhdari, Makoto Obata, Sia Nemat-Nasser

International Journal of Solids and Structures 37 ( 44 ) 6433 - 6478 2000

Language：English Publishing type：Research paper (scientific journal) Publisher：Elsevier Science Ltd

Two-dimensional crack problems of homogeneous, anisotropic, linear elasticity are solved using the Riemann-Hilbert method. To this end, the Riemann-Hilbert problem of line-discontinuity is formulated for anisotropic plane problems and the necessary parameters and functions are identified. For illustration, the method is applied to obtain the complete stress field and the stress intensity factors for a crack in an infinite anisotropic plate which is loaded on a part of one of its faces. Then, the well-established method of continuously distributed edge-dislocations is considered and illustrated via some example problems
e.g., an infinite anisotropic plate under uniform farfield loads containing: 1. a closed frictional crack and a pair of arbitrarily-located single edge-dislocations, and 2. an infinite row of equally-spaced parallel open cracks. The illustrative examples reveal that the first method offers an effective solution technique for problems where unbalanced tractions are applied on crack surfaces, whereas for problems with self-equilibrating loads applied on the crack faces, the second method is generally well suited. In addition, the method of resultant forces along the crack is discussed and its formulation in terms of the dislocation density functions and also the crack-opening displacements (which is new) is presented. The solutions to some of the example problems are provided in some detail, and for others, just the key formulae (e.g., stress functions and stress intensity factors) are calculated and analyzed. In brief, this paper presents the generalization of the Riemann-Hilbert method from isotropic to anisotropic in-plane elasticity problems, and also provides a collection of certain basic two-dimensional anisotropic crack problems
some of the results here are also new.

DOI： 10.1016/S0020-7683(99)00137-7

Numerical approach to the ductile fracture of steel members Reviewed

M.OBATA, A.MIZUTANI, Y.GOTO

Proc. of the Second International Conference on Advances in Steel Structures, Hong Kong, China, December 15-17, 1999 2 1021 - 1027 1999.04

Authorship：Lead author Language：English Publishing type：Research paper (international conference proceedings)

The verification of plastic constitutive relation and its application to FEM analysis of plastic fracture of steel members Reviewed

M. OBATA, A. MIZUTANI, Y. GOTO

J. Struct. Engineering, JSCE 626 ( 626 ) 185 - 196 1999.04

Authorship：Lead author Language：Japanese Publishing type：Research paper (scientific journal) Publisher：Japan Society of Civil Engineers

As observed in the Hyogoken Nanbu Earthquake, brittle fracture is often triggered by preceding ductile fracture of steel members. The estimation of ultimate behaviors and deformation capacity of steel structures, therefore, critically depends on the ductile characteristics of its members. However, no reliable numerical method to investigate the ductile fracture of members is available because of the lack of the understandings of the quantitative aspects of such material characteristics. The objective of this work is to show a basic approach to a practical numerical analysis of ductile fracture. In the present work, we determined Gurson's model parameters using the proposed method to show that the FEM analysis with Gurson's model could be a suitable tool for the estimation of ductility limit of steel members.

DOI： 10.2208/jscej.1999.626_185

Mechanical behaviors of a shock absorbing bridge restrainer plate Reviewed

M. OBATA, T. KURIHARA, Y. GOTO

J. Structural Mechanics and Earthquake Engineering, JSCE 612 239 - 250 1999.04

Authorship：Lead author Language：Japanese Publishing type：Research paper (scientific journal)

FEM analysis for hysteretic behavior of thin-walled columns Reviewed

Y. GOTO, Q. WANG, M. OBATA

J. of Struct Engrg., ASCE 124 1290 - 1301 1998.04

Language：English Publishing type：Research paper (scientific journal)

A rigorous method for the analysis of localization of axisymmetric buckling patterns in thick cylindrical shells Reviewed

Y.GOTO, C.ZHANG, Q.WANG, M.OBATA

Thin-walled structures 31 73 - 88 1998.04

Language：English Publishing type：Research paper (scientific journal)

The failure mechanism and the pull-out strength of a bond-type anchor near a free edge Reviewed

M. OBATA, M. INOUE, Y. GOTO

Mech. Mater. 28 113 - 122 1998.04

Authorship：Lead author Language：English Publishing type：Research paper (scientific journal)

Three surface cyclic plasticity model for fem analysis of steel bridge piers subjected to seismic loading Reviewed

Y. GOTO, Q. WANG, N. TAKAHASHI, M. OBATA

J. Structural Mechanics and Earthquake Engineering, JSCE 591 189 - 206 1998.04

Language：Japanese Publishing type：Research paper (scientific journal)

Cyclic loading test on steel pier base-to-footing connections with small edge distance Reviewed

Y. GOTO, T. KAMIJO, H. FUJIWARA, M. OBATA

J. Struct. Engineering, JSCE 44A 1271 - 1280 1998.04

Language：Japanese Publishing type：Research paper (scientific journal)

An alternative experimental method to determine elasto-plastic material parameters in large deformation Reviewed

M. OBATA, A. MIZUTANI, Y. GOTO

J. Struct. Engineering, JSCE 44A 29 - 36 1998.04

Authorship：Lead author Language：Japanese Publishing type：Research paper (scientific journal)

FEM analysis for hysteretic behavior of thin-walled columns Reviewed

Yoshiaki Goto, Qingyun Wang, Makoto Obata

Journal of Structural Engineering 124 ( 11 ) 1290 - 1301 1998

Language：English Publishing type：Research paper (scientific journal) Publisher：American Society of Civil Engineers (ASCE)

An accurate finite-element-method-based analysis to predict the ultimate hysteretic behavior of thin-walled steel columns subjected to seismic loading is presented in this paper. For this purpose, we develop the three-surface cyclic metal plasticity model. The three-surface model includes less material parameters and internal variables for the ease of its implementation in the finite-element method analysis. This model is characterized by a discontinuous surface inserted between the yield surface and the bounding surface. The discontinuous surface is used to express the yield plateau and the change of hardening coefficient. Most material parameters in the three-surface model can be determined by the tensile coupon test. However, three parameters independent of material types are calibrated by the existing cyclic loading test results of thin-walled steel columns. This is to improve the accuracy of this analysis specifically in the simulation of the localized buckling behavior, which accompanies extremely large plastic strains.

DOI： 10.1061/(ASCE)0733-9445(1998)124:11(1290)

Effect of constitutive models on the hysteretic behavior of thin-walled steel bridge piers subjected to seismic loading Reviewed

Y.GOTO, Q.WANG, M. OBATA

Proc. of the 7th International Conference on Computing in Civil and Building Engineering, Seoul, Korea, August 19-21, 1997 1 381 - 386 1997.04

Language：English Publishing type：Research paper (international conference proceedings)

A new experimental method to determine elasto-plastic material parameters Reviewed

M.OBATA, A. MIZUTANI, Y. GOTO

Proc. of the 7th International Conference on Computing in Civil and Building Engineering, Seoul, Korea, August 19-21, 1997 2 805 - 810 1997.04

Language：English Publishing type：Research paper (international conference proceedings)

Prevention of the fall out of bridge girders by slit-type restrainers Reviewed

M.OBATA, T. KURIHARA, Y. GOTO

Proc. of the Second International Conference on Behavior of Steel Structures in Seismic Areas, Kyoto, Japan, Aug. 3-8, 1997 947 - 954 1997.04

Authorship：Lead author Language：English Publishing type：Research paper (international conference proceedings)

Localization of axisymmetric plastic buckling patterns in thick cylindrical shells under monotonic/cyclic loading Reviewed

C.H. ZHANG, Y. GOTO, K. ONO, M. OBATA

Proc. of the 5th International Colloquium on Stability and Ductility of Steel Structures, Nagoya, Japan, July 29-30, 1997 1 441 - 448 1997.04

Language：English Publishing type：Research paper (international conference proceedings)

Analysis of strain localization of solids under cyclic loading using a corner theory of plasticity Reviewed

M.OBATA, T. SHOJI, Y. GOTO

Proc. of the 5th International Colloquium on Stability and Ductility of Steel Structures, Nagoya, Japan, July 29-30, 1997 2 817 - 824 1997.04

Authorship：Lead author Language：English Publishing type：Research paper (international conference proceedings)

A new experimental method to determine elasto-plastic material parameters Reviewed

M Obata, A Mizutani, Y Goto

PROCEEDINGS OF THE SEVENTH INTERNATIONAL CONFERENCE ON COMPUTING IN CIVIL AND BUILDING ENGINEERING, VOLS 1-4 2 805 - 810 1997

Language：English Publishing type：Research paper (international conference proceedings) Publisher：TECHNO-PRESS

The objective of this work is to propose a new experimental method to amend the current shortcomings regarding the determination of material parameters with the aids of FEM-based inverse analysis. The outline of the proposed method is as follows. In uni-axial tension test, we use a non-standard specimen that allows non-uniform deformation, Instead of strain, we measure displacement between appropriate two points together with external load. So obtained load-displacement curve indirectly reflects all the consequences of multi-axial plastic deformation. Then, we apply FEM-based inverse analysis to obtain the material parameters to reproduce the closest load-displacement curve to the observed one. This method provides a consistent way to determine the material parameters by a simple uniaxial test.

Effect of constitutive models on the hysteretic behavior of thin-walled steel bridge piers subjected to seismic loading Reviewed

Y Goto, QY Wang, M Obata

PROCEEDINGS OF THE SEVENTH INTERNATIONAL CONFERENCE ON COMPUTING IN CIVIL AND BUILDING ENGINEERING, VOLS 1-4 1 381 - 386 1997

Language：English Publishing type：Research paper (international conference proceedings) Publisher：TECHNO-PRESS

We herein present a three surface cyclic steel plasticity model and implement it in the FEM analysis in order to predict the ultimate hysteretic behavior of thin-walled steel columns subjected to seismic loading, The three-surface model is devised to include less material parameters and internal variables for the ease of its implementation in FEM. This model is characterized by two parameters independent of material types which is calibrated by the cyclic loading tests for thin-walled steel columns, These two parameters are used to improve the accuracy of our analysis specifically in the simulation of the local buckling behavior under extremely large plastic strains.

Effect of free edge on the pull-out strength of bond type anchor bolt Reviewed

M. OBATA, M. INOUE, Y. GOTO

J. Struct. Engineering, JSCE 42A 1131 - 1138 1996.04

Authorship：Lead author Language：Japanese Publishing type：Research paper (scientific journal)

Experimental stduy of energy absorbing restrainer tie plates Reviewed

M. OBATA, K. OHMI, Y. GOTO

J. of Construction Steel 4 385 - 390 1996.04

Authorship：Lead author Language：Japanese Publishing type：Research paper (scientific journal)

Analysis of the ultimate behavior of a slit-type bridge restrainer Reviewed

M. OBATA, T. KURIHARA, Y. GOTO

Proc. of International Conference on Advances in Steel Structures, Hong Kong, December 11-14, 1996 1 559 - 564 1996.04

Authorship：Lead author Language：English Publishing type：Research paper (international conference proceedings)

A rigorous method for the analysis of localization behavior of compression plate Reviewed

Y. GOTO, Q. WANG, M. OBATA

J. Structural Mechanics and Earthquake Engineering, JSCE 543 55 - 70 1996.04

Language：Japanese Publishing type：Research paper (scientific journal)

Localization of axisymmetric buckling patterns of cylindrical shells under cyclic loading Reviewed

Y. GOTO, Y. TOBA, K. ONO, M. OBATA

Proc. Of JSCE 543 41 - 53 1996.04

Language：Japanese Publishing type：Research paper (scientific journal)

Bending fracture of steel fiber reinforced concrete beam Reviewed

K. Hioki, T. UEHARA, M. OBATA, Y. NOBUTA

J. of JCI 18 ( 2 ) 1415 - 1420 1996.04

Language：Japanese Publishing type：Research paper (scientific journal)

Ultimate behavior of tie plates at high-speed tension Reviewed

M. OBATA, Y. GOTO, S. MATSUURA, H. FUJIWARA

J. of Struct Engrg. 122 416 - 422 1996.04

Authorship：Lead author Language：English Publishing type：Research paper (scientific journal)

Modeling of ultimate behavior of stgeel pier-to-footing connections Reviewed

Y. GOTO, T. KAMIJO, H. FUJIWARA, M. OBATA

J. Struct. Engineering, JSCE 42A 987 - 998 1996.04

Language：Japanese Publishing type：Research paper (scientific journal)

Ultimate behavior of the plates at high-speed tension Reviewed

M Obata, Y Goto, S Matsuura, H Fujiwara

JOURNAL OF STRUCTURAL ENGINEERING-ASCE 122 ( 4 ) 416 - 422 1996.04

Language：English Publishing type：Research paper (scientific journal) Publisher：ASCE-AMER SOC CIVIL ENG

Tie plates are integral components of pin connectors, lifting modules, and bridge restrainers. As a bridge restrainer, they are supposed to bear the dynamic seismic loads. In a previous work (Obata et al. 1991), the writers elucidated the ultimate behaviors of tie plates under quasi-static loading by the experiments and the numerical analysis. The objective of this work is to investigate the ultimate behaviors of tie plates at high-speed tension both experimentally and numerically. The high-speed tension experiments showed that the maximum strength increases with the increase of the tensile velocity. On the other hand, the deformation at the load maximum point is relatively insensitive to the tensile velocity. Therefore, the quasi-static test results always give the conservative values for the design. The numerical analysis is based on the J(2) power law strain-rate-dependent plasticity theory. Despite the simplification of the complex phenomena, the numerical results give useful insights into the experimental results and in the meantime serve as reliable tools for a rational design of these tie plates.

Localization of plastic buckling patterns of plates and cylindrical shells under cyclic loading Reviewed

Y Goto, QY Wang, K Ono, M Obata

ADVANCES IN STEEL STRUCTURES, VOLS 1 AND 2 869 - 874 1996

Language：English Publishing type：Research paper (international conference proceedings) Publisher：PERGAMON PRESS LTD

This paper theoretically investigates the localization of plastic buckling patterns in compression plates and cylindrical shells because this phenomenon has a large influence on the strength deterioration under cyclic loading. The localization behavior is caused by a plastic bifurcation on the decreasing equilibrium path subsequent to the maximum load point. Thus, we first show a rigorous numerical method based on the finite-element method technique to analyze the plastic bifurcation. Then, using this method, we examine the localization behavior of rectangular compression plate and that of the axisymmetric cylindrical shells under cyclic loading, Specifically, we investigate how the structural parameters and constitutive models affect the strength deterioration.

Analysis of the ultimate behavior of a slit-type bridge restrainer Reviewed

M Obata, T Kurihara, Y Goto

ADVANCES IN STEEL STRUCTURES, VOLS 1 AND 2 1 559 - 564 1996

Language：English Publishing type：Research paper (international conference proceedings) Publisher：PERGAMON PRESS LTD

The prevention of the falling out of girders is one of the important issues of the seismic design for highway bridges. A bridge restrainer is a structural element designed for this particular purpose that constraints the displacement by tying a girder to adjacent girders or piers during earthquake. The Hyogoken-Nanbu earthquake was the first major earthquake that the modern bridge restrainers have experienced since their installation. Unfortunately, some of them were destroyed to lead the falling out of girders. The objective of this work is to propose a new type bridge restrainer for steel bridge girders after the lessons of the disaster. The behaviors of the new type restrainers are investigated by Finite Element Analysis to give the fundamental basis of the rational design of them.

Experiment on cyclic behavior of steel column to base connections with double anchor beams Reviewed

Y. GOTO, K. HIBI, T. KAMIJO, H. FUJIWARA, M. OBATA

J. Struct. Engineering, JSCE 41A 1137 - 1143 1995.04

Language：Japanese Publishing type：Research paper (scientific journal)

Ultimate behaviors of tie plates under quasi-static and high speed loading Reviewed

M. OBATA, H. FUJIWARA, S. MATSUURA

Proc. the 4th PSSC 1 487 - 494 1995.04

Authorship：Lead author Language：English Publishing type：Research paper (international conference proceedings)

Study on the fracture toughness of the fiber reinforced high strength concrete Reviewed

K. YUKI, T. UEHARA, M. OBATA, Y. NOBUTA

J. of JCI 17 ( 1 ) 445 - 450 1995.04

Language：Japanese Publishing type：Research paper (scientific journal)

Analysis of Greenhill problem by a co-rotational method Reviewed

Y. GOTO, Xiao-Song LI, T. KASUGAI, M. OBATA

J. Struct. Engineering, JSCE 41A 411 - 420 1995.04

Language：English Publishing type：Research paper (scientific journal)

Localization of plastic buckling patterns and its effect on the ductility of structures under cyclic loading Reviewed

Y. GOTO, N. KAWANISHI, Y. TOBA,M. OBATA

J. Structural Mechanics and Earthquake Engineering, JSCE 483 ( 483 ) 87 - 96 1994.04

Language：Japanese Publishing type：Research paper (scientific journal) Publisher：Japan Society of Civil Engineers

In case of structures under compressive loading, it is often observed experimentally that the ductility of structures is considerably lost due to the localization of plastic buckling patterns. This implies that the phenomena of this kind has an unfavorable effect on the earthquake resistance. Herein, we present a versatile theoretical method to analyze the localization of buckling patterns including that under cyclic loading. As numerical examples, two types of structures, i. e. a multiply supported column and a truss tower under compressive force, are analyzed in order to show the validity of the proposed method. In these examples the cyclic localization phenomena is also discussed in terms of the influence on deformation capacity.

DOI： 10.2208/jscej.1994.483_87

On the behavior of the residual stresses near a notch after cyclic loadings Reviewed

M. OBATA, T. ITOH, Y. GOTO, S. MATSUURA

J. Struct. Engineering, JSCE 40A 135 - 142 1994.04

Authorship：Lead author Language：Japanese Publishing type：Research paper (scientific journal)

An advanced avaraging technique for multi-phase materials Reviewed

M.OBATA, Y.GOTO, S. MATSUURA

Proc. Of JSCE 459 ( 459 ) 63 - 71 1993.04

Authorship：Lead author Language：Japanese Publishing type：Research paper (scientific journal) Publisher：Japan Society of Civil Engineers

It is an important and interesting problem to obtain averaged mechanical behaviors of multi phase composite materials. We propose an advanced averaging technique for three or more phase materials. The new technique, which we call Generalized Periodic (GP) method, borrows basic idea from two different existing schemes, a periodic structure and a self consistent method. The GP accounts for the interaction among the same phase inclusions by the model of periodic distributions, while the homogeneity of surrounding inhomogeneous matrix is assumed. Simple numerical examples show the character of GP method. GP's character is appreciable when the number of phase is relatively small and each volume fraction is large. On the other hand, when the number of phases increases, the GP's estimation of averaged behavior rapidly gets close to that of the self consistent method.

DOI： 10.2208/jscej.1993.459_63

Mechanical properties of bond type anchor bolt in situ experiment Reviewed

M.OBATA, Y.GOTO, H. MAENO, S. MATSUURA

J. of Construction Steel 1 801 - 806 1993.04

Language：Japanese Publishing type：Research paper (scientific journal)

Failure mechanism of new bond-type anchor bolt subject to tension Reviewed

Y. GOTO, M. OBATA, H. MAENO, Y. KOBAYASHI

J. of Struct. Engrg. 119 ( 4 ) 1168 - 1187 1993.04

Language：English Publishing type：Research paper (scientific journal) Publisher：ASCE-AMER SOC CIVIL ENGINEERS

The objective of this study is to investigate the failure mechanism of a new bond-type anchor bolt under tensile force so that a design method may be established. A conventional headed anchor bolt embedded in a concrete footing normally fails by pulling out a stress cone; however, the bond-type anchor bolt exhibits a complex failure mode. here referred to as a mixed bond-cone failure. To date, the theoretical aspects of this failure mechanism have not been established. With the needs of design application in mind, an analytical model to predict the ultimate strength of the bond-type anchor bolt is presented. Experimental data confirm that this model can be used with acceptable accuracy to assess the ultimate strength and the failure mode of the bond-type anchorage system.

Experiment on the ultimate strength of steel pier base fastened by bond-type anchor bolts Reviewed

H. MAENO, Y. GOTO, M. OBATA, Y. KOBAYASHI, S. MATSUURA

J. Struct. Engineering, JSCE 39A 1321 - 1334 1993.04

Language：Japanese Publishing type：Research paper (scientific journal)

Bonding characteristics of a very large deformed bar with headed studs Reviewed

H. MAENO, Y. GOTO, M. OBATA, S. MATSUURA

Proc. Of JSCE 441 87 - 96 1992.04

Language：Japanese Publishing type：Research paper (scientific journal)

A new bond-type anchorage system for steel piers Reviewed

Y. GOTO, H. MAENO, M. OBATA, Y. KOBAYASHI

Proc. PSSC 971 - 978 1992.04

Language：English Publishing type：Research paper (international conference proceedings)

FEM estimation of the accuracy of self-consistent averaging method Reviewed

M.OBATA, J. OKUDA, Y.GOTO, S. MATSUURA

Proc. Of JSCE 450 ( 450 ) 103 - 112 1992.04

Authorship：Lead author Language：Japanese Publishing type：Research paper (scientific journal) Publisher：Japan Society of Civil Engineers

Self consistent averaging scheme is one of the prominent methods to estimate the finite elasto-plastic deformations of polycrystalline solids. Although it is a unique and potentially powerful method, its accuracy as averaging scheme has remained to be envisaged. To this end, we applied a direct numerical approach based on finite element computation to two dimensional elasto-plastic deformation of polycrystals under uni-axial tention. The results by these two methods depend heavily on the kinematic characteristics of a micro-constituent. While a double slip model yields different overall behaviors, triple or more slip models lead to surprisingly good coincidence. When real 3D behaviors are concerned, the self-consistent method seems to involve very much complicated numerical procedure. Direct numerical approach could be a better alternative.

DOI： 10.2208/jscej.1992.450_103

Elastic buckling phenomenon applicable to deployable rings Reviewed

Y. GOTO, Y. WATANABE, T. KASUGAI, M. OBATA

Int. J. Solids Struct. 29 893 - 909 1992.04

Language：English Publishing type：Research paper (scientific journal)

An elastic-plastic bifurcation analysis of multiple discrete systems and its application to trusses Reviewed

Y. GOTO, K. OSHIKA, N. KAWANISHI, M. OBATA

Proc. Of JSCE 446 ( 446 ) 117 - 126 1992.04

Language：Japanese Publishing type：Research paper (scientific journal)

The ultimate strength of bridge restrainer plates at high speed tension Reviewed

M. OBATA, Y. GOTO, S. MATSUURA, H. FUJIWARA

Proc. Of JSCE 441 ( 441 ) 97 - 105 1992.04

Authorship：Lead author Language：Japanese Publishing type：Research paper (scientific journal)

Ultimate strength of bond-type anchorage under tensile force. Reviewed

MAENO Hirofumi, GOTO Yoshiaki, OBATA Makoto, MATSUURA Sei

Doboku Gakkai Ronbunshu 1992 ( 441 ) 185 - 192 1992

Language：Japanese Publisher：Japan Society of Civil Engineers

While the anchorage with a headed anchor bolt in concrete usually fails almost by pulling out a concrete cone, the failure mechanism of the bond-type anchorage becomes complex because both bond and concrete cone failure are involved simultaneously. there have been few theoretical approaches to this bond-concrete-cone failure mechanism of bond type anchorage. In the present study, a new model of failure mechanism is proposed under the assumption that ultimate strength is not the sum of the strength of a stress cone and that of bond on a bolt surface. The assumption is justified because failure by concrete cone is extremely brittle. The validity of this model is confirmed by experimental results. With this mode, it is possible to identify the critical factors to the failure mechanism as well as to estimate the ultimate strength of bond-type anchorage with reasonable accuracy.

DOI： 10.2208/jscej.1992.185

ELASTIC BUCKLING PHENOMENON APPLICABLE TO DEPLOYABLE RINGS Reviewed

Y GOTO, Y WATANABE, T KASUGAI, M OBATA

INTERNATIONAL JOURNAL OF SOLIDS AND STRUCTURES 29 ( 7 ) 893 - 909 1992

Language：English Publishing type：Research paper (scientific journal) Publisher：PERGAMON-ELSEVIER SCIENCE LTD

There are various kinds of deployable members developed in order to improve the packing efficiency of space structures. Some of them ingeniously utilize elastic buckling phenomena, such as flexural buckling and torsional buckling. However, their application is primarily restricted to straight members. Herein, we present an interesting buckling phenomenon of a ring which considerably reduces its original volume and could be applied to a deployable ring. First, we show an accurate method which can be used to analyze this buckling phenomenon accompanying finite rotations in space. Then, with this method, we theoretically examine the effect of structural parameters on buckling behavior.

Accuracy of the numerical methods for the analysis of plane frames considering finite displacements and finite strains Reviewed

Y. GOTO, T. YOSHIMITSU, M. OBATA, F. NISHINO

Proc. Of JSCE 428 ( 428 ) 67 - 76 1991.04

Language：Japanese Publishing type：Research paper (scientific journal) Publisher：Japan Society of Civil Engineers

It is accurate to use the theory of finite displacements and finite strains for the analysis of geometrical nonlinearity of structures. However, the governing equation for this theory becomes highly nonlinear and its direct use makes the solution procedure very much complicated. So approximate numerical methods, respectively referred to as the corotational method and the method with the Rigid Bodies-Spring Model, are often used to simplify the solution procedure for the framed structures. Herein, we precisely examine their theoretical accuracy as well as the convergence to the exact solutions. Based on this result, we further discuss an efficient method to be adopted in the analysis of frames considering finite displacements and finite strains.

DOI： 10.2208/jscej.1991.428_67

Ultimate behaviors of tie plates used as bridge restrainer Reviewed

M. OBATA, S. SUZUKI, Y. GOTO, S. MATSUURA

J. Struct. Engineering 117 2884 - 2899 1991.04

Authorship：Lead author Language：English Publishing type：Research paper (scientific journal)

Some basic issues in dynamic crack growth in elastic-plastic solids Reviewed

S.NEMAT-NASSER, M. OBATA

Int. J. Fracture 42 287 - 300 1990.04

Language：English Publishing type：Research paper (scientific journal)

Analysis of strain localization near a blunting crack tipin crystalline solids Reviewed

M.OBATA, J. OKUDA, Y.GOTO, S. MATSUURA

J. Struct. Engineering, JSCE 36A 343 - 351 1990.04

Authorship：Lead author Language：Japanese Publishing type：Research paper (scientific journal)

On a new anchorage system for a steel pier Reviewed

Y. GOTO, M. OBATA, S. MATSUURA, H. MAENO, A. Morimoto

Proc. Int. conference on structural engineering and computations 803 - 810 1990.04

Language：English Publishing type：Research paper (international conference proceedings)

On the micro and macroscopic approaches to the finite elasto-plastic deformations Reviewed

M. OBATA, Y. GOTO, S. MATSUURA

Proc. Int. conference on structural engineering and computations 96 - 104 1990.04

Authorship：Lead author Language：English Publishing type：Research paper (international conference proceedings)

Elliptic integral solutions of plane elastica with axial and shear deformations Reviewed

Y. GOTO, T. YOSHIMITSU, M. OBATA

Int. J. Solids Struct. 26 375 - 390 1990.04

Language：English Publishing type：Research paper (scientific journal)

Micromechanical consideration on the theory of elasto-plasticity at finite deformations Reviewed

M. OBATA, Y. GOTO, S. MATSUURA

Int. J. Engrg. Sci. 28 241 - 241 1990.04

Authorship：Lead author Language：English Publishing type：Research paper (scientific journal)

Elasto-plastic analysis of a blunting crack tip in crystalline solids Reviewed

M.OBATA, J. OKUDA, Y.GOTO, S. MATSUURA

Proc. Of JSCE 422 ( 422 ) 235 - 243 1990.04

Authorship：Lead author Language：Japanese Publishing type：Research paper (scientific journal) Publisher：Japan Society of Civil Engineers

Large elasto-plastic deformation around a blunting crack tip is analyzed with help of the theory of physically based crystal plasticity. A boundary value problem is formulated by use of boundary layer analysis under the condition of small scale yielding. The results are compared with those predicted by the usual macroscopic (J2) plasticity. It is shown that deformation tends to localize when crystal plasticity is used. The effects of microstructures on the ductile crack growth are also discussed.

DOI： 10.2208/jscej.1990.422_235

Analysis of the static ultimate strength of a bridge restrainer plate Reviewed

M.OBATA, S. SUZUKI, Y.GOTO, S. MATSUURA

Proc. Of JSCE 422 ( 422 ) 295 - 302 1990.04

Authorship：Lead author Language：Japanese Publishing type：Research paper (scientific journal)

ELLIPTIC INTEGRAL SOLUTIONS OF PLANE ELASTICA WITH AXIAL AND SHEAR DEFORMATIONS Reviewed

Y GOTO, T YOSHIMITSU, M OBATA

INTERNATIONAL JOURNAL OF SOLIDS AND STRUCTURES 26 ( 4 ) 375 - 390 1990

Language：English Publishing type：Research paper (scientific journal) Publisher：PERGAMON-ELSEVIER SCIENCE LTD

MICROMECHANICAL CONSIDERATION ON THE THEORY OF ELASTOPLASTICITY AT FINITE DEFORMATIONS Reviewed

M OBATA, Y GOTO, S MATSUURA

INTERNATIONAL JOURNAL OF ENGINEERING SCIENCE 28 ( 3 ) 241 - 252 1990

Language：English Publishing type：Research paper (scientific journal) Publisher：PERGAMON-ELSEVIER SCIENCE LTD

Residual stress due to overload and their effects on fatigue strength on notched elements Reviewed

M.OBATA, Y.GOTO, M. MITSURU, S. MATSUURA

J. Struct. Engineering, JSCE 35A 301 - 307 1989.04

Authorship：Lead author Language：Japanese Publishing type：Research paper (scientific journal)

Micromechanics of dilatancy in brittle materials Reviewed

M. OBATA, S. NEMAT-NASSER

Proc. of the MRS Int. Meeting on Advanced Materials 449 - 453 1989.04

Authorship：Lead author Language：English Publishing type：Research paper (international conference proceedings)

Branched cracks in anisotropic elastic solids Reviewed

M. OBATA, S. NEMAT-NASSER, Y. GOTO

J. Appl. Mech. 56 858 - 864 1989.04

Authorship：Lead author Language：English Publishing type：Research paper (scientific journal)

Branched cracks in anisotropic elastic solids Reviewed

Makoto Obata, Siavouche Nemat-Nasser, Yoshiaki Goto

Journal of Applied Mechanics, Transactions ASME 56 ( 4 ) 858 - 864 1989

Language：English Publishing type：Research paper (scientific journal)

Branched crack problems are analyzed in two-dimensional, anisotropically elastic homogeneous solids. The method of analysis is based on the complex variable approach of Savin and Lekhnitskii. The Hilbert problem in an anisotropic body is defined, and a pair of singular integral equations are derived for dislocation density functions associated with a branched crack. For both symmetric and nonsymmetric geometries, and under symmetric and antisymmetric loads, the stress intensity factors and the energy release rate are computed numerically by extrapolation for infinitesimally small lengths of branched cracks. The results are compared with those of the isotropic case given in the literature and the effects of anisotropy are discussed. © 1989 by ASME.

DOI： 10.1115/1.3176182

A microcrack model of dilatancy in brittle materials Reviewed

S. NEMAT-NASSER, M. OBATA

J. Appl. Mech. 55 24 - 35 1988.04

Language：English Publishing type：Research paper (scientific journal)

Analysis of internal cracks around reinforcement in brittle materials Reviewed

M.OBATA, Y.GOTO, S. MATSUURA

J. Struct. Engineering, JSCE 34A 421 - 421 1988.04

Authorship：Lead author Language：Japanese Publishing type：Research paper (scientific journal)

Micromechanics of plastic flow Reviewed

S. NEMAT-NASSER, M. OBATA

Proc. 2nd Int. Conf. on Constitutive Laws for Engineering Materials 295 - 306 1987.04

Language：English Publishing type：Research paper (international conference proceedings)

Rate-dependent, finite elasto-plastic deformation of polyctystals Reviewed

S. NEMAT-NASSER, M. OBATA

Proc. Roy. Soc. Lond. A407 343 - 375 1986.04

Language：English Publishing type：Research paper (scientific journal)

On stress field near a stationary crack tip Reviewed

S. NEMAT-NASSER, M. OBATA

Mechanics of Materials 3 235 - 243 1984.04

Language：English Publishing type：Research paper (scientific journal)

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