Gakuji NAGAI
Research Associate, Institute
of Industrial Science, The University
of Tokyo
Japanese | English
Last update on April 9, 2002
My Dissertation
"Finite Element Procedure for Failure Simulation of Mesoscopic
Structure in Concrete Materials"
supervised by Assoc. Prof. Takahiro
YAMADA (Yokohama National
University) and Prof. A.
Wada (Structural Engineering Research Center, Tokyo
Institute of Technology)
Motivation
-
To try to explain the detailed mechanical behavior of concrete
materials subjected to compression
Objective
-
To develop a 3-D finite element procedure for the macroscopic
compressive failure simulation only with many local tensile failures in
mesoscopic scale
Approach
-
Assumption of two-phase composites consisting of coarse aggregates,
mortar and their interfaces in mesoscopic scale due to the scale effect
-
Configuration of mesoscopic 3-D geometry would be important
for stress distribution
-
FE modeling by using a real 3-D digital image of concrete
material (Digital-Image-Based Finite Element Method, DIB-FEM)
-
A novel FE for interface modeling with DIB-FEM (we call it
interfacial
FE) so that interfaces are independent of the uniform DIB-FE mesh
-
Tensile failures as only nonlinear ingredients
Current Status
The first stage of the nonlinearity before commpressive peak
can be simulated.
Movie (QuickTime
2.2MB) of tensile damage progression on the interfaces between coarse aggregates
and mortar with macroscopic uni-axial compression applied. (Currently,
tensile failures on the interfaces are only modeled in the sense of continuum
iso-tropic damage model)
Future Works
All is to capture the compressive peak in macoroscopic scale
only with tensile failures in mesoscopic scale and furthermore to simulate
post-peak behaviors
-
Geometrical and numerical modeling of 3-D cracks launching
into homogenious mortar
-
Parallel computation to solve larger mesoscopic domains such
as 1003mm cube (1003
FEs)
-
Development of robust nonlinear equation solver
Publications & Presentations
Some papers are available in pdf format and all presentations
are automatically generated by MS-PowerPoint
Journal papers
in English
-
G. Nagai, T. Yamada and A. Wada: "Accurate Modeling
and Fast Solver for the Stress Analysis of Concrete Materials Based on
Digital Image Processing Technique",
International Journal for Computational
Civil and Structural Engineering, Vol. 1, 2001 in printing (paper)
-
J. Fish, W. Chen and G. Nagai: "Nonlocal Dispersive
Model For Wave Propagation In Heterogeneous Media. Part 1: One-Dimensional
Case", International Journal for Numerical Methods in Engineering,
2001 (submitting)
-
J. Fish, W. Chen and G. Nagai: "Nonlocal Dispersive
Model For Wave Propagation In Heterogeneous Media. Part 2: Multi-Dimensional
Case", International Journal for Numerical Methods in Engineering,
2001 (submitting)
in Japanese
-
G. Nagai, T. Yamada and A. Wada: "On a Finite Element
Procedure Based on the Real 3-Dimensional Image for Concrete Materials",
Journal
of Structural and Construction Engineering (Transactions of AIJ), No.
509, pp. 77-82, 1998.7
-
G. Nagai, T. Yamada and A. Wada: "On a Nonlinear Finite
Element Analysis Procedure Based on Hierarchical Digital Image for Concrete
Materials with Consideration of Coarse-Aggregates-and-Mortar Interface",Journal
of Structural and Construction Engineering (Transactions of AIJ), No.
528, pp. 91-98, 2000.2
Refereed conference papers
in English
-
G. Nagai, T. Yamada and A. Wada: "Stress Analysis
of Concrete Material Based on Geometrically Accurate Finite Element Modeling",
Fracture
Mechanics of Concrete Structures, Proceedings FRAMCOS-3 (eds H. Mihashi
and K. Rokugo), AEDIFICATIO Publishers, pp. 1077-1086, 1998.10 (paper,
presentation)
in Japanese
-
G. Nagai, T. Yamada and A. Wada: "Image-Based Finite
Element Analysis of Compressive Failure of Concrete Materials", Proceedings
of the Japan Concrete Institute, Vol. 21, No. 3, pp. 157-162, 1999.7
Conference papers (not all)
in English
-
G. Nagai, T. Yamada and A. Wada: "Finite Element Analysis
of Concrete Material Based on the 3-dimensional real image data", in CD-ROM,
4th
World Congress on Computational Mechanics (WCCM4), Buenos Aires, 1998.7
-
G. Nagai, T. Yamada and A. Wada: "Three-dimensional
Nonlinear Finite Element Analysis of the Macroscopic Compressive Failure
of Concrete Materials Based on Real Digital Image", 8th International
Conference on Computing in Civil & Building Engineering (ICCCBE2000),
pp. 449-456, California, 2000.8 (paper,
presentation)
-
G. Nagai, T. Yamada and A. Wada: "3-D Mesoscopic Failure
Simulation of Concrete Materials by Using Image-Based Finite Element Method",
The
20th International Congress of Theoretical and Applied Mechanics (ICTAM2000),
Chicago, 2000.8 (poster)
-
G. Nagai, T. Yamada and A. Wada: "A 3-D Finite Element
Modeling of Mesoscopic Structure in Concrete Materials for Compressive
Failure Simulation", Fracture Mechanics of Concrete Structures, Proceedings
FRAMCOS-4 (eds R. de Borst), AEDIFICATIO Publishers, 2001.5 (in
preparing)
in Japanese
-
G. Nagai, T. Yamada and A. Wada: "Finite Element Analysis
of Concrete Materials Based on Digital Image Data", Proceedings of the
Conference on Computational Engineering and Science, Vol. 2, No. 3,
pp. 1103-1106, 1997.5
-
G. Nagai, T. Yamada and A. Wada: "Development of a
Mixed Finite Element Containing Smooth Interface for Digital Image-Based
Mesh",
Proceedings of the Conference on Computational Engineering and
Science, Vol. 3, pp. 393-396, 1998.5
-
G. Nagai, T. Yamada and A. Wada: "Numerical Analysis
of Macroscopic Compressive Behavior of Concrete Materials Caused by Tensile
Failure in Microscopic Structure", Proceedings of the Conference on
Computational Engineering and Science, Vol. 4, No. 2, pp. 729-732,
1999.5
-
G. Nagai, T. Yamada and A. Wada: "Three-Dimensional
Image-Based Finite Element Procedure for the Compressive Failure Simulation
of Concrete Materials", Proceedings of the Conference on Computational
Engineering and Science, Vol. 5, 2000.5
Miscellaneous articles
in Japanese
-
G. Nagai, T. Yamada and A. Wada: "Numerical Modeling
of Concrete Materials", KEISAN KOGAKU (Journal of the Japan Society
of Computational Engineering and Science), Vol. 4, No. 3, pp. 18-23,
1999.9
-
G. Nagai: Cover figure, Concrete Journal, Japan
Concrete Institute, Vol. 37, No. 9, 1999.9
-
T. Yamada and G. Nagai: "Mesoscopic Simulation of
Concrete Materials by Using Image-Based Finite Element Method", Concrete
Journal, Japan Concrete Institute, Vol. 38, No. 1, pp. 64, 2000.1
Personal Resume
Education
April 1991 - March 1995
Department of Architecture, Faculty of Engineering, Science
University of Tokyo, Japan
Bachelor degree of Engineering
Graduation project: Development of a program for 3-D
nonlinear analysis of building frames
Keywords: Winkler Model, Fiber Beam Element
April 1995 - March 1997
Department of Environmental and Physical Engineering,
Interdisciplinary Graduate School of Science and Engineering, Tokyo
Institute of Technology, Japan
Master degree of Engineering
April 1997 - March 2000
Department of Environmental and Physical Engineering,
Interdisciplinary Graduate School of Science and Engineering, Tokyo Institute
of Technology, Japan
Doctor degree of Engineering
Thesis: gFinite Element Procedure for Failure Simulation
of Mesoscopic Structure in Concrete Materialsh (Compressed
PDF files in Japanese)
Keywords: 3-D, Composite Materials, Multi-Scale Problem,
Digital Image Processing, Mixed Finite Element, Parallel Computing
April 2000 - March 2001
Research Fellow, Structural Engineering Research Center,
Tokyo Institute of Technology, Japan
July 2000 - May 2001
Visiting Scholar, Dept. of Civil Engineering, Rensselaer
Polytechnic Institute, USA
Scholarships and Grants
-
38th Takenaka Scholarship
(April 1998 - March 1999)
-
Research Fellow of the Japan Society for the Promotion of
Science (JSPS) (January
1999 - March 2001)
-
Research Fellow of the Japan Society for the Promotion of
Science (JSPS) (April 2001
- May 2001)
-
JSPS Grant-in-Aid
for Scientific Research (April 1999 - March 2001)
Awards
Academic Memberships
Institute of Industrial Science, University of Tokyo
4-1-6, Komaba, Meguro, Tokyo 153-8505, JAPAN
e-mail: gakuji@iis.u-tokyo.ac.jp
phone/fax: +81-3-5452-6128/6129