1995 Fiscal Year Final Research Report Summary
Process of Cracking and Damage Due to Plastic Fatigue of Steel Elements and Members under Very Low Cycle Loading
| Project/Area Number |
06650632
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| Research Category |
Grant-in-Aid for General Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Research Field |
Building structures/materials
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| Research Institution | KYOTO UNIVERSITY |
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Principal Investigator |
IWAI Satoshi Kyoto University, Disaster Prevention Research Institute, Instructor, 防災研究所, 助手 (60184850)
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| Co-Investigator(Kenkyū-buntansha) |
KAMEDA Hiroyuki Kyoto University, Disaster Prevention Research Institute, Professor, 防災研究所, 教授 (80025949)
NONAKA Taijiro Kyoto University, Disaster Prevention Research Institute, Professor, 防災研究所, 教授 (60027224)
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| Project Period (FY) |
1994 – 1995
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| Keywords | Steel Structure / Repeated Loading / Low Cycle Fatigue / Local Buckling / Finite Element Method / Strain History / Crack |
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| Research Abstract |
An experimental investigation has been performed on very low-cycle fatigue failure of steel elements and angles under repeated loading. The objective of this study is to extract decisive factors causing cracks and rupture in the course of loading repetitions of the order of a few to twenty cycles. The test specimen was subjected to axial load repeatedly after undergoing inelastic buckling. The experimental results show that visible cracks were initiated on the concave side of the bending deformation when it was stretching. The number of load cycles at rupture decreases as width-to-thickness ratio becomes smaller and slenderness ratio becomes larger. Energy dissipation capacity depends heavily on the entire history of loading, failure mode, slenderness ratio and width-to-thickness ratio. The maximum values of residual "net" strains, excluding contributions from the crack opening, of all the specimens are of the order of 25-40% and they do not depend on loading pattern, failure mode, slenderness ratio and width-to-thickness ratio. Furthermore, to simulate the experimental behavior of steel angles, previously done by the authors, and to make clear the local stress-strain history at the member's critical part, the nonlinear numerical analysis of steel angles under very low-cycle loading was performed by using the FEM program, MSC/NASTRAN.From the results of the numerical study, the significance of finite element method has been established in the description of local behavior and the step-by-atep tracing of deformation for steel members under severe cyclic deformations in the post-buckling range. On this basis, a concept is proposed that cumulative plastic strain of critical parts of the steel members subjected to large repeated deformations can be a key index of failure.
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