Papers - OBATA Makoto
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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)
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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)
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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)
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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)
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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)
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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)
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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.
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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)
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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)
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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.
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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)
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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)
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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
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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.
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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
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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)
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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)
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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)
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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)
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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.
